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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 ...
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]
Velocity made good, or VMG, is a term used in sailing, especially in yacht racing, indicating the speed of a sailboat towards (or from) the direction of the wind. [1] [2] The concept is useful because a sailboat cannot sail directly upwind, and thus often can not, or should not, sail directly to a mark to reach it as quickly as possible.
Sailing hydrofoils achieve boat speeds up to twice the speed of the wind, as did the AC72 catamarans used for the 2013 America's Cup. [20] Ice boats can sail up to five times the speed of the wind. [21] [22] Lateral force is a reaction supplied by the underwater shape of a sailboat, the blades of an ice boat and the wheels of a land sailing craft.
In recent years ultrasonic speed sensors have become available. These use two ultrasonic transducers—one forward, one aft—that send ultrasonic pulses through the water flowing past the hull. By calculating the time differential in pulse propagation from one sensor to the other, the device calculates the speed of the hull through the water.
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 ...
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).
A vessel's length at the waterline (abbreviated to L.W.L) [1] is the length of a ship or boat at the level where it sits in the water (the waterline). The LWL will be shorter than the length of the boat overall (length overall or LOA) as most boats have bows and stern protrusions that make the LOA greater than the LWL. As a ship becomes more ...