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Example Formula. The primary formula used to calculate the displacement of a ship is based on its physical dimensions and block coefficient. The block coefficient is a dimensionless number that describes how closely the shape of a ship resembles a rectangular block. Displacement = Length × Breadth × Draft × Block Coefficient. Where:
The displacement or displacement tonnage of a ship is its weight. As the term indicates, it is measured indirectly, using Archimedes' principle, by first calculating the volume of water displaced by the ship, then converting that value into weight.
HULL FORM AND GEOMETRY. Be familiar with ship classifications. Explain the difference between aerostatic, hydrostatic, and hydrodynamic support. Be familiar with the following types of marine vehicles: displacement ships, catamarans, planing vessels, hydrofoil, hovercraft, SWATH, and submarines.
The Sail Area/Displacement Ratio. SA/D = SA/D 0.67. Where SA is sail area in square feet, and D is displacement in cubic feet.
DISPLACEMENT: Literally taken, displacement refers to the cubic feet or cubic meters of water that are "displaced" when the vessel floats. For a given weight, the amount of water that is displaced in order to float the vessel will vary according to the salinity or density of the water.
By Archimedes' principle, displacement mass is equal to displacement volume multiplied by the density of the water (nominally 1000 kg/m 3 or 62.4 lb/ft 3 for fresh water, 1025 kg/m 3 or 64 lb/ft 3 for seawater). This is the figure that should be used for all performance ratios and comparisons.
There are several interpretations of displacement in ships and boats. Displacement speed is a general guideline for non-planning boats to determine their theoretical maximum speed. Displacement hull: a moving hull whose weight is supported by buoyancy alone and which must displace water from its course.
