Fin retention system for a water craft

A fin box for a water craft including: a fin box body having an elongated slot open at a first surface of the fix box and extending to a closed base of the fin box; a peripheral flange extending outwardly from the slot and defining an area of the first surface around the slot; the peripheral flange having a second lower surface and a third upper surface both offset vertically from the first surface and extending laterally from the fin box body, the second lower surface and said third upper surface further comprising a left and right side, each said left and right side surfaces extending transversely from the body portion to peripheral extremities of said peripheral flange, wherein at least one surface of said peripheral flange forms a transverse angle of taper with an axial median vertical plane of the fin box body.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to watercraft, such as surfboards and surf skis, and particularly relates to fins on watercraft.

2. Description of the Background Art

Water craft such as surfboards, surf skis and wind surfers for example, are provided with one or more fins at their underside for stability and to allow a rider better control of direction and manoeuvrability. Many riders prefer certain fin profiles for particular conditions or riding styles so that it has become commonplace to provide such craft with slots capable of accepting interchangeable fins.

The designs of watercraft and specifically surfboards have advanced to include multi-fin systems. The first fin system was a single center fin to enable the basic maneuvering of the board. Developments in the 1980s resulted in the addition of side fins, either as a 3 (tri) fin system comprising a center fin and 2 side fins, or just two side fins (twin). Differing board performance can be achieved by extending the number of fins to 4 fins (quad) that is 2 sets of fins per side.

Of these combinations the one that provides the maximum flexibility is the 5 fin box system, as illustrated inFIG. 13, in that it combines the quad and the tri fin setups. This enables the user to use a standard tri fin set up of a center and a side fin each side, or the alternative of removing the center fin and adding two trailing rear side fins behind the existing side fins of the tri setup to create the quad.

For the tri side fins to provide the required steering characteristics, the inside face of the fin blade is generally flat or has a concave profile. The design of the trailing rear side fins in a 4 fin configuration, differ to the tri side fins, being generally smaller, can be symmetrical double foiled fins, enabling their use in either center or rear side trailing fin positions.

Another characteristic of the trailing rear side fins is that they are generally canted at a smaller angle (typically 2 degrees) than those of the tri Side fins (6 degrees). The fin placement for the tri configuration is well known by the industry, however, when the center fin of the tri configuration is removed and replaced by the two trailing side fins of the quad configuration the relative distance between the two sets of side fins needs to be adjusted for optimum performance.

It would be an advantage to the industry if a standard double foiled symmetrical axial aligned fin with a fin tab arrangement shorter than the length of the fin box slot, containing elongated dual-sided screw receiving slots, enabling the variable adjustment of the fin can be used along with a standard fin box that can be installed at a variable cant angle enabling a single fin and fin box to be used in multiple positions on the board at the time of manufacture.

Another feature particularly of high performance surf boards is that the underside surface of the board is provided with scalloped channels between the center fin and the side fins. These concave formations can cause the edges of the flanges of the fin boxes to protrude through the fiberglass surface of the underside surface of the board.

The present applicant disclosed in WO2006/077470 arrangements of fin boxes adapted to accept a variety of proprietary fin tab configurations.

One problem with fin boxes adapted to accept various fin tab configurations is that the length of slot required is such that distortion of the box may occur when heavy lateral loads are applied to large fins, or when the side retention screws are over tightened. This distortion takes the form of a spreading of the side walls of the slot.

To ensure waterproofing and increased structural strength of the fin box bond to the watercraft core it is preferred to have a layer of re-inforcing cloth to cover the external section of the outer surface of the fin box, and for sections of that surface to be perforated or grooved, to improve the resin bond to the fin box.

A disadvantage with the fixing of a fin box into the core of a water craft is that in some fin box installations a cavity is cut through the outer glassed surface of the board. This causes some inherent weakness as there is no direct bond between the fin box and the glassed surface.

A common feature of systems which provide for interchangeable fins to be retained within a fin box is the securing of the fin tab in the fin box by means of one or more grub screws. Such screws are generally provided with a hexagon drive socket at one end and threaded for their entire length. A problem with this arrangement is that it is easy for a user, anxious not to lose a fin from the box, to over-drive the screw with the associated risk of damage to the fin tab and/or the fin box, or even of stripping the thread of the screw hole within the fin box.

The fin box disclosed herein addresses or at least ameliorates all or some of the above disadvantages.

The term “comprising” (and grammatical variations thereof) is used in this specification in the inclusive sense of “having” or “including”, and not in the exclusive sense of “consisting only of”.

The above discussion of the prior art in the Background of the invention, is not an admission that any information discussed therein is citable prior art or part of the common general knowledge of persons skilled in the art in any country.

In this specification, terms such as upper, under, lower and vertical etc. refer to surfaces and directions when a water craft is oriented for use with its median plane substantially horizontal.

SUMMARY OF THE INVENTION

A fin attachment system for a water craft is disclosed including a fin box adapted for insertion and releasable attachment of a fin to an underside of said craft; said fin box comprising a body portion provided with at least one elongate slot open at a first surface of said body, and extending to the closed base of the body portion, said fin box further comprising a peripheral flange; a first surface of said flange forming a continuation of said first surface of said body; said fin box characterised by a tapered flange arrangement allowing use of said fin box for each of a central vertical fin and a left side and right side canted fin, wherein a first surface of at least one flange side forms an angle of taper with a axial median plane of said body portion.

The fin attachment system for a water craft may include a fin box adapted for insertion and releasable attachment of a fin to an underside of said water craft; said fin box comprising a body portion provided with at least one elongate slot open at a first surface of said body, and extending to the closed base of the said body portion, said fin box further provided with a peripheral flange extending outwardly from said body portion at said first surface, a first portion of said flange defining an area of said first surface around said elongate slot, a second portion of said flange defining a second lower surface and a third upper surface, both said second and third surfaces offset vertically from said first surface and extending laterally from said body portion, said second lower surface and said third upper surface further comprising a left and right side, each said left and right side surfaces extending transversely from the said body portion to the peripheral extremities of said peripheral flange, said fin box further characterised by a tapered flange arrangement allowing use of said fin box for each of a central vertical fin and a left side and right side canted fin, wherein at least one surface of said peripheral flange forms a transverse angle of taper with an axial median vertical plane of said body portion, said transverse angle of taper being uniformly distributed across the width of at least one of the said surface areas of said peripheral flange.

The body portion of said fin box may be inserted into a body portion recess machined into a core of said water craft; said peripheral flange nesting in a peripheral recess machined around said body portion recess.

The fin box may have a vertical slot and be inserted into a core of said water craft for a central fin, has an upper surface of a peripheral first flange side forming an angle of taper with said axial median plane of said body portion; and an upper surface of the peripheral second opposite flange side, forming an angle of taper with said axial median plane of said body portion; an under surface of said first flange side forming an angle of taper with said axial median plane of said body portion, and an under surface of said second flange side forming an angle of taper with said axial median plane of said body portion.

A fin box is disclosed herein with a vertical slot, inserted into a core of said water craft for a central fin, has an upper surface of said peripheral first flange side forming an angle of taper with said axial median plane of said body portion; and an upper surface of said peripheral second opposite flange side, forming a right angle with a axial median plane of said body portion; said upper surface of second opposite flange side abutting a surface of said peripheral recess; said under surface of said opposite second flange side forms an angle of taper with said axial median plane of said body portion said fin box being in said first fore/aft orientation.

The a fin box with a vertical slot is inserted at an angle into a core of said water craft for a left side canted fin, has an upper surface of said peripheral first flange side forming an angle of taper with said axial median plane of said body portion; said upper surface abutting a surface of said peripheral recess; said under surface of said opposite second flange side forms an angle of taper with said axial median plane of said body portion, said under surface abutting an inner surface of said glassed skin of said water craft; said fin box being in said first fore/aft orientation.

A fin box with a vertical slot is inserted at an angle into a core of said water craft for a right side canted fin, has an upper surface of said peripheral first flange side forming an angle of taper with said axial median plane of said body portion; said upper surface abutting a surface of said peripheral recess; said under surface of said opposite second flange side forms an angle of taper with said axial median plane of said body portion; said under surface abutting an inner surface of said glassed skin of said water craft; said fin box being in a second opposite fore/aft orientation.

A fin box with a canted slot is inserted vertically into a core of said water craft for a left side canted fin, said peripheral first flange side has an upper surface forming a right angle with said axial median plane of said body portion; said upper surface abutting a surface of said peripheral recess; said under surface of said opposite second flange side forms an angle of taper with said axial median plane of said body portion; said under surface abutting an inner surface of said glassed skin of said water craft; said fin box being in said first fore/aft orientation.

A fin box with a canted slot is inserted vertically into a core of said water craft for a right side canted fin, said peripheral first flange side has an upper surface forming a right angle with said axial median plane of said body portion; said upper surface abutting a surface of said peripheral recess; said under surface of said opposite second flange side forms an angle of taper with said axial median plane of said body portion, said under surface abutting an inner surface of said glassed skin of said water craft; said fin box being in a second opposite fore/aft orientation.

A fin box with a vertical elongate slot, with the said body portion inserted vertically into a core of said water craft for a central fin, has a said third upper right side surface of said peripheral flange forming an angle of taper with said axial median plane of said body portion; and a said third upper left surface of said peripheral flange, forming a right angle with said axial median plane of said body portion; said third upper left side surface abutting a surface of said peripheral recess; a said second lower left side surface of said peripheral flange forms an angle of taper with the said axial median plane of said body portion, said fin box inserted into the core of the said watercraft in a first fore/aft orientation.

A fin box with a vertical elongate slot, with said body portion inserted at an angle into a core of said water craft for a right side canted fin, has a said third upper right side surface of said peripheral flange forming an angle of taper with said axial median plane of said body portion; said third upper right side surface abutting a surface of said peripheral recess; a second lower left side surface of said peripheral flange forms an angle of taper with said axial median plane of said body portion, said second lower left side surface abutting an inner surface of the glassed skin of said water craft; said fin box inserted into the core of the said watercraft in said first fore/aft orientation.

A fin box with a vertical elongate slot, with said body portion inserted at an angle into a core of said water craft for a left side canted fin, has a third upper left side surface of said peripheral flange forming an angle of taper with said axial median plane of said body portion; said third upper left side surface abutting a surface of said peripheral recess; a second lower right side surface of said flange forms an angle of taper with said axial median plane of said body portion; said second lower right side surface abutting an inner surface of said glassed skin of said water craft; said fin box being in a second opposite fore/aft orientation.

A fin box with a vertical elongate slot, with said body portion is inserted into a core of said water craft for a central fin or a side fin, has a third upper right side surface of a peripheral flange forming an angle of taper with said axial median plane of said body portion; and a said third upper left side surface of the said peripheral flange, forming an angle of taper with said axial median plane of said body portion; a second lower right side surface of said peripheral flange forming an angle of taper with said axial median plane of said body portion, and a second lower left side surface of said peripheral flange forming an angle of taper with said axial median plane of said body portion, said fin box inserted into the core of the said watercraft in either the first or second fore/aft orientation.

A fin box with a canted elongate slot, with said body portion inserted vertically into a core of said water craft for a right side canted fin, has a said third upper left side surface of said peripheral flange forming a right angle with said axial median plane of said body portion; said third upper left side surface abutting a surface of said peripheral recess; a second lower left side surface of said peripheral flange forms an angle of taper with said axial median plane of said body portion; said second lower left side surface abutting an inner surface of said glassed skin of said water craft; said fin box being in said first fore/aft orientation.

A fin box with a canted elongate slot, with said body portion is inserted vertically into a core of said water craft for a left side canted fin, has a said third upper right side surface of said peripheral flange forming a right angle with said axial median plane of said body portion; said third upper right side surface abutting a surface of said peripheral recess; a second lower right side surface of said peripheral flange forms an angle of taper with said axial median plane of said body portion, said second lower right side surface abutting an inner surface of said glassed skin of said water craft; said fin box being in a second opposite fore/aft orientation.

A fin box with a canted elongate slot, with said body portion is inserted at an angle into a core of said water craft for a right side canted fin, has a said third upper left side surface of said peripheral flange forming an angle of taper with said axial median plane of said body portion; said third upper left side surface abutting a surface of said peripheral recess; a second lower left side surface of said peripheral flange forms an angle of taper with said axial median plane of said body portion; said second lower left side surface abutting an inner surface of said glassed skin of said water craft; said fin box being in said first fore/aft orientation, the said fin box when rotated in a second opposite fore/aft orientation used as a left side canted fin.

A fin box with an associated tapered flange may include a body portion and at least two elongated slots, said slots separated by a transverse strengthening rib; said strengthening rib extending substantially the depth of said slots.

The fin box with an associated tapered flange may also include a body portion and at least two elongated slots, said slots separated by a transverse strengthening rib.

A fin attachment system for a water craft includes a fin box with a tapered flange, a fin having a foil section and a fin tab section, said fin suitable for insertion, releasable attachment and securable positioning within the said elongated slot of the said fin box, said fin is retained in a said elongate slot by at least one screw driven through at least one angled screw hole extending from a first surface of said fin box to at least one internal surface of said elongate slot; said screw engaging with a fin tab of a fin inserted in said elongate slot.

The fin may have a fin tab or multiple fin tabs, the overall length of any combination of said fin tab(s) being shorter than the overall length of the said elongate slot of the said fin box, said fin tab of the said fin contains elongated screw retaining recesses on both sides of the said fin tab, allowing the fin to be inserted into the said elongate slot of the said fin box, and adjusted in a longitudinal direction within the said elongate slot; said fin tab of said fin secured by the said angular screw emerging within the said elongate slot and abutting the said elongated screw retaining recess of the fin tab in the adjusted position.

The screw may be a stainless steel screw, and include an unthreaded head portion and a threaded shank portion.

The at least one angled hole may include a threaded portion and a recessed portion slightly larger than the root diameter of said threaded portion. The recessed portion may be adapted to accommodate said unthreaded head portion of a said screw; said screw and said recessed portion arranged so as to limit the extent to which said screw may be driven through said hole.

The fin tab of the said fin may contain screw retention recesses on both sides of the said fin tab, said headed screw when inserted into the dual diameter multi-level angled threaded retention hole, securely holds the said fin tab of the said fin in position at a pre-determined position within said elongated slot within said fin box, wherein the said headed screw emerges within the said elongate slot and abuts the said screw retaining recess of the fin tab; the head of the said headed screw remaining embedded below the first surface of the body portion whilst securing the fin to the fin box and to the water craft when seated in the said dual diameter multi-level angled threaded retention hole and abutting the said fin tab.

The peripheral flange may contain a perforated trademark, logo or identifying symbol located on the lateral side of the said peripheral flange. The peripheral flange may further contain grooves on the surface of the said peripheral flange.

DESCRIPTION OF THE PREFERRED

The fin boxes disclosed herein typically comprise a body portion consisting of a generally rectangular block in which is provided at least one elongate slot extending from a fin insertion side to the closed base, (or upper portion when installed and in use) of the block.

Additionally, the fin box can comprise a peripheral flange at or adjacent to the fin insertion side extending outwardly from the body portion. The installation of the fin box into a water craft is by cutting a body portion recess in the core of the craft for the nesting of the body portion, and a peripheral recess to accommodate the flange.

The flange may be offset a little from the fin insertion side surface of the body portion to allow glassing over of the flange to lock the fin box within the underside of the craft, creating a water-proof seal over the fin box and leaving only an area around the slot exposed. Set-screws, driven through angled threaded holes extending from the exposed fin insertion side surface area of the fin box to the inside surface or surfaces of the slot, engage the fin tab(s) of a fin, securing the fin in the slot.

The fin box may include a mid-height center cross-brace to minimizes distortion of the fin box due to over-tightening of side screws. Tapered flanges on the fin box allow the fin box to have multiple orientations for the varying bottom contours on different surfboards. Significantly large perforations in the flange to allow resin around the base of the fin box to pass through the perforations and create a bond with the fiberglass skin of the surfboard surface. Flange surface grooves increase the bonding area for resin saturated fibreglass skin. Dual-diameter screws limit the depth of penetration, (less distortion and damage to fin tabs) and still extend below the surface of the fin box lip.

A fin for a water craft may have fin tabs with elongated slots in some or all sides of the tabs. A mid-height strengthening bar may extend the fin tabs to increase the support of the fin base in the fin box and reduce the risk of breakage of the fin tabs.

There is a requirement to be able to vary the longitudinal position of all fins and in particular the vertical angle (cant) of the side fins, especially with the new development of multi-fin watercraft, and specifically for 4 and 5 fin box configurations. The major change is that the traditional 3 fin setup has two additional side fins added at the rear between the existing side fins and center fin as illustrated inFIGS. 13A and 13B. This enables a surfer to use a traditional 3 fin setup as illustrated inFIG. 13Aor switch to a 4 fin setup (2 sets of side fins) as illustrated inFIG. 13B, by removing the center fin and adding the two rear side fins, to change the performance features of the watercraft.

The side fin cant in a typical tri fin setup is usually 5 to 6 degrees outwardly toward the rail of the watercraft, and can be achieved by either having the cant angle molded into the fin box for accepting a fin with an axially aligned fin tab, or alternatively a fin box with a vertical recess that accepts fins with the fin tab offset at the required cant angle. The former means that the cant angle is fixed within the fin box, whereas with the latter the only option to vary the cant is to change the fin tab offset.

FIGS. 10Aand B andFIGS. 11Aand B show cross-sectional views of two preferred embodiments of fin boxes which have tapered flange configurations. The tapering of the peripheral flange allows the cant angle of the fin box itself to be set during installation and using fins with standard axially aligned fin-tabs, so that multiple fin cant angles can be achieved. This is particularly important as typically the rear side fins of a 4 fin setup are at a reduced cant angle of approximately 2 to 3 degrees, thus allowing the same fin box to be used as a centre fin box or a side fin box.

The tapered flanges also assist in resolving manufacturing issues related to the installation of fin boxes in performance water craft with contoured bottom profiles. Typically the fins are secured with two screws on one side of the flange (for side box installation) and two screws one on each side of the flange for the centre fin box installation or a single end screw as shown in FIGS.4,7and8respectively. To further facilitate this flexibility, the number of side securing screws to lock a fin in the fin slot can be increased to at least three, as shown inFIG. 12. This is a combination of the existing side and center configurations. A symmetrical configuration of four screws, two on each side accommodates all types of fins in any fin box position, fin tabs containing elongated dual-sided screw receiving recesses facilitate the flexibility of securing any fin with any of the above screw combinations. A perforated identifying mark, such as a trade mark is located on the flange side with the taper on the lower side of the flange, so as to be used as an alignment reference (the perforated mark always adjacent the watercraft rail). Rotating the symmetrical fin box longitudinally allows for left and right side installation, again with the perforated mark adjacent the rail.

The fin box ofFIG. 10Ahas tapers on both top and bottom surfaces of both side flanges, andFIG. 10Bhas tapers on only the two top surfaces and one bottom surface.

FIG. 11A, shows a vertical centre fin box configuration, the left hand side flange has a taper on top with a flat section on the bottom of the flange, and is the side that contains the perforated mark. The right hand side flange has a taper on the bottom with a flat section on top of the flange.FIG. 11Bshows a left side fin box configuration in which the fin box ofFIG. 11Ais canted toward the outside rail of the watercraft.

FIGS. 12Ato C are further embodiments of the fin box11A. InFIG. 12A, the fin box is in the vertical position for a center installation. Referring toFIG. 12B, for a left side installation, the fin box is angled outwardly toward the left rail; this raises the tapered upper surface of the left side flange up into the flange recess in the foam core. Simultaneously the right side flange rotates down but as the under surface of this flange is tapered, the outside edge of the flange remains below the surface of the glass surface.

Referring toFIG. 12C, for a right side installation, the fin box is rotated longitudinally such that the perforated mark is adjacent the right rail. Again, as the fin box is angled outwardly toward the right rail, the tapered upper surface of the right side flange containing the perforated mark is raised up into the flange recess in the foam core. Simultaneously the left side flange rotates down but as the under surface of this flange is tapered, the outside edge of the flange remains below the surface of the glass surface.

First Embodiment

With reference toFIGS. 1,2A and2B, a fin box10comprises a body portion12a slot15extending substantially the full length of body portion12, a fin insertion surface16, a tapered flange18, and a pair of angled screw holes14located one on each side of the elongate slot.

An associated fin20, comprising a foil section21and a fin tab22containing multiple elongated screw retaining recesses23on both sides of the fin tab arranged to be co-incident with the angled screw holes.

The fin tab length is shorter than the elongated fin box slot allowing adjustment of the position of the fin within the fin box slot.

Elongated screw retaining recesses on both sides of the fin tab, as shown for various fin tab configurations inFIGS. 21A to 21Dfacilitate secure connection of the fin to the fin box and surfboard with multiple possible combinations of retaining screws with the fin in the preferred adjusted position.

In a first arrangement of the first embodiment, turning specifically toFIG. 10A, a fin box400according to any of the above described embodiments, is shown assembled within the core402of a water craft404. It can be seen that the core402of the craft404has been provided with a recess406adapted to accept the body portion412of the fin box400. Likewise a peripheral recess408has been machined to a depth to accommodate peripheral flange414to the extent that only the surface411of the fin insertion side of body portion412is exposed and flush with the outer surface405of glassed skin407. In this instance, the peripheral flange414on either side of body portion412is symmetrically tapered on all four upper and lower surfaces416,417,418and419and a plane403defined by flange414is normal to the median axis409of the body portion412, such that a centre fin420projects from slot415normal to the surface405.

In a second arrangement of the first embodiment, a fin box420according to any of the above described embodiments is shown assembled within the core422of a water craft424. It can be seen that the core422of the craft424has been provided with a recess426adapted to accept the body portion432of the fin box420. Likewise a peripheral recess428has been machined to a depth to accommodate peripheral flange434to the extent that only the surface431of the fin insertion side of body portion432is exposed and flush with the outer surface425of glassed skin427. In this instance, the peripheral flange434has only three tapered surfaces, the upper first side surface436, the under first side surface437and under second side surface439.

The second flange side upper surface438is at a right angle to the axial median plane429of body portion432, a plane423defined by flange434is normal to the median axis429of the body portion432, such that a centre fin440projects from slot435normal to the surface425.

Second Embodiment

In the second embodiment, with reference toFIG. 11Athe peripheral flange sides514A and514B of fin box500are not symmetrically tapered on either side of body portion512. Peripheral flange sides514A and514B are tapered towards the outer edge517A and517B respectively. The upper or first surface530A of flange side514A forms a right angle with the side of body portion512. Similarly the lower or first surface530B of flange side514B forms a right angle with the opposite side of body portion512. The tapering of flange sides514A and514B is such that the angle between each of the second surfaces531A and531B opposite the first surfaces530A and530B respectively, is equal to the angle a between the planes of canted left hand side fin520B (seeFIG. 12B) and canted right hand side fin520C (seeFIG. 12C), and the vertical.

Still with reference toFIG. 11A, the depth of the peripheral recess508, and the vertical offset between surfaces530A and530B, are arranged so that with the fin box inserted into a recess506for a central vertical fin520, upper surface530A is in contact with the surface of the peripheral recess508, while lower surface530B is in contact with the inner surface of glassed skin507.

Turning now toFIGS. 12A to 12C, in which a three fin arrangement for a surf craft comprises a central fin520A, a left side fin520B and a right side fin520C. It will be noted that the two outer fins520B and520C are canted outwardly towards opposing edges (not shown) of the water craft to which they are fitted. This arrangement of a vertical central fin and outwardly canted side fins can be accommodated in the one configuration of a fin box as described above with reference toFIGS. 11A and 11B.

It will be seen inFIG. 12Athat the fin box500is the same as that ofFIG. 11A. The sides of the recess506accommodating the body portion512of the fin box are normal to the surface505. The surfaces530A and530B (which are at right angles to body portion512) of opposing flange sides514A and514B respectively abutting the surface of the flange recess508and inner surface of glassed skin507, again as previously described.

With reference toFIG. 12B, the fin box500is the same as that ofFIG. 11A, the recess for the body portion512of the fin box is cut into the core560normal to the surface of the core. The foam material of the core is sufficiently resilient to allow the canting of the fin box. When the fin box body portion512is then fully inserted into its recess, it can be held in its canted position so that after the application of the skin, the upper surface531B of left hand flange side514B abuts the surface of the peripheral flange recess, while the under surface531A of right hand flange side514A abuts the inner surface of glassed skin507.

It will be noted from the plan view of the fin boxes for the central location ofFIG. 12Aand the left hand location ofFIG. 12B, that the fin boxes are oriented fore/aft in the same direction, as can be seen by the perforated logo “SurFinz” and the disposition of the securing screw holes524. The logo in fact serves as a reference guide in that for side fins the fin box is always oriented with the logo towards the rail or outer edge of the craft.

For the canting of fin520C, again a recess is cut into the core560normal to the surface of the core. However in this case, the fin box is turned end for end before insertion, so that the logo “SurFinz” is now at the opposite side of the slot515. The flange sides514A and514B are then also reversed so that it is now the lower surface531A of flange side514A which abuts the inner surface of glassed skin507, while the upper surface531B of flange side514B abuts the surface of peripheral recess508.

By this arrangement of the peripheral flange514, a single configuration of a fin box can be utilised for the three positions of fins, allowing for a vertical central fin and outwardly canted side fins.

Typically, the maximum angle of canting desirable for the outer fins of a surf craft for a two or three fin arrangement is 6 degrees, while for a four fin arrangement the secondary outer fins (that is the pair of outer fins between the rear end of the craft and the forward outer fins) (seeFIG. 13B), is 2 degrees. It will be understood that the arrangement of the tapered peripheral flange as described for the present embodiment allows a fin box to be canted to any angle between 0 degrees and the angle of taper which preferably is 6 degrees.

It will readily understood that conversely the flange tapers can be reversed if the market requires the side fins to be secured by screws on the opposite side (rail side flange) of the fin box.

Third Embodiment

As shown inFIGS. 13A and 15A, B, C and D, a feature particularly of high performance surf boards is that the underside surface of a board600is provided with scalloped channels601between the center fin617and the two side fins615and616. If a fin box with a canted slot is installed in the normal vertical position there is a risk that the lower flange surfaces of the center fin box and at least one of the inside lower flange surfaces of each of the left and right hand fin boxes, may protrude through the fiberglass surface of the underside of the board.

FIG. 14Ashows in detail a fin insertion side and cross section of a fin box308with a canted slot, according to a third embodiment, installed in the normal vertical position and arranged as a side fin box with a single outwardly extending tapered flange surface containing grooves303and perforations302.

In this third embodiment, a fin box installed to accept a left side fin, has only the lower surface331of the right side peripheral flange314tapered towards its outer edge. The upper surface332, of flange side314forms a right angle with the side of body portion312. Both the lower and upper surfaces333and334of the left side flange315also form right angles with the opposite side of body portion312. The tapering of flange side314is at an angle (X Degrees) equivalent to the angle created by the concave channel. Rotating this fin box will provide a fin box for a right side fin.

Fourth Embodiment

FIG. 14Bshows a fin insertion side and cross section of a fin box309, according to a fourth embodiment arranged as a center fin with two outwardly extending tapered flange surfaces containing grooves303and perforations302.

Still with reference toFIG. 14B, the peripheral flange sides317and318on either side of body322, have both their lower surfaces336and338tapered towards their respective outer edges. Both their upper surfaces337and339form right angles with the side of body portion312.

FIGS. 15A, B, C and D exhibit the use of these embodiments to enable the fin box to be installed in a vertical alignment and eliminate the issues associated with channels in the bottom of surfboards.

InFIG. 15Bboth underside surfaces661of the peripheral flanges640of the central fin box630are angled away from surface667, so as to ensure that the flange remains under the outer skin of the board. Similarly, inFIGS. 15Aand C the inward facing underside surfaces662and664of the flanges642of the left hand and644of the right hand fin boxes622and624respectively are also angled away from surface667, whilst the upper surfaces of all the flanges remain at right angles to the fin box body portions602,610and604.

The underside portion of the peripheral flanges640,642and644are provided with a plurality of surface grooves635and apertures631, distributed at intervals around the recess680(also shown as grooves303and perforations302inFIGS. 14Aand B around recess301). These apertures are adapted to allow passage through the apertures of resin or bonding agent and any trapped air, additionally the surface grooves increase the bonding strength of the flange to the external fiber glass skin, thereby increasing the retention strength of the fin box to the foam core of a surfboard when lateral and axial forces act on a fin inserted in the fin box.

Fifth Embodiment

In a fifth embodimentFIGS. 9Ato D show arrangements for the strengthening of a fin box to reduce distortion in the fin box as a result of lateral forces applied to a fin tab of a fin (not shown) inserted into the fin box, secured by screws driven through angular threaded screw holes220A and220B and emerging within elongated slots240A and240B.

In a first arrangement of the fifth embodiment with reference toFIGS. 9A and 9Ba fin box200comprises a recess that is divided into two sections by divider portion230, effectively forming two longitudinally aligned recesses240A and240B, that contain angular threaded screw holes220A and220B that accept fin securing screws.

In a second arrangement of the fifth embodiment with reference toFIGS. 9C and 9D, a fin box250comprises a recess that is divided into two sections by divider portion280, effectively forming two longitudinally aligned recesses290A and290B, also containing angular threaded screw holes270A and270B that accept fin securing screws; in this arrangement the divider portion280partially fills the recess.

An advantage of these particular arrangements of the fin box is that there is a considerable strengthening of the box compared with that of a single continuous recess.

Sixth Embodiment

With reference toFIGS. 1,2A and2B, a fin box10according to the sixth preferred embodiment, comprises a body portion12a slot15extending substantially the full length of body portion12, a fin insertion surface16, a tapered flange18, and in this embodiment a pair of dual diameter multi-level angled screw holes14located one on each side of the elongate slot.

An associated fin20, comprising a foil section21and a fin tab22containing multiple elongated screw retaining recesses23on both sides of the fin tab arranged to be co-incident with the angled screw holes.

The fin tab length is shorter than the elongated fin box slot allowing adjustment of the position of the fin within the fin box slot and ensuring secure connection of the fin to the fin box and surfboard by the headed screw50.

Headed screw50, as shown inFIGS. 2A and 2Bis the preferred screw securing system, which is formed with an unthreaded head portion52and a threaded shank portion54.

Threaded hole14as shown inFIG. 2A, is formed with a plain sided recess section58, to a depth sufficient to allow the head portion52to be below the level of the fin box insertion surface16as seen inFIG. 2B. The diameter of the recess section58is such as to provide a close sliding fit with the head portion52of the screw50. The threaded shank portion54is of a length sufficient to lock a fin21, shown with screw recesses23in both sides of the fin tab, in the fin box slot15without applying excessive force on the fin tab of the fin so as to prevent damage to the fin or to the fin box itself.

In the illustrated example ofFIG. 2Bthe unthreaded head portion52is of a diameter larger than the root diameter of the threaded shank portion54, thereby limiting the extent to which the screw can be driven into the threaded hole and thus prevent damage to fin tabs and the fin box.

A user of a board with one or more fin boxes as described herein may interchange a variety of preferred fins simply by selecting the fin, inserting it into the fin box and securing it. As shown inFIGS. 16 to 20a preferred screw securing system includes stainless screws850, which are formed with an unthreaded head portion852and a threaded shank portion854.

Threaded hole856as shown inFIG. 17, is formed with a plain sided recess section858, to a depth sufficient to allow the head portion852to be below the level of the fin box outer surface860as seen inFIG. 18. The diameter of the recess section858is such as to provide a close sliding fit with the head portion852of the screws850. The threaded shank portion854is of a length sufficient to lock a fin (not shown) in the fin box slot862without applying excessive force on the fin tab of the fin so as to prevent damage to it or to cause damage to the fin box itself.

In the illustrated example ofFIG. 16the unthreaded head portion852is of a diameter larger than the root diameter of the threaded shank portion854, thereby limiting the extent to which the screw can be driven into the threaded hole and thus prevent damage to fin tabs and the fin box. The unthreaded head portion852, contains a hexagon slot for the use of a standard Allen key, but can be various other configurations such as a Phillips head or straight slot interface.

FIGS. 19 and 20show a further embodiment using a countersunk unthreaded head section of the screw.