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GRADUATION PROJECT DEVELOPMENT OF A SCRIPT BASED
STABILITY AND RESISTANCE PREDICTION SOFTWARE
AY YIL
Student: Sinan GURBUZ 080100151
Thesis Advisor: Asst. Prof. Ebru SARIOZ
ISTANBUL TECHNICAL UNIVERSITY
FACULTY OF NAVAL ARCHITECTURE AND OCEAN ENGINEERING
MAY 2015
TABLE OF CONTENTS DEDICATION ............................................................................................................ ii ACKNOWLEDGMENT .......................................................................................... iii ABSTRACT ............................................................................................................... iv
LIST OF FIGURES ................................................................................................... v
LIST OF TABLES .................................................................................................... vi 1. INTRODUCTION .................................................................................................. 1
2. ABOUT HYDROLAB ........................................................................................... 2
3. INSTALLATION ................................................................................................... 3
4. CAPABILITIES ..................................................................................................... 4
4.1. Generation of Lines Plan ................................................................................... 4
4.2. Calculation of Upright Hydrostatics ................................................................. 4
4.3. Calculation of Hull Resistance .......................................................................... 4
5. USING HYDROLAB ............................................................................................. 5
5.1. File .................................................................................................................... 5
5.2. Interpolation ...................................................................................................... 6
5.3. Lines Plan ........................................................................................................ 11
5.4. AutoCAD Script .............................................................................................. 11
5.5. Hydrostatic ...................................................................................................... 11
5.6. Results ............................................................................................................. 14
5.7. Resistance ........................................................................................................ 18
6. CONCLUSIONS .................................................................................................. 21
REFERENCES ......................................................................................................... 24
i
DEDICATION
This work is dedicated to;
My Father Mr. Sadik GURBUZ
My Mother Mrs. Nese GURBUZ
My Sister Miss. Sanem GURBUZ
My Brother Mr. Kerem GURBUZ
ii
ACKNOWLEDGMENT
I would like to express my greatest appreciation and gratitude to my teacher Prof.
Kadir SARIOZ, who introduced me to programming and gave me the opportunity to
write first program of my career.
I also would like to thank and dedicate this thesis to my family for their love, support
and encouragements. Specially, I am deeply grateful to my parents, who regardless
of every adversity strove to give me better options for my life.
Sinan GURBUZ
May, 2015
iii
ABSTRACT
Ship design is an iterative process, which is difficult to find a solution in the first
attempt. Process follows a design spiral that converges to an optimum point as the
design progresses. Each cycle includes several calculations like weight distribution,
stability, resistance and powering etc.
In this thesis, tailor made software is developed for stability and resistance
calculations of monohull displacement ships. Program is written with MATLAB
language and a simple graphical user interface is created. After information about
installation and capabilities, usage of the program is given in detail. Finally, stability
calculation of a ship is added for benchmarking code performance against external
criteria.
Sinan GURBUZ
iv
LIST OF FIGURES
Figure 2.1. Flowchart ................................................................................................... 2
Figure 5.1. HydroLAB main menu .............................................................................. 5
Figure 5.2. Offset file format ....................................................................................... 6
Figure 5.3. Interpolation methods ................................................................................ 6
Figure 5.4. Slope of pchip method ............................................................................. 10
Figure 5.5. Comparison between cubic spline and pchip method.............................. 10
Figure 5.6. Types of views ......................................................................................... 12
Figure 5.7. Script file ................................................................................................. 13
Figure 5.8. Complete report ....................................................................................... 15
Figure 5.9. HydroCurve menu ................................................................................... 16
Figure 5.10. Hydrostatics graph ................................................................................. 17
Figure 5.11. Holtrop & Mennen menu ....................................................................... 20
v
LIST OF TABLES
Table 6.1. Fishing vessel offset............................................................................... 22
Table 6.2. Stability results (HydroLAB & Maxsurf).............................................. 23
vi
1. INTRODUCTION
The computer usage in shipbuilding industry was started in 1960’s. Because of the
high cost, they were only used by the largest shipbuilders for hull lines fairing,
hydrostatics, powering calculations etc. In the late 1970’s, computer cost
considerably less than the earlier ones and several commercial ship design and
construction software became available for them. Today, availability of Personal
Computers (PC) make software usage indispensable in all areas of shipbuilding
process [1].
The focus of this thesis is to develop an application that can be used for hydrostatic
and resistance calculations. An important aspect of the work is the development of a
graphical user interface (GUI) that makes the program user friendly.
The thesis contains six chapters including an introduction. In chapter two, an
overview of the program is provided with the algorithm. In chapter three, installation
procedure is given. Chapter four is about the capabilities of the program. In chapter
five, usage of HydroLAB is given in detail. In the last chapter, conclusions are made
and further work is discussed.
1
2. ABOUT HYDROLAB
HydroLAB is an analyses program that uses offset values to calculate upright
hydrostatics and resistance of ships. HydroLAB fulfills this objective by generating a
mesh structure of ships that uses its interpolated offset values. Flowchart of the
program is shown in Figure 2.1. Codes are given in the attachment.
Figure 2.1. Flowchart
HydroLAB User Input
Offset
Interpolation
Cubic Spline
Cubic Hermite Spline
Mesh
Resistance
AutoCAD Script
Hydrostatic
Result HydroCurve Excel
Result
Excel
Graph
2
3. INSTALLATION
HydroLAB is a standalone application that is compiled by using MATLAB R2013a.
In order to run the program on Windows, user must install the MATLAB Compiler
Runtime (MCR) before starting the HydroLAB.exe. MCR enables execution of
compiled MATLAB applications on computers that do not have MATLAB installed.
MCR version R2013a (8.1) 32-bit must be used and can be downloaded free of
charge from;
http://www.mathworks.com/supportfiles/MCR_Runtime/R2013a/MCR_R2013a_win
32_installer.exe
For more information about MCR, visit;
http://www.mathworks.com/products/compiler/mcr/
3
4. CAPABILITIES
HydroLAB has three main features;
Creates lines plan
Calculates upright hydrostatics
Calculates hull resistance
4.1. Generation of Lines Plan
HydroLAB creates AutoCAD script file to generate lines plan of ships. Script is a
text file with one command on each line. By means of this file, lines plan of ships
can easily be obtained without creating surface.
4.2. Calculation of Upright Hydrostatics
Upright hydrostatics at any waterline can be checked by HydroLAB. Furthermore,
this results can be saved as an excel file and several types of graphs can be drawn via
HydroCurve module.
4.3. Calculation of Hull Resistance
HyroLAB has a resistance module that calculates ship hull resistance by using the
regression-based method of Holtrop & Mennen. Resistance module can directly read
hull characteristics itself from offset file or it can be used by entering the
characteristic values of ship manually.
4
5. USING HYDROLAB
When the program is started, graphical user interface appears. The layout of main
menu is shown in Figure 5.1 below:
Figure 5.1. HydroLAB main menu
5.1. File
This section is used for importing offset file with .txt extension. This file must be
arranged with four column format. First three columns are respectively; longitudinal
position, half breadth and height of the point. Last column is used for naming
stations with numbers. (Please see the file format in Figure 5.2). Sample offset files
are also included in the program.
After importing offset file, some information appears on screen for verifying
correctness of the imported data.
5
Figure 5.2. Offset file format
5.2. Interpolation
Mesh structure of ship can be created by using two interpolation methods; cubic
spline or piecewise cubic hermite interpolating polynomial (Figure 5.3).
Figure 5.3. Interpolation methods
6
5.2.1. Cubic Spline
Assume { }1 2, mK x x x= ,..., is to be a set of given knots. Cubic spline for each
interval can be written as equation 5.1
3 2( ) ( ) ( ) ( )i i i i i i i is x a x x b x x c x x d= − + − + − + (5.1)
For m knot, m-1 interval and 4m-4 unknown; , , ,i i i ia b c d ( 1: 1)i m= − . We need
4m-4 conditions to find the coefficients;
1
1 1 1
1) ( ) , ( 1: 1) 12)3) ( ) ( )
i i i
m m
i i i i
s x y for i m m conditions y conditions x s x
−
+ + +
= = − − = 1 =
1 1 1
1 1 1
( 1: 2) 2
4) ( ) ( ) ( 1: 2) 2
5) ( ) ( ) ( 1: 2) 2i i i i
i i i i
for i m m condition
s x s x for i m m condition
s x s x for i m m condition+ + +
+ + +
= − −
′ ′ = = − −
′′ ′′ = = − −
These are 4m − 6 conditions, but we need two extra conditions. There are several
options for the final two equations;
Natural end conditions; assume the second derivative at the end knots are zero
(equation 5.2).
0 0( ) 0s x′′ = (5.2.a)
1 ( ) 0m ms x−′′ = (5.2.b)
Clamped end conditions; assume the first derivatives at the first and last knots are
known (equation 5.3).
0 0 0( )s x y′ ′= (5.3.a)
1 ( )m m ms x y−′ ′= (5.3.a)
7
“Not-a-knot” end conditions; force continuity of the third derivative at the second
and penultimate points (results in the first two intervals having the same spline
function and the last two intervals having the same spline function) (equation 5.4).
0 1 1 1( ) ( )s x s x′′′ ′′′= (5.4.a)
2 1 1 1( ) ( )m m m ms x s x− − − −′′′ ′′′= (5.4.a)
By default, Matlab therefore HydroLAB uses splines with a not-a-knot condition [2].
5.2.2. Piecewise Cubic Hermite Interpolating Polynomial (Pchip)
As with cubic splines, pchip uses cubic polynomials to connect data points with
continuous first derivatives. However, it differs from cubic splines in that the second
derivatives are not necessarily continuous. Further, the first derivatives at the knots
will not be the same as for cubic splines. Rather, they are expressly chosen so that
the interpolation is “shape preserving”. That is, the interpolated values do not tend to
overshoot the data points as can sometimes happen with cubic splines. The results of
using spline will generally appear smoother because the human eye can detect
discontinuities in the second derivative. In addition, it will be more accurate if the
data are values of a smooth function. On the other hand, pchip has no overshoots and
less oscillation if the data are not smooth [2].
The main idea of pchip is to specify the slopes so that so that the function values do
not overshoot the data values [3].
The length of the k. interval can be written as equation 5.5
1k k kl x x+= − (5.5)
The first divided difference is given in equation 5.6
8
1k kk
k
y yl
+ −∆ =
(5.6)
If k∆ and 1k−∆ have opposite signs or if either of them is zero, then kx is a discrete
local minimum or maximum. Then the slope at kx is zero ( 0)kα = . This situation is
illustrated in the left side of the Figure 5.4. The slopes on either side are opposite
signs, so that the dashed line has slope zero. The red line is piecewise cubic hermite
interpolating polynomial consist of two different cubic and their derivatives are both
zero at kx .
If k∆ and 1k−∆ have the same sign and the two interval have the same length, then
slope at kx is calculated as the average of the reciprocal slopes on either side
(equation 5.7). This is shown in the right side of the Figure 5.4.
1
1 1 1 12k k kα −
= + ∆ ∆
(5.7)
If k∆ and 1k−∆ have the same sign but the two interval have different length, then
slope at kx is calculated as a weighted harmonic mean (equation 5.8).
1 2 1 2
1k k k
w w w wα −
+= +
∆ ∆ (5.8)
Where w1 and w2 are weights and determined by equation 5.9.
1 12 k kw l k −= + (5.9.a)
2 12k kw l k −= + (5.9.b)
9
Figure 5.4. Slope of pchip method
A comparison between cubic spline and pchip method is given in Figure 5.5.
Figure 5.5. Comparison between cubic spline and pchip method
10
5.3. Lines Plan
This section is useful for checking imported data visually. Beside 2D views (body
plan, sheer plan and waterline plan), user can check the 3D view of mesh structure of
a ship by the 3D Hull option. Different types of views are displayed in Figure 5.6.
5.4. AutoCAD Script
A script is a list of commands which allows you to automate tasks that would take a
long time if you did them manually. After importing offset, lines plan script file
(compatible with AutoCAD) can be generated. 3D Mesh option also generates script
file that creates mesh grid of offset in 3D. Sample drawings can be seen in
Figure 5.7.
5.5. Hydrostatic
5.5.1. Precision
HydroLAB hydrostatic calculations use trapezium integration method on a specified
number of transverse sections in the offset file up to the depth of vessel. Transverse
sections are divided in vertical direction into small strips. The height of those strips
determines the accuracy of results. In most cases, medium precision is enough; but if
the ships cross section has irregular changes, precision should be increased.
5.5.2. Density
User can change the prespecified water density before calculation.
5.5.3. KG
If the value of the KG (ship's center of gravity above keel) is known, it can be
entered. Otherwise, the calculations proceed with default value zero.
11
12
Body Plan
Sheer Plan
Waterline Plan
3D Hull
Figure 5.6. Types of views
Lines Plan
3D Mesh
Figure 5.7. Script file
13
5.5.4. Calculate
After checking the above parameters, hydrostatic calculation can be started.
Computation time depends on precision.
5.6. Results
5.6.1 Select Draft(s)
When calculation is completed, user can select a draft or draft range. After selecting
draft(s), click on draft from list to examine the result.
5.6.2 Complete report
Selected results can be displayed in tabulated form for comparison purpose. Sample
output can be seen in Figure 5.8 below.
14
15
Figure 5.8. Complete report
5.6.3 HydroCurve
Graphical illustration is important because of the great volume of data created during
hydrostatic calculation. The HydroCurve module allows you to view the results
graphically. When the module starts, HydroCurve menu appears and it can be seen in
Figure 5.9.
Figure 5.9. HydroCurve menu
5.6.3.1 Hydrostatics
Hydrostatic values created during calculation can be visually checked from this
section. Sample hydrostatics graph can be seen in Figure 5.10.
16
17
Figure 5.10. Hydrostatics graph
5.6.3.2 Form
Form coefficients can be drawn by using this section. Range of graph can be
adjusted. “0-1” option plots all results in same scale in the range of 0-1. If “Auto”
option is selected, all coefficients are drawn in their own scales.
5.6.3.3 Sectional Areas
This part is used for drawing sectional areas curve at the selected draft.
5.6.3.4 Bonjean Curves
Bonjean curve data is calculated as a part of a hydrostatic calculation and can be
visualized from this section.
5.6.4 Excel
In addition to the graphical capabilities described above, selected results can be
exported into excel file.
5.7. Resistance
Resistance module implements the statistical ship power estimation method
presented by Holtrop and Mennen and Holtrop [4, 5]. Required input parameters are
automatically computed from offset, although the user can input or override the
values. When the module starts, Holtrop & Mennen menu appears and it can be seen
in Figure 5.11. The speed range on which the analysis is to be carried out is needed
to be set. At the right bottom of the menu, there is a speed section. User can choose
speed unit as “knot” or “m/s”. At the same time, initial and final speed can be
entered to define a range for analysis, as well as the user can enter number of
calculation point in this range from here. After all parameters are checked,
calculation can be started from analysis section. By using results button, calculation
results will be tabulated in the results window. Graph button can be used for
18
visualizing these tabulated results. Data created during analysis can be exported into
excel file via Excel button.
There is tooltips option at the left bottom. If this option is “on”, when the user hovers
the pointer over an abbreviation without clicking it, a small "hover box" with
information about the item appears.
19
20
Figure 5.11. Holtrop & Mennen menu
6. CONCLUSIONS
For a comparison purpose, stability calculation for a fishing vessel is done by using
HydroLAB and Maxsurf. Offset table of the vessel is given in Table 6.1. Stability
results for both program is given in Table 6.2 and can be seen to be in close
agreement with each other.
Currently, HydroLAB can only calculate the upright hydrostatics with zero trim
condition. An algorithm that calculates hydrostatics under trim condition can be
added. Large angle stability analysis will also extend the usage of the program.
The representation of the ship model via offset table sometimes can be restrictive.
Since this limitation can be overcome by providing more data (e.g. station and/or
waterline) with offset file, a geometry (Iges, Step, etc.) import function will be less
time consuming and will improve the quality of the results.
Table 6.1. Fishing vessel offset
WL 0.0 WL 0.1 WL 0.2 WL 0.3 WL 0.4 WL 0.6 WL 0.8 WL 1.0 WL 1.2 WL 1.4 WL 1.60.5 0.000 0.198 0.252 0.288 0.450 0.540 1.683 4.545 6.669 7.740 8.217
0.75 0.000 0.360 0.531 0.639 0.837 1.233 2.682 5.328 7.110 8.001 8.3971 0.000 0.540 0.828 1.053 1.287 1.998 3.600 5.967 7.515 8.235 8.559
1.5 0.000 1.017 1.557 2.025 2.448 3.654 5.328 7.074 8.109 8.559 8.7842 0.000 1.602 2.484 3.159 3.798 5.175 6.696 7.875 8.487 8.775 8.910
2.5 0.000 2.304 3.555 4.383 5.112 6.444 7.668 8.397 8.766 8.919 8.9823 0.000 3.132 4.581 5.508 6.246 7.407 8.271 8.739 8.928 8.991 9.0004 0.000 4.806 6.525 7.389 7.974 8.604 8.892 9.000 9.000 9.000 9.0005 0.000 5.922 7.677 8.370 8.730 8.982 9.000 9.000 9.000 9.000 9.0006 0.000 5.184 6.894 7.623 8.010 8.460 8.694 8.811 8.892 8.955 9.0007 0.000 3.258 4.491 5.283 5.859 6.642 7.218 7.686 8.100 8.442 8.730
7.5 0.000 2.331 3.366 4.068 4.680 5.499 6.120 6.750 7.335 7.839 8.3348 0.000 1.557 2.358 2.934 3.429 4.203 4.914 5.616 6.300 6.984 7.668
8.5 0.000 0.945 1.521 1.944 2.322 2.988 3.663 4.320 5.058 5.850 6.6789 0.000 0.441 0.801 1.107 1.368 1.845 2.358 2.934 3.609 4.374 5.247
9.25 0.000 0.225 0.486 0.720 0.936 1.314 1.728 2.232 2.862 3.537 4.410
STERN WL 0.0 WL 0.1 WL 0.2 WL 0.3 WL 0.4 WL 0.6 WL 0.8 WL 1.0 WL 1.2 WL 1.4 WL 1.6x 3.100 3.100 3.100 3.100 3.100 2.988 1.017 -1.519 -2.499 -2.889 -3.100y 0.000 0.000 0.000 0.000 0.000 0.000 0.000 2.250 5.220 6.750 7.200
BOW WL 0.0 WL 0.1 WL 0.2 WL 0.3 WL 0.4 WL 0.6 WL 0.8 WL 1.0 WL 1.2 WL 1.4 WL 1.6x 55.800 57.400 58.175 58.590 59.210 59.830 60.450 61.070 61.690 62.310 62.930y 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000
21
22
Table 6.2. Stability results (HydroLAB & Maxsurf)
Program Draft Amidship (m) 0.700 1.400 2.100 2.800 4.200 5.600 7.000 8.400 9.800 11.200HydroLAB Displacement (tons) 130.769 413.208 762.377 1155.221 2038.290 3036.312 4166.665 5442.601 6826.787 8282.556Maxsurf Displacement (tons) 116.000 392.900 740.200 1132.000 2013.000 3011.000 4140.000 5411.000 6781.000 8217.000
HydroLAB Length WL (m) 54.300 55.075 55.490 56.110 56.842 59.434 62.590 64.190 65.200 66.030Maxsurf Length WL (m) 54.300 55.075 55.490 56.110 56.842 59.433 62.589 64.189 65.199 66.029
HydroLAB Beam WL (m) 11.845 15.354 16.740 17.460 17.964 18.000 18.000 18.000 18.000 18.000Maxsurf Beam WL (m) 11.823 15.332 16.721 17.446 17.957 17.998 18.000 18.000 18.000 18.000
HydroLAB Max. cross sectional area (m^2) 4.764 14.485 25.780 37.783 62.667 87.852 113.055 138.257 163.460 188.642Maxsurf Max. cross sectional area (m^2) 4.138 13.642 24.861 36.819 61.601 86.769 111.968 137.168 162.368 187.550
HydroLAB LCB from aft extremity (m) 34.112 34.054 34.016 33.979 33.853 33.613 33.156 32.531 31.992 31.638Maxsurf LCB from aft extremity (m) 34.080 34.045 34.011 33.973 33.837 33.602 33.151 32.553 32.075 31.787
HydroLAB LCF from aft extremity (m) 34.073 33.996 33.945 33.860 33.496 32.694 31.104 30.024 29.837 30.182Maxsurf LCF from aft extremity (m) 34.088 34.007 33.954 33.870 33.507 32.717 31.120 30.192 30.190 30.670
HydroLAB Waterplane area (m^2) 323.585 448.758 519.572 572.970 654.904 737.127 841.555 932.533 992.582 1035.690Maxsurf Waterplane area (m^2) 323.413 448.538 519.383 572.812 654.882 736.983 841.410 927.848 981.731 1020.258
HydroLAB Wetted surface area (m^2) 339.322 492.601 601.158 700.166 887.035 1101.873 1356.662 1595.636 1812.530 2023.399Maxsurf Wetted surface area (m^2) 339.584 490.040 597.383 693.873 877.396 1061.571 1280.874 1494.276 1691.638 1886.258
HydroLAB KB (m) 0.455 0.874 1.279 1.679 2.475 3.277 4.101 4.948 5.792 6.620Maxsurf KB (m) 0.467 0.891 1.298 1.699 2.494 3.296 4.120 4.963 5.800 6.622
HydroLAB BMt (m) 16.993 12.898 9.902 8.073 5.943 4.850 4.236 3.817 3.421 3.054Maxsurf BMt (m) 18.421 13.145 9.952 8.080 5.942 4.851 4.236 3.814 3.409 3.029
23
Table 6.2 (Continue). Stability results (HydroLAB & Maxsurf)
Program Draft Amidship (m) 0.700 1.400 2.100 2.800 4.200 5.600 7.000 8.400 9.800 11.200HydroLAB BML (m) 292.984 138.803 92.927 71.929 51.951 45.212 46.033 45.253 41.652 37.794Maxsurf BML (m) 329.354 145.277 95.139 72.909 52.240 45.279 46.206 44.649 40.437 36.404
HydroLAB GMt (m) 14.448 10.772 8.182 6.753 5.419 5.127 5.337 5.765 6.213 6.675Maxsurf GMt (m) 15.888 11.036 8.250 6.779 5.436 5.147 5.355 5.777 6.209 6.651
HydroLAB GML (m) 290.439 136.678 91.206 70.609 51.426 45.489 47.134 47.202 44.444 41.414Maxsurf GML (m) 326.821 143.169 93.437 71.608 51.733 45.575 47.325 46.612 43.238 40.026
HydroLAB TPC (t/cm) 3.317 4.600 5.326 5.873 6.713 7.556 8.626 9.558 10.174 10.616Maxsurf TPC (t/cm) 3.315 4.598 5.324 5.871 6.713 7.554 8.624 9.510 10.063 10.458
HydroLAB MCTC (t.m) 6.995 10.254 12.531 14.537 18.441 23.239 31.378 40.022 46.536 51.948Maxsurf MCTC (t.m) 6.057 8.987 11.050 12.953 16.643 21.923 31.304 40.295 46.843 52.545
HydroLAB CB 0.283 0.340 0.381 0.411 0.464 0.494 0.515 0.547 0.579 0.607Maxsurf CB 0.252 0.324 0.371 0.403 0.458 0.490 0.512 0.544 0.575 0.602
HydroLAB CM 0.575 0.674 0.733 0.773 0.831 0.871 0.897 0.914 0.927 0.936Maxsurf CM 0.500 0.636 0.708 0.754 0.817 0.861 0.889 0.907 0.920 0.930
HydroLAB CWP 0.503 0.531 0.559 0.585 0.641 0.689 0.747 0.807 0.846 0.871Maxsurf CWP 0.504 0.531 0.560 0.585 0.642 0.689 0.747 0.803 0.837 0.858
HydroLAB CP 0.493 0.505 0.520 0.532 0.558 0.567 0.574 0.598 0.625 0.649Maxsurf CP 0.504 0.510 0.523 0.535 0.561 0.570 0.576 0.600 0.625 0.647
REFERENCES
[1] Eyres, D.J., 2007. Ship Construction, 6th ed., Elsevier Ltd, Burlington.
[2] Chapra, S.C., 2012. Applied Numerical Methods with MATLAB for Engineers
and Scientists, 3th ed., McGraw-Hill, New York.
[3] Moler, C., 2004. Numerical Computing with Matlab, SIAM, Philadelphia.
[4] Holtrop, J. and G.G.J. Mennen., 1982. An Approximate Power Prediction
Method, International Shipbuilding Progress, Vol. 29, No. 335.
[5] Holtrop J., 1984. A Statistical Re-analysis of Resistance and Propulsion Data,
International Shipbuilding Progress, Vol. 31, No. 363.
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