The ship propeller is the most common means of propulsion for ships. This device consists of several blades, resembling those of a fan, mounted on the end of a drive shaft. Propellers differ in their materials (bronze, aluminum, etc.) and functional details (fixed or variable pitch, surface-piercing propeller, etc.).
The propeller transforms the engine's rotary power into thrust with each revolution it makes.
Boat propellers work in the same way as airplane propellers. Each blade is shaped like an airfoil. Rotation creates a pressure difference between the forward and aft surfaces due to blade profile and angle of attack. This difference results in thrust.
Propeller size must be adapted to vessel size and engine power, since undersized blades cannot handle all the engine's power. Constituent material is also a factor. Ship propellers often are custom-built. Manufacturers have software and special equipment to aid in selection.
