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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 ...
A velocity prediction program (VPP) is a computer program which solves for the performance of a sailing yacht in various wind conditions by balancing hull and sail forces. VPPs are used by yacht designers, boat builders, model testers, sailors, sailmakers, also America's Cup teams, to predict the performance of a sailboat before it has been built or prior to major modifications.
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 ...
A polar diagram, or polar plot, is a graph that shows a sailboat's potential speed over a range of wind speeds and relative wind angles. [1] It normally consists of the right side of a line chart with the radius representing the yacht speed and the angle representing the wind direction blowing from top to bottom. Several lines are normally ...
For the International rule, the rating number is approximately equal to the sailing length of the hull. These boats have long overhangs which allow the waterline length to increase as the boat heels over. A displacement hull's maximum speed (the hull speed) is directly proportional to the square root of its waterline length. [2] The first ...
This nomenclature dates back to the days of sail, when sailors attached a piece of lumber (a "log" of wood) to a rope knotted at regular intervals off the stern of a ship. Sailors counted the number of knots that passed through their hands in a given time to determine the ship's speed. Today, sailors and aircraft pilots still express speed in ...
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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]