Ship Stability for Masters and Mates, Sixth edition – Consolidated 2006

# Chapter 9: Form Coefficients

## The Coefficient of Fineness of the Water-Plane Area (C w)

The coefficient of fineness of the water-plane area is the ratio of the area of the water-plane to the area of a rectangle having the same length and maximum breadth.

In Figure 9.1 the area of the ship s water-plane is shown shaded and ABCD is a rectangle having the same length and maximum breadth:

Fig. 9.1
Example 1

Find the area of the water-plane of a ship 36 metres long, 6 metres beam, which has a coefficient of fineness of 0.8.

Ans. Area of water-plane = 173sq.m

Example 2

A ship 128 metres long has a maximum beam of 20 metres at the waterline, and coefficient of fineness of 0.85. Calculate the TPC at this draft.

Ans. TPC SW = 22.3 tonnes

## The Block Coefficient of Fineness of Displacement (C b)

The block coefficient of a ship at any particular draft is the ratio of the volume of displacement at that draft to the volume of a rectangular block having the same overall length, breadth and depth.

In Figure 9.2 the shaded portion represents the volume of the ship s displacement at the draft concerned, enclosed in a rectangular block having the same overall length, breadth and depth.

Fig. 9.2

## Ship s Lifeboats

The cubic capacity of a lifeboat should be determined by Simpson s rules or by any other method giving the same degree of accuracy. The accepted C b for a ship s lifeboat constructed of wooden...