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Power-to-weight ratio (PWR, also called specific power, or power-to-mass ratio) is a calculation commonly applied to engines and mobile power sources to enable the comparison of one unit or design to another. Power-to-weight ratio is a measurement of actual performance of any engine or power source.
To plane, especially to initiate planing, the power-to-weight ratio must be high, since the planing mode of operation involves moving the hull at speeds higher than its natural hull speed. All boat designs for planing benefit from minimised weight; planing powerboats are commonly made from light alloy or use other reduced-weight construction ...
The marine steam turbine developed by Sir Charles Algernon Parsons [3] raised the power-to-weight ratio. He achieved publicity by demonstrating it unofficially in the 100-foot (30 m) Turbinia at the Spithead Naval Review in 1897. This facilitated a generation of high-speed liners in the first half of the 20th century, and rendered the ...
A gasoline engine burns a mix of gasoline and air, consisting of a range of about twelve to eighteen parts (by weight) of air to one part of fuel (by weight). A mixture with a 14.7:1 air/fuel ratio is stoichiometric, that is when burned, 100% of the fuel and the oxygen are consumed.
The Deltic-powered Hunt-class mine countermeasures vessel HMS Ledbury. Development began in 1947 and the first Deltic model was the D18-11B, produced in 1950. It was designed to produce 2,500 hp (1,900 kW) at 2000 rpm for a 15-minute rating; the continuous rating being 1,875 hp (1,398 kW) at 1700 rpm, based on a 10,000-hour overhaul or replacement life. [3]
This is possible through the very high sail-carrying power to total weight ratio, which is above 30% with the no. 1 rig and approaches 40% with the no. 3 rig (for reference, a 30% ratio is needed to plane upwind and a 10% ratio is needed to plane at all. Most cruising boats have a ratio under 5%).
They are shaped like an upside-down mushroom which can be easily buried in mud or silt. The advantage is that it has up to ten times the holding-power-to-weight ratio compared to a dead weight mooring; disadvantages include high cost, limited success on rocky or pebbly substrates, and the long time it takes to reach full holding capacity. [4]
A body in water which is stationary with respect to water, experiences only hydrostatic pressure. Hydrostatic pressure always acts to oppose the weight of the body. The total (upward) force due to this buoyancy is equal to the (downward) weight of the displaced water. If the body is in motion, then there are also hydrodynamic pressures that act ...
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