Ships – Apparatus held by or attached to rider to control sailboard... – Foot strap means
Patent
1995-12-29
1997-10-07
Avila, Stephen
Ships
Apparatus held by or attached to rider to control sailboard...
Foot strap means
114 61, 114274, B63B 124
Patent
active
056736410
DESCRIPTION:
BRIEF SUMMARY
The present invention concerns a wind-propelled hydrofoil of the type comprising a forward assembly with at least partially submerged forward foils and a fully submerged aft foil.
The theory of balancing the weight of a vessel by a hydrodynamic lift effect produced by the speed of the water acting on submerged, semi-submerged or surface-piercing aerofoil shape members, as opposed to use of only the Archimedian upthrust effect due to the submerged volumes, goes back a long way and powered vessels fitted with this type of device date from the beginning of the twentieth century.
The first patent application concerning a hydrofoil, filed by the French inventor FARCOT, dates back to 1869.
In 1909 Roger RAVAUD built a powered vessel called the "motoscaphe".
Another powered hydrofoil built by the Italian FORLANINI in 1911 had foils arranged like the rungs of a ladder.
In 1907 CROCCO and RICALDONI built a monoplane machine with V-shape surface-piercing aerofoils. The submerged surface area varied automatically with the weight and the speed which made the machine stable and gave it a particular heave characteristic. This V-shape arrangement of surface-piercing foils was very widely used on first generation hydrofoils and has the drawback that the foils tend to follow undulations of the swell, which makes a vessel of this kind uncomfortable for passengers. What is more, once the swell height exceeds 1.5 m it is necessary to reduce the speed of the hydrofoil very substantially.
The V-shape foil design was therefore abandoned in second generation hydrofoils which have simple, variable angle of incidence, totally submerged foils controlled automatically according to the speed, the trim and the height of the vessel above the water, a control system sending the necessary corrections to the foils. The second generation powered hydrofoils were introduced during the 1960s and have mainly been used in military applications. The design of these hydrofoils is inherently unstable, stability being achieved only dynamically by means of a dedicated control system.
Turning to wind-propelled hydrofoils, racing vessels have been built that can achieve high speeds in calm water. However, these vessels have major stability problems and become virtually unusable if there is any swell.
Patents U.S. Pat. No. 5,054,410 (SCARBOROUGH) and U.S. Pat. No. 3,789,789 (CLEARY) describe wind-propelled hydrofoils having a forward foil that is partially submerged, an aft foil and a dynamic compensator device. These hydrofoils are not inherently stable. In patent U.S. Pat. No. 5,054,410 the aft foil is totally submerged and the hydrofoil is not inherently stable, stability being achieved entirely dynamically. In patent U.S. Pat. No. 3,789,789, the aft foil is not totally submerged; it rises to the surface of the water and no longer acts as a foil but as a water ski or skate, imposing a fixed height above the water at the stern.
A dynamically stabilized hydrofoil is described in "Model tests for a wind-propelled hydrofoil trimaran" by Neil BOSE published in HIGH-SPEED SURFACE CRAFT, vol. 20, n.degree. 10, Oct. 1981, London, p28-31. This hydrofoil has a surface-piercing V-shape forward foil, like the aft foil, and which is not totally submerged.
An object of the present invention is to provide a wind-propelled hydrofoil that is inherently stable.
The basic idea of the invention is to start from a prior art wind-propelled hydrofoil having a forward assembly comprising at least partially submerged forward foils and a fully submerged aft foil, the latter accordingly having no heave characteristic.
The basis of the present invention is recognition of the fact that a particular arrangement of the component parts of a wind-propelled hydrofoil of this type can provide longitudinal stability and in particular longitudinal stability compatible with sailing in high seas.
The present invention therefore concerns a wind-propelled hydrofoil of the above type characterized in that the forward foils are such that the resultant of the vertical forces: resultant having
REFERENCES:
patent: 2890672 (1959-06-01), Boericke
patent: 3789789 (1974-02-01), Cleary
patent: 4100876 (1978-07-01), Feleus
patent: 5054410 (1991-10-01), Scarborough
patent: 5113775 (1992-05-01), Imhoff
Charles Heidsieck, l'albatros, Bateaux, No. 316, Sep., 1984; Model Tests For A Wind-Propelled Hydrofoil Trimaran, By Neil Bose, High Speed Surface Craft.
De Bergh Alain
Lauriot-Prevost Vincent
Perrier Philippe
Sournat Andre
Thebault Alain
Architecture Navale MVPVLP
Avila Stephen
Dassault Aviation
De Bergh Alain
Perrier Philippe
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