Deformable shrouded water foil

US4538539A · kind A · utility

Inventor

• David Martin · Hamilton, NZ

Key dates

• Filing date: Mar 20, 1984
• Grant date: Sep 3, 1985
• Expiry date: Mar 20, 2004

Classification

• Technology area (CPC B): Performing Operations; Transporting
• CPC primary: B63B2035/009
• WIPO field: Transport
• WIPO sector: Mechanical engineering

Abstract

An underwater appendage for sailboats, such as a keel or rudder, is fitted with an external shell-like shroud, which is placed around a core portion of the appendage such that the outer shroud forms a deformable water foil which is fastened on both sides of the core near its rear or trailing edge, and which shroud is everywhere else spaced away from the core. This deformable shroud forms a hydrofoil, the leading edge of which can be displaced to either side of the core by means of inflatable bladders placed on either side of the core, thus creating a desired angle of attack for the deformable foil, either to port or starboard. Inflation of the bladder on the windward side of the boat creates an angle of attack to windward and also a bulging of the shrouded water foil on the windward side creating the desired hydrodynamic lift to counter the lateral component of the aerodynamic force on the sail. As the boat is turned through the wind, onto the opposite tack, the pressure on the bladder is relaxed as it becomes the leeward bladder, and pressure on the opposite bladder is increased as it becomes the windward bladder. Pressure on both bladders can be relaxed when no lift is desired as…