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The power-to-weight ratio (specific power) is defined as the power generated by the engine(s) divided by the mass. In this context, the term "weight" can be considered a misnomer, as it colloquially refers to mass. In a zero-gravity (weightless) environment, the power-to-weight ratio would not be considered infinite.
Wave-making resistance is a form of drag that affects surface watercraft, such as boats and ships, and reflects the energy required to push the water out of the way of the hull. The hull of a moving watercraft creates waves (a wake ) which carry energy away and resist the motion of the watercraft.
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 ...
Gas turbines are used in many naval vessels, where they are valued for their high power-to-weight ratio and their ships' resulting acceleration and ability to get underway quickly. The first gas-turbine-powered naval vessel was the Royal Navy's motor gunboat MGB 2009 (formerly MGB 509) converted in 1947.
Tugboats usually have an extreme power:tonnage-ratio; normal cargo and passenger ships have a P:T-ratio (in kW:GRT) of 0.35 to 1.20, whereas large tugs typically are 2.20 to 4.50 and small harbour-tugs 4.0 to 9.5. [3]
This trend of increase in wave-making resistance continues up to a Froude number of ~0.45 (speed/length ratio ~1.50), and peaks at a Froude number of ~0.50 (speed/length ratio ~1.70). This very sharp rise in resistance at speed/length ratio around 1.3 to 1.5 probably seemed insurmountable in early sailing ships and so became an apparent barrier.
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.