The following invention relates to a water craft and more particularly, though not exclusively to a surface skimming water craft. Disclosure of the Invention

There is disclosed herein a water craft comprising: a hull , a pair of discs, each attached to and below the hull, each disc comprising an essentially circular surface adapted to skim upon the water as the craft moves at speed.

Preferably, the discs are laterally located at respective sides of the hull.

Preferably, the hull comprises a further pair of discs located fore or aft of the first pair. Preferably, the discs are rotatably mounted to the hull, and may be free spinning or rotatably driven.

Preferably, the discs are acutely angled with respect to a horizontal reference plane.

Preferably, said acute angle is less than 45°. Preferably, the circular surface of each disc is convex.

Preferably, the contour of the under side of the hull is such that a point of maximum air pressure therebeneath corresponds with the centre of gravity of the craft.

Preferably, the hull body and discs are formed of moulded plastics material .

Preferably, the discs are pivotal ly mounted to the hull. Preferably, said pivotal mounting is by way of a ball joint. Preferably, the ball joint comprises a ball affixed to or integrally formed with a leg extending from the hull, the ball extending into a socket formed within the disc and being retained therein by a retention flange secured to the disc.

There is further disclosed herein a disc adapted to be attached below the hull of a water craft, the disc comprising an essentially circular surface adapted to skim upon the water as the craft moves at speed.

Preferably, the disc further comprises mounting means to mount the disc to the water craft, the mounting means comprising a ball and socket arrangement.

Typically, the main craft body or hull is supported above and out of the water as a result of buoyancy of the discs. The discs may be considered the main or only buoyancy for the water craft. That is, the total buoyancy of the craft is dependent upon the configuration, size and/or number of discs attached.

As the discs are for use in a liquid environment, it is necessary to lay them down so as, when stationary, the maximum of surface area is in contact with the water, thus gaining the maximum of buoyant effect.

Beneficially, it is necessary to predispose the angles of the discs relative to the water surface, in such a way as to place the inside, rear quadrant of the bottom disc surface at the lowest point. This area is considered to be the maximum area of grip upon the disc. To achieve this, it is typical to provide a forward uptilt and an outside uptilt so as to give this contact area the maximum effect and increase in performance as forward motion is applied to the craft. This enables the discs to become controlled, forward rotating, deflected, multi-directonal discs.

Typically, there are provided circular, non-directional, concave indentations on the underside surface near the outer perimeter of each disc to provide grip and decrease slippage on the disc surface.

It might be necessary, dependent upon the size and configuration of the craft and discs to limit the angle through which the discs may pivot. At no time should the leading edge of the discs drop below the horizontal as this would allow the disc to penetrate or dive below the surface, thus "tripping" the craft. To this end, pivot limitation devices may be adapted to cooperate with each disc.

The bearing surfaces of the discs consist, typically of one dimpled, spherical, non-rotating fixture and one matching smooth surfaced cup located within the disc. The dimples might act to reduce the surface area and friction whilst capturing water and air within the assembly which acts as a lubricant and negates the need for mechanical metal adaptions.

Brief Description of the Drawings

Preferred forms of the present invention will now be described by way of example with reference to the accompanying drawings, wherein: Fig. 1 is a schematic perspective view of a water craft, Fig. 2 is a schematic side elevational view depicting the arrangement of the discs of the craft in Fig. 1,

Fig. 3 is a schematic plan view of the arrangement of Fig. 2, Fig. 4 is a schematic forward elevational view of the arrangement of Fig. 2 and 3,

Fig. 5 is a schematic perspective view of a disc, Fig. 6 is a schematic perspective exploded view of an alternative disc comprising a ball and socket arrangement, and

Fig. 7 is a schematic cross sectional elevational view of the assembly of Fig. 6.

Description of the Preferred Embodiments In Figs. 1 to 5 of the accompanying drawings there is schematically depicted a water craft 10. Water craft 10 comprises a hull 17 having an upper surface 18, a lower surface 19, a bow 20 and a stern 21.

Spaced from the underside 19 of craft 10 at the stern end 20 thereof is a pair of outwardly extending arms 22 rotatably supporting discs 13 and 14. Likewise, at the stern 21 of hull 17 a pair of arms 15 rotatably supports an additional pair of discs 11 and 12.

Propulsion for craft 10 may be provided by an outboard motor mounted at the stern 21, or by jet propulsion or any other suitable means. For example, craft 10 may be a sail craft. The contour of the underside 19 of the craft may be designed to provide a positive pressure below the craft at speed.

With reference to Figs. 2 to 5, discs 11, 12, 13 and 14 are rotatably mounted upon bearings or the like.

As shown in Fig. 5, disc 11, which may be formed of moulded plastics, fibreglass, aluminium steel or any other suitable material may be rotatably mounted upon a fixed hub 16. Hub 16 is in turn connected by suitable means to arm 15. A sealing skirt 17 may be provided to protect the bearings within disc 11 from water.

With reference to Figs. 2 and 4, each disc is acutely angled from a horizontal reference plane. When viewed laterally, the rotational axis 22 of disc 11 might be at a fixed angle α relative to the horizontal. Angle α might be somewhere between 45 and 90°.

When viewed from the front or rear, the rotational axis 22 of disc 11 extends at a fixed angle β relative to the horizontal. Angle β might also be somewhere between 45 and 90°.

It should be appreciated that angles α and β, although preferably fixed, may be adjustable. That is, for high speed applications, α and β might be quite close to 90°, whereas for low

speed applications, angles α and β may be closer to 45°.

With reference to Fig. 3, as craft 10 moves in a forward direction indicated by arrow C, discs 12 and 13, which are free spinning, will rotate in an anti-clockwise direction as indicated by arrows A.

5 Similarly, discs 11 and 13, which are free spinning, will rotate in a clockwise direction as indicated by arrows B.

The discs rotate as a result of the flow of water therepast. In the case of disc 11, and as shown in Fig. 3, zone D of the underside of the disc is acted upon by water flowing in the direction indicated by

10 arrow E. It is that flow that causes rotation of disc 11 in the direction indicated by arrow B.

As a result, the relative contact velocity between the underside of disc 11 and the water is substantially reduced as compared to a disc which were fixed. It is this reduction in contact friction which, it is

15 believed, will result in high speed capabilities of craft 10 with relatively low powered power units.

Discs 11, 12, 13 and 14 may be separately rotatably driven. In this case, a number of radially extending fins may be provided on the underside of each disc. That is, the discs may form a means of

20 propulsion of craft 10, should a separate hull mounted power unit not be provided. Electric motors may be provided in each disc, or alternatively, torque may be transmitted to the discs from shafts which extend to a power unit within hull 17.

In Figs. 6 and 7 of the accompanying drawings there is

25 schematically depicted an alternative disc fixing arrangement 60. Arrangement 60 comprises a ball joint 61 integrally formed with or attached to a leg extension 62. Leg extension 62 might be adapted to pivot about a pivot joint 67 affixed to the hull of a water craft or might be telescopically associated with another part to allow for

30 vertical displacement of the ball joint 61. Ball 61 comprises a plurality of pits 65 within which there might be received a lubricant such as oil or water or the like. Disc 63 is secured to rotate and pivot relative to ball joint 61 and is retained by retaining flange 64 secured to disc 63. Where water is the intended lubricant, a pair of apertures

35 68 might extend through the base of disc 63 for the ingress of water as the disc skims thereupon. A number of pits or grooves 66 may be provided in the lower surface of the disc 63.

A water craft may be provided not only with four discs but with a

multitude of discs, say for example as a pair of rows, one along each side of the craft, each of which may be individually mounted upon telescopic arms to accommodate peaks and troughs of waves as the craft is in motion. It should be appreciated that modifications and alterations obvious to those skilled in the art are not to be considered as beyond the scope of the present invention. For example, any number of discs may be provided. For instance, where two rotating discs are provided, each located at laterally opposed positions upon the craft, a centrally located, forward skimming means may be provided. Such a skimming means might be a non-rotating disc.