Bilgeboard
Encyclopedia
A bilgeboard is a lift
ing foil
used in a sailboat
, which resembles a cross between a centerboard and a leeboard
. Bilgeboards are mounted between the centerline of the boat and the sides, and are almost always asymmetric foils mounted at an angle to maximize lateral lift while minimizing drag
. They are most often found on racing scow
s.
When sailing, the windward side bilgeboard is retracted into the hull
of the boat, so that it produces no drag. The leeward side foil provides the lift to counter the lateral force of the sail, and converts it into forward motion. The bilgeboards are angled so that as the boat heels, or leans under the force of the wind, the leeward bilgeboard becomes more upright, and provides the greatest possible force in the desired direction.
The 'Red Fox' is a modern cruising yacht that uses bilgeboards to allow a lifting keel with minimal interference in cabin space.
Lift (force)
A fluid flowing past the surface of a body exerts a surface force on it. Lift is the component of this force that is perpendicular to the oncoming flow direction. It contrasts with the drag force, which is the component of the surface force parallel to the flow direction...
ing foil
Foil (fluid mechanics)
A foil is a solid object with a shape such that when placed in a moving fluid at a suitable angle of attack the lift is substantially larger than the drag...
used in a sailboat
Sailboat
A sailboat or sailing boat is a boat propelled partly or entirely by sails. The term covers a variety of boats, larger than small vessels such as sailboards and smaller than sailing ships, but distinctions in the size are not strictly defined and what constitutes a sailing ship, sailboat, or a...
, which resembles a cross between a centerboard and a leeboard
Leeboard
A leeboard is a lifting foil used by a sailboat, much like a centerboard, but located on the leeward side of the boat. The leeward side is used so that the leeboard isn't lifted from the water when the boat heels, or leans under the force of the wind....
. Bilgeboards are mounted between the centerline of the boat and the sides, and are almost always asymmetric foils mounted at an angle to maximize lateral lift while minimizing drag
Drag (physics)
In fluid dynamics, drag refers to forces which act on a solid object in the direction of the relative fluid flow velocity...
. They are most often found on racing scow
Scow
A scow, in the original sense, is a flat-bottomed boat with a blunt bow, often used to haul bulk freight; cf. barge. The etymology of the word is from the Dutch schouwe, meaning such a boat.-Sailing scows:...
s.
When sailing, the windward side bilgeboard is retracted into the hull
Hull (watercraft)
A hull is the watertight body of a ship or boat. Above the hull is the superstructure and/or deckhouse, where present. The line where the hull meets the water surface is called the waterline.The structure of the hull varies depending on the vessel type...
of the boat, so that it produces no drag. The leeward side foil provides the lift to counter the lateral force of the sail, and converts it into forward motion. The bilgeboards are angled so that as the boat heels, or leans under the force of the wind, the leeward bilgeboard becomes more upright, and provides the greatest possible force in the desired direction.
The 'Red Fox' is a modern cruising yacht that uses bilgeboards to allow a lifting keel with minimal interference in cabin space.