Ship Stability for Masters and Mates (eBook)

Cover 1
Contents 6
Acknowledgements 10
Preface 12
Note 12
Introduction 14
Changes to the Sixth edition 14
Part 1 Linking Ship Stability and Ship Motions 16
1 Forces and moments 18
Forces 18
Moments of forces 22
Mass 23
Moments of mass 24
2 Centroids and the centre of gravity 26
Effect of removing or discharging mass 27
Application to ships 28
Effect of adding or loading mass 29
Application to ships 30
Effect of shifting weights 30
Effect of suspended weights 31
Conclusions 31
3 Density and specific gravity 36
4 Laws of flotation 39
The variable immersion hydrometer 41
Tonnes per centimetre immersion (TPC) 43
TPC in dock water 43
Reserve buoyancy 44
Homogeneous logs of rectangular section 46
Conclusion 47
5 Group weights, water draft, air draft and density 49
Group weights in a ship 49
Effect of change of density when the displacement is constant 50
The effect on box-shaped vessels 50
The effect on ship-shaped vessels 52
Effect of density on displacement when the draft is constant 55
6 Transverse statical stability 59
Recapitulation 59
Definitions 59
The metacentre 59
Equilibrium 61
Stable equilibrium 61
Unstable equilibrium 62
Neutral equilibrium 62
Correcting unstable and neutral equilibrium 63
Stiff and tender ships 63
Negative GM and angle of loll 64
The GM value 65
7 Effect of free surface of liquids on stability 66
Correcting an angle of loll 67
8 TPC and displacement curves 71
Recapitulation 71
TPC curves 71
Displacement curves 73
9 Form coefficients 77
The coefficient of fineness of the water-plane area (C[sub(w)]) 77
The block coefficient of fineness of displacement (C[sub(b)]) 78
Ship’s lifeboats 79
The midships coefficient (C[sub(m)]) 80
The prismatic coefficient (C[sub(p)]) 80
Note 81
10 Simpson's Rules for areas and centroids 84
Areas and volumes 84
Simpson’s First Rule 84
Summary 85
Simpson’s Second Rule 86
Summary 87
Simpson’s Third Rule 87
Summary 88
Areas of water-planes and similar figures using extensions of Simpson’s Rules 88
Using Simpson’s First Rule 88
Using the extension of Simpson’s Second Rule 90
The Five/Eight Rule (Simpson’s Third Rule) 92
Volumes of ship shapes and similar figures 93
Appendages and intermediate ordinates 95
Appendages 95
Subdivided common intervals 96
Areas and volumes having an awkward number of ordinates 99
Centroids and centres of gravity 101
To find the centre of flotation 101
To find the KB 104
Summary 107
11 Second moments of area – moments of inertia 109
The theorem of parallel axes 111
Summary 116
12 Calculating KB, BM and metacentric diagrams 118
To find KB 118
To find transverse BM 121
Metacentric diagrams 126
13 Final KG plus twenty reasons for a rise in G 133
Twenty reasons for a rise in G 136
14 Angle of list 139
Summary 146
15 Moments of statical stability 149
The moment of statical stability at a small angle of heel 150
The moment of statical stability at a large angle of heel 151
16 Trim or longitudinal stability 158
The moment to change trim one centimetre (denoted by MCT 1 cm or MCTC) 161
To find the change of draft forward and aft due to change of trim 163
The effect of shifting weights already on board 165
The effect of loading and/or discharging weights 166
Using trim to find the position of the centre of flotation 173
Loading a weight to keep the after draft constant 174
Loading a weight to produce a required draft 176
Using change of trim to find the longitudinal metacentric height (GM[sub(L)]) 178
Which way will the ship trim? 181
Observations 181
Summary 181
17 Stability and hydrostatic curves 187
Cross curves of stability 187
GZ cross curves of stability 187
KN cross curves of stability 191
Statical stability curves 191
Hydrostatic curves 196
Using the hydrostatic curves 198
18 Increase in draft due to list 204
Box-shaped vessels 204
Vessels having a rise of floor 207
19 Water pressure 209
Pressure at any depth 209
20 Combined list and trim 213
21 Calculating the effect of free surface of liquids (FSE) 217
22 Bilging and permeability 228
Bilging amidships compartments 228
Permeability, & #956
Bilging end compartments 234
Effect of bilging on stability 238
Summary 240
23 Dynamical stability 242
24 Effect of beam and freeboard on stability 248
The effect of increasing the beam 248
The effect of increasing the freeboard 249
Summary 250
25 Effects of side winds on stability 251
26 Icing allowances plus effects on trim and stability 254
27 Type A, Type B and Type (B-60) vessels plus FL and PL curves (as governed by DfT regulations) 258
Definitions 258
Summary of procedure steps 262
28 Load lines and freeboard marks 263
The link 263
Historical note 263
Definitions 263
Freeboards of oil tankers and general cargo ships 264
Tabulated freeboard values 264
The procedure 264
The corrections in detail 267
Depth correction 267
C[sub(b)] correction 268
Bow height correction 268
Superstructure correction 268
Sheer correction 271
Strength correction 272
Summary statement 272
The Freeboard Marks 272
29 Timber ship freeboard marks 276
30 IMO Grain Rules for the safe carriage of grain in bulk 281
31 Angle of loll 291
To calculate the angle of loll 293
Angle of list 295
Angle of loll 295
32 True mean draft 296
Rule 298
Effect of hog and sag on draft amidships 298
33 The inclining experiment plus fluctuations in a ship's lightweight 301
Summary 304
Fluctuations in a ship’s lightweight over a period of time 305
34 The calibration book plus soundings and ullages 308
Methods for reading soundings and ullages 308
Adjustments for angle of heel and trim 313
Adjustments for temperature 314
35 Drydocking and grounding 316
The virtual loss of GM after taking the blocks overall 323
Note to students 324
36 Liquid pressure and thrust plus centres of pressure 327
Pressure in liquids 327
Total thrust and resultant thrust 327
To find the resultant thrust 327
The centre of pressure 328
Centres of pressure by Simpson’s Rules 331
Using horizontal ordinates 331
Using vertical ordinates 333
Summary 337
37 Ship squat in open water and in confined channels 339
What exactly is ship squat? 339
Recent ship groundings 340
What are the factors governing ship squat? 341
Ship squat for ships with static trim 346
Worked example – ship squat for a supertanker 347
Ship squat in wide and narrow rivers 348
Procedure for using Figure 37.6 349
Calculation of maximum squat 349
38 Interaction, including two case studies 352
What exactly is interaction? 352
Ship to ground (squat) interaction 353
Ship to ship interaction 356
Methods for reducing the effects of interaction in Cases 1 to 5 358
Ship to shore interaction 358
Summary 360
39 Heel due to turning 368
40 Rolling, pitching and heaving motions 371
Pitching motions 377
Heaving motions 378
41 Synchronous rolling and parametric rolling of ships 381
Synchronous rolling of ships 381
Parametric rolling of ships 382
42 List due to bilging side compartments 384
Summary 388
43 Effect of change of density on draft and trim 390
44 List with zero metacentric height 394
45 The deadweight scale 397
46 The Trim and Stability book 400
Summary 402
47 Simplified stability information 403
Maximum Permissible Deadweight Moment Diagram 404
Departure condition 407
Arrival Condition 407
48 The stability pro-forma 409
Nomenclature of ship terms 418
Photographs of merchant ships 424
Ships of this millennium 427
Part 2 Linking Ship Stability and Ship Strength 430
49 Bending of beams 432
Beam theory 432
Stresses 432
Tensile and compressive stresses 432
Shearing stresses 433
Complementary stress 434
Bending moments in beams 437
Shear force and bending moment diagrams 437
Case I 437
Case II 439
Freely supported beams 440
Case I 440
Case II 442
50 Bending of ships 446
Longitudinal stresses in still water 446
Longitudinal stresses in waves 447
Weight, buoyancy and load diagrams 449
The weight diagram 450
Bonjean curves 450
51 Strength curves for ships 452
Buoyancy curves 452
Load curves 453
Shear forces and bending moments of ships 453
Murray’s method 456
The Still Water Bending Moment (SWBM) 456
The Wave Bending Moment (WBM) 459
52 Bending and shear stresses 462
Bending stresses 462
Shearing stresses 468
Bending stresses in the hull girder 475
Summary 476
Part 3 Endnotes 480
53 Draft Surveys 482
Summary 483
54 Quality control plus the work of ship surveyors 485
55 Extracts from the 1998 Merchant Shipping (Load Line) Regulations Reference Number MSN 1752 (M) 488
56 Keeping up to date 495
Part 4 Appendices 498
I Summary of stability formulae 500
Form coefficients 500
Drafts 500
Trim 501
Simpson’s rules 501
KB and BM 502
Transverse stability 502
Longitudinal stability 502
Transverse statical stability 503
Effect of free surface 504
Drydocking and grounding 504
Pressure of liquids 504
Bilging and permeability 505
Strength of ships 505
Freeboard marks 505
Ship squat 505
Miscellaneous 506
Permeability (& #956
Drafts and trim considerations 507
Note 508
Summary 511
II SQA/MCA 2004 syllabuses for masters and mates 512
(a) Chief mate unlimited stability and structure syllabus 512
(b) 00W unlimited stability and operations syllabus 517
III Specimen exam questions with marking scheme 520
Recent Examination questions for Ship Stability @ 032-72 level: (a) STCW 95 Chief Mate/Master Reg.11/2 (unlimited) 520
General Ship Knowledge @ 035–22 level: (b) STCW 95 Officer in Charge of Navigational Watch < 500 gt Reg.11/3 (Near Coastal)
IV 100 Revision one-liners 531
V How to pass exams in maritime studies 535
Before your examination 535
In your examination 536
After the examination 536
References 537
Answers to exercises 539
Index 546