The traditional agent employed to move a ship is a propeller. The necessary propeller thrust, T, required to move the ship at speed V, is normally greater than the pertaining resistance Rt. The thrust of a propeller depends on its size, the angle of attack of its blades and the speed at which it spins. By convention, propellers are described by diameter and pitch in that order. The diameter of propeller is governed by its speed of rotation and the power of the engine rotating it. For example a 20 H.P. engine would drive a 14 inch propeller at about 1500 rpm. If the propeller had too small surface area for the power provided it would over speed and cavitate at high revolution, providing little or no thrust. Pitch is dictated by the propeller’s speed of rotation, its percentage of slippage, and the speed required from ship. The diagram power vs shaft speed, the so cal...
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