What is "centreboard"

centreboard \centreboard\ n. same as centerboard.

Syn: centerboard, drop keel, sliding keel.

n. (context British spelling nautical English) The adjustable keel on a small yacht or dinghy that acts, among other things, as ballast and to counteract the sideways force of the wind.

n. a retractable fin keel used on sailboats to prevent drifting to leeward [syn: centerboard, drop keel, sliding keel]

A centreboard or centerboard (US) is a retractable keel which pivots out of a slot in the hull of a sailboat, known as a centreboard trunk (UK) or centerboard case (US). The retractability allows the centreboard to be raised to operate in shallow waters, to move the centre of lateral resistance (offsetting changes to the sailplan that move the centre of effort aft), to reduce drag when the full area of the centreboard is not needed, or when removing the boat from the water, as when trailering. A centreboard which consists of just a pivoting metal plate is called a centerplate. A daggerboard is similar but slides vertically rather than pivoting.

The analog in a scow is a bilgeboard: these are fitted in pairs and used one at a time.

Lt. John Schank (c. 1740 – 6 February 1823) was an officer of the British Royal Navy and is credited with the invention of the centerboard. Schank, however, gave credit for the idea to British Brigadier General Earl Percy.