FIELD OF INVENTION

THIS INVENTION relates to integral foils for surf craft fins. The invention has particular application to fins on surfboards. However, the invention is not limited to this field of use and may be used on other surf craft.

BACKGROUND ART

In order to describe accurately the elements of surf craft, it is pertinent to establish terminology relating thereto as follows: Surf craft are generally elongate in the direction of intended travel, and therefore have a longitudinal axis and a transverse axis abeam the surf craft somewhat parallel to the water upon which the surf craft is intended to float. For convenience, the axis which runs at right angles to both the elongate and the transverse axis will be herein referred to as the mast axis. The plane in which the elongate and mast axes lie will be herein referred to as the longitudinal plane. The plane in which the elongate and the transverse axes lie will be referred to as the floating plane. The plane in which the transverse and mast axes lie will be referred to as the transverse plane.

Fins normally project from the underside generally in the direction of the mast axis. Fins are often parallel to or straddle the elongate plane. Sometimes fins are provided in pairs with the bow ends closer to one another than the stern ends. Since users often seek surf craft designs having enhanced performance and increased speed, fin design has been the focus of surf craft development for many years.

In marine craft generally, the term foil is used as a shorthand term for hydrofoil, thereby generally importing the same meaning to the word foil. The function of a hydrofoil is normally to provide lift or some other force to the marine craft reactionary to its motion through the water. Accordingly, the term foil as used in this specification will refer to a formation which produces a reactionary force as a result of motion of the marine craft, or more specifically, the surf craft, through the water unless the context indicates otherwise. Foils would normally be parallel to, or at an acute angle to, the floating plane of the surf craft.

Fins and fin arrangements on the underside of surf craft are provided to facilitate manoeuvrability of the surf craft in use. Refinements in fin design are generally directed to increasing such manoeuvrability.

Fins for surf craft have sometimes been provided with wings which act as foils. For example, a fin design such as that known as the Webber fin design have been published from about 2004, but the Webber fin is not efficient for surfing or relevant to lift as it slides across the face of the wave and does not hold into the wave face and has no defining tip separated from the curve, this is causing the fin to slide across the wave face when it exits the wave.

The present invention aims to provide integral foils for surf craft fins which alleviate one or more of the problems inherent in typical fins and fin arrangements. The invention also aims to provide integral foils for surf craft fins which beneficially affect surf craft manoeuvrability. Other aims and advantages of the invention may become apparent from the following description.

DISCLOSURE OF THE INVENTION

With the foregoing in view, this invention in one aspect resides broadly in an integral foil for a surf craft fin comprising :

a base portion extending in generally planar fashion between a base edge and a transitional edge spaced from the base edge; a foil portion extending in a generally planar fashion at an angle to the base portion from the transitional edge of the base portion to an intermediate edge spaced from the transitional edge;

a tip portion extending in a generally planar fashion substantially parallel to the base portion from the intermediate edge of the foil portion;

fastening means for fastening the surf craft fin to a surf craft having a floating plane; and

wherein the base portion, foil portion and tip portion are of an integral and coextensive form.

Typically, the fin is mounted to the body of the surf craft by mounting means associated with the base edge. When mounted to the body of the surf craft, the base and tip portions are preferably substantially parallel to the mast axis. In one preferred embodiment, the foil portion may be provided at substantially right angles to the base and tip portions and the transitional edge of the base portion may be substantially parallel to the base edge. In such form, the foil portion is substantially parallel to the floating plane of the surf craft with attached to the body of the surf craft. In other preferred embodiments, the foil portion may be provided at an obtuse angle to the base and tip portions, or the base, transitional and intermediate edges may be slightly non-parallel. It will be appreciated that fine adjustments of the relative angles determining the uxtaposition of the part may have a profound effect on the performance of the fin of the present invention when mounted to the underside of a surf craft.

Preferably the angle between the foil portion and the base and tip portions is in the range of from 90° to 110°. Preferably the angle subtended by the intersection of the base and transitional edges is between 0° and 20°. Preferably, the angle subtended between the transitional and intermediate edges of the foil portion is between 0° and 5°. It is also preferred that the transitional and intermediate edges be rounded to provide a smooth transition between the intersecting planes of the respective portions of the fin of the present invention. Preferably, the rounded edges have a radius between 5 mm and 40 mm.

It is also preferred that the fin of the present invention be formed from flexible material having resilience which permits flexing of the portions thereof with respect to one another. For example, flexing of up to 20° in the angle between the foil portion and the other portions may be provided. It is also preferred that fins in accordance with the present invention be provided in opposite handed pairs.

The base, foil and tip portions have been described as being generally planar in form. However, it will be appreciated that the various portions of the fin are not strictly planar, and will have smooth, slightly curved surfaces as would be understood in the art of surf craft fins. Moreover, the generally planar surfaces transition smoothly to rounded or radiused edges as would be understood in the art of surf craft fins.

BRIEF DESCRIPTION OF THE DRAWINGS

In order that this invention may be more readily understood and put into practical effect, reference will now be made to the accompanying drawings which illustrate preferred embodiments and diagrammatic forms of the invention, wherein :-

Figs. 1 to 4 are perspective views each of an integral foil for a surf craft fin according to the invention; Figs. 5 to 7 are diagrammatic pictorial views showing the working of the fins of Figs. 1 to 4 ;

Figs. 8 to 10 are diagrammatic pictorial views further showing the working of the fins of Figs. 1 to 4 ;

Fig. 11 shows three diagrammatic views collectively illustrating the relationships between various portions of the fins of Figs. 1 to 4; and Fig. 12 is a representation showing in diagrammatic form a of a software generated integral foil for a surf craft fin with the pressure exerted on the fin by motion indicated thereon .

DETAILED DESCRIPTION OF THE DRAWINGS

The fin 10 shown in Figs. 1 to 4 has a base portion 11, a foil portion 12 extending from the base portion and a tip portion 13 extending from the foil portion.

The transition from the base portion to the foil portion is along a transitional edge 16 which in Figs. 1 and 2 is substantially parallel to a base edge 15 extending along the base of the base portion. In Figs. 3 and 4, the transitional edge is non-parallel with respect to the base edge and slightly curved within the plane of the base and tip portions. Projecting from the base edge of the base portion are two mounting lugs 14 in spaced apart relationship and substantially in the form of a rectangular prism, each also being substantially the same size as the other. The configuration of the mounting lugs is such that the fin can be mounted in popular fin boxes in surf craft by way of the mounting lugs.

An intermediate edge 17 is provided between the foil portion and the tip portion of the fin. In Fig. 3, the intermediate edge is somewhat angular, but in Figs. 1, 2 and 4, the intermediate edge is somewhat rounded. It can also be seen that in Fig. 3 at least the foil portion is at an obtuse angle to both the base portion and the tip portion. In each of the embodiments shown in Figs. 1 to 4, the tip portion is substantially parallel to the base portion. Each of the fins terminates at a tip 18 which is somewhat curved in the normal manner for fins for surf craft.

The fin shown in Fig. 5 is arranged to be somewhat curved rather than planer, the base portion transitioning to the foil portion through a curve, the tip portion is not provided in this embodiment of the fin (or at least is not parallel to the base portion) . The foil has a foil angle 25 at a 90° angle to the fin angle, but has a flexion at 26 of up to 20°.

The fins in Figs . 6 and 7 are shown mounted to a surfboard 28 without tip portions (or with the tip portions removed for clarity) to show expected flexure of the foil portion from the positions shown in solid outline to those shown in dashed outline at 19 and 20 by flexion as indicated by the arrows at 21. For example, the foil portion may flex to a flex angle 27 of by as much as 20° away from the natural position which in the case of the fins shown in Figs. 6 and 7 is at a rest angle 29 of 90° to the base portion. Also shown in Figs. 6 and 7 is the relationship between the base portion and a surf craft 22 to which the fins are mounted. The pictorial view of the fin shown in Fig. 8 is also shown in edge-on view in Fig. 9, the elements of the fin having the same reference numerals as in the other drawings. The fin shown edge-on in Fig 10 has a foil portion at a very obtuse angle to the base and tip portions.

The fins have a leading edge 23 and a trailing edge 24 configured to conform to the typical fin shape of a surf craft fin. That is, the leading and trailing edges are curved to meet one another tangentially to form a curve incorporating the tip.

The ratio of the height of the base portion to the tip portion may also vary as indicated in Fig. 11. For example, the base height 31, being the height of the base portion may constitute between one third and two thirds of the total height 32 of the fin, the height also being accommodated by the tip height 33, being the height of the tip portion plus or minus an amount equivalent to the degree of angularity of the foil portion to the base and tip portions. The width of the foil portion between the transversal and intermediate edges is typically between 5% and 20% of the height of the fin.

The software generated integral foil 40 for a surf craft illustrated in Fig. 12 has shading graduated from high pressure in the darker shades to lighter pressure in the lighter shades. It can be seen that the darker areas of higher pressure at 41 at the leading edge 51 of the fin. The areas of lighter graduated shades at 42, 43, 44 and 45 indicate successively lower pressures, the lessening of the pressure proceeding across the fin and foil surfaces from forward to the trailing edge 52.

In use, an integral foil for surf craft fins according to the present invention may provide a surf craft with better maneuverability when mounted to the body of a surf craft. For example, a fin of the present invention when mounted to the base of a surfboard body may provide some hydrofoil effect as the surfboard moves through the water. Flexure of the fin, either because the entire fin is made from flexible material, or the fin has flexible regions between rigid regions, may be provided by the surfer turning the surf board or otherwise maneuvering through the water when for example riding a wave which may produce a lateral force against the fin. The fins may be mounted to the body of a surf craft in the normal manner such as that known in the art as "FCS", but it would be appreciated that other fin mounting systems may be used for mounting fins for the present invention to the body of a surf craft with different mounting means from the lugs hereinbefore described. It is envisaged that surfers may prefer to have removable fins so that standard fins without foils can be replaced by fins of the present invention for different surfing conditions.

It is believed that the integral foils for surf craft fins according to invention create lift and a different dynamic performance for surf craft, as opposed to having added winglets to the fin base such as those known to surfers as "Bruce Lexton type wings" at the bottom of the fin base. The integral foils for surf craft fins according to the invention allow a larger area of foil section without the movement or the flex of the winglet or foil section. An aim of the design of the integral foils for surf craft fins according to invention is to create maximum lift and water release in turns through having a larger negative and positive water pressure flowing through the fin allowing for maximum lift and control.

This design also allows for the tip of the fin to flex from the foil section up only, which allows for load and release of the fin creating maximum drive through the turns as opposed to the whole fin flexing which also creates unwanted movement in the winglets as they are attached to the fin in the mid section.

As with the winglets the area has to be smaller so the negative and positive water flow does not put too much pressure on the winglets where they are connected to the main fin and creates flex that is not wanted. This restricts the size of the winglets which in turn restricts the amount of lift possible.

Also having a larger foil section as with the integral foils for surf craft fins according to invention on either side of the surf craft in the main fin design, provides maximum lift (which may be changed by varying the width of the foil section) in the craft to create the right amount of maximum balance across the hull of the craft they are attached to creating the greatest control, without the flex.

Accordingly, the angles the inventor has experimented with are described herein, and the foil section may be wider or narrower with some foil angles lesser or more than 90° to the base. A prototype of an integral foil for a surf craft fin according to invention with the angles at ^" about 30° and about 60° degrees with a 5° degree angle on the foil section has been found to work well to create lift. The 5° may vary a couple of degrees for less lift or more lift and a fin box may be developed to accommodate these slightly different angles of lift without having to change the fin.

It is believed that the integral foils for surf craft fins according to invention provide sufficient extra lift to permit less foot movement up and down the board to create the acceleration or deceleration as compared with typical straight fins. Also having the tip of the fin wider than the base of the fin allows for more grab or hold onto the face of the wave, which holds the surf craft into the face of the wave and also allows for easier turns on the face of the wave and off the bottom of the wave in the bottom turn.

The integral foils for surf craft fins according to invention are moulded in one piece with the foil section for lift incorporated in the main design of the overall fin to create lift and maximum control. The aim of the design of the foil surface of the fin is to create minimum drag through the water and maximum lift of the surf craft through the water to minimise the water tension and drag of the surf craft that the fins are attached to with the water.

Although the invention has been described with reference to a specific example, it will be appreciated by persons skilled in the art the invention may be embodied in other forms within the broad scope and ambit of the invention as herein set forth and defined by the following claims.