2. Background and Prior Art It is known to produce a releasable fin for surfboards and the like, such that the fin can be replaced if damaged, or conditions of the water changes, 10 e. g. different wave conditions. In the prior art, such as Australian patent no.

665804, some of the replaceable fins are affixed to the boards by screws, which requires tools to remove and replace the fin, or by a cam, as in Australian patent 718340. In other situations the replaceable fins have a tab, which fits into a slot cut into the board and has backwardly facing barbed sides, which 15 lock into the core of the board to resist removal.

Another prior art replaceable fin is shown in Australian Patent no.

693962, in which the replaceable fin system has a pot fitted into the board. The

pot has a central slot with reversed tapered walls flaring from its opening to its base within the board. The fin has a tab portion to fit into the central slot. The tab has tapered sides, complementary to the flared central slot, which at least one vertically longitudinally extending cutout in the tab to form wings, which are forced together to allow the tab to fit within the slot opening.

Whilst this system is acceptable, it has been found that the reverse taper on the wings of the tab, allows the tab to wiggle partway out of the slot in certain conditions of high stress, which greatly reduces the efficiency of the fin.

Summary of the Invention The present invention seeks to ameliorate the above disadvantages by providing a replaceable fin system for an aquafoil, such as surfboards, body boards, wave skis, sail boards, wake boards and the like, comprising: a pot having a slot therein, and adapted to be fitted into the surface of the aquafoil ; a first connection means extending into said slot ; a fin having a tab which fits within said slot, and a second connection means located on said tab, which releaseably engages with said first connection means to retain said tab in said slot.

In one embodiment the wall or walls of the slot are substantially parallel In another form, the invention comprises a replaceable fin system for an aquafoil, such as surfboards, body boards, wave skis, sail boards, wake boards and the like, comprising: a pot having a slot, therein, and adapted to be fitted into the surface of the aquafoil ; a fin having a leading edge, a trailing edge, a bottom surface and a tab extending from the bottom surface away from the fin and extending along the bottom surface from the leading edge to a point intermediate the leading and trailing edges of the fin, said tab fitting within said slot ; and a connection means located on said tab, which releaseably engages in said slot.

In one embodiment, the second connection means is formed integrally with said pot.

In a further embodiment, the second connection means fits into the base of the slot where it is held against the base of the pot.

In a further form the invention comprise a method of inserting a pot for a replaceable fin system for an aquafoil, such as surfboards, body boards, wave skis, sail boards, wake boards and the like, as described before comprising the steps of: marking aligning points on the aquafoil, for the fin position; positioning a first jig having registration points and a central cutout, such that the registration points align with the registration markers on the aquafoil and securing said first jig in position; routing out a cavity bounded by the periphery of the central cavity of the first jig; attaching one of said pots to a setup jig and positioning said setup jig on said first jig such that said pot is positioned within said cavity; introducing a setting compound into said cavity around said pot and allowing said setting compound to set to secure said pot in said cavity; and removing said setup jig from said pot.

Preferably the setting compound is a resin.

Preferably the registration markers are cross hair lines, and the opening of the pot cavity is bevelled.

Brief Description of the Drawings The present invention will now be described with reference to the accompanying drawings in which: Figure 1 illustrates a bottom exploded perspective view of a fin system according to one embodiment of the present invention ; Figure 2 illustrates a top exploded perspective view of the fin system show in figure 1; Figure 3 illustrates a sectional view of the fin system according to figures 1 & 2, with the components connected; Figure 4 illustrates schematically, stages in aligning the first jig on the surfboard ; Figure 5 illustrates the stage of affixing the setup jig to a pot of the fin system as shown in figures 1 to 3 of the accompanying drawings; Figure 6 illustrates schematically the positioning of the pot of the fin system as shown in figures 1 to 3 of the accompanying drawings into the board cavity;

Figure 7 illustrates schematically a further stage in affixing the pot of the fin system as shown in figures 1 to 3 of the accompanying drawings into the board cavity; Figure 8 illustrates schematically the affixing of a fin into the fin system according to the embodiment shown in figures 1 to 3 of the accompanying drawings; Figure 9 illustrates a top exploded perspective view of a fin system according to another embodiment of the present invention, with a cut away view of the pot; and Figure 10 illustrates a sectional view of the fin system according to figure 9, with the components connected.

Detailed Description of the preferred Embodiments As shown in figures 1,2 and 3, a replaceable fin system according to one embodiment of the present invention comprises a clip (1), a fin (2) and a pot (3). The clip (1) comprises a base (4) having two arms (5), terminating in free ends (6), forming a c-shaped cavity (7) therebetween. The clip (1) also has two shoulders (8) extending outwardly from the base (4) beyond the arms (5).

The pot (3) comprises a central body (9) having an array of outwardly extending wings (10) on each side thereof. A longitudinally extending closed slot (11) extends into the central body (9) and a cutout (12) is formed in the base (13) of the pot (3) to receive the clip (1). Whereby the clip (1) extends into the slot (11) with the shoulders (8) of the clip (1) abutting against the recessed shoulders (14) of the cutout (12).

The fin (2) comprises a leading edge (15), a trailing edge (16) and a base (17), with a tab (18) extending therefrom. In the described embodiment, the tab (18) starts at the leading edge (15) of fin and extends along the base (17) to approximately mid point of the base (17). The tab (18) has two end portions (19), which are of substantially the same width as the width of the slot (11) and has an intermediate section (20) an outer rail (21) with two recesses (22) located behind the rail (21).

Therefore when the clip (1) is in position in said cutout (12), and the tab (18) of the fin (2) is pushed into the slot (11), the rail (21) forces the free ends (6) of the arms (5) of the clip (1) apart and mates in the c-shaped cavity (7) of clip (1), with the free ends (6) of the arms (5) engaging behind the rail (21) in the recesses (22), as shown in figure 3, to exert vertical pressure on the rail (21), drawing the fin (2) downwardly into the slot (11).

The fin system can be affixed to board as shown in figures 4 to 8, wherein the pot (3) and clip (1) are embedded in the board (23).

As shown in figure 4, two reference points (24) are marked on the board (23) for each fin (2) position. A suitable adhesive in the case a double sided 5 adhesive tape (25) is applied to the board (23). The jig (26) is positioned on the adhesive by aligning the respective reference lines (27) with the reference points (24) on the board. (23). With the back central fin the middle cross hairs (28) are used to align with the reference points (24), while with the forward angled fins the respective inside cross hairs (29) are used to align with the 10 reference points (24).

The jig (26) is then secured by the adhesive tape (25) and a router is used to follow the periphery of the central opening (30) of the jig (26) to form a cavity (31) in the board (23) to receive the pot (3). Preferably the edges of the cavity are bevelled or under cut.

15 As shown in figure 5, a set up jig (32) is inserted into the slot (11) and the pot (3) placed in the cavity (31) in the board (23), with the set up jig (32) resting upon the jig (26), with part of the central body (9) standing proud of the cavity (31). A suitable setting compound, such as a resin mixture, is poured to

fill the cavity (31) around the pot (3). The resin is allowed to cure for a suitable time, and the set up jig (32) and the jig (26) are removed.

Then as shown in figure 7, the central body (9) of the pot (3), standing proud of the cavity (31) and any additional resin is sanded away, to a smooth finish, leaving the slot (11) substantially flush with the surface of the board (23).

The fin (2) is simple affixed to the board (23) by pushing the tab (18) into the slot (11), where the tab (18) locks into the clip (1) as described previously.

In the prior art, fins have a tab adjacent each end of the base, or a full length tab, both of which prevents pivoting of the trailing edge of the fin, or as shown in Australian Patent no. 693962, a centrally located tab, which does not allow for full pivoting of the trailing edge of the fin. In the embodiments of the present invention, by positioning the tab (18) at the leading edge (15) of the fin (2) and having it finish at approximately the mid point of the base (17) of the fin (2), the trailing edge is free of the board (23), and can pivot, to a greater degree, under the hydraulic forces to reduce drag and cavitation and increase the power of the fin (2). However the tab (18) can finish any suitable distance along the fin provided that the tab starts at the leading edge (15) of the fin (2).

A further embodiment of the fin system is shown in figures 9 & 10 in which the pot (3) has locking arms (5), which operate in the same manner to engage the rail (21) and engage in the recesses (22) as the arms (5) of the clip (1) described previously.

Further the shape of the rail and the form of the arms and the respective recesses can be any suitable shape. Further any suitable male and female 5 connections involving a positive locking fit as compared to a frictional fit can be used to connect the tab of the fin in the slot of the pot. Further the male component could be in the slot with the female component on the fin.

The pot can be made of any suitable polymer material, such as polycarbonate with a 20% glass fill ; the clip could be made from any suitable 10 polymer, such as nylon 66, acetyl or polyethylene or polypropylene or an elastomer ; the fin could be made from any suitable material.

It should be obvious to people skilled in the art that alterations and modifications could be made to the above described embodiment without departing from the scope and the spirit of the present invention.

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