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These marks allow a ship's displacement to be determined to an accuracy of 0.5%. [3] The draft observed at each set of marks is averaged to find a mean draft. The ship's hydrostatic tables show the corresponding volume displaced. [4] To calculate the weight of the displaced water, it is necessary to know its density.
Hull speed or displacement speed is the speed at which the wavelength of a vessel's bow wave is equal to the waterline length of the vessel. As boat speed increases from rest, the wavelength of the bow wave increases, and usually its crest-to-trough dimension (height) increases as well. When hull speed is exceeded, a vessel in displacement mode ...
Used mainly to determine the minimum water depth for safe passage of a vessel and to calculate the vessel's displacement (obtained from ship's stability tables) so as to determine the mass of cargo on board. Draft, Air – Air Draft/Draught is the distance from the water line to the highest point on a ship (including antennas) while it is ...
Simpson's rules are used to calculate the volume of lifeboats, [6] and by surveyors to calculate the volume of sludge in a ship's oil tanks. For instance, in the latter, Simpson's 3rd rule is used to find the volume between two co-ordinates. To calculate the entire area / volume, Simpson's first rule is used. [7]
The displacement–length ratio (DLR or D/L ratio) is a calculation used to express how heavy a boat is relative to its waterline length. [1] DLR was first published in Taylor, David W. (1910). The Speed and Power of Ships: A Manual of Marine Propulsion. John Wiley & Sons. p. 99. [2]
The sail area-displacement ratio (SA/D) is a calculation used to express how much sail a boat carries relative to its weight. [1]/ = [() /] = () In the first equation, the denominator in pounds is divided by 64 to convert it to cubic feet (because 1 cubic foot of salt water weights 64 pounds).
In particular, any "displacement" or non-planing boat requires much greater power to accelerate beyond its hull speed, which is determined by the length of the waterline, and can be calculated using the formula: Vmax (in knots) = square root of LWL (in feet) x 1.34. The hull speed is the speed at which the wavelength of the bow wave stretches ...
Deadweight tonnage is a measure of a vessel's weight carrying capacity, not including the empty weight of the ship. It is distinct from the displacement (weight of water displaced), which includes the ship's own weight, or the volumetric measures of gross tonnage or net tonnage (and the legacy measures gross register tonnage and net register tonnage).