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Understanding and calculating marine displacement is essential for the design and operation of ships. This tutorial delves into the formulas and calculations associated with marine displacement, focusing on length, breadth, draft, and block coefficient.
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.
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.
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.
The prismatic coefficient is the ratio of actual underbody volume to the volume of a prism having a length equal to the DWL, and a section equal to the boat's maximum sectional area. The prismatic coefficient provides an indication of the distribution of displacement.
19 lut 2024 · The waterplane coefficient (Cw) is calculated by dividing the area of the waterplane by the area of a rectangle with the same length and breadth as the ship’s waterplane but with a constant depth equal to the ship’s draft. Cw = Area of water-plane. L * B. Area of water-plane = L * B * Cw.
17 paź 2012 · The traditional calculation for SA/D compares sail area in square feet to displacement in cubic feet. In the formula, displacement in pounds is divided by 64 (the density of seawater) to obtain cubic feet, which are in turn converted to square feet to make the ratio unit-free.
