### [4S/yim243] The Management of Merchant Ship : Stability, Trim and Strength

Sebagai pedoman dalam memahami teori, peraturan dan perhitungan yang harus dilakukan untuk memastikan bahwa kapal masih laiklaut dalam hal stabilitas dan trim dengan tetap memperhatikan batasan kekuatannya.

SUMMARY OF CHAPTER CONTENTS

1) An Introduction to the shape of a ship's,hullform and the principles of hydrostatics that act upon it.

Basic requirements of a good hullform.

Definitions of hull measurements and features.

The linesplan and table of offsets.

Calculations for waterplane areas and submerged volume.

The basic principles of buoyancy and floatation.

Definitions of TPC and FWA.

An introduction to the principle of moments with regard to the force of Weight, acting through the ship's Centre of Gravity, and Buoyancy acting through the immersed hull's Centre of Buoyancy.

Definitions of a ship's motion in a seaway and the basic features of seawaves.

2) Locating the Centre of Buoyancy for different angles of heel.

Introduction to changes of a hull's underwater shape with changing angle of heel.

The shift in the Centre of Buoyancy off the centreline towards the low side of the ship and how this can produce a Righting Moment, providing that the C of B is outboard of the Centre of Gravity.

The Righting Lever GZ defined.

The Metacentre 'M' defined as the point at which the C of B rotates about during a small change in heel angle.

The upright GM value is introduced as a measure of stability.

The effects of hull beam and draft on the upright BM value and the changes in both the Metacentre's position and BM value with increasing angles of heel.

The Wall-sided equation is explained and the Trapezium rules are used to show how the Centre Buoyancy can he located at different angles of heel by applying the principles of moments to areas and volumes derived from the tables of offsets.

KN Curves are defined as the means of expressing the shift of 'B'.

3) Transverse stability characteristics and the GZ Curve.

Stable, neutral and unstable conditions are defined in terms of the Centre of Buoyancy 'B', the Centre of Gravity 'G'and the Metacentre 'M'.

The GZ curve is used to illustrate how a vessel's transverse stability changes with increasing angles of heel

The effects of a hull's beam, freeboard, draft, fineness of lines and sheer upon the GZ curve are discussed.

The six basic criteria of seaworthiness, which must be met by a ship's GZ curve, are defined with an alternative set of criteria for High Forecastle vessels.

4) Operational transverse stability.

The inclining experiment is explained as the means bv which the Lightship KG value is measured.

The loaded KG calculation is described by applying the Principle of Moments the known loaded weight distribution.

The Free Surface Effect of partly filled tanks and its importance in stability calculation is explained.

The process of drawing an actual GZ curve from the supplied KN curves and the calculated fluid KG value is described.

Use of simplified data diagrams.

Calculating the heeling moment and the list when 'G' is not on the centreline.

Calculation the increase in draft due to a list.

The effective centre of gravity of suspended loads and the stability calculations involved i loading a heavy lift.

Heeling effect due to a ship turning under the action of the rudder.

The unstable upright condition and the Roll angle are defined and the procedures for regaining stability are outlined.

A study into an incident of lost stability in the case of a ship loaded with timber.

5) Stability requirements for ships operating under special circumstances.

Passenger vessels

Ship's carrying deck timber cargo.

Ships solid bulk cargo including grain.

Ships operating heavy lifts at sea.

Windage allowance for ships carrying high deck stows of containers and ships operating in high latitudes where ice build up is a danger

6) Longitudinal stability and practical trim calculations.

Longitudinal Centre of Buoyancy (LCB) and Longitudinal Metacentre. Longitudinal righting moments.

The trim axis and centre of floatation (LCF), location (LCF) for a given draft, shift in the LCB due to change of draft, estimating the longitudinal BM value for a vessel, the moment required to change trim by lcm (MCTC).

Taking moments of weights about the aft perpendicular (AP) to predict a ship's fore and aft drafts.

Average and mean drafts defined.

The change of trim due a fore and aft shift of weight.

The change of trim when moving from salt to fresh water

Trim and stability calculations during drydocking.

Beaching and stranding.

7) A ship's motion in a seawav and anti-roll measures.

The Simple harmonic nature of a ship's natural roll period.

Determining a ship's radius of gyration.

Estimating the natural roll period in terms of ship's beam and GM values.

Synchronized rolling.

The effect of bilge keels.

The action of flume tanks.

Managing a ship in heavy weather to minimize rolling.

Torsional and wracking stresses induced by rolling.

Active anti-rolling devices, gyroscopic controlled stabilisers.

The pitching characteristics of a ship.

The natural pitching period of a ship.

The pitching characteristics of a ship in a seaway.

The problems of exceptional head seas.

Pitch induced or parametric rolling.

8) Shear forces, bending moments and longitudinal strength.

The elastic properties of shipbuilding materials.

Shear,forces and bending moments defined.

Longitudinal bending in a ship's hull, hogging and sagging.

Bending moment calculations for a box shaped hull in various loaded conditions.

The weight distribution of a ship.

The still water buoyancy distribution of a ship shaped hull.

Changes of buoyancy distribution in a seawav.

Bonjean curves and Muckle's method for buoyancy distribution calculations.

Bending stresses defined.

Moments of inertia for different girder sections.

Stress calculations for a ship's midships section.

Stress distribution within a ship's structure.

Composite hulls

Cracking

Some brief notes on ship building methods

9) The consequences of flooding through bilging.

The term 'bilging' and its effect upon a ship's draft, trim and stability explained.

The lost buoyancy approach to bilging calculations is compared to the 'added weight' method.

Stability and trim calculations by the lost buoyancy method explained by examples of bilging different compartments in a box-shaped hull.

Permeabilitiy of partially loadd spaces defined.

Predicting the of bilging different compartements in a real ship.

The consequences of bilging a real ship and the need for cross flooding examined.

Comparison made between the sinking of the 'Titanic' and 'Andrea Doria'.

10)The 'SOLAS' subdivision and damage stability requirements for passenger ships and cargo vessels and the 'MARPOL' tanker subdivision regulations.

These rules are explained and examined with regard to their effects upon a ship's damage stability

11)The International Load Line regulations for merchant ships.

An outline to the background and aims of the load line regulations.

Terms used in the regulations defined.

Loadline markings described.

Conditions of freeboard assignment explained.

Tabulated and corrected freeboard explained.

Seasonal and regional load lines explained.

Compliance with the regulations explained.

# Title : The Management of Merchant Ship : Stability, Trim and Strength

# Author : Clark, I C

The Nautical Institute, 2002

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