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A ducted propeller, also known as a Kort nozzle, is a marine propeller fitted with a non-rotating nozzle. It is used to improve the efficiency of the propeller and is especially used on heavily loaded propellers or propellers with limited diameter. It was developed first by Luigi Stipa (1931) and later by Ludwig Kort (1934). The Kort nozzle is ...
Other vessels may have twin, triple or quadruple screws. Power is transmitted from the engine to the screw by way of a propeller shaft, which may be connected to a gearbox. The propeller then moves the vessel by creating thrust. When the propeller rotates the pressure in front of the propeller is lower than the pressure behind the propeller.
In marine propulsion, a variable-pitch propeller is a type of propeller with blades that can be rotated around their long axis to change the blade pitch. Reversible propellers—those where the pitch can be set to negative values—can also create reverse thrust for braking or going backwards without the need to change the direction of shaft revolution.
A 260-horsepower (190 kW) diesel inboard motor An inboard motor is a marine propulsion system for boats.As opposed to an outboard motor, where an engine is mounted outside the hull of the craft, an inboard motor is an engine enclosed within the hull of the boat, usually connected to a propulsion screw by a driveshaft.
The difference between a saildrive and a Z-drive is that a saildrive's propeller shaft is fixed in place, pointing aft, whereas a Z-drive's propeller shaft can be rotated to any azimuth. Traditional sailboat transmissions consist of a simple horizontal output shaft extended rearward from the engine, through the stern via a stuffing box. The ...
A motorboat with an outboard motor. A motorboat or powerboat is a boat that is exclusively powered by an engine; faster examples may be called "speedboats".. Some motorboats are fitted with inboard engines, others have an outboard motor installed on the rear, containing the internal combustion engine, the gearbox and the propeller in one portable unit.
A more serious problem with this type of propeller is a "frozen-on" spline bushing, which makes propeller removal impossible. In such cases the propeller must be heated in order to deliberately destroy the rubber insert. Once the propeller is removed, the splined tube can be cut away with a grinder and a new spline bushing is then required.
Being smaller in size and mass and being completely submerged, it was also far less prone to damage. James Watt of Scotland is widely given credit for applying the first screw propeller to an engine at his Birmingham works, an early steam engine, beginning the use of a hydrodynamic screw for propulsion.