Production of composite ship hulls - TU Delft

MSc thesis by Jacob Meijer SDPO.15.002.m

Faculty of Mechanical Engineering and Marine Technology Ship Design, Production & Operation

Production of composite ship hulls

Developing cost price estimations for composite ship hulls

Thesis for the degree of MSc in Marine Technology in the specialization of production

Production of composite ship hulls Developing cost price estimations for composite ship hulls

By

Jacob Meijer

Performed at

Defensie Materiaal Organisatie

This thesis SDPO.15.002.m is classified as confidential in accordance with the general conditions for projects performed by

the TUDelft.

29-01-20115

Company supervisor

Responsible supervisor: P. Everts

E-mail: [email protected]

Thesis exam committee

Chair/Responsible Professor: Prof. Ir. J.J. Hopman

Staff Member: Dr. Ir. J.M.G. Coenen

Staff Member: X. Jiang

Company Member: Ir. P. Everts

Author Details

Studynumber: 1508288

Author contact e-mail: [email protected]

Preface This report is the result of a study where I developed a model for cost prices estimations of composite

ship hulls. This report is my MSc thesis and is the final part of my study Marine Technology with

specialization in production.

The study is performed at the Defensie Materieel Organisatie (DMO). The DMO takes care of all the

material for the Royal Netherlands Army. I would really thank DMO for the oppurtunity to graduate

there. The topic is very interesting and I learned a lot about how the Royal Netherlands Army works.

I would like to thank P. Everts, head of the life cycle management deparment for his daily supervision

during the research. I would also like to thank H. post of DMO for answering my question about cost

price estimation for minecounter measure vessels. I also want to thank J.M.G. Coenen of the TU Delft for

the supervision. I would like to thank W. Leenders of Airborne and L. Morel of Damen Navel Shipbuilding

for their help during the development of the model. I also want to thank my fiance, Rinske, for her

support during my graduation

Jacob Meijer

Den Haag, January 2015

Production of composite ship hulls 1 Summary

Summary This report describes the study of the production of composite ship hulls. The graduation project is about

the structural composite work for the hulls. It does not include the whole building process including all

the work for the installation of the equipment which is partially composite building. The first part of the

study is the investigation of possible production methods for composite ship hulls and the description of

the production of the Alkmaar class vessels of the Royal Netherlands Navy. This production method is

used to develop a model to estimate the cost price for composite ship hulls in the second part of this

report.

Different production methods can be used for the production of maritime structures. Hand lay-up is used

for the production of the Alkmaar class vessels. However, this technique is quite old. Due to emissions of

styrene, this method is prohibited today. Examples of production techniques are vacuum injection, resin

transfer method. Different structures types can be used for the production of composite hulls. These

structure types are: monocoque structure, sandwich structure and single skin stiffened structure. Several

materials can be used for the construction of the vessels. Most used materials are glass fibres, carbon

fibres, polyester resin, and vinyl ester resin. Materials for the core of sandwich panels are balsawood and

foams.

The aim of the model is to be able to make estimates for the production for monohull vessels. These

estimates can be made in early design stages but also in later stages in more detail. The size and the

form of the hull should not matter for the estimates. The calculations necessary to come from a hull to

production parameters for that hull are independent of the calculations for the production process itself.

As a result the hull form can be changed easily in the model

The production process is used to determine the necessary steps in the production of these vessels. The

process order is determined and every step in the production of the vessels is described. Lots of different

processes has to be done. Production rates for each type of work were established to be able to estimate

the time necessary for each step in the process. However, the most time consuming are the lay-up of the

fibre, the lamination of the fibres, the placing and positioning of the decks, bulkheads and the scouring

of the materials. The developed model uses three parts to calculate the cost price for the production of

composite vessels. The three parts are the man-hour cost, the material cost and the investments or the

non man-hour related cost. Only the cost directly related to the production of the vessel are used for the

calculation. The cost for the production of the Alkmaar class vessels produced nowadays with the

production technique used in the 1980s depends on the number of ship. For one ship is the price

€123/kg and the cost price for fifteen ships is €81,80.

The model can be used to determine improvements in the production of composite ship hulls. The model

gives insight in the process necessary for the production but is made in such a way that change in the

production can be evaluated easily. Future use of the model could be the evaluation of the whole

process and calculation the effect of applying for different techniques to lower the cost price for

composite ship hulls.

Production of composite ship hulls 2 Content

Content

Preface ........................................................................................................................................................... 3

Summary ....................................................................................................................................................... 1

Content .......................................................................................................................................................... 2

List of figures ................................................................................................................................................. 6

List of tables .................................................................................................................................................. 7

Abbreviations ................................................................................................................................................ 9

1. Introduction .........................................................................................................................................10

1.1 Background .................................................................................................................................. 10

1.2 Problem ....................................................................................................................................... 11

1.3 Research question and sub questions ......................................................................................... 12

1.4 Structure thesis ........................................................................................................................... 12

2. Production of composite ship hulls .....................................................................................................14

2.1 Materials ...................................................................................................................................... 14

2.1.1 Resin .................................................................................................................................... 14

2.1.2 Reinforcement ..................................................................................................................... 16

2.1.3 Core materials for sandwich ................................................................................................ 17

2.2 Joints ............................................................................................................................................ 18

2.2.1 Adhesive bonding ................................................................................................................ 18

2.2.2 Secondary bonding .............................................................................................................. 18

2.2.3 Butt joints ............................................................................................................................ 19

2.3 Production methods .................................................................................................................... 19

2.3.1 Contact moulding ................................................................................................................ 21

2.3.2 Closed moulding .................................................................................................................. 23

2.4 Structure design ‘philosophy’ ...................................................................................................... 24

2.4.1 Framed single skin structure ‘philosophy’ ........................................................................... 24

2.4.2 Monocoque ......................................................................................................................... 25

2.4.3 Sandwich structure .............................................................................................................. 25

2.4.4 Corrugated hull .................................................................................................................... 25

2.4.5 Possible construction methods ........................................................................................... 26

3. Why a production model? ...................................................................................................................27


3.1 Cost aspects ................................................................................................................................. 27

3.2 Model aspects ............................................................................................................................. 27

3.3 Production aspects ...................................................................................................................... 27

4. Requirements model ...........................................................................................................................28

4.1 Model type .................................................................................................................................. 28

4.1.1 Production cost estimation ................................................................................................. 28

4.1.2 Cost price estimation ........................................................................................................... 28

4.1.3 Production process oriented ............................................................................................... 28

4.1.4 Accuracy .............................................................................................................................. 29

4.2 Requirements regarding hull to be estimated ............................................................................ 29

4.2.1 Hull type and dimensions .................................................................................................... 29

4.2.2 ‘Structure philosophies’....................................................................................................... 29

4.3 Use during a project .................................................................................................................... 29

4.3.1 Applicability ......................................................................................................................... 30

4.3.2 Multiple production of the same hull ................................................................................. 30

4.3.3 Compare different concepts ................................................................................................ 30

4.3.4 Evaluation improvements production ................................................................................. 30

5. Production process AMBV ...................................................................................................................31

5.1 Lay out production yard .............................................................................................................. 31

5.1.1 Station 1............................................................................................................................... 33

5.1.2 Station 2............................................................................................................................... 34

5.1.3 Station 3............................................................................................................................... 34

5.1.4 Station 4............................................................................................................................... 34

5.2 Production steps .......................................................................................................................... 34

5.2.1 Make mould ready .............................................................................................................. 34

5.2.2 Apply release-/separation agent ......................................................................................... 34

5.2.3 Lay-up fibres ........................................................................................................................ 35

5.2.4 Lamination ........................................................................................................................... 35

5.2.5 Scour surface ....................................................................................................................... 35

5.2.6 Make water courses holes ................................................................................................... 35

5.2.7 Make foam core .................................................................................................................. 36

5.2.8 Glue foam cores................................................................................................................... 36


5.2.9 Apply rubber emulsion ........................................................................................................ 36

5.2.10 Drilling holes ........................................................................................................................ 36

5.2.11 Glue glas pens ...................................................................................................................... 36

5.2.12 Positioning of the components of the ship ......................................................................... 36

5.2.13 Making angle connection deck/bulkheads/skin .................................................................. 37

5.2.14 Production sandwich panel ................................................................................................. 37

5.2.15 Placing sandwich panel........................................................................................................ 37

5.2.16 Remove release-/separation agent ..................................................................................... 37

5.2.17 Break off mould ................................................................................................................... 37

5.3 Production order AMBV .............................................................................................................. 37

5.3.1 Station 1 production order .................................................................................................. 41



6. Conceptual model ...............................................................................................................................43

6.1 Structure model ........................................................................................................................... 43

6.1.1 Global bending moment ...................................................................................................... 43

6.1.2 Local water pressure ........................................................................................................... 43

6.2 Cost price estimation model ....................................................................................................... 46

6.2.1 Dimensions .......................................................................................................................... 46

6.2.2 Production parameters ....................................................................................................... 46

6.2.3 Production process en man-hours ...................................................................................... 46

6.2.4 Material cost ........................................................................................................................ 47

6.2.5 Non man-hour related costs................................................................................................ 47

6.2.6 Learning curve ..................................................................................................................... 47

7. Parameters production model ............................................................................................................50

7.1 Process parameters ..................................................................................................................... 50

7.1.1 Preparatory work................................................................................................................. 50

7.1.2 Producing laminate.............................................................................................................. 50

7.1.3 Scouring ............................................................................................................................... 51

7.1.4 Making stiffeners ................................................................................................................. 52

7.1.5 Placing decks and bulkheads ............................................................................................... 52

7.1.6 Super structure .................................................................................................................... 52


7.1.7 Overview process parameter .............................................................................................. 52

7.2 Structure and material parameters ............................................................................................. 53

7.2.1 Number of layers ................................................................................................................. 53

7.2.2 Buffer layer and strength layer............................................................................................ 54

7.2.3 Glass pins ............................................................................................................................. 55

7.3 Cost parameters .......................................................................................................................... 55

7.3.1 Inflation rate ........................................................................................................................ 55

7.3.2 Material prices ..................................................................................................................... 55

7.3.3 Investment ........................................................................................................................... 56

8. Experimental model ............................................................................................................................57

8.1 Dimensions ship .......................................................................................................................... 57

8.1.1 Hull form .............................................................................................................................. 57

8.1.2 Macro’s dimensions ship ..................................................................................................... 58

8.2 Characteristics ship ...................................................................................................................... 59

8.2.1 Main dimensions ................................................................................................................. 59

8.2.2 Stiffeners ............................................................................................................................. 59

8.2.3 Bulkheads ............................................................................................................................ 60

8.2.4 Decks ................................................................................................................................... 62

8.3 Production parameters ............................................................................................................... 62

8.4 Production process ...................................................................................................................... 63

8.5 Determination material cost ....................................................................................................... 63

8.6 Total cost calculation series ........................................................................................................ 64

8.7 Optional steps conceptual model................................................................................................ 64

9. Results and sensitivity analysis ............................................................................................................65

9.1 Results ......................................................................................................................................... 65

9.2 Sensitivity analysis ....................................................................................................................... 68

9.2.1 Sensitivity other ship ........................................................................................................... 70

9.2.2 Sensitivity other materials ................................................................................................... 70

9.3 Building other structure .............................................................................................................. 71

9.4 Using other process ..................................................................................................................... 71

10. Verification and validation model ...................................................................................................73

10.1 Verification weight structure ...................................................................................................... 73

Production of composite ship hulls 6 List of figures

10.2 Verification production skin ........................................................................................................ 74

10.3 Verification production stiffeners ............................................................................................... 74

10.4 Verification investment ............................................................................................................... 75

10.5 Verification other processes ........................................................................................................ 75

10.6 Comparison decks and bulkheads ............................................................................................... 75

11. Implementation in DMO estimation model ....................................................................................76

12. Conclusion and recommendations ..................................................................................................77

12.1 Conclusion ................................................................................................................................... 77

12.2 Recommendations....................................................................................................................... 78

Bibliography .................................................................................................................................................79

Appendix 1. Midship section AMBV ........................................................................................................83

Appendix 2. Description hull form ...........................................................................................................84

Appendix 3. Production parameters .......................................................................................................85

Appendix 4. Weight parts of the ship ......................................................................................................87

List of figures Figure 1. Alkmaar class mine hunter. .......................................................................................................... 10

Figure 2. Most used weave patterns (Xu, sd). ............................................................................................. 17

Figure 3. Different sandwich structures (Vinson, 1999). ............................................................................. 18

Figure 4. Examples of butt joints (Smith, 1990). ......................................................................................... 19

Figure 5. Male en female mould (Empire West Inc., sd). ........................................................................... 20

Figure 6. Impregnation (MagnumVenusPlastech, sd). ................................................................................ 23

Figure 7. Gantry crane for the construction of a GRP minehunter for the Royal Navy (Smith, 1990). ....... 23

Figure 8. Connection types hat stiffeners. .................................................................................................. 24

Figure 9. Layout GNM yard (GNM Naval construction, 1985). ................................................................... 31

Figure 10. Layout van der Giessen-de Noord marinebouw (GNM Naval construction, 1985) ................... 32

Figure 11. Flowchart production process AMBV. ........................................................................................ 38

Figure 12. Flowchart station 1. ................................................................................................................... 39

Figure 13. Flowchart station 2. .................................................................................................................... 40

Figure 14. Butt wise built laminate. ............................................................................................................ 41

Figure 15. First two stations. ....................................................................................................................... 42

Figure 16. Last two stations ......................................................................................................................... 42

Figure 17. Schematic overview cost price estimation model. ..................................................................... 44

Figure 18. Static water pressure (Van der Giessen - de Noord marinebouw BV, 1988) ............................. 45

Figure 19. Dynamic pressure caused by the relative motion. ..................................................................... 45

Figure 20. Difference between NATA formula and the DMO formula for the learning curve. ................... 49

Figure 21. Graph thickness vs. layers. ......................................................................................................... 54

Production of composite ship hulls 7 List of tables

Figure 22. Division ship ................................................................................................................................ 57

Figure 23. Width decks ................................................................................................................................ 57

Figure 24. Cross sections ............................................................................................................................. 57

Figure 25. Division ship ................................................................................................................................ 59

Figure 26. Bulkheads in the ship.................................................................................................................. 61

Figure 27. Decks in ship ............................................................................................................................... 62

Figure 28. Cost per ship for series of different sizes ................................................................................... 65

Figure 29. Effect learning curve ................................................................................................................... 65

Figure 30. Decomposition of the material cost. .......................................................................................... 66

Figure 31. Decomposition different processes. .......................................................................................... 67

Figure 32. Production parts of the construction. ........................................................................................ 68

Figure 33. Cost of a project. ........................................................................................................................ 68

Figure 34. Influence manhour cost. ............................................................................................................ 69

Figure 35. Influence of the price of the fibres. ............................................................................................ 69

Figure 36. Influence production stiffeners ratio ......................................................................................... 70

Figure 37. Midship section AMBV ............................................................................................................... 83

List of tables Table 1. Main dimensions AMBV ................................................................................................................ 10

Table 2. GRP MCMV's in service at 1999-12-03 .......................................................................................... 24

Table 3. Production speed several part of the ship. .................................................................................... 50

Table 4. Characteristics buffer layer and strength layer. ............................................................................ 51

Table 5. Overview process parameters. ...................................................................................................... 53

Table 6. Thickness vs. layers ........................................................................................................................ 53

Table 7. Mass percentage fibre and thickness buffer layer ........................................................................ 54

Table 8. Weight composite material ........................................................................................................... 55

Table 9. Mixing ratio matrix ........................................................................................................................ 55

Table 10. Cost price different material to be used. ..................................................................................... 55

Table 11. Height waterlines ......................................................................................................................... 58

Table 12. Main dimensions ......................................................................................................................... 59

Table 13. Changes stiffener spacing ............................................................................................................ 60

Table 14. Stiffener spacings ......................................................................................................................... 60

Table 15. Dimensions deck girder ............................................................................................................... 60

Table 16. Longtidunal stiffener end location. ............................................................................................. 60

Table 17. Bulkheads ..................................................................................................................................... 61

Table 18. Decks ............................................................................................................................................ 63

Table 19. 'Normal' Alkmaar class vessels and Alkmaar class vessel with thicker skin. ............................... 71

Table 20. Weight different parts according to the model and to the GNM calculation ............................. 74

Table 21. Production skin. ........................................................................................................................... 74

Table 22. Production times girder and stiffeners ........................................................................................ 74

Table 23. Percentage of the time used for the lay-up and lamination of the stiffeners. ............................ 75

Table 24. Overview production times processes not directly related to the GRP work. ............................ 75

Production of composite ship hulls 8 List of tables

Table 25. Production cost decks and bulkheads. ........................................................................................ 75

Table 26. Description hull form ................................................................................................................... 84

Table 27. Production parameters skin. ....................................................................................................... 85

Table 28. Production parameters bulkheads. ............................................................................................ 85

Table 29. Production parameters deck. ...................................................................................................... 86

Table 30. Material buffer layer skin ............................................................................................................ 87

Table 31. Material strength layer skin ......................................................................................................... 87

Table 32. Material decks and bulkheads ..................................................................................................... 87

Table 33. Material buffer layer skin ............................................................................................................ 87

Table 34. Material strength layer skin ......................................................................................................... 88

Table 35. Material decks and bulkheads ..................................................................................................... 88

Table 36. Material matrix buffer layer skin ................................................................................................. 88


Table 38. Foam core. ................................................................................................................................... 89


Production of composite ship hulls 9 Abbreviations

Abbreviations AMBV Alkmaarklasse Mijnenbestrijdingsvaartuig CSM Chopped Strand Mats DG Dutch Guilder DMO Defensie Materiaal Organisatie/ Defence Material organisation DMP Defensie Materieel Proces ELFE Extreme Low Frequency Electric GNM Giessen-de Noord Marinebouw GRP Glass-Reinforced Plastic ICC Initial Construction Costs LCC Life Cycle Costing LCM Life Cycle Management LCU Landing Craft Utility MCMV Mine Counter Measure Vessel NATO North Atlantic Treaty Organisation RNLN Royal Netherlands Navy RTM Resin Transfer Moulding SCRIMP Seemann Composites Resin Infusion Moulding process (SCRIMP) SPRINT SP resin infusion technology SWBS Ship Work Breakdown Structure TSSE Total Ship System Engineering UEP Underwater Electric Potential VARTM Vacuum-assisted Resin transfer Moulding

Production of composite ship hulls 10 1. Introduction

1. Introduction The first part of this chapter describes the background of this graduation project. The second part of this

chapter is the problem to be solved, the third part gives the research question for this graduation project

and the associated sub question and subsequent questions. The fourth part describes also the structure

of this thesis.

1.1 Background The Alkmaar class mine hunters (AMBV), see

figure 1 of the Royal Netherlands Navy reach the

end of their expected lifetime around 2020. The

main dimensions of the AMBV can be found in

table 1. The mine hunters are planned to be

replaced by other vessels. The Defence Material

Organisation (DMO) is performing feasibility

studies for a new Mine Counter Measure Vessel

(MCMV). DMO uses the Total Ship System

Engineering (TSSE) process as a framework for

managing the developed concept studies

(Defence Material Organisation, 2012). This

process has several standard steps to come to a

design. A key step in this process is the verification

of the proposed concept(s). The costs are

estimated during this step. Furthermore, the

compliance with the performance requirements

and available budget is checked.

The development of the concepts has reached the stage that it is necessary to make a cost estimation.

However that does not imply that the development is almost ready. The TSSE process is an iterative

process.

The cost estimates are important for the Defensie Materiaal Proces (DMP). This process is used to inform

the government and the politics about investment programs of the army for their decision-making

(Ministerie van defensie, 2007).

Main dimensions AMBV

Breadth 8,9 m

Depth 6, 75 m

Draft 3,8 m

Length overall 51,5 m

Displacement 543 ton

Table 1. Main dimensions AMBV

Figure 1. Alkmaar class mine hunter.


Being almost undetectable for mines is an important feature for a MCMV. Sea mines can use one of the

six signatures or combinations of those signatures to detect a ship in their circumference, these

signatures are: acoustic, seismic, magnetic, pressure, extreme low frequency electric (ELFE) and

underwater electric potential (UEP). A magnetic steel MCMV is thus not possible due to the signature

produced by the ship. Therefore, nonmagnetic materials are necessary for a MCMV.

Three concept designs are proposed for a MCMV by the designers of DMO.

Two materials are used for these concept designs. The first concept is a proposal to use glass-reinforced

plastic (GRP) (Takken, 17 December 2013). The second one is also a proposal in GRP, although this design

is smaller compared with the first one (Takken, 17 December 2013). The current AMBV's at the Royal

Netherlands Navy (RNLN) have also been built in GRP.

The third concept design is to use stainless steel with nonmagnetic properties (Bruijn, 17 December

2013). The RNLN does not have experience with the design, cost estimation and production of

nonmagnetic steel vessels.

1.2 Problem Normally, warships are built in normal shipbuilding steel. Changing material requires other production

methods, depending on which material will be used. Other production methods and other materials lead

to a change in the acquisition price of the MCMV's.

The Life Cycle Management (LCM) department of DMO makes cost estimates for the total life of the

ships developed by DMO as part of the TSSE process. Due to the proposed different materials, difficulties

arise for the LCM department. Estimates based on the use of magnetic shipbuilding steel cannot be used

and proper estimates for nonmagnetic material are not yet known. The estimates based on the use of

magnetic shipbuilding cannot be used because the different nature of the production processes in

nonmagnetic steel.

The man-hours related to the Alkmaar class have been registered during the building of the first Alkmaar

class AMBV in 1982. The current estimates used for the concept studies where the structure is made of

GRP material are based on that data. However, it became clear during the analysis of the estimation that

an update of the method is required due to development of production techniques. DMO has got a price

indication for an Alkmaar class build with newer techniques. The results of this price indication will be

used in this graduation project.

The LCM department of DMO uses the NATO Ship LCC hierarchy as a structure to estimate the costs of a

project. Part of the NATO ship LCC hierarchy is the Initial Construction Costs (ICC), all the costs related to

the actual building of the vessel (Anon., 2005). The NATO Ship Work Breakdown Structure (SWBS) is used

to make an estimated for the ICC (Anon., 2005).The NATO SWBS uses a division of the ship to come to an

estimate for the LCC. At the first level of the breakdown structure, four main groups can be

distinguished: design and support, hardware, software and programmatic. Design and support are all the

costs related to the development of a vessel. Hardware are the cost of all the physical parts of the vessel,

software are all the costs related to computer programs to be used on the vessel and programmatic are

all the costs the other costs. These four groups can be broken down into several subgroups related to

several functions of the vessel.


1.3 Research question and sub questions The problem described above results in the following research question with associated sub questions.

The research question will be:

How can construction costs for ships with composite hulls be estimated by means of a model and can

such a cost model be employed to evaluate possible improvements in the ship production process?

The sub questions are:

1. What are alternative production methods for composite hulls and can a costs model be used to

determine which method is preferable?

2. Would such a model be suitable to estimate the production costs for the specific ship type

AMBV?

3. Could such a model be helpful in identifying process or product improvements that can lower

the production costs significantly and what are these improvements?

A subsequent question is:

How can the developed hull construction costs method be implemented and integrated in the current

existing costs estimation methods used by the Defence Material Organisation?

One of the groups within the hardware group is selected for investigation in more detail during the

graduation project. From a ship production point of view, the hardware costs are of interest most.

Within the hardware group are the biggest changes due to the use of another material, the others ones

do not have that big change. The hardware group is divided in seven sub groups. This graduation

research focuses on group 100, which is the hull structure group. The newer production techniques have

the most consequences for the production of the hull. Most of the work related to the composite work is

within this group.

The developed concept designs for the replacement of the AMBV class vessels are in a preliminary

phase. As a result, no detailed construction plans are available; the concepts are in the stage that only 3d

hull shapes are available. The model will be developed to predict the price already in this stage. The first

step is to come from the general arrangements to information about the production and to relate that to

production parameters. A section plan is necessary and also a building strategy.

This graduation focuses on the effect of the use of composite materials on parameters used to estimate

the initial construction costs (ICC). The ICC has two parts, the material costs and the man-hour cost. The

ICC for the stainless steel concept will not be reviewed in this graduation project.

1.4 Structure thesis The second chapter of the thesis is the part that gives an overview of the materials used for maritime

composite applications, the structure types used in composite shipbuilding, a overview of methods used

nowadays for the production of composite applications for the maritime industry. It describes also some

important aspects about the production in composite materials.


The third chapter gives reason for the development of a cost price estimation model during this

graduation project. The fourth chapter describes the requirements used for the cost price estimation

model. The fifth chapter describes the production process of the AMBV class vessel, this production

process is used as benchmark for the model. The sixth chapter describes the conceptual model, thus how

the model should be build theoritically. The seventh chapter gives the parameters for the production of a

composite ship hull, this is the input of the model. The next chapter is the experimental model, the

actual building of the cost price estimation model. Chapter nine describes the results of the model. The

tenth chapter is about the verificaiton and validation of the model. The implementation in the DMO

estimation model is described in chapter eleven and chapter twelve contains the conclusions and

recommendation regarding this graduation project.

Production of composite ship hulls 14 2. Production of composite ship hulls

2. Production of composite ship hulls This first chapter will describe the characteristics of composite materials. It will cover four subjects

related to producing ships in composite materials: the materials, joints to produce the materials,

production methods and construction philosophies. The literature describing these concepts sometimes

uses different wording for concepts. In this chapter, most of the different names of the concepts will all

be addressed.

A composite is a material which consists of two or, in some cases, three elements. The first part is called

the fibre or reinforcement. Its function is to carry the loads. The second part is called the matrix or resin

and this gives the material ductility and toughness. Another important feature of the resin is to protect

the fibres for damage (Ashby, 2013). The optional third part is called the core. Constructions made from

materials with a core are called sandwich constructions. Cores are normally added to create additional

stiffness and strength for a low weight penalty (Stewart, 2010). The advantages of a lighter construction

are lower fuel consumption, a higher payload or a higher speed. For the construction of composite

products it is not necessary to use a core.

Composites have been used for building naval ships since the 1940s. The first boat built was a 28-foot

fiberglass personnel boat in 1947 (Spaudling jr., April 1966). The first successfully composite mine

counter measure vessel was built in 1973 (Mouritz, et al., 2001). Globally, the use of composites

increased at a high speed during the last decades. This increased use of composites has led to the

development and improval of production techniques for composite products.

This chapter describes the possible production techniques of marine structures. Its purpose is to present

an overview of the techniques suitable for the production of ship hulls; not to present an overview of all

production techniques for composite materials.

Not only the production methods are important to investigate, the construction methods are important

as well. This is because the choice for a structure method influences the production method and its

different steps.

2.1 Materials Many different materials may be used to produce ship hulls made from composite materials. The choice

of the materials for ship hulls influences their design. It is therefore important to have some knowledge

about the key features of the materials used. The following paragraphs describe they key features of the

most commonly used materials for the production of marine structures.

2.1.1 Resin

A resin or matrix is used to hold the fibre together. Resins can be divided in two categories: thermoset

resins and thermoplastic resins (Biron, 2013). The difference between these two groups is the behaviour

at higher temperatures and the curing of the materials. Curing of a thermoset materials is a catalytic

chemical reaction. During the curing, the molecules are cross-linked. The result is a strong binding and

solidification. The chemical reaction is irreversible, therefore thermoset materials are hard to recycle.

Curing of a thermoplastic is not a chemical reaction. A thermoplastic resin is liquid if it is heated and/or

pressure is applied. Thermoplastic resin is solid at room temperature, during the cooling the material

undergoes a physical change, from liquid to solid (Johnson, sd).


Thermoplastics are hardly used for maritime structures, some small boats and recreational boats have

been build using this material (Eric Green Associates, 1999). Thermoplastic boats up to 7.2m have been

build (Antosiewicz, 2007). Therefore, thermoplastics are not yet applicable for the construction of a

vessel larger as the MCMV and will not be described in more detail.

2.1.1.1 Polyester resin

Polyester is a thermoset material. Polyester is the most applied material for the construction of maritime

structures (Otheguy, 2010). Polyester is the most used material for composite shipbuilding because of

relatively low cost, curing at room temperature and water immersion properties (Chalmers, 1988).

Polyester resin does not cure when exposed to air. Paraffin is added in order to make curing possible.

The paraffin creates a seal on the surface of the material. The material is no longer exposed to air and

the cure process can take place. The paraffin film creates problems if other parts have to be bonded to it.

The paraffin film has to be removed before another part can be bonded to the structure. An accelerator

is used if the construction should cure at room temperature.

Polyester resin can be divided in orthophtalic and isophtalic resins. The former is the most widely applied

polyester resin. The second one has water immersion properties and is mostly used for constructions

which are in contact with the water (Eric Green Associates, 1999, p. 70).

2.1.1.2 Vinylester

Vinylester is another thermoset material. The performance of vinylester resin is similar to the

performance of polyester resins. Polyester resins are cheaper but vinylester resins are better resistant

against corrosion, have better hydrolytic stability and have good properties against impact loads and

fatigue (Eric Green Associates, 1999, p. 71).

2.1.1.3 Epoxy resin

Epoxy is also a thermoset material. Epoxy resins have the best properties of all the resins used in

maritime applications. However epoxy is not commonly applied in maritime structures because it is not

easy to handle and expensive. Epoxies degrade fast when they are exposed to ultaviolet (UV) light. (Eric

Green Associates, 1999, p. 71).

2.1.1.4 Phenolic resin

The last possible thermoplastic material is a phenolic resin. An important feature of phenolic resin is the

mechanical property of it, which is between 10 to 20% lower compared to polyester, such as flexural

strength and elastic modulus (Chalmers, 1991). Using phenolic resins thus results in a heavier

construction with the same properties regarding to stiffness, shock, buckling and so on. However,

phenolic resins have excellent properties regarding to fire resistance (Chalmers, 1988). Fire resistance is

another important feature of a naval ship. Phenolic resin has good thermal properties, therefore is it

applied for products, which are in service in a tropical climate (Anon., 1996). The material cost are lower

compared to isopthalic resins however the production cost are higher due to higher material cost (Smith,

1990).

2.1.1.5 Conclusion resin

Based on the description of the resin, above one can conclude that vinylester should be applied for the

construction of composite vessels. It has relatively good properties compared with polyester and


benefits in production compared with epoxy resin. However, depending on the mission area phenolic

resin can have advantages due the thermal properties.

2.1.2 Reinforcement

The reinforcement gives the strength to the composite. Fibres are used to provide this strength. Several

materials may be used as reinforcement: glass, carbon and aramid (Smith, 1990). Glass fibre is used for

low performances applications. Several glass fibres are available as reinforcement. E-glass (lime

aluminium borosilicate) is the most commonly applied material. S-glass (silicon dioxide aluminium and

magnesium oxides) has better strength performance, but is more expensive (Eric Green Associates,

1999).

Carbon and aramid are used for high performance applications. An example of a high performance

application is the use of carbon fibre in the Visby class. The advantage of carbon and aramids fibres is the

strength of these materials. However, carbon and aramid fibres are not generally used because of their

high price (Eric Green Associates, 1999). Another advantage of the use of carbon fibre are the good radar

absorption properties of these fibres (Galanis, 2002). Making the superstructure in carbon fibre is thus a

manner to improve the stealth properties of a ship. A side effect is an improvement in stability when

carbon fibre is used, because carbon fibre structures have a lower weight and the KG is thus reduced.

A disadvantage of the use of aramid reinforcement is that aramids have low compressive properties. An

advantage is the high wear resistance (Departement of defense, 2002).

Different types of reinforcement are used for maritime applications. They can be distinguished into two

categories: continuous and non-continuous. Continuous fibres have better strength properties. The low

strength non-continuous properties are mostly used for fibreglass reinforced structures, this is due to

processing restrictions and economic reasons (Eric Green Associates, 1999). Different reinforcement

types will be treated in the next paragraphs.

2.1.2.1 Chopped strand mats

Chopped strand mats (CSM) are mats of short, up to 50 mm, randomly oriented fibres (Chalmers, 1988).

CSM is thus a non-continuous fibre. CSM has low strength properties, however it is easy to handle and it

has good wet-out properties. Production manners for CSM are hand lay-up, spray lay-up and automated

lay-up (Eric Green Associates, 1999).

A big advantage when spray lay-up is used is that it can sprayed directly on a mould together with the

resin (Smith, 1990). The production rate is thus higher. However, more material is necessary due to the

lower material properties.

A combination of woven roving (see 2.1.2.2) and CSM is for instance used for the hull of the Royal

Australian Navy mine hunter of the Bay class (Thomson, et al., 1998).

2.1.2.2 Woven roving fabric

The woven roving fabric reinforcements or woven fabric reinforcements are the most applied

reinforcement types used in maritime applications. Bundles reinforcement are woven to each other. The

materials properties depend on the weave pattern. The weave pattern has effect on materials properties

like deformability and strength (Fibreglas developments corporation, sd). Out-plane-stiffness, strength

and toughness are influenced by the weave pattern (Huang, 2000).


2.1.2.3 Prepreg

Prepreg is a resin already containing reinforcement. Prepregs are thin sheet materials, which can be

placed on a mould. A freezer is necessary to store the prepregs. Prepregs are used in high performance

vessel such as high-speed vessels and sail boats. The reason for that is the high production cost for

prepregs. For most applications are the costs to high compared to the benefits of the use of prepregs.

Prepreg has good strength properties.

Prepregs are cured in an autoclave or in an oven. An oven is applied in maritime applications due to the

big structures (Eric Green Associates, 1999, pp. 272-273). Difficulties occur for structures above 40-50m

due to the curing (Galanis, 2002).The difficulties arise due to size of the oven that has to be used for the

production of the ship. The product has to be put in the oven as a whole. Prepreg can thus not be used

for the construction of an MCMV because an MCMV is a big structure.

2.1.2.4 Unidirectional reinforcements

Unidirectional reinforcement has fibres only in one direction. The material is very strong in the direction

of the reinforcement, but has much less strength properties in the transverse direction of the fibres.

Typical applications for unidirectional reinforcements are stem and centreline stiffening and tops of

stiffeners. Entire hulls are seldom produced in unidirectional reinforcements, only if ultra-high

performance is required for instance if an extreme light structure is required for a race boat (Eric Green

Associates, 1999).

2.1.3 Core materials for sandwich

The reason why constructors choose a sandwich construction is the possible achievement in hull weight

reduction. The reduction in weight can be used for higher payload, increasing speed or range. A core

material has a low weight and strength properties. A sandwich construction has thin composites layers

with thick core materials between those layers (Galanis, 2002). Several structures types can be used for

making a sandwich, among these are foam core sandwich (figure 3a.), honeycomb core sandwich (figure

3b.), web core sandwich (figure 3c.) and truss core sandwich (figure 3d.). Cores can be PVC’s, plywood

and balsa wood.

One of the features of a honeycomb sandwich constructions are the good absorbing properties regarding

to mechanical and sound energy (Vinson, 1999). Given that it is important for a MCMV to reduce the

signatures, the use of a honeycomb sandwich structure could be preferred. However honeycomb

sandwich structures have big downsides: curved geometries are hard to make and the possible

absorption of water is high (Eric Green Associates, 1999). In addition, vacuum infusion and transfer

methods cannot be used because the liquid resin goes into the honeycombs. The costs for foams are

Figure 2. Most used weave patterns (Xu, sd).


lower than the cost for honeycomb structures. Foams are mostly applied in structures for the

automotive industry and transport, honeycomb is used in aerospace structures (Biron, 2014).

2.2 Joints In the construction of ships joints are important. Loads have to be transferred from one part to another.

Therefore joining of the different members of the construction is crucial in the design of a marine

structure. This section treats different type of joining.

2.2.1 Adhesive bonding

Adhesive bonding is used to transfer the loads between the core and laminate. The tensile strength and

the shear strength of the bonding should be at least the tensile strength and the shear strength of core.

(Gullberg & Olsson, 1990). The quality of the adhesive bond is determined by the resin type, size of the

reinforcement, processing techniques and laminate void content. This type of bonding is important for

sandwich constructions. It is the most common type of failure for these structures. Therefore, it is

necessary to take care of the changes from the core to the laminate (Eric Green Associates, 1999).

2.2.2 Secondary bonding

Secondary bindings are bonds, which attach a structural part to another already cured structural part

(Simpson & Burchill, 2004). Primary bonds are the bonds, which are made before the material is cured.

The difference between the secondary bonds and the primary bonds is that the primary bond is both

chemical and physical linked and the secondary bond is only physical linked. The secondary bond can

Figure 3. Different sandwich structures (Vinson, 1999).


withstand less stress because the absence of the chemical linking. Preferably, the linking to the part

takes places before the curing. However, that is not always possible (Murphy, 2014).

Examples of secondary bonding are the connection of stiffeners to panels, decks and skin and bulkheads.

These connections cause stress concentrations. Secondary bindings are the reason for many structural

failures (Eric Green Associates, 1999). If stiffeners are used in the design of the secondary bonding it is

important to prevent these failure types.

The function of these bindings is to carry shear stress and local bending stress. Especially in a MCMV hull

the design of these bondings is important. Stiffeners are sensitive for debonding if they are exposed to

shock loads.

2.2.3 Butt joints

Butt joints are connections between two construction parts in the same plane. These connections can for

instance be used to connect different parts of prefabricated decks. Their main function is to transfer

membrane tension, compression and shear from one part to the other. Several connection types have

been developed to make these butt joints, some of these can be found in figure 4. (Smith, 1990).

Figure 4. Examples of butt joints (Smith, 1990).

2.3 Production methods Composite products can be produced in a variety of ways, which are all variations of a few basic

processes (Owen, et al., 2000, p. 5). The production methods can be divided in contact moulding and

closed moulding. Although the methods may vary, the production of composites always follows the

same key steps (Owen, et al., 2000). These key steps are:

Mould preparation

Placing reinforcement


Introduction of the resin matrix

Wet out and wet trough of the reinforcement

Matrix cure

Removal of the cured material from the mould

Trimming

Post curing if required

Mould cleaning (only if the mould is used again)

The exact building process for the Alkmaar class AMBV will be described in chapter 5.

Some general remarks have to be made before diving into the details of the different production

methods, reinforcements and resins.

First of all, the ratio between the matrix and the resin is very important for the strength of the material.

The higher the content of reinforcement, the larger the strength of the composite (Chalmers, 1991). The

fact that higher content of reinforcement gives a higher strength is important with regard to types of

reinforcement. Unidirectional rovings have the highest possible ratio 0.5-0.65, for woven fabrics this is

between 0.4 and 0.55. Random mats have a fibre content between 0.23 and 0.33 (Shenoi & Dodkins,

2000). The production manner also influences the fibre content.

In most cases, moulds are used to produce composite product. The two types of moulds that are used

here are called male moulds and female moulds. Female moulds can also be called negative moulds or

cavity moulds and male moulds can also be referred to as positive moulds. The difference between the

two moulding methods is related to the side of the construction that is on the mould. The side, which

has to be smooth is always on the mould (Lee,

1993). The sides of the vessel for instance, which

have to be in the water, because a smooth side

reduces the resistance of the vessel. The closed

moulding techniques combine a male and a

female mould. The advantage of a closed

moulding technique is that both surfaces are

smooth.

The choice for a moulding type does not depend only on the required smoothness of the side of the

construction. Often it also depends on the costs of the production. If a product has to be produced five

to ten times or fewer, the male mould would be the cheapest way of producing. It would also be the

least time consuming. The use of the more expensive female moulds can be justified if more than 5-10

products are produced (Fibre glast developments corporation, sd).

Bulkheads, decks and stiffeners are produced elsewhere. They can be bound onto the hull when the

production is in the stage where the bulkheads and decks need to be installed. (Karlsson & Aström,

1996).

Some environmental conditions should be controlled during the fifth step of the process, the curing.

Figure 5. Male en female mould (Empire West Inc., sd).


2.3.1 Contact moulding

2.3.1.1.1 Hand lay-up

The first production technique for composite materials was the hand lay-up method or wet lay-up

method (Marsh, 2006). It is also the easiest way in terms of equipment to produce a marine structure. A

part of the reinforcement is placed on the mould. Resin is applied with the use of hand-held rollers. Air

bubbles possible present in the material are removed due to the pressure applied with the rollers.

However, the void content is high compared with other techniques. The required thickness can be

reached by repeating the process (Dharmawan, 2008).

Hand lay-up is a good production method for large products with a low production rate. However, hand

lay-up has several disadvantages. The content of the fibre is low. As a result, the strength of the material

is also low, resulting in a thicker construction compared with other production methods in order to get a

product with the same strength and stiffness. Furthermore, the manufacturing time is high and the

biggest part of the work is manual work. As a result are the man-hour costs high. However tooling cost is

low for hand lay-up. The reproducibility of the materials is poor (Drechsler, 1999), due to the high

percentage hand labour, it is difficult to produce identic products.

The advantage of hand lay-up is the curing at room temperature and the absence of pressure beside the

atmospheric pressure (Owen, et al., 2000). As a result, a product can be made without major

investments in tooling.

Hand lay-up is hardly any used due to regulatory requirements. During the curing of the material styrene

will release. Other production techniques do not have this disadvantage due to sealing or a closed mould

(Shenoi & Dodkins, 2000). These techniques are described in 2.3.1.1.3, 2.3.1.1.4 and 2.3.2.

2.3.1.1.2 Spray-up

During the 1960s other methods were developed. Due to the labour intensive hand lay-up process,

possibilities to reduce the labour part in the production process investigated. Mechanisation was the key

factor in developing less labour intensive methods. The first developed method beside hand lay-up is the

spray lay-up method. Spray lay-up uses a chopper gun to spray the material onto the mould.

Reinforcement as well as fibres are sprayed together onto the mould (Owen, et al., 2000).

Chopped strand mats are mostly used for the spray lay-up method. A disadvantage of the spray lay-up

methods is the poor quality of the product. Hand lay-up products have a better quality compared with

spray lay-up methods. (Owen, et al., 2000). The reinforcement can also be placed on the mould

manually. This gives better strength properties, however the work and thereby the cost are increased.

(Biron, 2014).

The advantage of the spray-up method is the speed compared to hand lay-up method and the extent to

which the process can be automated. Disadvantages are the control of thickness of the material, losses

of resin due to the spraying and the need for experienced workers (Biron, 2014).

2.3.1.1.3 Vacuum bag moulding

This method was applied for the first time in a marine application at the end of the 1970s (Reuterlöv,

2002). Vacuum bag moulding or vacuum-assisted resin injection (VARI) requires more tooling compared

with the hand lay-up and spray-up method. The reinforcements are placed on the mould and if

applicable the core material. The reinforcements and core material are sealed with plastic, this creates


an airtight bag, called vacuum bag. Vacuum is applied and the resin is sucked into the vacuum bag. The

construction is held vacuum until all the material is cured (Owen, 2000). Air bubbles in the material are

reduced due to the vacuum applied (Biron, 2014).

The vacuum bag moulding has many advantages over the hand lay-up method and the spay-up methods,

among these are less styrene emissions, independent set-up time and better mechanical properties.

Disadvantage of the vacuum bag moulding process are a mat necessary for the distribution of the resin

and peel ply layer. These two increase the cost and production time. (Reuterlöv, 2002). The lay-up is

expensive part of the production when vacuum bag moulding is used, the reinforcement is laid up by

hand, resulting in high production times (Judy, et al., 1994). Automation of the lay-up could possible save

a lot of money. The surface, which is not on the mould, is more smooth compared with spray-up or hand

lay-up although a single side mould is used. The vacuum bag takes care of the finishing the outer surface

(Biron, 2014).

Vacuum bag moulding is called dry bag moulding if a core is bonded to an already cured laminate. It is

called wet bag moulding if a laminate is made with the vacuum bag moulding technique (Eric Green

Associates, 1999).

The reinforcements and if applicable the cores are placed dry on the mould. This results in better

controllable quality of the structures because visible inspection can take places without any time limit.

(Eric Green Associates, 1999, p. 269).

2.3.1.1.3.1 SCRIMP

Seemann Composites Resin Infusion Moulding process (SCRIMP) is a process similar to the vacuum bag

moulding technique. This technique is developed by the Seemann composites company. Advantage of

the SCRIMP process are the high ratio between reinforcement and resin. Weight fraction up to 80%

reinforcement has been achieved for unidirectional reinforcement and up to 75% percent for woven

rovings. (Eric Green Associates, 1999).

The difference between the SCRIMP method and the ‘normal’ vacuum bag moulding is the point in time

where the reinforcements are place on the mould. For the vacuum bag moulding first some resin has to

be cured before the reinforcement can be laid-up. This is not necessary with the SCRIMP process.

Reinforcements and cores are being pressed together by the applied vacuum. The resin is sucked into

the reinforcements and cores. As a result of this type of injection of the resin no void content is present

in the construction (Eric Green Associates, 1999).

The SCRIMP process has been used for the production of the superstructure and some internal

structures of the RN Sandown class mine hunters (Naval technology, sd). Yachts have also been built

using the SCRIMP process. The biggest vessel made with this technique is a yacht produced by Horizon

yachts. This vessel has a displacement of 211 ton and is almost 40 metres long (TPI composites, 2006).

2.3.1.1.3.2 SPRINT

This method is developed by the company SP high modulus, currently named Gurit (Gurit, 2013). SP resin

infusion technology (SPRINT) is method which uses advance prepreg to make construction with.. SPRINT

uses a vacuum bag, but instead of adding the resin after the reinforcement is placed on the mould and a

vacuum is applied, are prefabricated resin films placed on both sides of the reinforcement. The

reinforcement melts and goes in to the reinforcement. A big advantage of the SPRINT method is that


that it ensures that the resin takes up all void space. The resin is near the reinforcement and does not

have to flow through the mould to reach every place (Ness & Jones, 2000).

An example of the use of the SPRINT technique in shipbuilding is the M67 RS, a 20 m long yacht, built by

Murti yachts (Murtic yachts, sd).

2.3.1.1.4 Impregnation

Impregnation is an technique to automate the lay-up of the

reinforcement. Normally, the lay-up is a costly process, reducing the

amount of work necessary to place the reinforcement on the mould

can result in tremendous cost savings. Big rolls of reinforcement are

feed onto a platform of a gantry crane. Rollers are on this platform

where the reinforcement is wetted. The gantry crane is positioned

transversely with respect to the mould, see figure 7. The

reinforcement is placed on the mould due to horizontal and vertically

movement of the gantry. This method has been used for the

production of a GRP minehunter of the Royal Navy (Smith, 1990). The

advantages of impregnation are higher output, higher efficiency of

materials and a constant quality of the material. Only reinforcement

that can be handled when wetted can be used for this method

(Chalmers, 1991). A disadvantage of the impregnation is the constant

output of impregnated mats. An impregnator is used during the production of the AMBV class vessels.

The occupation of the impregnator was only 15 weeks a year. The other part of the year the impregnator

could not be used because of the constant output. (Lohuizen, 1985).

2.3.2 Closed moulding

Closed moulding uses two mould sides to close the mould. This paragraph describes two methods of

closed moulding.

2.3.2.1 RTM

Resin transfer moulding (RTM) is a closed moulding

process. The fibres are placed on one side of the

mould. The other side of the mould is placed on top

of the mould when all the reinforcement is placed.

This creates a closed mould. Pressure is applied and

the mould will be filled with the matrix.

RTM is expensive for small series due to the

expensive tooling used for the process. Another

disadvantage of RTM is the production difficulties for

parts over five to six meters in length (Reuterlöv,

2002). There is a risk of moving reinforcement if RTM

is used (Biron, 2014). Therefore is it hard to control

the quality of the construction.

Figure 6. Impregnation (MagnumVenusPlastech, sd).

Figure 7. Gantry crane for the construction of a GRP minehunter for the Royal Navy (Smith, 1990).


2.3.2.2 VARTM

The difference between VARTM (vacuum assisted resin transfer method) and RTM is the use of vacuum

instead of pressure to transport the resin into the mould. Another difference between VARTM and RTM

is that VARTM can either use closed or open mould or RTM only closed mould. VARTM closed moulding

technique has been used for the production of the Landing Craft Utilities (LCU) for the RNLN. (Judy, et al.,

1994). If an open mould is used the process is the vacuum bag moulding as described in 2.3.1.1.3.

2.4 Structure design ‘philosophy’ Several main structure ‘philosophies’ can be distinguished for GRP MCMV’s. Three structure

‘philosophies’ are already applied for operational MCMVs, which are framed single skin, sandwich

composite and monocoque or single skin construction. Vessels of the MCMV-classes listed in table 2 are

in service or under construction at 1999-12-31 (Mouritz, et al., 2001). Each of the structure types is thus

feasible to construct MCMV’s. Other aspects, such as construction costs, LCC, material properties and

construction restraints, also have an influence on the choice for the composite materials.

Framed single skin Sandwich composite Monocoque

Hunt (UK) Landsort (SW) Lerici (IT, MA, SK, NI)

Sandown (UK) Stryso (SW) Gatea (IT ,TH, USA, AU)

Tripartite (NL, FR, BE, IN, PA) Flyvevisken (DM)

KMV (BE) Alta (NO)

Bay (AU)

Table 2. GRP MCMV's in service at 1999-12-03

2.4.1 Framed single skin structure ‘philosophy’

The framed single skin method is a structure ‘philosophy’ comparable with normal steel ships. Stiffeners

are bound on the shell. These stiffeners are either transverse or longitudinal stiffeners depending on the

size of the ship and the construction ‘philosophy’ used. A combination of the two stiffeners can be used

as well. Bulkheads and frames are used

as secondary stiffeners. The framed

single skin method is labour intensive

because each stiffener has to be bound

separately to the hull (Shenoi & Dodkins,

2000). The structure of the current

Alkmaar class AMBV’s is a framed single

skin. The connection between the

stiffeners and the skin are important for

this structure ‘philosophy’, because they

are sensitive for shock loads (Smith,

1990). The AMBV has hat stiffeners,

other stiffener types may be used as well.

Examples of connection for between the

skin and the hull can be found in figure 8

Figure 8. Connection types hat stiffeners.


2.4.2 Monocoque

The monocoque or single skin method is a structure ‘philosophy’, which does not use any stiffeners on

the hull. The shell of the hull is very thick in order to compensate for the absence of stiffeners. The result

is a heavier hull because a stiffened skin requires less material. The effect of a heavier hull are higher

material costs. The mine hunter of the Italian Navy has for instance a 150 mm thick construction at the

keel and 50 mm at the deck (Rusell, 2005). The difference with the skin of the Alkmaar class vessels is

huge. The shell thickness of the Alkmaar Class vessels is up to 34 mm at the keel.

However, the higher material costs are compensated by less man-hour costs, as there are no stiffeners

which, have to be bound to the shell. Since the bonding of stiffeners is labour intensive work and thus

costly (Smith, 1990), constructing hulls without stiffeners means that man-hour costs can be cut.

A disadvantage of the monocoque structure ‘philosophy’ is the cost of the mould, which tends to be high

especially for large vessels. As the MCMV counter measure will be a large vessel, the construction costs

for the mould are expected to be high. The higher cost for the mould can be justified if a series of six to

ten hulls has to be produced (Chalmers, 1991).

2.4.3 Sandwich structure

The third structure ‘philosophy’ is a sandwich structure. A sandwich structure has three parts: two

‘normal’ composite layers on the outside of the construction and a core of a light and cheap material in

between those layers (Chalmers, 1991). These three parts are produced in a certain order: first, one of

the outside layers is being produced. Then the core material is positioned on that outside layer, after

which at last the other outside layer is produced.

The main advantage of sandwich structures is that it gives a light construction at a reasonable price. A

sandwich construction is mostly used together with carbon as a matrix to benefit optimally from the low

weight of sandwich structures (Karlsson & Aström, 1996).

Sandwich structures can be produced without the use of an additional mould, because the core is used

as a mould. First one side of the reinforcement is placed on the core and that reinforcement is

laminated, after which the reinforcement is placed on the other side of the core and is laminated

afterwards (Biron, 2014).

2.4.4 Corrugated hull

A completely different manner to obtain a stiff hull is the use of corrugation in the material. Corrugation

has several advantages compared to the other construction ‘philosophies’. The first advantage is the

absence of the costs for the stiffeners bound onto the structures after the construction of the shell. The

second advantage is the shock resistance, which is much better compared to a structure where the

stiffeners are bound to the hull as described earlier.

Mine counter measure vessels with a corrugated hull are not produced yet. However, research has been

carried out on corrugated hulls. A corrugated hull is produced and tested for different conditions. It was

found that the total weight of a corrugated hull is 15% lighter compared to a conventional hull and the

production costs are 25% lower compared to a conventional transversely framed hull (Smith, 1990).


2.4.5 Possible construction methods

Sandwich structures can be used in combination with stiffeners or in combination with the monocoque

structures (Ship structure committee, 1997). Four construction philosophies can be used to design the

construction for a MCMV:

1. Monocoque single skin constructiion

2. Framed single skin construction

3. Monocoque sandwich single skin construction

4. Framed sandwich single skin construction

Three of these structure methods have previously been used for MCMV designs as mentioned in

paragraph 2.4. A monocoque sandwich single skin structures has not yet been applied for a MCMV

construction.

A fifth option is the use of corrugation to obtain the stiffness. This structure method is only used for

research projects.

Production of composite ship hulls 27 3. Why a production model?

3. Why a production model? The solution for solving the problem of the unknown production cost of a c0mpsite ship hull with a

production cost model is chosen for several reasons. The reasons include cost aspects, model aspects

and production aspect.

3.1 Cost aspects The choice for the production model is made because it is relatively cheap to make a production model.

Other solutions to solve the problem would be more expensive: one could for instance make a cost

estimation by producing prototype parts of the ship. However, that would cost more than making a

production model and model the production with production techniques used before.

A production model can be used for the budget aspects of the project. The Dutch government decides

about the budget for the MCMV’s. The developed the design has to fit within this budget. The model can

be used to determine the influence of change in the design on the price of the ship and whether the ship

is affordable or not.

3.2 Model aspects The production cost model can also be used to perform a sensitivity analysis of the estimators. The cost

prices estimation will be done for producing a hull in the (nearby) future. Meanwhile changes, which

have influence on the production cost, can happen. The future cannot be predicted; however, the effect

of possible change can be determined with a sensitivity analysis.

Models can easily handle change in the production. The effect of a change can be shown by comparing

the outcome before and after a change.

3.3 Production aspects The production model will be developed to get more insight in the steps necessary to come to a

composite ship hull. Due the nature of the production model, each required step has to be determined

to come to a good estimation of the production costs.

More detailed information will be known due the production model. The possible bottle necks can be

determined, expensive parts of the production can be determined. Also the consequences of some

structural choices can be found with the production model. The best way to produce composite ship

hulls can be calculated in this way.

It is easy to adapt the model after the use of the model to predict the cost and build a hull in a certain

way. The model can be adapted to review the consequences of the change in production if it becomes

clear that the production cost can be lowered in a certain way.

Production of composite ship hulls 28 4. Requirements model

4. Requirements model Requirements are important to measure whether the model does what it should do. The aim is to

develop a model, which is able to make cost estimations for a composite ship hull. The requirements for

the model can be divided in several groups. These groups are: requirements related to the model type to

be developed, requirements concerning the hull to be estimated, requirements regarding the use of the

model during a project. The requirements of the model will be described in this chapter.

4.1 Model type The model type to be developed determines several requirements for the model. This is the first group

of the requirements. The requirements in this group are: the model has to result in a production cost

estimation, a cost price estimation, should be production process oriented and it should have a certain

accuracy.

4.1.1 Production cost estimation

The model should be able to produce estimations for the production of composite ship hulls. Three main

parts can be distinguished in the cost estimation. The material cost should be part of the cost estimation,

the second parts are the man hour costs and the third part of the calculations should be the costs of the

production, which are not directly related to the man hour cost or material costs. The three main parts

of the cost estimation can be broken down further during the development of the model. However, that

will be described in chapter concerning the development of the model.

4.1.2 Cost price estimation

The model has to produce a cost price estimation for the production of a composite ship hull. The model

will be developed to give the ship owner insight in the production process, to provide information

regarding the affordability of the project and to support the DMO in the acquisition process. As a result,

no commercial information will be implemented or estimated. Profit and risk factors are not part of a

cost price estimation.

4.1.3 Production process oriented

The cost price estimations developed at DMO are product oriented price estimations. That means that

the cost price estimation is based on data from previous projects. Based on the production of previous

vessels estimates are made for the next vessels. The number of man-hours for certain parts of the

construction are used to determine the required work per kg construction. This data can be used to

determine the production rate for the construction of the vessel to be built. The data is used to make

cost price calculations for the project. However, this method cannot be used for the cost price

estimation of ships built in materials rarely used in Dutch naval projects. The data necessary for a

product oriented price estimation is simply not available or outdated due to developments and

improvements in the production process.

Due to the considerations described above, it is necessary to investigate the production steps necessary

to come to a good product. The production has to be split up in smaller production steps to estimate the

time necessary to make a certain part of the product.


4.1.4 Accuracy

The accuracy of the model has to be an improvement compared with the current method used at DMO.

With accuracy is meant the deviation due to the uncertainties, unknowns in the model, deviation as

consequences of the modelling of the production as well as the accuracy of the estimators used.

The requirement regarding accuracy is that the model to be developed should have a better accuracy

compared with the models now used at the DMO. It is hard to compare the accuracy of the model used

at the DMO and the model to be developed, because the two models are not the same type of models,

as described in 4.1.3. However if the accuracy of both models will be investigated, it will be possible to

compare the accuracy of the models.

4.2 Requirements regarding hull to be estimated The model does not have to be able to develop cost price estimation for every ship and construction

type. This part will describe the features and requirements for the ships for which the model can be

used. The first requirement in this part will be the requirement concerning the hull type and dimensions

of the ship. Another requirement in this part is a requirement regarding the structure philosophies of the

ship.

4.2.1 Hull type and dimensions

The model will be developed for the production of monohull vessels. The hull form should not matter as

long as the vessel is a monohull. The model will have constraints regarding the maximum main

dimensions of the hull to evaluate. At least it should be able to give estimations for all vessels between

the AMBV-class vessels and the concepts in the new project.

It has to be possible to change the position of the bulkheads and the decks as well as the number of

decks and bulkheads and the deck height of the vessel.

4.2.2 ‘Structure philosophies’

As described in 2.4 the structure of composite hull can have different forms. Each form has its own

features and a different production process. The main processes are the same however, some

construction philosophies has production steps others do not have. The model should thus have a

structure such that it is easy to switch production steps on and off.

Strength calculations have to be performed to make equivalent structures. It could be that not the whole

construction is known already if a cost estimation is necessary. Therefore, strength calculations should

be part of the cost estimation model. However, it is too much work to design the whole structure. Two

types of loading will be investigated, the first one is the global bending and the second one is the local

pressure caused by the water. Whether a construction can withstand the global bending moment is

determined by the dimensions of the midship section and the moment of inertia of the midship section.

Whether a construction can withstand the local pressure caused by the water is determined by the

thickness of the hull and the dimension of stiffeners if applicable.

4.3 Use during a project The aim of the model to be developed is to use in a project of the DMO. Some requirements are

connected with a project in which the model could be used. These requirements are: the applicability of


the model, the possibility of the model to evaluate multiple products of the same hull type, the

possibility to compare different concepts within a project and to evaluate improvements in the

production process.

4.3.1 Applicability

In the beginning of a project, little is known about the constructions and details of a ship hull. A cost

estimation has already to be made in that stage to evaluate the affordability of the project. The model

should be able to generate a cost estimation based on this few information. However, during the project

more and more will be known about the construction and details of a ship. The model should be able to

cope with these developments within a project. A consequence of this requirement is that the

estimation model could be made more and more detailed.

4.3.2 Multiple production of the same hull

The model should be able to evaluate the effect of more ships in one series. The ability to evaluate series

of ships has two main reasons: non-recurrent cost and learning curve.

The production of ships can be separated in non-recurrent and recurrent cost. The recurrent cost occurs

at every produced ship. The non-recurrent costs are costs that occur ones in a project, independent on

the number of ships produced as a result of the project. The first ship of the project is relatively

expensive because the non-recurrent costs have to be paid. Every next ship is cheaper due to the

absence of the non-recurrent cost.

The other factor is the effect of the learning curve. The production of a hull takes less time when the hull

is produced several times. The personnel learn how to produce the ship. This effect is expected to have a

big influence of the price of each next vessel in a series.

4.3.3 Compare different concepts

Different design concepts are mostly developed in a project to get more insight in the product to be

developed and to determine the affordability of a concept. The importance of this requirement for the

model to deal with different concepts depends highly on the required computing power to generate a

cost price estimation for one of the concepts. If the required computing power is high, this needs

attention.

It needs at least attention to create the possibility to compare different concepts within a project easily

and to assess the change in the concepts rapidly.

4.3.4 Evaluation improvements production

The aim of this project is to indicate possible improvements in the production of composite hull

constructions. The model should be able to cope with these improvements. Proposals for improvements

have to be assessed easily on their impact on the production cost. Promising improvements should be

implemented easily to investigate the effect of the improvement more thoroughly.

These improvements could by either organizational improvements or improvement in the production

process. The improvement in the production process could vary between a total new production

technique and just an improvement in one of the steps of the production.

Production of composite ship hulls 31 5. Production process AMBV

5. Production process AMBV This chapter will describe the production of the AMBV class vessels. The production process of this vessel

is used as benchmark during the development and testing of the production model. The production of

the Alkmaar class vessel has been done in a special developed production hall in Alblasserdam. Giessen-

de Noord Marinebouw (GNM) has made the ships in this hall. The description of the production hall will

be the first part of the description of the production process. Only a part of the yard is relevant for the

production of the composite hull. However, this chapter will describe the whole process of the

production to create insight in the total the production of an AMBV and the consequences of the whole

production for the production of the hull. The second part will be the rough description of the steps

necessary for the production process and the third part will be a more detailed description of the

different steps and sub steps in the production. Several documents are used to describe the production

process of an AMBV (Hage, 1984), (GNM Naval construction, 1985) and (Giessen, 1977).

5.1 Lay out production yard GNM naval construction had to take a decision regarding the yard of the AMBV. After investigation, they

came to the following conclusions: the existing locations were not suitable for the production of an

AMBV and the production of the facility has to be two or three ships per year. So GNM decided to design

a total new yard to produce the fifteen AMBV’s for the RNLN. The production hall is designed based on

these conclusions (GNM Naval construction, 1985). Thus, major investments were necessary for the

production of the AMBV’s. The processes that could be done in facilities already available would not be

done in the production facility (GNM Naval construction, 1985).. The facility to be designed is thus an

assembly facility. That meant that storage place was necessary to store half products such as bulkheads,

and decks.

The advantage of the yard is that it is

specifically designed for the production of

this type of vessels. The designers of the

production location concluded that the

ideal situation for the production was a

production line. The production hall has to

be arranged like a production line, such as

the production of cars. The production cost

would be lower as a result of this choice.

The cost for producing the whole ship

simultaneously would be much more

expensive compared to production line

(GNM Naval construction, 1985). If the

whole ships are produced simultaneously,

the amount of tooling has to be twice or

thrice as much. The learning curve for the

Figure 9. Layout GNM yard (GNM Naval construction, 1985).


production will also be higher in this situation.

This yard has been built in Alblasserdam. The layout of the yard can be found in figure 9. The design of

the yard is made for the production of ships up to a length of 75 meter and a lightweight of 1500 ton.

The costs to build the yard, initial tools and moulds were about 45 DG. 7 million of this was used for the

GRP production equipment and 6 million for the future use of the production facility (GNM Naval

construction, 1985).

The dimensions of the hall are 144 * 68 *23 metres. Along both sides are offices, stores and workplaces.

The yard has three main parts. The first part is the construction building. The ship will be built in this

building. The next parts are the facilities for launching of the ship. The ship is launched by the use of a

ships lift after completing the work in the main construction building. Once the ship is in the water, it is

brought to the quay where the mast is installed. The berth is also used for test and trials (GNM Naval


The main construction building consists of four different building stations. These stations can be found in

figure 10. In each of these building stations, the same production steps are executed for the production

of a ship. A flowchart of the building stations and a major description of the tasks in each station are

given later in this chapter. The production of a vessel starts in station 1, after a while the vessel is

transported to the next station.

The mould is located in station 1 and the production of the vessel is started if the required tasks on the

mould are finished. After 22 weeks, the production in the first station is finished and the hull will move

to the next station. The rest of the production processes related to the production of the composite

Figure 10. Layout van der Giessen-de Noord marinebouw (GNM Naval construction, 1985)


parts of the vessel are executed in that station. The vessel moves to third station after completing these

proceedings. The outfitting of the vessel starts in the third station and at the end, the vessel will move to

the fourth station of the production. The main construction building is divided in to parts, separated with

a door. The outfitting takes places at the last two station of the production line. At these two stations,

not much composite work has to be done. The composite work of the hull is performed in the first two

station of the yard. This part of the building is air-conditioned. The temperature is between 19 °C and 23

°C and the relative humidity is 65%. The air-conditioners can maintain these values if the outdoor

temperature is between -12 °C and 30 °C. The allowed styrene concentration is 50 ppm, this is

maintained by the use of a ventilation system (GNM Naval construction, 1985).

The yard is equipped with four cranes. One travelling crane with a capacity of 2*10 ton for the first two

stations and two cranes, one 2.5-ton crane and one 10-ton crane, for station 3 and 4(GNM Naval


The transport between the different stations is done with air cushions. By using this transport systems

GNM was able to transport four ships to the next station in a single weekend (GNM Naval construction,

1985).

The last two stations are thus not relevant for the scope of this project. However they put a constraint

on the production in station 1 and station 2 because the hulls has to move to next station before one is

able to start up the production of a next vessel. So the time in the stations has to be the same time.

The organisation of GNM has been divided in three disciplines. One of these disciplines was the GRP-

work. At this part of the organisation, 115 people were employed (GNM Naval construction, 1985)..

5.1.1 Station 1

In station 1 starts the production of the ships. The skin and its stiffeners are made in this station. Also are

some of the decks and the bulkheads. The starboard side of the mould is mounted to the floor and the

portside can be moved. The hull can be moved to the next station if the portside of the mould is

separated from the starboard side. Four moveable platforms can be used for the production of the hull.

The production starts in the middle of the ship and moves in both directions. The production is

cascading. Layers are made to reach the required laminate thickness. The production of the centre girder

and the sider girder can start if the required laminate thickness is reached. If the girder are produced the

transverse stiffeners can be brought on the hull. The production of the skin, girders and the stiffeners

can be done simultaneously in this way.

Important to note for the production are the different layers in the skin. The skin consists of a so-called

buffer layer and a so-called strength layer. The buffer layer is to maintain the water tightness of the ship,

it gives some strength but its main goal is keep the water outside. The strength layer is meant to gain the

strength and stiffness of the hull structure (Van Der Giessen-de Noord, 1984). The difference in layer

type has consequences for the production because the fibre content of the strength layer is higher as the

fibre content of the buffer layer. The fibre content of the layers differs but also the type of woven

rovings used for the layers differs.

A loop system is used to bring the resin into the hull. Buckets are used to transport the resin to the place

where it has to be applied.


5.1.2 Station 2

The remaining composite work will be done in the second station. The remaining decks and bulkheads

are placed in this area. The composite work is finished with exception of the superstructure which will be

placed in the third station.

5.1.3 Station 3

The vessel is moved to the other part of the production hall. This part of the production hall is meant for

the outfitting of the vessel. The two parts of the building are separated with big doors. The outfitting

part of the hall does not require the same stringent climate control as the other part. So separating the

two parts leads to fewer costs.

Some composite work is done there as well. The superstructure is placed in the third station. The

superstructure is largely build in sandwich composite material. Only the wheelhouse is made from

another material, namely aluminium. The panels for the sandwich are made at another company and

placed on the ship by GNM.

5.1.4 Station 4

Station 4 is the other station for the outfitting of the vessels. No structural composite work is done in this

station. Parts have to be connected to the structural components of the hull. Some embedding is

necessary to make the connection between a part and the hull. However, this work is only a small part.

5.2 Production steps The steps necessary for the production of a hull for an AMBV are described in this part of this chapter.

The steps described are the processes that take place in station 1 and station 2. The production of the

superstructure, done in station 3, will also be described.

Each type of production step is necessary for the production of the hull and has to be repeated if a next

hull has to be produced. An indication for a measure to estimate the amount of man-hours related to the

production steps is also given in the description of the processes. The order of the production steps as

described in this chapter does not necessarily reflect the order in the actual production of an AMBV.

Most of the processes are done several times during the production of a composite hull.

5.2.1 Make mould ready

The mould consist of different parts which has to be put together to make the total mould. The mould

has to be cleaned and build together before the actual production of the hull can start. The cleaning can

be done with water or toluene depending on which material is used for the mould.

The production can start if the dimensions are put on the mould. The amount of hours necessary to

make the mould ready depends on the size of the mould and the number of parts to be assembled.

The measure are hours per time that the mould has to be made ready thus, a fixed number of hours for

the production of each ship.

5.2.2 Apply release-/separation agent

A release-/ separation agent has to be brought on the mould to prevent that the materials bonds to the

mould. This agent has to be brought on the mould to ensure that the mould and the structure will be


separated if the product has to leave the mould. This step is necessary for the mould of the decks,

bulkheads and hull.

A metric for the production time for the application of the release- /separation agent are the amount of

square meters a worker is able to treat in one hour.

5.2.3 Lay-up fibres

The fibres have to be brought on the mould or the already existing structure. The fibre mats are laid

down and one has to be fasten it to ensure that the will not move when the lamination starts. These

mats have a weight of 580 gram/m2. These mats are applied dry and fixed such that they not can move.

Each layer of fibres has to be laid down separately. Included in this task is the customisation of the fibre

mats if necessary. The lay-up of the fibre includes the required work for the transportation of the fibres

from the storage to the production side. The fibres have to be laid up for the stiffeners and for the skin.

It might be that the production rate for these two differs.

A metric for the performance indicator of the lay-up of the fibre is the amount of square meters that can

be laid down in one hour.

5.2.4 Lamination

The resin has to be applied to produce the composite structure. Each fibre layer has to be laminate

separately. The lamination includes also the work to be done for the transport from the dosing unit to

the place where the resin has to be applied. The lamination includes also the work necessary preparing

the resin for the production by adding the accelerator and the catalyst. The resin is applied by using paint

rollers. The speed of the lamination depends on which part of the structure will be laminated. The

lamination of large areas such as deck or skin goes faster than the lamination of much smaller areas as

the stiffeners and knees.

A metric for the performance of the lamination of the fibre is the amount of square meters that can be

laminated in one hour.

5.2.5 Scour surface

Sometimes it might be necessary to scour surface before going to the next step in the production

process. For instance if the stiffeners has to be made on the skin, the skin has to be scoured before the

production of the stiffeners can take place. However, scouring is also necessary if a laminate is made on

a laminate that has cured for more than eight days. (Van der Giessen - de Noord Marinebouw BV, 85)

A metric for the scouring of material is the amount of square meters that can be scoured in one hour.

5.2.6 Make water courses holes

Some parts of the structure, which are not watertight, contain watercourses holes. Each of these holes

has to be made separately. The holes are half circle which have to be laminated on the structure.

A metric for production is the number of watercourse holes, which can be made in one hour.


5.2.7 Make foam core

The stiffeners on the decks, skin and bulkheads are made on a foam core. These foam cores are the

inside dimensions of the stiffeners. These foam cores are made from blocks and have to be sawn to the

right dimensions. Foam cores are also applied for the production of the knees.

A metric for the production of the foam core is meter per hour for the stiffeners and number per hour

for the foam cores for the knees. It also important to distinguish whether a foam core has to be made

underhand or overhand.

5.2.8 Glue foam cores

If the foam cores are made they have to be made fixed on the surface. This is doing by gluing the foam

cores to the underlying surface.

A metric for gluing the foam cores is the length of foam blocks that can be glued in one hour or the

number of foam core for the knees that can be made in one hour.

5.2.9 Apply rubber emulsion

A rubber emulsion is applied on the foam cores before the fibres are laid down on the foam core. The

rubber emulsion has to be applied to prevent that the resin draws into the material. The rubber

emulsion is brought on the foam core with a spatula.

A metric for how much rubber emulsion can be treated is the amount of area that can be done in one

hour.

5.2.10 Drilling holes

Glass pens are used to prevent the stiffeners releasing the surface. The glass pens are place in holes.

These holes have to be made before. So, holes have to be drilled and to be cleaned after the drilling of

the holes.

A metric for the drilling of the holes is the number of holes that can be made in one hour.

5.2.11 Glue glas pens

When the holes have been made, the glass pens can be placed in the holes. These glass pens are glued

into the hole. The glues have to be put in the hole and one has to press the pen in the hole. The glass

pens have to be controlled a few minutes after they are placed. The have to be pressed in the hole again.

This activity contains also the mixing of the glue, the resin and harder has to be put together.

A metric for gluing of the pens is the number of pens that can be placed in one hour.

5.2.12 Positioning of the components of the ship

The decks and the bulkheads are made separately. GNM has outsourced the production of these

components. The deck and bulkheads are transported to the production facility of the AMBV. The decks

and bulkheads are placed in the ship by the cranes in the production hall.

A metric for the positioning of the components is the amount of man-hours necessary for the positioning

of one component.


5.2.13 Making angle connection deck/bulkheads/skin

A laminate is made at the connection between the decks, bulkheads and skin to ensure the stiffness of

the structure. This laminate is a so-called angle lamination. The laminate is made with glass mats and

resin.

5.2.14 Production sandwich panel

The panels for the superstructure are basically two laminates with are core between these laminates.

The extra work compared to a normal laminate is thus only the connection between the core and the

laminates. The production rate can thus be deduced from the production parameters for the laying of

the fibres and the lamination of the fibres with the resin.

5.2.15 Placing sandwich panel

After the production of a sandwich panel, they have to be placed on the ship. The panel has to be

connected to the deck and some other panels. The sandwich panels have to be brought to the right

position and afterwards the connection can be made.

A metric for speed of the placing of the sandwich panels is the connection length, which can be made in

one hour.

5.2.16 Remove release-/separation agent

The release-/ separation agent has to be removed when the mould has to be prepared for the next hull.

This has to be done before the mould for the decks, bulkheads and the hull. The release-/separation

agent is removed by washing the moulds with water or toluene, depending on the material used on the

mould.

A metric for the production rate of the removing of the release-/separation agent is the amount of

square meters cleaned in one hour.

5.2.17 Break off mould

The mould has to be broken off if the production of the hull is complete to a phase where the hull can

leave the mould. The different parts have to be removed in order to prepare the transport from the first

production station to the next one.

The estimator for the production is the amount of man-hours for removing one part of the mould.

5.3 Production order AMBV As described before, the production hall for the AMBV has four stations for the production of AMBV’s. A

flowchart of the process can be found in figure 11. The aim of the cost price estimation is to estimate the

cost for the production of a composite hull. The first two station are the station where the main part of

the composite work for the hull of an AMBV. The main focus will thus be on this station. The third station

contains the installation of the superstructure on the ship. This is also incorporated in the research

because it is composite work to be done. The superstructure is only a small part of the work done in

station 3.


Each station contains one AMBV under construction. The four ships under construction move to the next

station simultaneously when they have been 22 weeks in a station. This is important to consider because

when the stations are not ready simultaneously, the shift cannot take place. In that case, only a few

people are able to work and the others not. A delay at one station costs a lot of money. For the

description of the process as described, it is assumed that if the stations are always ready at the same

time.

Flowcharts for the production of the composite work in station 1 and station 2 can be found in figure 12

and figure 13.

A figure of the first two station in the building hall is shown in figure 15. The vessel on the left is the

vessel in the first building station, the vessel on the right is in the second building station. Figure 16

shows the last two building stations. The vessel in the front of the photo is in the third station and the

vessel in the back is in the fourth production stations.

Main scope investigation

SSc Station 1 Station 2

Station 3

Station 4

Figure 11. Flowchart production process AMBV.


Figure 12. Flowchart station 1.


Figure 13. Flowchart station 2.


The production of the hull starts with the preparation of the building for the production of a new AMBV. The materials for the production have to be available, everything has to be ready. Both station 1 and 2 have their own preparations for the production. 5.3.1 Station 1 production order

The next step is to prepare the mould for the production of a new ship. The mould has to be cleaned and the parts of the mould have to be assembled. When the mould is assembled, the dimensioning can be put on the mould to ensure that the hull will be build according to the drawings. The release-/ separation agent can be applied on the mould. The moulds of the decks and bulkheads have also to be prepared for the production. The same process as for the mould of the hull is necessary. The production of a hull can the start if the mould is ready. The production of the hull starts in the middle of the mould. This has the advantage that one is able to work in two directions, the front direction and the back direction. The first step is lay-up of the fibres mats. The lamination of the fibres can start if the fibres are laid on their place. The process of lay-up of the fibres and lamination of the fibres has to be repeated until the required thickness has been achieved. The production is done butt wise as can be seen in figure 14 in that way the production propagates along the mould (Giessen, 1977). At a certain time, the skin reaches the required thickness at the start of the production point. Each following step a bigger area reaches the required thickness. If the area is big enough the production of the transverse stiffeners can start. The foam cores are glued to the skin and the stiffener is laminated on that foam core. The production of the transverse stiffeners can start after the production of the transverse stiffener. The longitudinal stiffeners are produced in the same way as the transverse stiffeners. The decks and the bulkheads are produced while the skin and the stiffeners are produced. The production of these components is outsourced and they are transported to the storage to be installed on the vessel if the production reaches the stage where the components have to be installed. The bulkheads are installed if the longitudinal stiffeners are completed. The decks are put in the vessel after the bulkheads. Not all decks and bulkheads are installed in the first station. The hull moves to the next station if the stiffness is high enough to move the structure to the next station. The structure and the mould are separated if the production in the first station is finished. The mould can be demounted if the structure and the mould are separated. The hull is moved to the next station by means of air cushions. 5.3.2 Station 2 production order

The production in the second station contains the installation of the decks and the bulkheads not yet

installed. The knees between the skin and the bulkheads can be made if the bulkheads are made.

When all bulkheads are in the vessel, the decks are placed in the vessel. The knees between the skin

and the deck and the deck and the bulkheads can be made when the decks are placed. The angle

laminates are made when the knees are finished.

Figure 14. Butt wise built laminate.


5.3.3 Station 3 production order

The superstructure is placed on this vessel in this station. The production of the sandwich panels is

outsourced to another company. The panels are produced on the foam core. The laminate is made

on one side first, then the foam will be turned and the laminate on the other side will be made.

The panels are placed on the vessel with a crane. If the sandwich panel is on the right position, the

connection to the hull or other materials has to be made. Stiffeners are not made on the panels

because the core gives the stiffness to the materials and the panels have a corrugated form.

Figure 15. First two stations.

Figure 16. Last two stations

Production of composite ship hulls 43 6. Conceptual model

6. Conceptual model The model will be developed to make an estimation for the production costs for a composite ship

hull. The AMBV class is thus used as benchmark for the model. The set up for the concept model can

be found in figure 17. The concept model starts, if necessary, with the determination of the

structure. This part determines the dimensions of the structure. The second part is the actual cost

price estimation model. The first step is the translation of the main dimensions and the structure

dimensions into production dimensions. The production dimensions can be used for the

determination of the overhead cost, the material cost and the man-hour cost. These parts can be

used for the calculation of the cost for a series of ships. This chapter describes all the aspects of the

concept model.

6.1 Structure model The model should be able to make cost estimations for different ships hulls. The idea is to be able to

compare different production techniques and structure philosophies. The ship hulls should be

comparable to each other. One structure is known, in this case the structure for the AMBV class

vessel. This is a single skin stiffened construction. The other structures to be calculated have to be

reviewed and designed to same criteria as the AMBV class vessel. Two types of loading will be

reviewed. The first one is the global bending moment and the other is the local stresses due to the

water pressure. These types of loadings are assessed to be the loadings determining the

construction. Important to keep in mind is that the aim of the structure models is not to design a

structure but to be a step between a concept design and the cost price estimation model.

The structure models are used to generate the information necessary to make a cost price

estimation. The structure model generates the dimensions of the construction. If a construction is

already known, it is no longer necessary to use the structure model. The structure model will only be

used in the beginning of project when not much is known about the structure. During the project, the

information of the structure becomes more and more and the structure model is no longer

necessary.

6.1.1 Global bending moment

Global bending moment is the moment caused due to the distribution of the weight of the ship and

the buoyancy. The stresses cause by the global bending moment can be calculated with the section

modulus of the midship section. If the proposed structure has the same material as the old structure,

the section modulus has to be same. If a proposed structure has another material, the maximum

allowable global bending moment has to be the same.

6.1.2 Local water pressure

The pressure on the skin caused by the water pressure has to be evaluated as well. Finite element

calculations to design a comparable structure will be used. Two terms of the water pressure will be

used for the calculations of the stresses. The first one is the static water pressure. This is the pressure

on the skin if the vessel is in flat water, see figure 18 . The second term is the dynamic water pressure

as a result of the relative motion, see figure 19. This model will give the local stresses and local

displacements cause by the water pressure.


Figure 17. Schematic overview cost price estimation model.


Figure 18. Static water pressure (Van der Giessen - de Noord marinebouw BV, 1988)

Figure 19. Dynamic pressure caused by the relative motion.


6.2 Cost price estimation model The information from the structure model, if necessary or the information already available can be

used for the cost price estimation. The cost price estimation model will be divided in several parts to

calculate the price for the production of a hull properly.

6.2.1 Dimensions

Some dimensions are important for the production. In the first part of the model the user will be able

to provide the dimensions of the vessel. Important dimension for the production process are the

main dimensions, stiffener spacing, place of decks and bulkheads. The dimension of the construction

at the midship section and the dimensions of the stiffener. The ship will be divided in three parts to

deal with the possibility of changes in stiffener spacing. The length at which the stiffener spacing has

to change has to be determined.

The aim of the model is to give a price estimation for the production of monohull ships. It should be

able to give a price estimation for different hull forms. Therefore, it is important to develop the

model such that the calculations are independent of the input value of the hull form. In the concept

phase of a project, the hull form is globally known. This geometrical form can be used as input for the

model. The geometrical form of the ship can be used to calculate the area of the skin and cross

section of the ship, circumferences of the cross section and so on. The input of these values should

be separated from calculations. To calculate the effect of a change in hull form one should be able to

change the input of the hull form and immediately get a new cost price estimation.

The combination of the information of the hull form and the dimensions of the ship can be used to

calculated areas of the decks, bulkheads and skin; total stiffener length, volume of the materials and

all other information necessary for the cost price estimation.

This part of the model contains the relevant production metric generator. This is the transformation

form structural dimensions to relevant production metrics, see figure 17.

6.2.2 Production parameters

The second part of the price estimation model are the production parameters. These parameters

determine the final cost price. The will be put together to create an overview and to be able to see

the effects of change in the parameters easily.

The production steps has been described in chapter 5. For each of these steps the production rate

will be determined. This part of the production model contains also some other production

parameters such as the mass percentage fibre in the different layers, the composition of the resin for

the different layers and the costs of the material.

6.2.3 Production process en man-hours

The third part of the model is the production process and the calculations of the man-hours. The

production process for an AMBV class vessel has been described in chapter 5. These process steps

have been incorporated in the model, this is the man-hour calculator, see figure 17. The production

process will be described such that it is possible to look at the production speed for each process and

for different parts of the vessel. This is important to be able determine which processes are the

bottlenecks of the production and to calculate the effect of change in the production process.

Another aspect is the planning of the production in a latter stadium of the project. The production

process can be planned easily with a detailed calculated production process and the required sub

steps.


The information about the dimensions (see 6.2.1), the production parameters (see 6.2.2) and the

process model leads to the man-hours necessary for the production of a certain item.

Two aspects are important to be able to assess changes in the production process. The first one is the

calculations of different sub steps in two processes. The production of stiffeners for instance has

several sub steps. To assess the effect of stiffeners in the structure it is important to determine the

total time of the production of the stiffeners easily. A second aspect is the total time for a certain

activity. For instance, the total time required for the layup of fibres. The lay-up of fibres takes place

at different stage in the production, first on the skin, on the decks, on the bulkheads and on the

stiffeners. Therefore, a quick overview of main processes in the production is necessary to assess the

impact of possible changes in the production process. The output of this part of the model is the

required number of man-hours to build a ship.

6.2.4 Material cost

The material costs are another part of the calculations. The weight of the material can be determined

with the part of the model where the dimensions are given.

The amount of volume necessary for each material can easily be determined with the known

dimensions. The density of the materials has to be known and the total weight for each material can

be determined. This is the weight calculator, see figure 17. The total amount of material is an

estimation for the lightweight of the ship.

For the production of composite materials, different materials are necessary. The main materials are

the fibres and the resin. Other materials are the foam to make the stiffeners and the balsa, which is

the core of the material. The cost for the material can be determined with the cost/kg. This is the

material costs calculator, see figure 17.

6.2.5 Non man-hour related costs

The fifth part of the model are the non man-hour related costs. Different costs aspect cannot be

caught with man-hour or material costs for a single ship. These are the so-called not man-hour

related costs. Among these costs are the costs for the investments, the investment for the yard, the

overhead, assurances, transportation cost, stock, mould and so on. Most of these costs are fixed

either in yearly production or for a series of ships. Some of them could be fixed cost per ship. This is

the overhead cost calculator, see figure 17.

6.2.6 Learning curve

The learning curve is the vital element of the series cost calculator, see figure 17. The not man-hour

related cost are independent on the number of ships to be produced. The material costs are linear

with the number of ships to be build. However, the man-hours necessary to produce a series of ships

are not linear. A learning curve is a model for the effect of producing a single structure several times.

The production of the parts will become faster if more than one structure is made. Learning can take

place on two aspects, the first one is the labour learning. The second one is the organizational

learning (NATO NG/6 Specialist Team on Ship Costing, 2001). NATO gives a mathematical relation for

the learning curve, see Eq. 6.1 (NATO NG/6 Specialist Team on Ship Costing, 2001). DMO uses a

somewhat different mathematical relation, Eq. 6.2. Important to mention is the difference in the two

formulas. NATO gives a formula with an average building time for a series. DMO uses a formula,

which gives a building time for a certain ship produced as part of a series. To compare those formulas

the average building time for the DMO has to be determined. The difference between the two


formulas is shown in figure 20. This figure shows that there is very little difference in the formula

used by DMO and the formula of NATO. The metric of learning for the graph in figure 20 is 90%. A

learning curve between 90% and 95% for labour learning is not uncommon for naval shipbuilding

(NATO NG/6 Specialist Team on Ship Costing, 2001).


( )

( )

Eq. 6.1

( )

( )

( )

Eq. 6.2

Figure 20. Difference between NATA formula and the DMO formula for the learning curve.

75,0%

80,0%

85,0%

90,0%

95,0%

100,0%

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15

Ave

rage

bu

ildin

g ti

me

of

the

sh

ip t

o b

e b

uild

ed

Number of ships to be build

NATO formula vs DMO formula

NATO formula

DMO-formula

Production of composite ship hulls 50 7. Parameters production model

7. Parameters production model Important for the model are the parameters. The accuracy of the parameters in the production

model is important for the final result of the model. The parameters will be described in this model.

7.1 Process parameters The steps necessary for the production of a composite vessel can be found in chapter 5.2. These

production steps are used in the model and the production rate has to be estimated. Two documents

are used to estimate these parameters. The first one is a report concerning the production in the first

station of the yard of GNM (Lohuizen, 1985). The second one is a GNM calculation (Van der Giessen -

De Noord Marinebouw BV, 1983).

7.1.1 Preparatory work

Before the production of the hull can start, several preparations have to be made. The assembly,

disassembly of the mall and the move to station 2 takes 2820 hours (Van der Giessen - De Noord

Marinebouw BV, 1983). This is including the building of the scaffolding necessary to make the GRP

hull. The assumption is made that half of the time is necessary for the assembly and half of it for the

disassembly. Another assumption is that the mould consists of six parts. So the assembly and

disassembly of one part of the mould needs 235 hours.

A separation medium has to be brought on the mould. GNM calculates that it take 600 hours (Van

der Giessen - De Noord Marinebouw BV, 1983) to apply that medium on the mould, resulting in a

production speed of 1,33 m2/h.

The measurements dimensioning has to be brought on the mould. The production speed is 2,34

m2/h.

7.1.2 Producing laminate

Different parts in the vessel have different production characteristics. The skin, stiffeners, girders and

the decks/bulkheads has their own production speed. The value for this speed can be found in table

3 (Lohuizen, 1985). A ratio between these production speeds can be found in the last column of that

table. This ratio is introduced to have one production speed in the model and to correct the

production of the other parts with the ratio.

Part of the ship Production speed (kg/h) Ratio

Skin 3,8 1,00 Stiffeners 1,8 0,47 Girders 1,2 0,32 Decks/bulkheads 3,0 0,79

Table 3. Production speed several part of the ship.

The GNM calculations gives value for the weight of the skin and the production time of the skin (Van

der Giessen - De Noord Marinebouw BV, 1983), see table 4 there is a remarkable difference between

the production speed of Lohuizen and the GNM calculation. But one has to keep in mind that during

the production of the skin several parts has to be cured when the previous layer is made more than

eight days ago, as described in 5.2.5.

According to Lohuizen the ratio between scouring of the material and the lamination of the material

is 0,36 (Lohuizen, 1985). Lohuizen takes the lamination as both the lay-up of the material and the


impregnation of the material. Based on the total amount for 17.900 hours necessary for the

production of the skin according to GNM (Van der Giessen - De Noord Marinebouw BV, 1983), the

amount of hours necessary for the production lay-up and lamination of the skin is 13.162 hour and

for the scouring 4.738 hours.

The total area of all the layers required to create the skin can be calculated. This area is 13.386 m2.

This has to be laid down and laminated in 13.162 hours resulting in a production speed of the

lamination and the lay-up of the material of 1,017 m2/hour. The weight of the skin is 40.049 kg (Van

der Giessen - De Noord Marinebouw BV, 1983). The weight per square meter is thus 2,99 kg.

Resulting in a production speed of 3,04 kg/hour for the lay-up and lamination of the material. There

is a difference with the production speed as presented in table 3. However, it is believed that the

GNM calculations have to be preferred in the calculations due to the measure of the production of

the first ship. The higher production speed in table 3 could be the result of a learning curve. Lohuizen

presented his report in 1985 while the production started in 1983. The ratio between the production

speed of the skin, stiffeners, girders and decks/bulkheads is maintained because the learning effect

does not affect the ratio between these values.

The next step to investigate is to determine the production of the lay-up and the lamination

separately. Lohuizen does not give values for the lay-up and lamination separately. However GNM

has given separated values for the production of the buffer layer and the strength layer (Van der

Giessen - De Noord Marinebouw BV, 1983), see table 4. The difference in fibre content, and thus the

difference in production speed between the lay-up of the fibres and the lamination, could be an

explanatory parameter for the difference in production speed of the buffer layer and strength layer.

A negative coefficient is necessary to solve that problem. The difference in lay-up speed and

lamination can thus not declare the difference between the production speed in the buffer layer and

the strength layer. The difference might be explained by the difference in vertical distance to keel. It

is easier to produce the composite close to the keel compared to composite further away from the

keel. The buffer layer has a constant thickness of 5 mm along the skin. The thickness of the strength

layer differs from 29 mm at the bottom of the ship to 13 mm in the sides of the ship, see appendix 1.

The strength layer has thus relative much volume close to the keel. This can explain the difference in

production speed. However, in the model this difference will be neglected due to the small weight of

the buffer layer compared to the strength layer and due to the few data available. It is assumed that

the time necessary for the lay-up of one square meter and the lamination of one square meter is the

same. Resulting in a production speed for lay-up of 2,03 m2, as well as for the lamination.

Buffer layer Strength layer

Fibre content (%) 25 50

Weight (kg) 3.222 36.827

Production (h) 2.400 15.500

Production speed (kg/h) 1,3425 2,3759

Table 4. Characteristics buffer layer and strength layer.

7.1.3 Scouring

The total time necessary for the scouring of the material is known based on the result of the product.

If a certain part has cured for eight days, it is necessary to scour the material as described in 5.2.5.

The assumption is made that half of the layers requires scouring before the lay-up of the material can


take place. Based on this assumption, 6.693 m2 has to be scoured in 4.738 hours, see 7.1.2. The

production speed for the scouring is thus 1,41 m2/h.

7.1.4 Making stiffeners

Before the production of the stiffeners on the skin and the stern can start the surface below the

stiffeners has to be scoured. Based on photos available of the production of the AMBV it was

estimated that the area to be scoured is 0,2m plus the breadth of the stiffeners including the flange.

Resulting in an area with a width of 0,5m that has to be scoured.

The estimated time for the production of the stiffeners on the skin is 15.170 hours (Van der Giessen -

De Noord Marinebouw BV, 1983). Based on the data described in 7.1.2 and 7.1.3 1864 hours are still

available for remaining steps in the production of the stiffeners. The assumption for the work

necessary for the scouring while making the stiffeners is that 1 out of 4 layers has to be scoured.

The 1953 hours has to be divided of the making the foam core, gluing the foam cores to the skin,

drilling the holes, applying the rubber emulsion on the foam core and for the glass pens and place

the glass pens and producing the angle laminate. The assumption is made that the same amount of

time is necessary to make the cores, to make the angle laminate and to place the glass pens, thus

650 hours for each of them.

The assumption for the production of the foam core is that the process of making the foam core

takes ½ of the time and the gluing of the foam core ¼ and ¼ for applying the rubber emulsion on the

foam core. Resulting in a production speed for making the foam core of 6,17 m/h, gluing the foam

core with 12,34 m/h and applying the rubber with 3,47 m2/h.

The assumption for the glass pens is that it takes the same time to drill a hole and to place a hole in

the hole. Both of them can take 325 hours in total for the production of the stiffeners on the skin.

The production speed is drilling 123 holes per hour and placing 123 pens per hour.

The total length of the angle laminate to be produced for the stiffeners is 2005,7 m. Resulting in a

production of the angle laminate 3,1 m/h.

7.1.5 Placing decks and bulkheads

The assumption is made that the placing of the decks and bulkheads takes a certain amount of time

for the decks and de bulkheads. GNM accounts 3.270 hours for the placing of the bulkheads,

approximately 250 hour per bulkhead and 16.570 for the placing of the decks, approximately 1.000

hours per part of the deck (Van der Giessen - De Noord Marinebouw BV, 1983).

Seams are filled when the decks and bulkheads are place. The filling of the seams is assumed to have

the same production as the angle laminate.

7.1.6 Super structure

The total production the placing of the superstructure is 7000 hours (Van der Giessen - De Noord

Marinebouw BV, 1983), approximately 1750 hours for each of the four panels. The area of the

sandwich panels is estimated to be 200 m2. The assumption is that it takes 10 hours to customize the

balsa. The balsa has to be glued to the laminates. The assumption that the production speed is the

same as applying the rubber emulsion to the stiffeners 3,47 m2/h.

7.1.7 Overview process parameter

A short overview of the process parameters related to the production of the hull can be found in

table 5.


Parameter Value

Hand lay-up 2,03 m2/h

Lamination 2,03 m2/h

Scouring 1,41 m2/h

Make foam core stiffener 6,17 m/h

Applying rubber emulsion 3,47 m2/h

Drill holes 123

Place pens 123

Glue balsawood 3,47 m2/h

Make angle laminate 3,1 m/h

Make measurements dimensioning 2,34 m2/h

Glue foam core 12,34

Filling seams 3,1 m/h

Place bulkhead 250 h/part

Place deck 1000 h/part

Make balsa wood 10 m2/h

Place sandwich panel 1750 h/part

Table 5. Overview process parameters.

7.2 Structure and material parameters Several parameters to be used in the production are related to the structure and material to be used

for the production of the hull. This paragraph gives an overview of these parameters.

7.2.1 Number of layers

The number of layers necessary to reach a certain thickness depends on the thickness and whether

the part to be made is a stiffener or a simple surface. The value for a certain thicknesses can be

found in table 6. These values are used for a regression analysis of the relation between the thickness

and the required number of layers. This analysis can be found in figure 21. The equations can be

found in eq. 7.1 and eq. 7.2.

Thickness (mm) Layers skin layers stiffeners

16 9 12

18 11 14

20 12 15

24 15 18

25 16 19

27 17 20

30 20 23

34 22 25

41 27 30

52 36 39

60 41 44

Table 6. Thickness vs. layers


Figure 21. Graph thickness vs. layers.

Eq. 7.1

Eq. 7.2

7.2.2 Buffer layer and strength layer

The skins consist of two types of material. The first one is the so-called buffer layer. This layer has

better water immersion properties and is on the outside of the skin. The other layer is the so-called

strength layer. This layer takes caries the most of the load on the skin. The buffer layer and the

strength layer differ in composition, fibre content and strength properties. The thickness and mass

percentage fibre content can be found in table 7. The weight of the matrix and the fibre can be found

in table 8. The mixing ratio of the different components of the matrix can be found in table 9.

Material Weight (ton/m3)

Matrix 1,166

Fibre 2,54

Strength layer 1,853

0

5

10

15

20

25

30

35

40

45

50

0 10 20 30 40 50 60 70

Laye

rs

Thickness

Thickness vs. layers

Skin

Stiffener

Linear (Skin)

Linear (Stiffener)

Mass percentage fibre strength layer 50%

Mass percentage fibre buffer layer 25%

Thickness buffer layer 5

Table 7. Mass percentage fibre and thickness buffer layer


Buffer layer 1,51

Table 8. Weight composite material

Component Strength layer

Buffer layer

Resin 100 100

Catalyst 2 3

accelerator 0,25 0,5

Total 102,25 103,5

Table 9. Mixing ratio matrix

7.2.3 Glass pins

Important for the amount of glass pens to be put in the structure depends on distance between the

glass pins. GNM has specified that the distance between the glass pins is 0,05m. The assumption for

the cost of a glass pin is €0,10

7.3 Cost parameters 7.3.1 Inflation rate

Some of the prices are known for the past. These prices have to be corrected for the price today. This

can be done with an inflation rate. DMO uses a 2.5% inflation rate. This rate is used also in the

model.

7.3.2 Material prices

To determine the total cost price, data regarding the price of material and the cost of man-hour is necessary to determine. Information from different source is found to define the price of the material. The price found in the source is converted to prices nowadays with the inflation rate and it is also converted to euros. An overview of some price found is given in table 10. The sources are numbered. The first source is a paper published in 2001 (Das, 2001). The second are data published in 1993. The third are data from 2000 (Shenoi & Dodkins, 2000). The fourth are data from 1988 (Smith, 1990) and the fifth from 1995 (Eric Green Associates, 1999).

E-glass fibre (€/kg)

S-glass fibre (€/kg)

Carbon fibre (€/kg)

Epoxy resin (€/kg)

Polyester resin (€/kg)

Vinyl ester resin (€/kg)

1 2,28 --- 18,12 --- --- --- 2 2,52 17,64 88,18 7,56 3,02 5,04 3 --- --- --- 7,06 2,12 3,89 4 1,82 22,80 142,52 8,79 2,43 6,89 5 3,01 13,22 31,73 10,31 3,15 4,60 Average 2,41 16,77 70,17 8,43 2,68 5,10 Table 10. Cost price different material to be used.


7.3.3 Investment

For the investment, it is important to know the cost of the yard and the mould. For the model the

cost for the yard including the equipment is taken as whole. The second part is the mould to be used

for the production of the hulls. Both of them are assumed to be dependent on the length of the ship.

The total investment for the yard and the mould was 45 million Dutch Guilder (DG) for GNM,

including 6 million DG for invested for future use of the facility (GNM Naval construction, 1985). The

cost of 6 million DG for the future use of the production facility will not be implemented in the cost

price model, because the cost are not related to the production of the Alkmaar class vessels. The

costs for a mould were 7- 15 million DG for a vessel of 140m long in 1982 (Brüggemann, 1984). Using

10 million DG, the cost for each meter of the ship is 70.000 DG, which is approximately €32.000/m.

The remaining investments cost are 36 million DG or 707.000 per meter ship, which is approximately

€321.000/m. However, one has to keep in mind that parts of the production are done on location

other than the production facility in Alblasserdam. Therefore, the investment costs per meter are

increased with 10%, becoming thus €353.000/m.

Production of composite ship hulls 57 8. Experimental model

8. Experimental model

This chapter gives a description of the developed production model. The aim of the model is to

estimate the cost of the production of composite vessels. The model shall be able to estimate the

cost for different structure philosophies as well as different production techniques. The model has

several parts. The first part is the characteristics of the ship to be estimated. The second parts are the

production parameters. The third part is actual building process of the ship. The fourth parts contains

the calculations to predict the material cost and the last one are the not man-hour related cost. Each

of these parts will be described separately.

The model is developed to be able to estimate the cost for a general composite ship. However, the

description of the model will be given with reference to the AMBV.

Some parts are modelled with the use of macros in Microsoft Excel 2010. The macro will not be

described in detail. However, a short description of the most important macro’s are given.

8.1 Dimensions ship In this part of the model the most important dimensions can be filled in. This part of the model has

basically two parts. The first part is the part where the information of the hull form has to filled in.

The second one is the more specific characteristics of the ship. These two parts are used to be able to

do the calculations for different hull forms and sizes of the ship.

8.1.1 Hull form

Several characteristics of the hull are used to describe the

hull. The Rhino model of the AMBV is used to obtain this

data.

The distribution in transverse and longitudinal direction of

the ship can be found in figure 22. The subdivision in the

transverse direction is done every 5 meter. For the

subdivision longitudinal direction are chosen some

waterlines. Waterline 5, 10 and 15 are used. The height of

the waterlines related to the keel of the ship can be found in

table 11. This subdivision result in several areas as can be

seen in figure 22. The area of these surfaces is the input for

the model. They can be found in fifth, sixth, seventh and

eight column of appendix 2. The first rows of that table are

the lower and upper value of the range. The other value in

the table is based on the lower value of the range.

The width of the ship can also be obtained from the Rhino

model of the AMBV. The width of the ship is measured at the

height of the tween decks, the main deck and the forecastle

deck, see figure 23. The widths can be found in the ninth,

tenth and eleventh column of table 26.

In the Rhino model is made an area every five meter.

These areas, see figure 23, represent the cross section at that

point. This cross section can be used to calculate the area for

the bulkheads. The part of the circumference directly on the

Figure 23. Width decks

Figure 22. Division ship

Figure 24. Cross sections


skin of the vessel can be used to calculate the stiffener length on the skin. That circumference can be

found in the third column of appendix 2. The cross section can be found in the fourth column of

appendix 2. The dimensions of the ship are translated to parameters, which can be used for

determining the amount of man-hours. These parameters can be found in appendix 3.

Waterline Height (m)

0 0

5 1,225

10 2,45

15 3,675

Table 11. Height waterlines

8.1.2 Macro’s dimensions ship

Several macros are used to calculate the dimensions of the ship. These macro’s are important to

name, because they explain how important aspect of the calculations haven been done.

8.1.2.1 Area_length_stiffener_bulkhead

This macro calculates the area of the bulkhead. The position of the bulkhead is not always on the

same position as the cross section shown in figure 23. Interpolation is used to determine the area of

the bullheads if it is not at such a position. Some of the bulkheads do not continue to fore castle deck

or tween deck. A correction based on the width at those decks has used to calculate the area of the

bulkhead.

The stiffener length on the bulkheads is also calculated in this macro. The calculation of the stiffener

length is based on the equation given in eq. 8.1.

This macro has to be runned when the column ‘Area’ behind a bulkhead is selected.

Eq. 8.1

8.1.2.2 Area_length_stiffenere_decks

This macro does basically the same as the previous macro. It calculates the area and the stiffener

length for the decks. The calculation of the area of the decks is based on the width as described in

8.1.18.1. The calculation of the stiffener length is done on as given in eq. 8.2. This macro calculates

also the number of brackets that has to be produced for a deck.

This macro has to be when the column Area behind a deck is selected.

( ) ( )

Eq. 8.2

8.1.2.3 Stiffener _length_foreship/midship/aftship

These macro’s are used to determine the stiffener length of fore ship, mid ship and aft ship. The

circumference as described in 8.1.1 is used to calculated the stiffener length. The stiffener length is

calculated for each stiffener separately. The circumference is interpolated to calculate the stiffener

spacing if the current stiffener is between the cross sections. The macro checks whether the stiffener


is at the place of a bulkhead or not. If not the stiffener length is calculated, if there is a bulkhead the

next stiffener is selected.

8.1.2.4 Determine_range_deckheight

This macro checks for each bulkhead to which deck it continues. A range is made for each deck and

when a bulkhead continues to a certain deck, it is put in that range. This macro is important for the

determination of the number brackets of the connection between the bulkheads and the skin.

8.2 Characteristics ship The other part of the necessary information is related to ship. It does not describe the hull form of

the ship but it is more specific information about the layout and construction of the ship.

8.2.1 Main dimensions

The first most important are the main dimensions of the ship. The required main dimensions can be

found in table 12.

Main dimensions (m)

Length oa 51,5

Length cwl 47,1

Breadth 8,9

Draft CWl 2,45

Depth to fore castle deck 6,55

Depth to main deck 4,25

Depth to tween deck 2,3

Table 12. Main dimensions

8.2.2 Stiffeners

The AMBV has different stiffener spacings at different parts of the ship. The ship is divided in three

parts to be able to handle to difference in stiffener spacings. The location of the division can be

found in figure 25. The locations of these transitions in stiffener spacing can be found in table 13.

Aft ship Fore ship Mid ship

Figure 25. Division ship


Separation Relative to AP (m)

Aft / mid 15,15

Mid / fore 33,9

Table 13. Changes stiffener spacing

The places of the change in stiffener spacings are a input in the model. The spacings can be found in

table 14. The spacing of the stiffeners of the bulkheads can be found in that table as well. However

not only the stiffener spacing can be varied also can the size of the stiffeners. The stiffeners used in a

AMBV are hat stiffeners. The dimensions of the hat stiffeners are different for several plates fields.

Stiffeners for decks and skin/bulkheads can be distinguished as well as the centre girder and de side

girders. An example of one of these stiffeners can be found in table 15.

Stiffeners spacing (m)

Fore ship 0,7

Mid ship 0,75

Aft ship 0,6

Bulkheads 0,7

Table 14. Stiffener spacings

Stiffener deck girder

Width of flange (m) 0,06

Thickness of flange (mm) 12

Heigth of web (m) 0,3

Thickness of web (mm) 12

Widht of cap (m) 0,28

Thickness of cap (mm) 22

Table 15. Dimensions deck girder

The longitudinal stiffener on the decks and at the bottom of the ship does not continue to the bow of

the vessel. The point relative to AP where these stiffeners top can be found in table 16.

Stiffener End location relative to AP

Longitudinal deck stiffening to 44,4

Longitudinal side girders to 33,9

Table 16. Longtidunal stiffener end location.

8.2.3 Bulkheads

Bulkheads can be placed on different positions in the ship. Not all bulkheads continue to same deck.

The AMBV has three different decks. A tween deck, a main deck and a fore castle deck. The position

of these decks can be found in figure 27.

The position of the bulkheads in an AMBV can be found in figure 26. The bulkheads are numbered

from the stern to bow. The most left is bulkhead 1 and the most right is bulkhead 11. The exact

positions, the thickness and the deck to which a bulkhead continues can be found in table 17.


Name Place bulkhead relative to AP (m)

To deck Thickness (mm)

Stern -0,95 Main deck 25

Bulkhead 1 3,75 Main deck 12

Bulkhead 2 10,35 Fore castle deck 12

Bulkhead 3 13,95 Tween deck 12







Bulkhead 10 43 Main deck 12


Bulkhead sonar dome 36,7 Tween deck 12

Bulkhead bow thruster

40,2 Tween deck 12

Table 17. Bulkheads

Figure 26. Bulkheads in the ship


8.2.4 Decks

The ship has three decks, a tween deck, the main deck and the fore castle deck. The depth to the decks

can be found in table 12. The fore castle deck starts not from the stern of the vessel, but somewhat later

as can be seen in figure 27. Therefore, the start point of the fore castle deck is one of the input

parameters in the model.

Each of the decks is divided in several sub parts. The bulkheads are place in the hull before the decks will

be place. The decks should thus be split in parts between bulkheads. The force castle deck is divided in

three parts due to the length of the deck. The thickness, start and end point of the decks can be found in

table 18. The tween deck does not exist over the whole length of the vessel. In table 18 can be found

where there is a tween deck and where not.

8.3 Production parameters The production parameters are important to determine the total man-hours necessary for the

production of an AMBV. The most important parameters will be described. Most of these parameters are

related to work people should do and how much they are able to do in a certain time period. However,

some of the production parameters have to do with the material and feature of design. The production

parameters can be changed in the tab used for the production parameters.

Figure 27. Decks in ship

Fore castle deck

Tween deck

Main deck


8.4 Production process This is the combination of the first part of the model containing the dimensions ship and the second part

containing the production parameters. It combines the data of the dimension of the ship with the

production parameters. The man-hours required for the production of the ship can be calculated in this

way. The production is split up in several parts of the ship. The sub steps are described in paragraph 5.2.

The several parts with separated calculations can be found below:

1. Production of the skin, decks and bulkheads

2. Production of the transverse stiffeners on the item produced in step 1.

3. Production of the centre girder on the skin

4. Production of the side girders on the skin

5. Production of the longitudinal stiffeners of the decks and bulkheads.

The production time necessary for the production of each particular product can be calculated. The total

production time for each product is used to calculate the man-hour cost of each vessel.

8.5 Determination material cost This part is used to calculate the material cost for the production of an AMBV. However, it is also used to

estimate the weight of the AMBV. This can be used to verify the model. For each part in the production

process is the weight calculated.

The buffer and strength layer for the skin have been calculated separately. This has been done due to the

difference in weight fraction of the fibres. The input in the tab ‘dimensions ship’ has been used to make

an estimation of the material to be used. The volume can be calculated with that input. If this is

combined with the information concerning the material the weight can be calculated. The composite

material is split in the fibre and the matrix. For detailed information about the weight of the

constructions, see appendix 4.

Deck Start deck End deck Thickness

(mm)

Tween deck 1 10,35 15,15 34

Tween deck 2 24,15 33,9 34

Tween deck 3 33,9 43 34

Main deck 1 -0,95 10,35 14

Main deck 2 10,35 24,15 14

Main deck 3 24,15 33,9 14

Main deck 4 33,9 43 14

Main deck 5 43 44,4 14

Main deck 6 44,4 46,6 14

Fore castle deck 1 6,75 24,15 26



Table 18. Decks


8.6 Total cost calculation series This part of the model is the final part of the model. Everything comes together in this tab. It is a

combination of the man-hour cost, material cost and the labour cost for the production of series of ship.

Series of ship has influence on the amount of work necessary for the production of the ship. This tab

calculates everything. The results are presented in 9.1 because they are an important part of the

research.

The material cost are assumed to be the same for each next ship. However, one can reason that the

costs of the material decrease if more ships has to be built. The costs for the investment are assumed to

be independent of the number of ship to be produced. The costs for the man-hour for each ship depend

on the learning curve. The learning curve is implemented in this part of the calculation.

8.7 Optional steps conceptual model Figure 17 shows optional steps to determine the parameters of the ship. These steps are not necessary

for the cost price estimation. During this graduation they are not uysed. However it is important to know

what the output is for the required steps of the cost price estimation.

One of these steps is the Ansys model. This model could be used to compare different structure types.

Other structures could be evaluatie for instance with the data known from the Alkmaar class vessels. The

structure and hull form of the Alkmaar class can be put in Anys. The deformation and maximum stresses

could be calcuated based on the loading described in 6.1.2.

The factor between the maximum allowable stress and the maximum stresses found during the

calcualtions could be used as a `safety factor´ in other designs. For instance if another material with

other maximum allowable stresses is used. Or to compare another structure ´philosophy´ with the

structure ´philosophy´ used for the Alkmaar class vessels. The deformation could be used to design

another structure with the more or less the same deformation. The Ansys model could also be used to

evaluatie other hull forms. A different only in length without a difference in the midschip section does

not effect the structure, because the draft and the depth remain the same.

The section modulus calculator is also an optional step. This calculator can be used to evaluate the

section modulus of a hull. The section modulus calculator could be used to compare the section modulus

of different hulls. The maximum global stress can be calculated with the definded maximum global

bending moment (for instance based on the rules) and the section modulus of the midship section. The

maximum allowable stress of the material can be used for determining the dimensions of the structure.

Production of composite ship hulls 65 9. Results and sensitivity analysis

9. Results and sensitivity analysis This chapter describes the result of the model. A sensitivity analysis will be performed to show the effect

of difference in the parameters on the final output of the model.

9.1 Results The price per ship depends on the number of ships produced. If a few ships are produced the ship is

more expensive than when lots of ships are produced. Originally, the current AMBV was built in a series

of 15 ships. The cost price per ship for series of different sizes can be found in figure 28. Clearly to see is

the effect of the decrease in cost due to dispersion of the cost of the investment over more vessels.

Included is also the effect of the learning curve. The effect of the learning curve can be found in figure

29. The cost price per kg for a series of fifteen ships is €81,80 and the cost price for a series of six ships is

€123,00.

Figure 28. Cost per ship for series of different sizes

Figure 29. Effect learning curve

€ 0

€ 10.000.000

€ 20.000.000

€ 30.000.000

€ 40.000.000

€ 50.000.000

€ 60.000.000

€ 70.000.000

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15

Decomposition cost for a serie of ships

Labor cost

Material cost

Fixed cost

€ 5.000.000

€ 6.000.000

€ 7.000.000

€ 8.000.000

€ 9.000.000

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15

Pri

ce (

€)

th ship

Influence learning curve


The decomposition of the man-hour cost and material cost are also important. By using the

decomposition of these two the major cost drivers for these cost can be established. Improvements in

the production can focus on these aspects because an improvement will have the most effect on these

aspects. A decomposition for the material cost can be found in figure 30 and for the man-hour cost can

be found in figure 31. Important to notice is that the majority of the material cost are the costs for the

fibre. Two factors are the cause for that. The first one is the amount of material that is fibre. Around 50%

of the material used is fibre. The other cause is the price if the material. The fibres are per kg the most

expensive material.

Figure 30. Decomposition of the material cost.

The different processes have different characteristics. The determination of the parameters is explained

in 7.1. The parameters have been combined with the data of the form of the ship. The total time spent

for each of the processes can be determined. An overview of these times is given in figure 31. Four of the

processes are more than 90% of the total amount of work. These processes are the lay-up of the fibre,

the lamination of the fibre, the scouring of the material and the positioning of the decks, bulkheads and

sandwich panels of the superstructure. If one wants to improve the production rate of the vessels one

has to focus on these tasks. The lay-up and the lamination process are of main interest for the

production of composite products. Improvements in newer techniques could lower the production time

necessary for the production of composite vessels. An improvement of 10% in the lay-up the fibres saves

around 3.200 hours of working for the first ship, resulting in a saving of €210.000.

To get more insight of the production of the different components the production steps for these

components are grouped and represented as whole. The proportion of main parts of the construction

can be found in figure 32. One can see that quite a number of hours (59% of the total time) is necessary

for the production of the stiffeners on different locations. The production of the stiffeners is less fast

than the production of skin, due to the geometrical form of the construction. One of the focuses of the

production should be on the production of the stiffeners.

83,0%

2,1%

0,3%

13,5%

0,7% 0,5%

Cost material

Fiber

Catalyst

Accelerator

Resin

Pins

Foam


The total cost of a project for series with different number of ship can be found in figure 33. It is clear

that adding an extra vessel to a series will have influence on the total cost of the project, but it lowers

the cost per vessel. Depending on the need the decision can be made to add an extra vessel to the series

without having to raise the budget for the vessel with the same portion.

Figure 31. Decomposition different processes.

29,76%

29,76%

11,48%

0,40%

0,20%

0,42%

0,81%

0,81%

1,80%

0,02%

0,10% 21,07%

0,23% 3,16%

Decomposition different processes Lay up fibers

Laminate

Scouring

Making foam core

Glue foam core

Applying rubber emulsie

Drilling holes

Places pens

Producing angle laminate

Make balsa core

Glue balsa core

Transport and positiondecks/bulkheads/sandwich panelsFilling seams


Figure 32. Production parts of the construction.

Figure 33. Cost of a project.

9.2 Sensitivity analysis This part investigated the sensitivity of the model for several parameters. The sensitivity analysis will be

based on a series of six vessels. This is done because DMO is investigating the production of a series of

six vessels replacing the current AMBV class vessels.

One of the important parameters is the influence of the man-hour cost on the total price of the vessels.

Figure 34 shows the influence of the man-hour cost. The price of a man-hour is €65. Varying the price

between €57 and €71 leads to a difference in man-hour cost of 9,5 million. If the price for a man-hour is

€57, the man-hour costs are 41% of the total costs. For a price of €65 per man-hour are the man-hour

costs 46% of the total price.

20,2%

16,6%

5,3% 2,2%

2,6%

8,2%

14,3%

26,8%

3,6%

Production construction parts

Skin

Stiffeners skin

Center girder

Side girders

Bulkheads

Stiffeners bulkheads

Decks

Stiffener decks

Sandwich panels

€ 0,00

€ 20.000.000,00

€ 40.000.000,00

€ 60.000.000,00

€ 80.000.000,00

€ 100.000.000,00

€ 120.000.000,00

€ 140.000.000,00

€ 160.000.000,00

€ 180.000.000,00

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15

Cost of project for a serie of # ships

Total cost project

Manhour cost

Material cost

Fixed cost


Figure 34. Influence manhour cost.

Figure 30 shows the largest part of the material cost are the cost for the fibres. The influence of the price

of the fibres is shown in figure 35. The price found for glass fibre vary between €13,00 and €23 per kg.

The influence of the fibre is low. The increase of the fibre price with 77% percent (difference between 13

and 23) has an effect of an increase of only 4% on the total cost of the hull.

Figure 35. Influence of the price of the fibres.

The ratio between the production of the skin and the production of stiffeners, girders, bulkheads and

decks has to be examined. The ratio of the production of the stiffeners has the biggest influence because

the production of the stiffeners takes the most man-hours compared to the other two.

€ 35.000.000

€ 37.000.000

€ 39.000.000

€ 41.000.000

€ 43.000.000

€ 45.000.000

€ 47.000.000

€ 49.000.000

€ 57 € 58 € 59 € 60 € 61 € 62 € 63 € 64 € 65 € 66 € 67 € 68 € 69 € 70 € 71

Tota

l man

ho

ur

cost

Cost price manhour (€/hour)

Influence manhour cost

€ -

€ 2.000.000

€ 4.000.000

€ 6.000.000

€ 8.000.000

€ 10.000.000

€ 12.000.000

€ 14.000.000

€ 16.000.000

€ 18.000.000

Pro

du

ctio

n c

ost

Fiber cost (€/kg)

Influence fiber cost

Fixed cost and manhour cost

Material cost


Figure 36. Influence production stiffeners ratio

An decrease from 250.998 (ratio 0,4) man-hours to 185.924 (ratio 0,54) or 26% of the ratio between the

production of the stiffeners and the production of the skin has an effect of 9,1% on the man-hours and

an effect of 4,1% on the total production cost of a series of six ships. The effect of the ratio factor can be

found in figure 36. Important to notice is that this is only the effect of the lay-up and the lamination of

the fibres. Changing the production ratio between the production of skin and bulkheads/decks from 0,72

to 0,86 has an effect of 16% on the lay-up and the lamination of the fibres, resulting in an decrease of

the total production cost of 0,8%.

9.2.1 Sensitivity other ship

The model could be used to determine the cost price for ships with other hull forms or other lengths.

The AMBV which is used as benchmark for the model is one of the biggest composite ships. The model

has been developed to give a price estimation for this type of ship. Change in the hull form and size of

the ship has to be handled carefully. One has to assure that the model could be applied for the

production of the desired hull form. For instance if one wants to estimate the cost price for a catamaran

one has to investigate how this can be applied in the model.

It is expected that the model can handle changes in size quite easy. Because as change in the hull form

does not lead to a change in the production of the vessel. However, the input parameters have to be

investigated for production of significant smaller or bigger ships.

9.2.2 Sensitivity other materials

The results presented before are based on the use of glass fibre and polyester resin. Changing the materials of the structures leads to change in the dimensions of the construction. Materials used for the production of composite vessels can be found in 2.1. Changing the materials used for the structure of the vessels does not necessarily affect the construction order and the processes required for the production of the ship. The same type of calculations have to

€ 0

€ 5.000.000

€ 10.000.000

€ 15.000.000

€ 20.000.000

€ 25.000.000

€ 30.000.000

€ 35.000.000

€ 40.000.000

€ 45.000.000

€ 50.000.000

0,4

0,4

1

0,4

2

0,4

3

0,4

4

0,4

5

0,4

6

0,4

7

0,4

8

0,4

9

0,5

0,5

1

0,5

2

0,5

3

0,5

4

Ratio production stiffeners

Influence ratio production stiffeners

Remaining manhour cost

Production stiffeners cost


be used. However, the input parameters could change as a result of a change in material. For instance, the lay-up of the fibres could change as a result of a change in materials. Another change due to a change in material are the material cost. The material cost for the most used materials for composite hulls can be found in 7.3.2 Important if one applies other materials is the check of the input parameters for the used materials. Are the production rates the same for the new materials or has one to conclude that the input parameters should change as well.

9.3 Building other structure Producting of the stiffeners is one of the main parts of the production of the Alkmaar class vessels.

Removing the stiffeners on the skin of the Alkmaar class vessels and making the skin stiffeners could be

an effective way to reduce the manhour cost. Removing the stiffeners save 38.462 man-hours and

€309.316 material costs. The skin of the ship should be made thicker to have the same deformation and

stresses in the material. Important to notice is that only the tranverse stiffeners on the skin are removed

and replaced by a thicker skin. The price for the ship can be compared when the skin with stiffeners is

made 2,6 times thicker compared with the skin of the Alkmaar class vessels. The result for the ‘normal’

Alkmaar class vessel and the Alkmaar class vessel with a thicker skin can be found table 19. The

investments costs are assumed to be same for both cases. Interesting to see is the change in costs from

material costs to labour costs. The vessel with a thicker skin has a higher weight but needs less

production others.

The effect of this change should be investigated further. The ship is much heavier as can be seen in table

19. One have also to investigate which dimensions of the skin are necessary to withstand the loadings.

A monocoque is always heavier than a single skin stiffened skin. This is what the model also gives. A

thickness at the keel of the ship of 90 mm (2,6 times the thickness at the keel of the an Alkmaar class

ship) is quite normal for a monocoque structure. The Lerici class minehunters for instance have at the

keel at thickness of 114mm. (Smith, 1990).

‘Normal’ Alkmaar class

vessel

Thicker skin Alkmaar class vessels

Material cost € 1.308.426 € 1.829.571

Labour cost € 8.655.291 € 8.129.372

Weight (ton) 135,299 184,751

Table 19. 'Normal' Alkmaar class vessels and Alkmaar class vessel with thicker skin.

9.4 Using other process An important improvement in the production of composite hulls is the use of the vacuum bag moulding

tech nique instead of the traditional hand lay-up method, see 2.3.1.1.3. Vacuum bag moulding is used

because the labour costs are reduced considerably for large structural applications and the fiber content

is higher (Brouwer, et al., 2002). The assumption for this example is that the improvement of the

lamination speed due to the use of vacuum bag moulding is 15%. Thus instead of a lamination speed of

2,03 m2/h a speed of 2,34 m2/h. Every other process has the same production speed as described earlier.

The total amount of man-hours in this case is 115.191 hours, resulting in a reduction of 4.651 man-hours

or 3,9% of the total production time. The resulting in a saving of about €336.000 for the first ship. If more


ship are produced the amount of money increases. Important to notice is that this is only the saving due

to a change in the process. This cases doesnot contain a change in the structure due to the higher fiber

content. The actual saving could be higher if the structures is redesigned. Weight savings of 15% has

been achieved with vacuum bag moulding (Shenoi & Dodkins, 2000). Another note is about the required

extra investments for the vacuum bag moulding. The cost for the investment are somewhat higher,

however not much. Vacuum bag moulding requires only small capital investments (Karlsson & Aström,

1996). Important to notice is that some other processes can be affected by the change in material. In this

case for instance the required amount of scouring will probably be lower. The amount of money save

when using vacuum bag moulding is thus probably bigger. However, that has to be investigated further.

Production of composite ship hulls 73 10. Verification and validation model

10. Verification and validation model Validation is the check of the model based on other data. The behaviour of the model has to be checked

with the production data of vessels produced elsewhere. Verification is the process of checking the

information in the situation used. In this case the production of the AMBV class vessels.

It is hard to validate the model and to verify the model with the available information. Validation is

difficult due to difficulties in obtaining information about the cost price for the production of composite

hulls. Companies do not want to give information about the production of such vessel because insight in

cost gives company information.

Verification is difficult based on the information available. The input parameters as described in chapter

7 are used to verify the model. The verification is done with a calculation of the cost. The information

that can be used for the verification of the model is a study to improvements in the first station of the

GNM production facility. The second part to verify the data is the GNM calculation (Van der Giessen - De

Noord Marinebouw BV, 1983). However, difficulties arise on several aspects of that calculation. The

model is a process-based estimation of the cost price. The GNM approach is a calculation of the cost.

Since the GNM approach of the production was to use existing production facilities as much as possible

as described in 5.1. GNM gives are total price for the items produced elsewhere. One does not know the

man-hour cost for GNM of these items. The total price of both calculations can thus not be compared.

However, there are certain parts that can be compared. The assumption is that if the model can be

verified for the parts representing all the processes done in the production the whole mode is verified.

The parts of the production that where outsourced are the decks and the bulkheads. The production of

the decks and the bulkheads does not differ much from the production of the skin.

Another difficulty with the verification of the model is that GNM gives not the calculations for the sub

processes defined in the model but for several of these sub steps. For instance, the production of the

stiffeners is taken as whole, but in the model it is divided in twelve sub steps. So it is impossible to verify

all the sub steps but the whole production of the stiffeners has to be compared.

10.1 Verification weight structure GNM calculates that the total amount fibre reinforced plastic used for one AMBV is 149.027 kg (Van der

Giessen - De Noord Marinebouw BV, 1983). The total weight of the hull calculated in the model is

135.299 kg. The difference between these two is 7,9%. The difference can be explained by the fact that

the model does not calculate the whole construction but only the GRP hull. For instance, the foundations

and the secondary bulkheads are not calculated.

The structure can be divided in several parts. The weights of the model and the difference between the

weights of the GNM calculation can be found in table 20. The difference between the different parts is

quite huge, however the different between the total weight is quite low.

Item GNM calculation (kg) Model (kg) Difference (%)

Skin total 40.049 37.361 -6,7

Buffer layer 3.222 5.454 69,3

Strength layer 36.827 31.907 -13,4


Stiffeners skin 15.056 13.209 -12,3

Centre girder 3.536 3.336 -5,7

Side girder 3.431 1.901 -44,6

Decks 49.360 57.998 17,5

Bulkheads 16.050 18.365 14,4

Table 20. Weight different parts according to the model and to the GNM calculation

10.2 Verification production skin The differences in the production of the skin are given in table 21. Especially the production of the buffer

layer differs quite much with the GNM calculation.

GNM calculation Model Difference (%)

Buffer layer 2.400 4.402 83,4

Strength layer 15.500 13.742 -11,3

Table 21. Production skin.

10.3 Verification production stiffeners The values for the production of the stiffeners can be tested with the values for the centre girder and

side girders. The production times for the production of the centre girder and the side girders can be

found in table 22. Important to notice is the difference between the side girder and the GNM calculation.

An explanation for the difference could be that the production of the sider girder is more like the

production of the stiffeners on the skin. Another explanation can be the difference in the weight of both

calculations. Less weight results in less work.


Stiffeners skin 15.170 14.915 - 1,7

Centre girder 4.820 4.784 - 0,7

Side girder 2190 2804 28,0

Side girder corrected 2190 1998 - 8,8

Table 22. Production times girder and stiffeners

In table 22 a correction is done for the production speed of the lay-up and the lamination of the fibres,

the ratio for stiffeners is used instead of the ratio for the side girders. The assumption for that correction

could be justified by the fact that the drawings show that the production of the centre girder is more

difficult compared to the side girder.

Important to notice is the amount of time that is used for the lay-up and lamination of the girders. The

percentage for the stiffeners can be found in table 23. The lay-up and lamination are thus a huge part of

the production of the stiffeners.

Stiffeners

skin

Side girders

(corrected)

Centre

girder

Bulkheads Decks Deck

longitudinal

% Lamination and 80,2 86,1 92,2 80,3 79,7 85,8


lay up

Table 23. Percentage of the time used for the lay-up and lamination of the stiffeners.

40.000 glass pins are necessary for the production of the stiffeners on the skin (Lohuizen, 1985). The

model calculates that 39.824 glass pins are necessary for the production of stiffeners. The difference

between those is 0,44%.

10.4 Verification investment If the investment is not corrected for the inflation, the investment is in 1980 44.024.406 DG. This is near

the investment of 45 million DG done by GNM. The difference is 2,2%. It is lower due to the investment

of GNM for further use of the facility.

10.5 Verification other processes A few processes are not directly related to the GRP work to be done for the production. These processes are preparing or finishing works. An overview of this work and the difference between the GNM calculation and the model is given in table 24.


Assembly and disassembly mould 2790 2820 1,1

Place sandwich panels 6870 7000 1,9

Measurements dimensioning 340 340 0,0

Make mould ready for production 600 596 -0,7

Build scaffoldings 30 30 0,0

Table 24. Overview production times processes not directly related to the GRP work.

10.6 Comparison decks and bulkheads The GNM has outsourced the production of the decks and the bulkheads to third parties. The costs for

these parts are given in the calculation (Van der Giessen - De Noord Marinebouw BV, 1983). The total

cost for both material and man-hours can be calculated with the model. The difference between the

GNM calculation and the model are given in table 25. Important to notice is the difference in costs for

the tween deck. An explanation for the difference is the absence of deck camber in the production of

this deck. The model is based on the production of the decks with deck camber. The parameters for the

processes should be different if a deck is produced without deck camber

Price GNM calculation 1983

(gulden)

Price GNM calculation

2014 (€)

Model (€) Difference

(%)

Main deck 969.250 945.630 1.087.793 15,1

Fore castle

deck

864.305 843.242 1.044.109 23,8

Tween deck 287.060 280.065 469.892 67,8

Bulkheads 783.070 763.987 802.879 5,1

Table 25. Production cost decks and bulkheads.

Production of composite ship hulls 76 11. Implementation in DMO estimation model

11. Implementation in DMO estimation model The implementation of the results of the model can be done easily. The model can be used to predict the

effect of the implementation of new production techniques or the effect of changing the way of the

production cost. The model can also be used to calculate the effect of changing the structure of the

vessels and changing the ‘structure philosophy’.

The cost estimation model currently used at DMO is based on product-based estimations. Therefore, it is

necessary to translate the results of the process oriented cost price estimation model to data, which can

be used in the product-based estimation. The DMO estimation model is based on a price per kilo

construction. That is the measure for the output of the developed model.

A disadvantage of the model used at DMO is that it is based on the production of AMBV-like vessels. The

effect of changing the geometry or changing the method of construction cannot be estimated. This

model developed is able to evaluate the effect in changes in the structure design ‘philosophy’ and the

hull form.

Also changes in stiffening spacing can be performed with the model. This model is thus able to establish

the stiffeners spacing with the lowest cost.

In fact, one can say that this model can be used to generate information for the cost price estimation

model of DMO. This model focuses only on a part of the cost price estimation model of DMO. However,

for that part more insight in the behaviour of the cost development can be obtained with the model

developed.

The part of the production costs of the whole costs of a project have to be known to say something

about the effect of changes in the production cost. However, in general can be concluded that when a

change in production process leads to lower construction costs leads to lower project costs.

Production of composite ship hulls 77 12. Conclusion and recommendations

12. Conclusion and recommendations

12.1 Conclusion In this study, the cost price estimation of a composite hull has been investigated. Two parts are

important in the estimation of a the cost price. The first one is the determination of the structure of the

vessels. This can be done already for other purpose. However sometimes it is necessary to establish the

dimensions of the structure. Possible structures types for the construction of composite ships are:

1. Monocoque single skin construction

2. Framed single skin construction

3. Monocoque sandwich single skin construction

4. Framed sandwich single skin construction

5. Corrugated hull

The structure can be built in different materials, this choice for the materials depend on the

requirements for the ship.

Different techniques may be used for the construction of composite vessels. The production technique

used for the production of the AMBV class vessels is hand lay-up. Other promising techniques are

vacuum injection and RTM.

The construction cost for ships with composite hulls are estimated by the use of the developed model.

The model is a process based cost price estimation model, which means that the model determines the

processes necessary for the production of such ships and determines the amount of work necessary to

produce the ship. Other aspects of the calculation are the material cost and the cost related to the

investment in the yard and the mould.

Improvements can be investigated with the model due to change in parameters. The model is developed

in such a way that the parameters can be changed and that the model is not dependent on one or a few

production methods.

The model is developed with the data of the AMBV class mine hunter. The ‘structure philosophy’ of a

AMBV class vessel is single skin stiffened vessel. The result for the production of this ship is €123/kg.

The fixed cost, the investment for the yard and the mould, are the substantial part of the production

cost. This effect is big especially for smaller series.

The glass fibre costs are 83% of the cost of the material. Fibres are the strength bearing parts of the

construction of the vessel. Improvements in the production of the should focus on the processes of the

lay-up of the fibres, the lamination of the fibres, the scouring of the material and the transportation and

position decks. Improvements in the production can also focus on certain parts of the structure of the

vessels. These structures are the stiffeners of the construction 63,6% of the production time is the

production of the stiffeners.

Improvements can be implemented easily in the production model. Parameters represented the

production process. The main parts of the processes are the same as used in the model. They are

independent of the production process.

DMO can use the results of the model to improve their estimations. Improvements in the production

could be evaluated with the model developed and implemented in the DMO-models. This can be done

by calculating the effect of a change in the structure, materials or production techniques on the price/kg

Production of composite ship hulls 78 12. Conclusion and recommendations

of the structure. The price/kg can be used for the estimation of DMO. The advantage of doing that in this

ways is that the effect has to be calculated ones and it can be applied for each calculation performed

with the model used at the DMO.

12.2 Recommendations The model can be improved in different manners and especially the input parameters can be improved

significantly.

The determination of the production parameters was based on the GNM calculation and based on a

report regarding improvements in the first station of the GNM production facility. This data is quite old

to make a cost price estimation for a ship build nowadays. Improvements in the production process can

be incorporated as long as the improvements have more or less the same productions steps. For

instance producing of the hull by using composite panels cannot be estimated with the current model.

The production speed of the different sub steps should be investigated more thoroughly. A further

investigation of the production speeds can lead to a higher accuracy of the model. Better data can for

instance be obtained due to measuring production times at a company, which produced sufficient big

ships such that the production can be compared with the production of a composite ship with more or

less the same length as an AMBV. Evaluation using other production processes is also an option for

further research.

One of the parts of the model was the calculation of the cost not directly related to material or man-

hours. This cost was split in cost for the mould and cost for the investment for a newly build yard. This

part of the model should be improved further. The model gives some consideration about the items that

are in this part of the model and it gives a consideration of the influence of each of this items. However,

the link between the size of the ship and the influence of the cost of this item should be established.

Another improvement part mentioned before is the influence of the use of a current existing production

place. The starting point of the model is a newly build yard. The consequence of that starting point is a

high investment with the advantage of an ideal production facility. Interesting is a research in the use of

an existing production facility and the consequences of using that facility on the cost for the investment

and the production time of the ship.

Also the effect of using totally different processes could be investigated. An example is a construction,

which consists of panels, used for the production of the Visby class corvettes of the Swedish Navy. The

production technique of this vessel was the infusion of panels up to 60m2. Resulting in a production

method comparable with the production of ‘normal’ steel vessels (Lindblom, 2003).

A recommendation which does not focus on the use of a model for the estimation of the cost price of the

ship is the production of test samples. One can use the production data of the test samples to estimate

the production price for the whole vessel. If the test samples are representative for the production of a

whole ship, one can assumed that the production data could be used for the production of the whole

ship.

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Production of composite ship hulls 83 Appendix 1. Midship section AMBV

Appendix 1. Midship section AMBV

Figure 37. Midship section AMBV

Production of composite ship hulls 84 Appendix 2. Description hull form

Appendix 2. Description hull form

Table 26. Description hull form

Are

a sk

in b

etw

een

wl 5

and

wl 1

0 (

m2)

14

,40

1

12

,97

4

7,7

25

7,0

31

6,8

68

7,0

95

7,6

15

7,8

81

7,1

37

1,8

81

Are

a sk

in b

etw

een

wl 0

an

d w

l 5 (

m2 )

0 12

,13

18

,98

1

20

,12

20

,52

9

18

,89

1

15

,25

2

10

,76

9

6,4

49

0,4

55

Are

a cr

oss

sec

tio

n

(m2 )

6,5

8

7,2

4

11

,06

14

,76

26

,97

27

,61

27

,14

25

,4

22

,15

17

,33

9,5

4

0,2

5

Cir

cum

fere

nce

(m)

4,7

6

4,9

4

5,9

4

6,4

4

9,3

2

9,6

6

9,5

5

9,1

8

8,6

4

8,1

7

7,4

4

0,9

Up

per

val

ue

ran

ge

rela

tive

to

AP

(m

)

0 5 10

15

20

25

30

35

40

45

50

,5

Low

er v

alu

e ra

nge

rela

tive

to

AP

(m

)

-0,9

5

0 5 10

15

20

25

30

35

40

45

50

Are

a sk

in b

etw

een

wl 1

5

and

fo

re c

astl

e d

eck

(m

2 )

0,9

88

4,5

03

5,9

92

14

,38

6

14

,37

7

14

,37

6

14

,39

5

14

,51

5

14

,94

15

,85

1

12

,33

3

Bre

adth

tw

een

de

ck (

m)

3,3

3,9

7

4,2

5

4,3

7

4,2

7

3,8

6

3,0

8

1,9

5

0,7

1

Bre

adth

mai

n

de

ck (

m)

3,5

2

3,5

9

3,9

6

4,2

3

4,4

4,4

6

4,4

3

4,3

3

3,7

6

2,8

9

1,3

8

Bre

adth

fo

re

cast

le d

eck

(m)

4,4

1

4,4

7

4,4

6

4,3

7

4,1

1

3,5

5

2,2

8

Are

a sk

in b

etw

een

wl 1

0

and

wl 1

5 (

m2)

3,9

2

8,6

86

6,3

72

6,1

98

6,1

5

6,1

46

6,1

99

6,4

05

6,7

83

6,9

15

3,0

48

Production of composite ship hulls 85 Appendix 3. Production parameters

Appendix 3. Production parameters

Area between wl 0 en wl 5 (m2)



aft 63,43 70,62 50,72

mid 141,67 53,45 46,61

fore 42,06 37,15 36,31

Total 247,152 161,216 133,644

Opp tussen wl 15 en FCD (m2)

Total Area (m2) Total area all strength layers (m2)

aft 52,60 237,37 3496

mid 108,08 349,80 4507

fore 92,63 208,15 2201

Total 253,312 795,32 10205

Table 27. Production parameters skin.

Plaatsen schotten relative to APP

(m) To deck Area (m2) Thickness (mm) Stiffener length (m)

Stern -0,95 Main deck 5,06 25 7,23

Bulkhead 1 3,75 Main deck 11,31 12 16,16

Bulkhead 2 10,35 Fore castle deck 31,23 12 44,61

Bulkhead 3 13,95 Tween deck 16,19 12 23,13







Bulkhead 10 43 Main deck 14,34 12 20,48


bulkhead sonar dome 36,7 Tween deck 12,91 12 18,44

Bulkhead bow thruster 40,2 Tween deck 11,09 12 15,84

Table 28. Production parameters bulkheads.

Production of composite ship hulls 86 Appendix 3. Production parameters

Deck Start deck relative to APP (m)

End deck relative to APP (m)

Area (m2) Thickness (mm)

Tween deck 1

Tween deck 2 10,35 15,15 39,59 14

Tween deck 3 24,15 33,9 75,66 14

Tween deck 4 33,9 40,2 32,88 14

Tween deck 5

Tween deck 6

Main deck 1 -0,95 10,35 88,33 14

Main deck 2 10,35 24,15 121,03 14

Main deck 3 24,15 33,9 81,54 14

Main deck 4 33,9 43 53,46 14

Main deck 5 43 44,4 5,38 14

Main deck 6 44,4 46,6 4,47 14

Fore castle deck 1 6,75 24,15 116,55 26

Fore castle deck 2 24,15 33,9 83,04 26

Fore castle deck 3 33,9 50,5 80,46 26

Deck Stiffener length decks (transverse) (m)

Stiffener length decks (longitudinal) (m)

Breadth begin deck (m)

Breadth end deck (m)

Circumference deck (m)

Tween deck 1

Tween deck 2 65,98 14,4 3,99 4,25 44,28

Tween deck 3 100,88 29,25 4,29 3,25 55,86

Tween deck 4 43,85 18,9 3,25 1,90 85,94

Tween deck 5

Tween deck 6

Main deck 1 147,21 27,3 3,25 1,21 53,32

Main deck 2 161,37 41,4 4,24 4,44 87,15

Main deck 3 108,72 29,25 4,44 3,89 58,46

Main deck 4 76,37 27,3 3,89 1,98 90,72

Main deck 5 7,69 4,2 1,98 1,53 22,99

Main deck 6 5,96 0 1,56 0,98 25,83

Fore castle deck 1

147,29 52,2 4,14 4,46 94,09

Fore castle deck 2

110,72 29,25 4,46 4,17 59,49

Fore castle deck 3

107,28 0 4,17 0,00 143,37

Table 29. Production parameters deck.

Production of composite ship hulls 87 Appendix 4. Weight parts of the ship

Appendix 4. Weight parts of the ship

Volume (m3) Weight (ton) Weight fibre (ton) Weight matrix (ton)

Aft 1,11 1,68 0,42 0,84

Mid 1,59 2,41 1,20 1,20

Fore 0,91 1,37 0,69 0,69

Total 3,61 5,45 2,73 2,73

Table 30. Material buffer layer skin


Aft skin 5,51 10,21 5,10 5,10

Mid skin 7,72 14,31 7,16 7,16

Fore skin 3,99 7,39 3,69 3,69

Aft stiffeners 2,39 4,43 2,22 2,22

Mid stiffeners 3,09 5,73 2,86 2,86

Fore stiffeners 1,64 3,05 1,52 1,52

Total 24,35 45,12 22,56 22,56

Table 31. Material strength layer skin

Material Volume (m3)

Weight (ton)

Weight fibre (ton)

Weight matrix (ton)

Material decks 19,39 35,94 17,97 17,97

Material bulkheads 3,93 7,28 3,64 3,64

Material stiffener decks transvers

14,38 26,65 13,32 13,32

Material stiffener deck longitudinal

3,81 7,06 3,53 3,53

Material stiffener bulkheads 5,98 11,09 5,54 5,54

Total 47,50 88,01 44,01 44,01

Table 32. Material decks and bulkheads


Aft 1,11 1,68 0,42 0,84

Mid 1,59 2,41 1,20 1,20

Fore 0,91 1,37 0,69 0,69

Total 3,61 5,45 2,73 2,73

Table 33. Material buffer layer skin



Aft skin 5,51 10,21 5,10 5,10

Mid skin 7,72 14,31 7,16 7,16

Fore skin 3,99 7,39 3,69 3,69

Aft stiffeners 2,39 4,43 2,22 2,22

Mid stiffeners 3,09 5,73 2,86 2,86

Fore stiffeners 1,64 3,05 1,52 1,52

Total 24,35 45,12 22,56 22,56

Table 34. Material strength layer skin

Material Volume (m3)

Weight (ton)

Weight fibre (ton)

Weight matrix (ton)

Material decks 19,39 35,94 17,97 17,97

Material bulkheads 3,93 7,28 3,64 3,64

Material stiffener decks transvers

14,38 26,65 13,32 13,32

Material stiffener deck longitudinal

3,81 7,06 3,53 3,53

Material stiffener bulkheads 5,98 11,09 5,54 5,54

Total 47,50 88,01 44,01 44,01

Table 35. Material decks and bulkheads

The matrix can be split further to catalyst, accelerator and resin. For the buffer layer this can be found in

table 36, for the strength layer in table 37, for the bulkheads and decks in table 39.

Weight catalyst (ton)

Weight accelerator (ton

Weight resin (ton)

Aft 0,024 0,004 0,81

Mid 0,035 0,006 1,16

Fore 0,020 0,003 0,66

Total 0,079 0,013 2,63

Table 36. Material matrix buffer layer skin



Weight resin (ton)

Aft skin 0,10 0,01 4,99

Mid skin 0,14 0,02 7,00

Fore skin 0,07 0,01 3,61

Aft stiffeners 0,04 0,01 2,17

Mid stiffeners 0,06 0,01 2,80

Fore stiffeners 0,03 0,00 1,49


Total 0,44 0,06 22,06


The volume and the material for the different stiffeners are calculated as well, see table 38.

Foam core Volume (m3) Weight foam core

stiffeners deck 33,11 1,32

longitudinal stiffeners deck 2,62 0,10

stiffeners skin 27,88 1,12

stiffeners bulkhead 2,62 0,10

centre girder 5,77 0,23

side girders 4,88 0,20

Total 76,88 3,08

Table 38. Foam core.



Weight resin (ton)

Material decks 0,35 0,04 17,57

Material

bulkheads

0,07 0,01 3,56

Material stiffener

decks transvers

0,26 0,03 13,03

Material stiffener

deck longitudinal

0,07 0,01 3,45

Material stiffener

bulkheads

0,11 0,01 5,42

Total 0,86 0,11 43,04


Documents

Production of composite ship hulls - TU Delft