GB2235905A - Hydrofoil craft - Google Patents

Abstract

A hydrofoil craft has one or more foils 6 carried by a wing 1. One end of the wing comprises a flange 5 and the foil contains a recess 7 adapted to receive the flange. One or more fixing means 2, 3 penetrate the foil and engage the end of the wing to hold it firmly within the recess. The fixing means preferably comprises one or more threaded studs which protrude from the end of the wing and engage apertures 8, 9 within the recess. The foil is firmly attached to the wing by means of wing nuts screwed on the studs. The ends of the studs and associated nuts are accommodated in one or more cavities below the surface of the foil which are fitted with covers. <IMAGE>

Description

HYROFOIL CRAFT This invention relates to hydrofoil craft and particularly to a method of attaching the foils to the craft.

Hydrofoil craft have one or more pairs of foils which are attached to the hull or hulls of the craft. As the crafts speed through the water increases the foils provide upward lift unloading the hull. Some types of hydrofoil craft take-off at a critical speed so that the entire weight of the croft is carried by the oils, In other forms of craft the foils act as stabilisers and the lift prevents a craft without keel from heeling and drifting to leeward. The design of foils, particularly their area and angle of attack, are most important. Foils are often fitted to the hull of a craft by means of a wing or beam.

It is most important that the foil is firmly attached to the wing and that the angle of attack remains constant when sailing regardless of the variations in load. However for convenience of transport and maintenance it is frequently necessary that the attachment is not permanent and that the foils can be removed easily.

Various means of attaching foils to wings have been used but they have seldom proved wholly satisfactory due to their lack of strength or causing unnecessary hydrodynamic drag. The present invention provides a hydrofoil craft with detachable foils which are firmly retained during sailing but which can easily be removed. The attachment method minimises hydrodynamic drag and has a pleasing aesthetic appearance.

According to the present invention there is provided a hydrofoil craft having one or more foils carried by a wing characterised in that one end of the wing comprises a flange, the foil contains a recess adapted to receive the flange and one or more fixing means penetrate the foil and engage the end of the wing to hold it firmly within the recess.

In a preferred form of the invention one or more threaded studs protrute from the end of the wing and engage apertures within the recess in the foil. The foil is attached to the wing by means of nuts screwed on to the studs. Preferably wing nuts are used as these may be screwed on to the studs tightly and unscrewed without the use of tools. The foil also carries one or more cavities on its outer surface adapted to contain the ends of the studs which carry the nuts. The studs preferably do not extend beyond the surface of the foil to prevent unnecessary drag. To reduce drag further covers are inserted into the cavities which enclose the nuts and provide a smooth outer surface. In an alternative embodiment the fixing means comprises one or more threaded bolts which pass through the foil and engage threaded bushes within the wing.In a similar manner the heads of the bolts are contained within cavities on the outer surface of the foil.

The cavities which enclose the nuts or the heads of the bolts are preferably circular. To reduce the size of the cavities there is preferably one circular cavity for each attachment stud or bolt with its associated circular cover.

The end of the wing is preferably flared and carries a smooth flange which engages the sides of the recess within the foil. Such a joint is strong and causes little drag.

The flange may be from 10 to 20 mm in depth according to the size of the wing and the load to be carried. In one embodiment a wing having an aerofoil section whose major axis is approximately 230 mm and minor axis 75 mm is flared by 33%. The flared end carries a flange 15 mm depth which ia accomodated in a recess in the foil having the same depth.

The wing is preferably fabricated from glass fibre reinforced plastic (GRP) preferably having a foam core.

Alternatively the wing may be fabricated from wood, metal or carbon fibre reinforced resin. The wing has an aerofoil shape and can provide lift if the angle of attack is positive when it passes through the water. The foil is preferably fabricated from the same materials as the wing.

The fixing studs are preferably metal and the ends are rigidly anchored within the body of the wing. If the wing is manufactured from zRP the studs are preferably w?lded to a rigid metal plate and incorporatcc' in the glass Fibre and resin composition. The metal is preferably either a corrosion resistant alloy such as a stainless steel or coated with a corrosion resistant metal layer by galvanising or cadmium plating.

In one form of hydrofoil craft the foils are carried at each end of a wing which is attached centrally to the upper surface of the hull of the craft. The foil at each end of the wing may be attached to the ends of the wing in the manner described above.

In order that the invention may be clearly understood it will now be described with reference to the accompanying drawings in which: Figure 1 is a perspective view of a wing and a foil showing the attachment system according to the invention, and Figure 2 is a cross sectional view of a wing and a foil when attached to each other.

A wing 1. see figure 1. carries two threaded studs 2 and 3. whose ends, not shown. are rigidly anchored within the body of the wing 1. The end 4 of the wing 1 has an outward flare which increases the cross sectional area.

The flared end 4 has a smooth flange 5. A foil 6 has a recess 7 adapted to receive the flange 5 of the wing 1.

The base of the recess 7 carries two apertures 8 and 9 adapted to receive the threaded studs 2 and 3 respectively.

When the flange 5 is inserted into the recess 7, see figure 2. the studs 2 and 3 pass through the apertures 8 and 9.

The end of each stud and its associated nut is contained within a pair of cavities in the outer surface of the foil 6; one cavity 11 is illustrated. The end of the wing 1 is held firmly within the recess 7 against the foil 6 by means of a nut 12 screwed on to the stud 2 and a second nut, not shown, screwed on the stud 3. The cavity 11 has sufficient depth to accomodate ends of the studs 2 and 3 with the securing nuts attached. To avoid unneccessary drag the studs 2 and 3 do not extend beyond the surface of the foil 3 and a cover 13 having a smooth outer surface closes the cavity 11. The cover 13 is held in position by frictional force. A second cover, not shown, closes the other cavity.

The recess and associated flange are preferably oval forming a joint which has minimum drag. While it is possible to use a single fixing stud it is preferred to use two to provide extra strength and to minimise the strain caused by any turning moment. When the craft takes off or when the sail receives a stong wind the joint will be subjected to considerable force. It is found that the described method of construction is able to withstand such forces.

The invention has been described in detail with particular reference to preferred embodiments thereof, but it will be understood that variations and modifications can be effected within the spirit and scope of the invention.

Claims (14)

1. A hydrofoil craft having one or more foils carried by a wing characterised in that one end of the wing comprises a flange, the foil contains a recess adapted to receive the flange and one or more fixing means penetrate the foil and engage the end of the wing to hold it firmly within the recess.

2. A craft as claimed in claim 1 characterised in that the fixing means comprises one or more threaded studs which protrute from the end of the wing and engage apertures within the recess.

3. A craft as claimed in claim 2 characterised in that the foil is attached to the wing by means of nuts screwed on the studs.

4. A craft as claimed in claim 3 characterised in that the foil is attached to the wing by means of wing nuts.

5. A craft as claimed in any of the claims 2 to 4, characterised in that the foil carries one or more cavities adapted to contain the nuts below the surface of the foil.

6. A craft as claimed in claim 1 characterised in that the fixing means comprises one or more threaded bolts which pass through the foil and engage threaded bushes within the wing.

7. A craft as claimed in claim 6 characterised in that the foil carries one or more cavities adapted to contain the heads of the bolts below the surface of the foil.

8. A craft as claimed in claim 5 or 7. characterised in that covers are fitted over the cavities in the foil.

9. A craft as claimed in claim 8 characterised in that the or each cavity is circular.

10. A craft as claimed in any of the preceding claims characterised in that the end of the wing carried by the flange is flared.

11. A craft as claimed in any of the preceding claims characterised in that the wing and the foil are fabricated from foam filled glass reinforced plastic.

12. A craft as claimed in any of the preceding claims characterised in that each end of the wing carries a foil.

13. A craft as claimed in claim 1 and as herein described.

14. A hydrofoil craft having one or more foils carried by a wing as herein described with reference to the drawings.