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When the vehicle is moving at low speed or the propeller is rotating at high speed, the advance ratio is a low number. The advance ratio is a useful non-dimensional quantity in helicopter and propeller theory, since propellers and rotors will experience the same angle of attack on every blade airfoil section at the same advance ratio regardless ...
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 Magnus rotor used to propel a ship is called a rotor sail and is mounted with its axis vertical. When the wind blows from the side, the Magnus effect creates a forward thrust. The most common form of rotor sail is the Flettner rotor. [4] [failed verification] The wind does not power the rotor, which is rotated by its own power source.
Taffrail Log Rotator Mechanical speed logs called patent logs [1] or taffrail logs, operating on physical principles in a manner similar to a car's odometer by towing a vane or rotor from the stern (or taffrail) by a long line, were developed in the eighteenth century (or earlier) but became practical in the nineteenth century and replaced the ...
The turning rotation of a vessel about its vertical/Z axis. An offset or deviation from normal on this axis is referred to as deviation or set. This is referred to as the heading of the boat relative to a magnetic compass (or true heading if referenced to the true north pole); it also affects the bearing.
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 hull is now starting to climb its own bow wave, and resistance begins to increase at a very high rate. While it is possible to drive a displacement hull faster than a speed-length ratio of 1.34, it is prohibitively expensive to do so. Most large vessels operate at speed-length ratios well below that level, at speed-length ratios of under 1.0.
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.