Outrigger on a contemporary Hawaiian sailing canoe
An outrigger is a part of a boat's rigging which is rigid and extends beyond the side or gunwale of a boat. Outrigger poles are typically made from aluminum to withstand the harsh environment of salt water. Outriggers telescope out away from a fishing boat to be able to drop fishing bait lines up to several feet away from the boat into the water. When a fish bites on the bait, the line rigged into the outrigger automatically transfers to a fishing pole that is properly secured into a gunnel on the boat. The pole collapses to allow for bridge clearance, trailering and storage.
In an outrigger canoe and in sailboats such as the proa, an outrigger is a thin, long, solid, hull used to stabilise an inherently unstable main hull. The outrigger is positioned rigidly and parallel to the main hull so that the main hull is less likely to capsize. If only one outrigger is used on a vessel, its weight reduces the tendency to capsize in one direction and its buoyancy reduces the tendency in the other direction.
In a rowing boat or galley, an outrigger (or just rigger) is a triangular frame that holds the rowlock (into which the oar is slotted) away from the gunwale to optimize leverage. Wooden outriggers appear on the new Trireme around the 7th or 6th centuries BC and later on Italian galleys around AD 1300 while Harry Clasper (1812–1870), a British professional rower, popularised the use of the modern metal version.