Ship Stability OOW

Author: Rhodes, Martin

Published: August 2009

Ship Stability OOW covers the syllabus requirements forming the underpinning ship stability knowledge required for certification to STCW 95 Officer of the Watch (OOW) level.

Many students worry that they do not have the mathematical ability for ship stability calculations. This publication addresses this problem by covering the subject in the simplest way possible at a level appropriate for a learner studying either independently or at college. Worked examples and self-assessment questions are provided throughout with tutorial questions at the end of each section.

CONTENTS:

SECTION 1 INTRODUCTION

SECTION 2 BASIC PRINCIPLES

2.1 Density, Mass and Volume
2.2 The Laws of Flotation
2.3 Simple box-shaped vessel calculations
Tutorial Questions

SECTION 3 FORM COEFFICIENTS

3.1 Coefficient of fineness of the water-plane area (Cw)
3.2 Block Coefficient (Cb)
3.3 Midships Coefficient (Cm)
3.4 Longitudinal Prismatic Coefficient (Cp)
Tutorial Questions

SECTION 4 TONNES PER CENTIMETRE IMMERSION

4.1 TPC Formula
4.2 Factors affecting TPC
4.3 Interpolation of hydrostatic data
4.4 Load/Discharge problems
Tutorial Questions


SECTION 5 LOAD LINES

5.1 Factors for consideration in assigning a freeboard
5.2 Type A and Type B ships
5.3 Load Line dimensions
5.4 Fresh Water Allowance (FWA)
5.5 Dock Water Allowance (DWA)
5.6 Load Line Calculations
Tutorial Questions


SECTION 6 CENTRE OF GRAVITY (G) AND CENTRE OF BUOYANCY (B)

6.1 Centre of Gravity
6.2 Effect of shifting a weight already onboard
6.3 Effect of loading a weight
6.4 Effect of discharging a weight
6.5 Multiple weight problems
6.6 Centre of buoyancy (B)
Tutorial Questions


SECTION 7 TRANSVERSE STATICAL STABILITY

7.1 Transverse Statical Stability
7.2 Righting Lever (GZ)
7.3 Moment of statical stability (Righting Moment)
7.4 Initial Transverse Metacentre
7.5 Metacentric Height (GM)
7.6 Calculating the Righting Moment at small angles of heel tutorial questions


SECTION 8 CONDITIONS OF STABILITY

8.1 Stable Condition
8.2 Neutral Condition
8.3 Unstable condition and angle of loll
Tutorial Questions


SECTION 9 INTIAL TRANSVERSE METACENTRE

9.1 Initial Transverse metacentre explained
9.2 Calculating KM for a box shaped vessel
9.3 Use of the metacentre diagram
9.4 To determine the final KG required completing loading with a required GM
9.5 Factors affecting KM
Tutorial Questions


SECTION 10 FREE SURFACE EFFECT

10.1 Free surface effect and transverse statical stability
10.2 To calculate the effect of free surface in a rectangular-shaped tank
10.3 Free surface moments
10.4 Representation of free surface data in ships tank sounding / ullage tables.
10.5 Factors influencing free surface effect
Tutorial Questions


SECTION 11 CURVES OF STATICAL STABILITY (GZ CURVES)

11.1 Calculating GZ Values
11.2 Procedure for constructing a curve of statical stability
11.3 Information available from a curve of statical stability
11.4 Curves of statical stability for stiff and tender ships
Tutorial Questions


SECTION 12 LIST

12.1 Calculating list caused by transverse shift of weight the basic list triangle
12.2 Calculating list caused by transverse and vertical shift of weight ship initially upright
12.3 Calculating the list due to a single weight being loaded or discharged
12.4 Shifting a weight already onboard to bring a listed ship upright
12.5 Multiple weight problems ship initially upright
12.6 Multiple weight problems ship initially listed
12.7 Loading weight about the centreline to complete upright
12.8 List and free surface effect
Tutorial Questions


SECTION 13 CURVES OF STATICAL STABILITY FOR VARYING CONDITIONS OF STABILITY

13.1 Curves of statical stability for a ship in a stable condition
13.2 Curve of statical stability for a ship in a neutral condition of stability
13.3 Curve of statical stability for a ship in a unstable condition
13.4 Curve of statical stability for a ship that is listed
13.5 Correcting an angle of loll
Tutorial Questions


SECTION 14 SUSPENDED WEIGHTS

41.1 Effect on KG lifting a weight using ships gear
14.2 Loading a weight using ships lifting gear
14.3 To calculate the maximum permissible KG required prior to loading or discharging a weight to ensure that a certain list limit is not exceeded
Tutorial Questions


SECTION 15 INTRODUCTION TO TRIM

15.1 Terms relating to ship length
15.2 Draught marks and reading the draught
15.3 Trim
15.4 Change of Trim
15.5 Moment to change trim by one centimetre (MCTC)
15.6 Formula for calculating MCTC
15.7 Longitudinal centre of floatation (LCF or F)
15.8 Calculating the final draughts when a weight is shifted
15.9 The effect of loading and discharging weights
15.10 Multiple weight problems
15.11 Weight to shift to reduce the trim by a specific amount
15.12 Weight to load to bring a ship to an even keel
15.13Weight to transfer to reduce the deepest draught by a specific amount
Tutorial Questions

SECTION 16 TRIM USING HYDROSTATIC DATA

16.1 True mean draught displacement when out of trim
16.2 Calculating the true mean draught
16.3 Trim calculations using hydrostatic data
16.4 Trim by consideration of the relative positions of the LCB and LCG
Tutorial Questions

SECTION 17 INCLINING EXPERIMENT

17.1 Calculating the KG as inclined
17.2 Calculating the lightship KG and displacement
17.3 Precautions to prior to conducting the experiment
17.4 Precautions to ensure accuracy of the calculation
Tutorial Questions

SECTION 18 ASSESING COMPLIANCE OF A SHIPS LOADED CONDITION WITH IMO CRITERIA

18.1 Simpsons First Rule
18.2 Simpsons second Rule
18.3 Intact stability the relevance of area under the curve of statical stability
Tutorial Questions

SECTION 19 PRACTICAL SHIP LOADING PROBLEMS

19.1 Introduction to loading sheet data
19.2 Practical Ship load problem
Tutorial Questions

Publication date: 15 Sep 2011
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