Ships

Notes on Design, Construction, Displacement, and Repair

For use with the Pilots’ Almanac™

By James S. Watson

Displacement:

Ship displacement can be calculated in two ways. The first method, which is commonly used to calculate the displacement of merchant ships, is to calculate the cubic volume of the ship with one hundred cubic feet of volume equaling one ton of displacement. This is the method used in the Pilots’ Almanac™. The second method of calculating the displacement of a ship is to use what is called naval displacement. This is the method used to calculating the displacement of war ships. In this method the displacement is calculated by using the weight of the number of cubic feet of water, which the ship displaces. For example: an eighty-four foot Karune displaces three hundred seventy-eight (378) tons according to the table in the Pilots’ Almanac™.[1] This table gives the gross burden[2] for carrying cargo. This ship displaces 22,680 cubic feet of water. This figure is obtained by multiplying the length times the beam times the draft. The naval displacement of the Karune works out to be about 708 tons. This figure is the total weight of the Karune and everything on it when it is loaded to a draft of nine feet.