4th Year Group Design Project Offshore Wind Farm Access Vessel
Sam Naylor – Nicholas Brophy - Boyang Wang
Department of Naval Architecture, Ocean and
Marine Engineering
The University of Strathclyde
May 2014
1
Contents
INTRODUCTION .................................................................................................................................. 2
HULL FORM ......................................................................................................................................... 3
INITIAL DESIGN PROCESS ...................................................................................................................... 3
THE BENEFIT OF A SWATH OVER A CONVENTIONAL CATAMARAN ....................................................... 4
THE DISADVANTAGES OF A SWATH .................................................................................................... 4
CHOSEN DESIGN ................................................................................................................................... 5
SPEED OF INCEPTION ............................................................................................................................. 6
FIN DIMENSIONS .................................................................................................................................... 6
PERSPECTIVE VIEW OF THE HULL .......................................................................................................... 9
BASIC PRINCIPALS OF MOTHERSHIP ...................................................................................................... 9
RESISTANCE AND POWER PREDICTION ................................................................................... 10
SEAKEEPING ANALYSIS ................................................................................................................. 13
DATA INPUT ........................................................................................................................................ 13
DATA OUTPUT ..................................................................................................................................... 13
MOTION SICKNESS INCIDENCE ............................................................................................................ 14
RAO’S ................................................................................................................................................ 14
PROPULSION AND MACHINERY SELECTION .......................................................................... 14
HOW MUCH POWER WE WANT ............................................................................................................. 14
GREEN CREDENTIALS ......................................................................................................................... 15
EXISTING DIESEL-ELECTRIC SYSTEMS ................................................................................................ 15
MORE TRADITIONAL OPTION ............................................................................................................... 16
CREW TRANSFER SYSTEM ................................................................................................................... 17
GENERAL ARRANGEMENT ........................................................................................................... 18
APPENDICES ...................................................................................................................................... 20
APPENDIX A: DESIGN BRIEF ............................................................................................................... 20
APPENDIX B: CATALOGUE OF COMPARABLE SWATH DESIGNS ........................................................ 21
APPENDIX C: SEAKEEPING RESULTS ................................................................................................... 23
APPENDIX D: MSI ............................................................................................................................... 26
APPENDIX E: RAO’S ........................................................................................................................... 32
APPENDIX F: WEIGHT DETAILS OF SWATH ....................................................................................... 39
2
Introduction
In 2008, The Crown Estate announced ‘Round 3’, the largest offshore wind
programme in the world, proposing nine offshore zones to develop wind farms of
varying sizes. Due to the much larger scale of this round, there was the potential to
produce triple the collective energy of rounds 1 and 2, which in combination with
round 2 extensions and Scottish Territorial Waters projects would provide a total
output of nearly 50GW.
As a result, there has been a drive for designs which can operate safely and efficiently
within such global locations, which are outside of current operable vessels’ abilities.
This includes areas which are further from land and exhibit sea states greater than
those which are operated in at present. These zones provide suitable locations with a
sufficient area to host these vast wind farms with up to 1500 turbines, which is much
larger than current wind farms. Consequently, the design and construction of transfer
vessels with the ability to operate in a safe and efficient manner in areas portraying
the inevitable increase in wave characteristics is crucial.
A small water-plane area twin hull (SWATH) design is selected as a base for the
vessel, as this is fundamentally an efficient design in reducing the motions of the
vessel whilst stationary. With the inclusion of fins protruding from the torpedo hulls,
the Munk Moment (which can be detrimental to the SWATH hullform) can be
reduced to improve the selected design whilst travelling at a forward speed.
Performing a seakeeping analysis on a model of the vessel allows its seakeeping
abilities to be established for the specified sea state. The resistance prediction and
therefore powering requirements are calculated, allowing for the selection of a main
propulsion system. An appropriate method of crew and supply transfer is included in
the design, with the general arrangement of the vessel described.
3
Hull Form
Initial Design Process
The principle design imperatives that the new design had to address were:
The ability to carry out all operational aspects of crew transfer to turbines at
significant wave heights of greater than 2m.
A top speed in the range of 25-30kts.
A method of rendezvous with a mothership, with freedom to determine the
design basics of both the method and the mothership.
An appropriate range to be able to operate on deep-water windfarms that may
consist of 1000-1500 turbines up to 300km from shore.
The initial design brain-storming process was approached in two steps.
Firstly, several innovative ideas for the transfer (daughter) vessel with widely varying
concepts were sketched out. In parallel to this, the group came up with some concepts
for a mothership and rendezvous system for the daughter craft.
Second, once the general craft-type and approximate dimensions were decided on
along with an appropriate design for a mothership, a focus was made on the method of
transferring crew to the turbine safely.
With regards to the design of the daughter craft, emphasis was made on the ability of
the vessel to remain stable in waves. The brain-storming technique produced some
rather unconventional ideas including floating ‘stabilisers’, a hybrid between a
catamaran and a SWATH and a tri-SWATH with azimuthing torpedo hulls. Several
designs incorporated integral attachment systems for connecting to turbines although
some merely provided a reasonably stable platform on which to mount an existing
standalone motion-compensating gangway.
The conclusion was reached that the best hull type for providing a stable platform
would most likely be a SWATH.
4
The benefit of a SWATH over a conventional catamaran
SWATH stands for Small Waterplane Area Twin Hull. It is a class of catamaran
defined by very narrow hulls at the waterline, with the vast majority of the buoyancy
underneath the free surface. The hull itself may be considered as 3 different parts; the
torpedo-shaped lower hulls that provide the buoyancy; the thin struts that pierce the
waterline and connect the lower hulls to the wet deck, which sits above the waterline
between the struts and houses the superstructure.
There are two main advantages for a SWATH over a conventional catamaran, both of
which are related to the fact that the waterplane area (that is to say the horizontal
sectional area through the struts at the waterline) is exceptionally small. The first
advantage is improved sea-keeping qualities as a vessel’s response to a wave
excitation is dependent on waterplane area. Considering a wave profile raising the
level of the water above the at-rest waterline on the strut, the increase in hydrostatic
pressure against that part of the hull is increased leading to an increase in buoyancy,
hence upthrust. For a thin strut (in relation to the vessel’s total breadth) the volume
contributing to the change in buoyancy is very small and so the upthrust has little
effect on the vessel. The effect is to make the vessel slow to react to waves, hence it
has very large natural periods of roll, pitch and heave - much larger the periods of
wave normally encountered at sea – leading to small responses in normal conditions.
The second advantage is related to wave-making resistance, which is smaller for a
SWATH than a conventional catamaran (excluding any hull interactions) as the
wavemaking body at the waterplane is thin.
The disadvantages of a SWATH
Despite the gains to be made with the reduction in wave resistance, there is a penalty
to pay in terms of viscous resistance, composed of frictional and viscous pressure
resistance. Due to their largely cylindrical shape, the wetted surface area of the lower
hulls is higher than it would be for a catamaran of equal displacement. This leads to a
large frictional component of resistance. The form factor (1+k) correction made to
frictional resistance takes account of the 3-dimensional shape of the wetted surface.
In general it is much higher for a catamaran than for a monohull, and higher again for
a SWATH. Therefore it is not only the wetted surface area that is larger for
5
SWATH’s, but also the sectional shape leads to higher total viscous resistance which
can outweigh the reduction in wave resistance.
Although the small water-plane area gives favourable sea-keeping characteristics,
particular care needs to be given to the Munk Moment. The small water-plane area
means a SWATH vessel has a pitch restoring moment which does not change with
speed. The largest portion of its underwater volume is contained in the deeply
submerged torpedo hull. Therefore as a SWATH vessel moves forward the Bernoulli
pressure will generate a destabilizing pitching moment which is known as Munk
Moment, which is proportional to the square of the speed. The result is that at a
certain speed the Munk Moment will be as large as the pitch restoring force, leading
to pitching instability. In order to prevent pitch-instability fins are added to the lower
hulls. Their foil section means they create lift in proportion to the square of speed so
therefore they balance out the Munk Moment.
Chosen Design
After compiling a catalogue of data for existing SWATH designs (see Appendix B)
and drawing comparisons between them the principal dimensions for the current
design were selected (given below). It was decided to make the SWATH design
smaller than the majority of those researched in order to maximise the operational
feasibility of the mothership. The target maximum speed chosen was 25 knots.
Displacement 28.581 tonnes
Volume 27.883 m^3
Draft to Baseline 2.2 m
Immersed depth 2.2 m
Length on water line 12.407 m
Beam on water line 6.104 m
WSA 185.719 m^2
Max cross sect area 3.213 m^2
Water plane area 20.268 m^2
Cp 0.699
Cb 0.598
Cm 0.859
Cwp 0.956
LCB from zero pt. (+ve fwd) m -0.264 m
LCF from zero pt. (+ve fwd) m -0.24 m
LCB from zero pt. (+ve fwd) % Lwl -2.127 %
LCF from zero pt. (+ve fwd) % Lwl -1.932 %
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Speed of Inception
The speed of inception is the critical speed where the munk moment equals to the
pitching moment. It can be found as follows:
Speed of inception:
√
√
As the vessel is required to travel at 25kts a method of remaining pitch stability
needed to be used.
Fin dimensions
Assumed Inputs:
Max speed: U=25.5 knots = 13.117 m/s
Added mass: A33=0.5*displacement=14.29 tonnes
Lower hull viscous lift coefficient: A0=0.7
Water density: ρ=1025 kg/m^3
Acceleration of gravity: g= 9.81m/s^2
Aspect ratio: Ar=1.2 (assumption)
Strut length: Ls=10.28 m
Fins centroid separation from the LCG: l=4.2m
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Calculation of Static Moment:
The static moment of the lower hull about LCG is:
∫ ( ) ( )
The calculation of the static moment can be done using Microsoft Excel.
X(m) B(x)m S.M Area
product
Distance
from
LCG
Moment
product
-6.482 0.996 stern 1 0.996 -6.002 -5.977992
-5.184 1.384 4 5.536 -4.704 -26.041344
-3.888 1.472 2 2.944 -3.408 -10.033152
-2.592 1.472 4 5.888 -2.112 -12.435456
-1.296 1.472 2 2.944 -0.816 -2.402304
0 1.472 midship 4 5.888 0.48 2.82624
1.296 1.472 2 2.944 1.776 5.228544
2.5925 1.472 4 5.888 3.0725 18.09088
3.888 1.472 2 2.944 4.368 12.859392
5.184 1.382 4 5.528 5.664 31.310592
6.482 0.62 bow 1 0.62 6.962 4.31644
42.12 5.2805 17.74184
Moment 22.9934246
Therefore the static moment is about 23 m^3.
The lift coefficient is:
( )
√ (
)
The longitudinal metacentric height GMl can be estimated with equation below:
( )
The area of one fin is:
8
( ) ( )
The span & chord of the fin:
Span:
√ √
Chord:
The max thickness can be assumed as:
The area of both aft fins is:
The area of both forward canards:
Increment of the aft fin area due to canards:
Total fin area:
Fin dimension summary
Span 1.17 m
Chord 1 m
One fin
area
1.168 m^2
Two
forward
area
2.34 m^2
Two aft
area
4.68 m^2
Total
area
7.02 m^2
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Perspective view of the hull
Basic Principals of Mothership
It was decided that the mothership for the vessel should be of a similar design to semi-
submersible naval amphibious assault support ships or superyacht transport ships.
These comprise a large dock at the stern of the ship. The ship is equipped with a
ballasting system which allows it to ‘sit down’ at the stern to flood the dock and
permit the daughter craft to enter or exit. Upon the arrival and docking of a daughter
vessel the ballast system is emptied, causing the mothership to rise. This lifts the
dock out of the water until it becomes dry. This allows maintenance to be carried out
on the daughter craft and prevents the underwater area becoming fouled when not in
use.
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Resistance and Power Prediction
Importing the Maxsurf Modeller file which was created in to Maxsurf Resistance, the
resistance of the vessel for various forward speeds (also depicted by Froude number)
and consequent powering requirements are calculated. The software uses the slender
body method, and the form factor (1 + k) is calculated automatically for the hull using
the Molland formula and is found to be 1.594.
The calculated resistance and power graphs against speed and Froude number are
shown below.
Resistance vs Speed (& Froude Number)
11
Power vs Speed (& Froude Number)
Tabulating allows for a direct comparison of the required power and resistance of the
vessel for the range of speeds from 0 knots to 30 knots.
12
These values are for the towing resistance and power. Based on previous studies for
a SWATH a quasi-propulsion coefficient of 70% was chosen with a further seaway
Speed Resistance Power
Knots KN KW
0 -- --
0.75 0.09 0.03
1.5 0.4 0.31
2.25 0.85 0.99
3 1.58 2.43
3.75 2.18 4.2
4.5 3.25 7.52
5.25 4.97 13.41
6 6.25 19.3
6.75 10.83 37.61
7.5 12.17 46.95
8.25 11.46 48.66
9 15.81 73.22
9.75 24.59 123.34
10.5 34.16 184.53
11.25 42.23 244.43
12 48.23 297.71
12.75 52.09 341.64
13.5 54.67 379.7
14.25 56.55 414.56
15 57.69 445.16
15.75 58.77 476.17
16.5 59.94 508.76
17.25 60.83 539.8
18 62.1 575
18.75 63.29 610.49
19.5 64.78 649.88
20.25 66.5 692.79
21 68.14 736.17
21.75 70.12 784.55
22.5 72.09 834.4
23.25 74.5 891.04
24 76.74 947.46
24.75 79.12 1007.34
25.5 81.61 1070.59
26.25 84.26 1137.91
27 87.27 1212.14
27.75 90.07 1285.85
28.5 93.04 1364.14
29.25 96.04 1445.15
30 99.35 1533.25
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margin of 10%. The seaway margin is lower than traditionally for a monohull as a
SWATH is less impeded by wave action. With the Margins applied the total required
shaft power at 25 knots was 1616kW.
Seakeeping Analysis
As a vital step in any vessel design process, a seakeeping analysis was performed on
the chosen hullform. This gave an indication of the vessels responses to differing
wave characteristics at various speeds.
Data input
This analysis was carried out for speeds from 0 to 30 knots, with an increment of 10
knots. The headings selected are head (180°), beam (90°) and stern/following (0°)
seas. The wave characteristics are defined using the ITTC (2 parameter) spectrum,
based on Sea States 4 (HS ≈ 1.25m-2.5m), 5 (HS ≈ 2.5m-4m) and 6 (HS ≈ 4m-6m) of
the World Meteorological Organization (WMO) sea state code. All of these values are
utilised as, whilst the given wave characteristic value is HS > 2m, the design brief
does not specify how large this value can become in these locations and so this
selection of data will provide results of the vessels seakeeping ability in all of these
sea states.
The vessel type is selected to be a catamaran and the spacing between the underwater
torpedo hulls is 5.24m. The pitch and roll radii of gyration are given in the Seakeeper
program as 25% of LOA and 50.91% of BOA, respectively for this type of vessel.
Also given is the VCG value, which is equal to 60% of the depth of the vessel.
Data output
The sea-keeping analysis is performed by Maxsurf Seakeeper and the results are
tabulated and represented pictorially by Microsoft Excel. The heave (m), roll(°) and
pitch (°) values for the three aforementioned headings are plotted for the three sea
states of increasing HS. These results can be found in Appendix C.
14
Motion Sickness Incidence
The MSI graphs (Appendix D) are provided for the differing speeds and sea states by
the software from the motions analysis, and is based on the ISO 2631 method. These
graphs, showing the severe discomfort limitations, are given by means of a graph of
RMS Acceleration versus Encounter Frequency.
RAO’s
The RAO’s for roll, pitch and heave against wave period are given in Appendix E.
This is again provided for the three selected headings and for the increasing speed of
the vessel from 0knots to 30knots with 10knot increments.
Also included in these graphs are the relative added resistances of the hull due to the
motions of the vessel and consequent change in wetted surface area.
Propulsion and Machinery selection
How much power we want
The total required installed propulsive power was 1616kW. The SWATH form lends
itself naturally to having twin engines; one in either lower hull. This provides several
benefits, including:
Redundancy in the case of one unit becoming inoperative. There is another
propulsor to ‘get you home’ which is vital when operating far offshore and
away from rescue.
Increased manoeuvrability. Having two propulsors gives far more
manoeuvring ability than a single engine. The large hull separation distance of
a SWATH magnifies this advantage which is useful for close-quarters
manoeuvring/holding station at a turbine.
However there are one or two drawbacks:
Reduced economy of scale. Using two smaller engines results in a smaller
overall fuel efficiency as loss are suffered in both engines.
15
Increased maintenance costs/downtime.
On the basis of using twin engines, the total installed power required in each was
1616/2 = 808kW.
Auxiliary power would be supplied by stand-alone generators. Based on data from
other SWATH designs a generation capacity of 15kW was sought. This would be
enough to run the on-board systems as well as provide power for the MaXccess crew
transfer vessel.
Green Credentials
Part of the design brief required that the vessel be “as green as possible and
economical to run”. To this end the suitability of a diesel-electric system was
investigated; the idea being that the propellers would be driven by electric motors in
turn powered by electrical power from either a diesel engine, a battery bank or the two
in tandem. The diesel engine can be used to provide power at moderate to high
speeds, although at lower speeds power could be supplied by the battery cells thus
avoiding the larger losses incurred when running an engine below its optimal loading.
This is especially useful during low-speed manoeuvring when the power drawn
undergoes large fluctuations. Extra power can be provided instantly from the batteries
and the losses due to constant revving of the engine are eliminated.
At sea the diesel engine is used to charge the battery; meaning the engine can be run
at a constant optimal loading. In this way the engine can always be run as efficiently
as possible. A further benefit would be the possibility of charging the batteries from
the mothership when the daughter craft is docked/stored there. Economies of scale
apply here as the electrical power generated by the much larger equipment aboard the
mothership would be more efficient in terms of fuel per kWh.
Existing Diesel-Electric Systems
There are mainly two companies can provide the system directly MAN B&W and
Rolls-Royce.
From Rolls-Royce there is the HSG system which has five running mode: Boost mode;
Diesel-electric mode; Parallel mode; Transit mode and shore connection mode.
16
The maximum output of this system is 8500 kW, which is well beyond the operational
needs of the SWATH in this study.
From MAN B&W we can find an example which can provide more than 10800 KW.
Again this is far in excess of the current requirements. However it may be possible to
commission a lower-powered system specifically for the current design. Therefore if
the design is pursued further hybrid power could be an option.
More traditional option
As mentioned above there is currently no example of a hybrid system fit for the
current design so it was decided on balance to seek a conventional medium speed
diesel engine for the prime movers.
The unit chosen was a MAN D2842 LE410 medium duty engine which has a
maximum output of 809kW, which almost exactly matches the required output.
Its details were as follows:
Make MAN
Model D2842
Variant LE410
Max Output(kW) 809
Length (m) 1.795
Breadth (m) 1.23
Height (m) 1.105
Dry Weight (kg) 1860
Max Consumption(l/hr) 202
Two generator were chosen for redundancy, with the intentional of running one at any
one time. The other would be in maintenance/standby mode. Therefore a generation
capacity would be retained in the event of one breaking down.
Make Kohler
Model 15EOZD
Max output (kW) 15
Length (m) 0.95
Breadth (m) 0.58
Height (m) 0.66
Wet Weight (kg) 308
Max Consumption (l/hr) 5
Voltage (V) 24
17
Crew transfer system
In order to transport the crew and the equipment safely we have to make sure that
there is no motion at all when people walking on the connection facility. Although the
ship is SWATH type which already decrease the motion a lot compare to other type of
boat but we still need a transfer system from the market.
The one is available called MaXccess-T12 sold by OSBITPOWER.
Specification:
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General Arrangement
The traditional propulsion system is the first choice of us and as mentioned we need
two engines to supply the power. Consider the vessel has two parallel underwater
hulls we can use a parallel power configuration which means the each one of engines
will be mounted in one hull and of the consumption like fuel will equally separate.
The crew transfer system will be mounted on the deck and all of the systems will be
controlled by a power monitor in the control cabin.
Plane View:
Profile View:
19
20
Appendices
Appendix A: Design Brief
21
Appendix B: Catalogue of Comparable SWATH Designs
Name Type Length (m) Breadth (m) Draught (m) Disp (t) Power (kW) Speed (kts) Range (km)
USNS Able Military 72.0 29.0 7.6 3293 1200 9.6 N/A
CCGS Frederick G. Creed Hydrographic Survey 20.4 9.8 2.6 151.4 N/A 14 1610
USNS Impeccable Oceanic Survey 85.8 29.2 7.9 4870 3750 12 N/A
Kilo Moana Oceanic Survey 57.0 27.0 7.6 2507 N/A 15 15000
Planet Research 73.0 27.2 6.8 3500 N/A 15 N/A
Skrunda Class Patrol Boat 25.7 13.5 2.7 113 1627.5 20 1900 (12kts)
Sea Slice N/A 32.0 17.0 N/A 163 N/A 50 N/A
Tri Swath Turbine Transfer 27.2 10.5 2.4 N/A 1800 23 N/A
Sea Breeze Turbine Transfer 24.8 10.6 2.5 102.5 1800 18 N/A
Fob Swath Turbine Transfer 25.0 10.6 2.5 86 1800 23 (cat-mode) 1850 (cat-mode)
Cwhisper Turbine Transfer 19.5 7.8 1.5 30 915 23 N/A
Elbe Pilot Boat 49.9 22.6 5.9 1500 2720 14 N/A
Dose / Duhnen Pilot Boat 25.2 13.0 2.7 125 1580 20 N/A
25m SWATH A&R Pilot Tender 25.7 14.3 2.7 N/A 1420 18 N/A
Natalia Bekker Turbine Transfer 26.4 13.0 2.7 N/A 1800 18 N/A
Silver Cloud Pleasure Yacht 41.0 17.8 4.1 544 1640 12.5 N/A
Tabulated data for a variety of SWATH vessels with a large range of sizes.
y = 0.100x + 0.144R² = 0.924
0.01.02.03.04.05.06.0
7.08.09.0
10.0
0.0 10.0 20.0 30.0 40.0 50.0 60.0 70.0 80.0 90.0 100.0
Dra
ugh
t (m
)
Length (m)
Draught vs Length
y = 0.335x + 3.819R² = 0.924
0.0
5.0
10.0
15.0
20.0
25.0
30.0
35.0
0.0 10.0 20.0 30.0 40.0 50.0 60.0 70.0 80.0 90.0 100.0
Be
am (
m)
Length (m)
Beam/Length
A very strong correlation can be seen between both length vs draught and length vs
beam. There is very little variation in the length to draught and length to beam ratios
which have respective mean values of 2.3 and 9.8.
22
0
500
1000
1500
2000
2500
3000
3500
4000
0 1000 2000 3000 4000 5000 6000
Po
we
r (k
W)
Displacement (tonne)
Power vs Displacement
0
1000
2000
3000
4000
5000
6000
0.0 20.0 40.0 60.0 80.0 100.0
Dis
pla
cem
en
t (t
on
ne
)
Length (m)
Displacement vs Length
23
Appendix C: Seakeeping Results
24
25
0
1
2
3
4
5
0 50 100 150 200
Met
re
Heading
Heave with SW5m
0 10 20 30
0
5
10
15
20
0 50 100 150 200
Deg
Heading
Roll with SW5m
0 10 20 30
0
5
10
15
20
25
0 50 100 150 200
Deg
Heading
Pitch with SW5m
0 10 20 30
26
Appendix D: MSI
Speed=0 Wave state 4:
Speed=10 Wave state 4:
27
Speed=20 Wave state 4:
Speed=30 Wave state 4:
28
Speed=0 Wave state 5:
Speed=10 Wave state 5:
29
Speed=20 Wave state 5:
Speed=30 Wave state 5:
30
Speed=0 Wave state 6:
Speed=10 Wave state 6:
31
Speed=20 Wave state 6:
Speed=30 Wave state 6:
32
Appendix E: RAO’s
Speed=0 heading=0
Speed=0 heading=90
33
Speed=0 heading=180
Speed=10 heading=0
34
Speed=10 heading=90
Speed=10 heading=180
35
Speed=20 heading=0
Speed=20 heading=90
36
Speed=20 heading=180
Speed=30 heading=0
37
Speed=30 heading=90
Speed=30 heading=180
38
39
Appendix F: Weight Details of SWATH
Item 1 item (l)/ (kg) No. Items Weight (kg)
Fuel 5075 2 8526
Waste 381 2 762
Gen Fuel 508 2 853.44
Lub Oil 200 2 180
F. Water 254 2 508
Tanks 10829.44
Engine 1860 2 3720
Gen 308 2 616
Transfer System 1500 1 1500
Structure (carbon fibre) 6000 1 6000
Fit-out 3000 1 3000
Provisons 500 1 500
Cargo 2500 1 2500
Total 1 28665.44
Ballast tanks Capacity (l) No. Items Capacity (tonne)
Ballast Fore 651 2 667.275
Ballast Aft 809 2 829.225
Ballast Strut 3750 2 3843.75
Total 10420 1 10680.5