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AAW An acronym for anti-aircraft warfare. aback (of a sail) Filled by the wind on the opposite side to the one normally used to move the vessel forward.On a square-rigged ship, any of the square sails can be braced round to be aback, the purpose of which may be to reduce speed (such as when a ship-of-the-line is keeping station with others), to heave to, or to assist moving the ship's head ...
A V-shaped bow introduced in the late 1920s which allowed a ship to maintain a given speed with less power, improved seakeeping, increased reserve buoyancy, reduced pitching movements, and improved propeller immersion to increase performance in rough seas. main The high sea; the open ocean. main deck The uppermost continuous deck extending from ...
When this happens wetted surface area drops radically and the boats accelerate up to 1.2 to 1.5 times the speed of the prevailing wind. These boats are very light (all up weight is less than 40 kg) and very fast, They hydrofoil in as little as 8 knots (15 km/h) of breeze ("sit on the deck breeze" for most dinghy classes).
Pure jets and pure plumes define flows that are driven entirely by momentum and buoyancy effects, respectively. Flows between these two limits are usually described as forced plumes or buoyant jets. "Buoyancy is defined as being positive" when, in the absence of other forces or initial motion, the entering fluid would tend to rise.
Buoyancy also applies to fluid mixtures, and is the most common driving force of convection currents. In these cases, the mathematical modelling is altered to apply to continua, but the principles remain the same. Examples of buoyancy driven flows include the spontaneous separation of air and water or oil and water.
All sailing craft reach a constant forward speed (V B) for a given wind speed (V T) and point of sail, when the forward driving force (F R) equals the forward resisting force (R l). [8] For an ice boat, the dominant forward resisting force is aerodynamic, since the coefficient of friction on smooth ice is as low as 0.02. Accordingly, high ...
The downward force of gravity (F g) equals the restraining force of drag (F d) plus the buoyancy. The net force on the object is zero, and the result is that the velocity of the object remains constant. Terminal velocity is the maximum speed attainable by an object as it falls through a fluid (air is the most common example).
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 ...