A large casting extending outboard from the main hull for supporting for the ends of the propeller shafts in a multi-screw ship


Related Terms

GEARBOX

A system of gears which alter the ratio between the revolution of the engine and the propeller shaft so the propeller operates in a relatively efficient speed range. By using a gearbox the engine and the propeller shaft will revolve at different speeds.

INSERTION METER

A type of flowmeter which measures the rotation rate of a small propeller or turbine rotor mounted at right angles to the end of a support rod and inserted into the flowing stream or closed pipe.

PROPELLER

An arrangement which consists of hub and number of blades mounted on a rigid shaft protruding from the hull of a vessel, usually driven by an inboard motor.

INBOARD MOTOR

An engine mounted within the hull of a vessel, usually driving a fixed propeller by a shaft protruding through the stern. Generally used on larger vessels. See also stern drive and outboard motor.

FIXED PROPELLER

A propeller mounted on a rigid shaft protruding from the hull of a vessel, usually driven by an inboard motor; steering must be done using a rudder. See also outboard motor and sterndrive.

PROPELLER WALK

The tendency for a propeller to push the stern sideways. In theory a right hand propeller in reverse will walk the stern to port.

TAILSHAFT

A kind of metallic shafting (a rod of metal) to hold the propeller and connected to the power engine. When the tailshaft is moved, the propeller may also be moved for propulsion.

STERNDRIVE

A propeller drive system similar to the lower part of an outboard motor extending below the hull of a larger power boat or yacht, but driven by an engine mounted within the hull. Unlike a fixed propeller (but like an outboard), the boat may be steered by twisting the drive.

SHEAR PIN

A safety device, used to fasten a propeller to its shaft; it breaks when the propeller hits a solid object, thus preventing further damage.

SCREW

1. propeller. 2. propeller-driven.

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