Adjustable fin system

Abstract

A fin for use on a surfboard or another watercraft comprising a fin section that can be releasably coupled to the base of the fin, and the fin section can be slidably adjusted relative to the base in a direction towards the leading edge or the trailing edge of the fin. Following adjustment, the position of the fin section can be secured to the base with one or more locking means.

Claims

1. A fin for use on a surfboard, the fin comprising: a base comprising a mount for attaching the fin to a surfboard; and the base comprising an insert member extending in a direction contrary to the mount; a fin section comprising two outer fin surfaces which meet at a leading edge and a trailing edge; the fin section comprising an underside surface comprising an opening to an internal cavity within the fin section, the internal cavity within the fin section configured to house the insert member of the base and enable slidable movement of the insert member in a direction towards the leading edge or the trailing edge; wherein the base is coupled to the fin section by at least a portion of a sliding joint; and wherein the fin section comprises a lock that is manipulable and which projects into the internal cavity, wherein the lock can releasably couple to the insert member at one or more locking positions thereby preventing slidable movement of the insert member.

2. The fin according to claim 1, wherein the base can be uncoupled from the fin section by slidable movement of the fin section relative to the base.

3. The fin according to claim 2, wherein the sliding joint comprises at least a wall and a portion of the base of a tongue slidably engaged with at least a wall and a portion of the base of a groove.

4. The fin according to claim 3, wherein the base comprises at least a wall and a portion of the base of the groove on either side of the insert member, and the fin section comprises at least the walls and a portion of the base of the tongue.

5. The fin according to claim 4, wherein the fin section comprises a wall and at least a portion of the base of the tongue on opposing sides of the internal cavity.

6. The fin according to claim 4, wherein the sliding joint comprises a sliding dovetail joint, and the base comprises at least a wall and a portion of the base of a sliding dovetail groove on either side of the insert member, and the fin section comprises at least the walls and a portion of the base of a dovetail tongue.

7. The fin according to claim 6, wherein the fin section comprises at least a wall and a portion of the base of the dovetail tongue on opposing sides of the internal cavity and adjacent to the underside surface of the internal cavity.

8. The fin according to claim 3, wherein the fin section comprises at least a wall and a portion of the base of the groove on opposing sides of the internal cavity, and the insert member comprises at least a wall and a portion of the base of the tongue either side of the insert member.

9. The fin according to claim 8, wherein the sliding joint comprises a sliding dovetail joint, and the fin section comprises at least a wall and a portion of the base of a sliding dovetail groove on opposing sides of the internal cavity, and the insert member comprises at least a wall and a portion of the base of the dovetail tongue either side of the insert member.

10. The fin according to claim 3, wherein the base can be uncoupled from the fin section by slidable movement of the at least walls and a portion of the base of the tongue into a gap in the at least walls and a portion of the base of the groove.

11. The fin according to claim 1, wherein the lock comprises a knob that is accessible for a user at an outer fin surface to manipulate the lock, and turning the knob uncouples or recouples the lock to the insert member.

12. The fin according to claim 11, wherein the fin section is configured to adjust relative to the base by manipulating the lock by turning the knob to uncouple the lock from the insert member at a first locking position, slidably moving the insert member through the internal cavity, and turning the knob to releasably couple the lock to the insert member at a second locking position.

13. The fin according to claim 12, wherein the knob can be finger turned by a user.

14. The fin according to claim 1, wherein the insert member comprises at least two teeth, and a valley between two teeth forms a locking position.

15. The fin according to claim 14, wherein the at least two teeth are located at an end of the insert member and extend in a direction contrary to the mount.

16. The fin according to claim 14, wherein the lock comprises a cam which is received at a locking position in a valley thereby coupling the lock to the insert member, and turning the knob moves the cam out of the valley and the locking position, thereby uncoupling the lock from the insert member and enabling slidable movement of the insert member through the internal cavity.

17. The fin according to claim 16, wherein following slidable movement of the insert member through the internal cavity, turning the knob moves the cam into the same or a different valley and a locking position, thereby recoupling the lock to the insert member.

18. The fin according to claim 1, wherein the base comprises: a base attachment plate comprising a substantially flat base attachment surface which contacts the external bottom surface of a surfboard to which it is mounted; and wherein the base attachment plate is attached to the external bottom surface of the surfboard with adhesive and/or screws.

19. The fin according to claim 1, wherein the mount comprises one or more mounting blocks capable of attaching to commercially available fin plug and fin box systems.

20. The fin according to claim 1, wherein a second fin section is directly attached to the fin section, or the second fin section is attached to the fin section by one or more rods, plates, pins, bars, and/or ribs.

21. The fin according to claim 1, wherein a portion of the fin comprises titanium and/or a titanium alloy.

22. The fin according to claim 1, for mounting to any one of the boards in the group comprising: surfboard, shortboard, kneeboard, longboard, minimal, soft board, kiteboard, wind surfer, stand up paddleboard, wakeboard, rescue board, bodyboard, or another board used in surface water sports or activities.

23. A process comprising the step of mounting the fin according to claim 1, to any one of the boards in the group comprising: surfboard, shortboard, kneeboard, longboard, minimal, soft board, kiteboard, wind surfer, stand up paddleboard, wakeboard, rescue board, bodyboard, or another board used in surface water sports or activities.

Description

BRIEF DESCRIPTION OF DRAWINGS

(1) FIG. 1. are illustrations showing (A) a perspective view; (B) a top view; (C) a side view; and (D) a front view, of a preferred embodiment of a bottom portion of a fin section according to a first aspect of the adjustable fin of the invention.

(2) FIG. 2. are illustrations showing (A) a perspective view; (B) a top view; (C) a side view; (D) a front view; and (E) a bottom perspective view, of a preferred embodiment of a base according to a first aspect of the adjustable fin of the invention.

(3) FIG. 3. are illustrations showing (A) a perspective view; (B) a top view; and (C) a front view, of an exploded complete bottom portion of a preferred embodiment of an adjustable fin of the invention according to a first aspect.

(4) FIG. 4. are illustrations showing (A) an underside perspective view; and (B) an exploded bottom perspective view, of a preferred embodiment of a bottom portion of an adjustable fin of the invention according to a first aspect.

(5) FIG. 5. are illustrations showing (A) a side view, (B) a side view showing locking screws, and (C) a bottom view, of a preferred embodiment of a bottom portion of an adjustable fin of the invention according to a first aspect; and a side view (D) of a preferred embodiment of a complete adjustable fin of the invention according to a first aspect.

(6) FIG. 6. is an illustration showing (A) an exploded bottom perspective view; (B) a partially exploded perspective view from above; and (C) a bottom view, of a fin section of a preferred embodiment according to the second aspect of the adjustable fin of the invention.

(7) FIG. 7. is an illustration showing (A) a front and side view of a base assembly; and (B) a cross-sectional front view and an bottom perspective view of a fin section of a preferred embodiment according to the second aspect of the adjustable fin of the invention.

(8) FIG. 8. is an illustration showing a cross section through an incomplete front view of a preferred embodiment according to the second aspect of the adjustable fin of the invention.

(9) FIG. 9. is an illustration showing (A) an exploded perspective view of a base and base attachment plate; and (B) an exploded bottom perspective view of a preferred embodiment according to the second aspect of the adjustable fin of the invention.

(10) FIG. 10. is an illustration showing (A) a side view, (B) a front view, (C) a perspective view, and (D) a bottom view, of a further preferred embodiment according to the second aspect of the adjustable fin of the invention. Mounting means comprises mounting blocks which attach to FCS fin plugs.

(11) FIG. 11. is an illustration showing (A) an exploded front view, and (B) an exploded perspective view, of the embodiment shown in FIG. 10.

(12) FIG. 12. is an illustration showing (A) a side view, (B) a front view, (C) a cross sectional front view, and (D) a bottom view, of a further preferred embodiment according to the second aspect of the adjustable fin of the invention.

(13) FIG. 13. is an illustration showing (A) an exploded front view, and (B) an exploded perspective view, of the embodiment shown in FIG. 12; and (C) an underside perspective view of the base of the embodiment.

(14) FIG. 14. is an illustration showing (A) an exploded front view, (B) a front view, (C) a cross sectional front view, (D) a perspective view, and (E) an exploded perspective view, of a further preferred embodiment according to the second aspect of the adjustable fin of the invention.

(15) FIG. 15. is an illustration showing (A) a perspective view (B) an exploded perspective view, and (C) a front view, of an embodiment according to the second aspect of the adjustable fin of the invention; and (D) a front view, of a further embodiment according to the second aspect of the adjustable fin of the invention.

(16) FIG. 16. is an illustration showing (A) a perspective view, (B) an exploded perspective view, (C) an exploded front view, (D) a front view, and (E) a bottom view, of an embodiment according to the second aspect of the adjustable fin of the invention.

(17) FIG. 17. is an illustration showing (A) a side view, (B) a front view, (C) a perspective view, (D) a bottom perspective view, of an embodiment according to the second aspect of the adjustable fin of the invention.

(18) FIG. 18. is an illustration showing (A) an exploded perspective view, and (B) an exploded bottom perspective view, and (C) an exploded front view (of the base), of the embodiment shown in FIG. 17.

(19) FIG. 19. is an illustration showing (A) an exploded side perspective view, (B) an exploded side perspective view, of the bottom portion of the fin section of the embodiment shown in FIGS. 10 to 15.

(20) FIG. 20. is an illustration showing (A) a side view, (B) the alternative side view, (C) an exploded perspective view (excluding the upper fin portion), of an embodiment according to the second aspect of the adjustable fin of the invention.

(21) FIG. 21. is an illustration showing (A) a side view, (B) the alternative side view, (C) a front view, and (D) a bottom view, of an embodiment according to the third aspect of the adjustable fin of the invention.

(22) FIG. 22. is an illustration showing (A) a side cutaway view, and (B) an exploded perspective view, of the embodiment shown in FIG. 21.

DESCRIPTION OF PREFERRED EMBODIMENTS

(23) Those skilled in the art will appreciate that the invention described herein is susceptible to variations and modifications other than those specifically described. It is to be understood that the invention includes all such variations and modifications. The invention also includes all of the steps, features, compositions and compounds referred to or indicated in the specification, individually or collectively and any and all combinations or any two or more of the steps or features.

(24) The present invention is not to be limited in scope by the specific embodiments described herein, which are intended for the purpose of exemplification only. Functionally equivalent products, compositions and methods are clearly within the scope of the invention as described herein.

(25) Throughout this specification, unless the context requires otherwise, the word comprise, or variations such as comprises or comprising, will be understood to imply the inclusion of a stated integer or group of integers but not the exclusion of any other integer or group of integers.

(26) Other definitions for selected terms used herein may be found within the detailed description of the invention and apply throughout. Unless otherwise defined, all other scientific and technical terms used herein have the same meaning as commonly understood to one of ordinary skill in the art to which the invention belongs.

(27) Features of the invention will now be discussed with reference to the following preferred embodiments.

First Aspect of the Invention

(28) A preferred embodiment of a bottom portion of the fin section according to a first aspect of an adjustable fin of the invention is shown in FIG. 1. The fin section 100 in FIG. 1A comprises a leading edge 102 and a trailing edge 104 and outer fin surfaces 106 of which only one is visible in FIG. 1A.

(29) The outer fin surface 106 adjacent to the underside surface of the adjustable fin is flared 108. There is also a ridge 110 protruding from the outer fin surface 106 which is parallel with the underside surface 120 as shown in FIGS. 1B and 1C. At a gap between two sections of the ridge 110 is the hole 112 which accommodates the locking means which is not shown in this figure. The ridge 110 comprises flared sides.

(30) A biscuit joint 114 shown in FIG. 1 forms an upper fin portion attachment means for attaching an upper portion of a fin section, comprising one or more parts, to the bottom portion of the adjustable fin. The biscuit joint 114 may be formed as part of the bottom portion of the adjustable fin, or attached separately, and in this embodiment comprises holes for use in attaching an upper fin portion of a fin section, or parts thereof, to complete the adjustable fin of the invention.

(31) This allows the attachment of many different types of upper fin portions to the bottom portion of an adjustable fin of the invention to complete the adjustable fin. A key benefit of this type of construction is the bottom portion of the adjustable fin can be conserved and consistently constructed, while upper fin sections of different templates, sizes, materials, colours, and patterns can be made by the same or different manufacturers and attached to the bottom portion to form many different variations of complete adjustable fins of the invention.

(32) Similarly to the large number of different fins currently available for mounting to a surfboard or another type of board described herein, these different variations of adjustable fins of the invention can comprise a variety of different: shapes or templates or even cants; outer fin surface shapes or features; sizes; types of foils; colours; materials from which the fin section is constructed including interior honeycomb portions; rakes; depths; widths; cants; cut-outs; and other designs and extensions including channels, tunnels and wings, amongst others. In this regard, a user can select and mount an adjustable fin of the invention to a board with attributes that is desired by the user or suitable for the user's requirements and appropriate for the board the adjustable fin or fins are mounted on.

(33) A preferred embodiment of the base 200 according to the first aspect of the adjustable fin of the invention is shown in FIG. 2. The base 200 comprises a mount 201 comprising two mounting blocks 202 which are compatible with the existing commercially available FCS fin plugs fitted to a majority of existing surfboards. When the adjustable fin is mounted on to a surfboard, the mounting blocks 202 are secured within FCS fin plugs.

(34) The base 200 comprises a substantially planar adjustment member comprising an insert member 204 which extends in a direction contrary to that of the mounting blocks 202. At the end of the insert member 204 furthest from the mounting blocks 202 are teeth 206. Between the teeth are valleys 208.

(35) The base 200 also comprises two sliding dovetail joint groove walls 210 and a portion of the base of the groove on either side of the insert member 204.

(36) FIG. 3 shows an exploded view of the preferred embodiment of the bottom portion according to the first aspect of the adjustable fin of the invention. The substantially planar insert member 204 of the base 202 comprises teeth 206 and valleys 208, and when the base 200 is coupled with the fin section 100, these teeth 206 and valleys 208 are visible from the slot 116 where there can interact with the locking means comprising the assembly shown. The locking means comprises a knob 300 and O rings 302 which enter the hole 112 from one outer fin surface 106, and a back piece 304 enters the hole 112 from the other outer fin surface 106 of the fin section 100, and a pin 306 holds the parts of the locking means together when in position in the fin section 100.

(37) An assembled bottom portion of the preferred embodiment of the adjustable fin of the invention according to a first aspect is shown in FIG. 4A. An exploded view of the same bottom portion is shown in FIG. 4B. Four wedge-shaped extensions 116 project from within an indentation 118 in the underside surface 120 of the fin section 100 and the wedge-shaped extensions 116 form the cheeks of a sliding dovetail joint. The sliding dovetail joint groove walls 210 in the base 200 form a sliding dovetail joint groove. The term groove has been used herein for the purposes of describing the invention. However, groove may be used interchangeably with dado, slot, or socket, and identify the formation of a sliding groove which can accept the walls of the dovetail (also known as a dovetail tenon) therein coupling the base 200 to the fin section 100.

(38) In the coupling of the base 200 with the fin section 100, the insert member 204 is inserted into the internal cavity 122 and the sliding dovetail joint groove walls 210 are directed into the indentation 118 at two gaps 124 between the wedge-shaped extensions 116, the gaps 124 of a size to allow the sliding dovetail joint groove walls 210 to pass through. Preceding or following this step, the knob 300 of the locking means is manually turned clockwise 90 degrees by a user to prevent the locking portion which comprises a non-circular (preferably wedge-shaped) cam from restricting movement of the teeth 206 and therefore the insert member 204 through the internal cavity 122. The base 200 is then slidably moved in a direction towards the leading edge 102 of the fin section 100 so that the wedge-shaped extensions 116 pass between and slidably engage with the sliding dovetail joint groove walls 210 therein coupling the base 200 with the fin section 100. The knob 300 is turned anti-clockwise 90 degrees when the locking portion is aligned with a valley 208 so that the locking portion enters the valley and prevents sliding movement of the fin section 100 relative to the base 200. The base 200 is now securely engaged to the fin section 100.

(39) When the base 200 is coupled to the fin section 100, the process of adjusting the fin section 100 relative to the base 200 comprises a user turning the knob 300 90 degrees in a clockwise direction with their fingers which removes the locking portion from the valley it was located in, i.e. the first locking position. The user can then slide the fin section 100 relative to the base 200 towards the leading edge 102 or the trailing edge 104. When the locking portion is aligned with a second valley, the knob 300 can be turned 90 degrees in an anti-clockwise direction by the user, thereby moving the locking portion into the valley, i.e. the second locking position, and restraining further slidable movement of the fin section 100 relative to the base 200.

(40) The benefit of the indentation 118 is so that once the base 200 is coupled with the fin section 100, the underside surface 120 will be in contact with the external bottom surface of the surfboard on which it is mounted.

(41) FIG. 5 shows a side view (FIG. 5A), a side view showing locking screws 802 (FIG. 5B), and a bottom view (FIG. 5C) of the embodiment of the bottom portion of the adjustable fin of the invention. FIG. 5C shows an embodiment of a side view of a complete adjustable fin of the invention.

Second Aspect of the Invention

(42) FIG. 6 shows an (A) exploded view, and a (B) partially exploded view of a preferred embodiment of a bottom portion of an adjustable fin of the invention according to a second aspect.

(43) The bottom portion of the fin section 100 is consistent with the bottom portion of the fin section of the herein described preferred embodiment according to the first aspect of the adjustable fin of the invention, with a key difference. This difference is in relation to the position and form of the parts of the dovetail-type sliding joint for coupling the fin section to the base. In the preferred embodiment according to the first aspect of the adjustable fin of the invention, the base comprises sliding dovetail joint groove walls which can slidably engage to couple with the wedge-shaped extensions on the fin section the dovetail joint is formed from. In the preferred embodiment according to the second aspect of the adjustable fin of the invention, and as shown in FIG. 7A, the base 400 comprises wedge-shaped extensions 402 from the insert member; and the fin section 100 shown in FIG. 7B comprises sliding dovetail joint groove corners 150 located in the internal cavity 122. A sliding dovetail joint groove corner 150 comprises a sliding dovetail groove wall and a portion of the groove floor adjacent to the wall. As a result of this arrangement, for this embodiment no indentation is required in the underside surface 120 of the fin section 100.

(44) To couple and securely engage the base 400 to the fin section 100, similarly to the hereinbefore described preferred embodiment according to the first aspect of the adjustable fin of the invention, the insert member 404 of the base 400 is inserted in the internal cavity 122 of the fin section 100 with the wedge-shaped extensions 402 aligned with the gaps 124 so they have unobstructed passage either side of the sliding dovetail joint groove corners 150. Preceding or following this step, the knob of the locking means is manually turned clockwise 90 degrees by a user to prevent the locking portion comprising a non-circular (preferably wedge-shaped) cam from restricting movement of the teeth and therefore the insert member 404 through the internal cavity 122. The base 400 is then slidably moved in a direction towards the leading edge of the fin section 100 so that the wedge-shaped extensions 402 pass into and engage with the sliding dovetail joint groove corners 150 to couple the base 400 to the fin section 100. The knob is turned anti-clockwise 90 degrees when the locking portion is aligned with a valley so that the locking portion enters the valley and prevents sliding movement of the fin section 100 relative to the base 400. The base 400 is now securely engaged with the fin section 100.

(45) In FIG. 8, a cross-section of a fin section 100 coupled to a base 400 shows the wedge-shaped extensions 402 of the base 400 engaging with the sliding dovetail joint groove corners 150 to couple the base 400 to the fin section 100.

(46) The base assembly of the preferred embodiment according to the second aspect of the adjustable fin of the invention comprises three components as shown in FIG. 6A: the base 400, a base attachment plate 420 comprising the mount in this embodiment, and a base cover plate 440. Screws 450 secure the base assembly together as shown in FIG. 6B.

(47) The base attachment plate 420 comprises a substantially flat base attachment surface 424 for contacting to the external bottom surface of a surfboard to which it is to be mounted (FIG. 6C). Cavities 426 (which could also be referred to as indents) which are oval-shaped in this embodiment but may comprise a variety of different shapes are locations for adhesive which will be one means by which the adjustable fin according to this second aspect is attached to the external bottom surface of a surfboard. Preferably, the adhesive is injected into each cavity 426 through an injection conduit 428, the conduit in the form of a tunnel or injection hole, once the base attachment plate 420 is placed in the desired position on the surfboard to which it is to be mounted. A second injection conduit 428 in each cavity 426 enables air to be released from the cavity 426 as the adhesive is injected into a first injection conduit 428 and spreads throughout the cavity 426. Thus, the formation of air bubbles and therefore weaknesses in the adhesive attachment can be avoided. Once the cavity 426 is full of adhesive, excess adhesive will exit the second injection conduit 428 indicating that the cavity 426 is full, and the excess adhesive can be wiped away before it dries. Preferably, screws are driven through injection conduits 428 and into the surfboard prior to, or after the adhesive has dried, to provide additional strength in the attachment of adjustable fin to the surfboard to which it is mounted.

(48) An exploded view of the base 400 and base attachment plate 420 in FIG. 9A shows the base 400 comprises a saddle portion 410, the engagement surface of which substantially in the shape of a semi-cylindrical shell, extending longitudinally the length of the insert member 404. The saddle portion 410 pivotably engages with a semi cylindrical rod shaped projection 422 extending longitudinally on the base attachment plate 420.

(49) The pivotable engagement of the base 400 at the saddle portion 410 with the base attachment plate 420 at the semi cylindrical rod shaped projection 422 is an important feature of this second aspect of the adjustable fin of the invention. In this regard, some shortboard surfboard shapers have been for many years including usually between 4 and 8 longitudinal bevels or channels in the rear half of their board's underside. These channels are thought to increase board speed by directing water flow along the length of each channel toward the tail. Hard channel bottoms, as developed by the shaper Allan Byrne, cut up to a half-inch into the bottom of the board, forming table-edged ridges that run all the way to the end of the tail. While interest in these channels has increased in recent times, one of the issues faced by shapers is in attaching the two or four side fins to the board within these channels at a suitable cant that matches the cant of the corresponding side fin on the opposite side of the stringer. This is due to the difficulty (or almost impossibility) in manually cutting channels into the board which exactly match corresponding channels on the board on the opposite side of the stringer or centre line in terms of the angle of the channel surface when measured perpendicular to the length of the channel. The pivotable engagement of the base 400 at the saddle portion 410 with the base attachment plate 420 at the semi cylindrical rod shaped projection 422, enables the shaper to adjust the cant of the base 400 and therefore fin section to a preferred angle which importantly, matches the corresponding side fin irrespective of the angle of the channel the base attachment plate 420 is attached to.

(50) Once the shaper has pivotably adjusted the base 400 at the saddle portion 410 with the base attachment plate 420 at the semi cylindrical rod shaped projection 422 to the desired cant, the saddle portion 410 is secured to the semi cylindrical rod shaped projection 422. This preferably involves securing the saddle portion 410 to the semi cylindrical rod shaped projection 422 using small screws, though other known methods of securing a saddle to a rod may be employed.

(51) Following attachment of the base attachment plate 420 to the external bottom surface of the surfboard; and securing the pivotably adjusted base 400 to the base attachment plate 420 at a desired cant; the base cover plate 440 is placed over the securely attached base 400 to base attachment plate 420. As shown in FIG. 9B, the base cover plate 440 comprises a centre hole 442 through which the insert member 404 of the base 400 can pass through so that the base cover plate 440 can contact and be secured to the base attachment surface by two screws 450.

(52) The fin section 100 can then be coupled and securely engaged to the base 400 as described above to complete the embodiment of the adjustable fin of the invention according to the second aspect.

(53) Further preferred embodiments of the adjustable fin of the invention according to the second aspect are shown in FIGS. 10 to 15.

(54) FIG. 10 shows collapsed views and FIG. 11 shows exploded views of an embodiment of the adjustable fin of the invention according to the second aspect, wherein the base comprises mounting blocks 202 that can attach to FCS fin plugs. While the locking means comprises a knob 300, this embodiment does not comprise a ridge protruding from the outer fin surface 106. The outer fin surface 106 adjacent to the underside surface of the adjustable fin is not flared in this embodiment but forms a shape resembling a submarine from a view from the front (FIG. 10B). This submarine shape comprises a ridge 107 from which the outer fin surface 106 between the ridge 107 and underside surface, angles toward the underside surface of the fin section in the location of the opening of the internal cavity.

(55) FIG. 10A further shows an upper fin section attached to the bottom portion of the fin section, the upper fin section comprising a titanium alloy (comprising approximately 4% vanadium and approximately 6% aluminium) upper fin 500 covered with an overmolding 510 of protective safety polymer. The titanium alloy upper fin section is up to approximately 2 mm to 2.5 mm thick in the widest section 505 as compared to the thickness of approximately 6.5 mm to 8 mm of many commercially available fins. The titanium upper fin 500 has many beneficial features including its high tensile strength, it is of relatively low weight, a high rebound strength and an ineluctable quality to return to its original shape and position after flexing and the whip effect this provides to assist the surfer to power out of turns on a board upon which one or more adjustable fin(s) of the invention are mounted. In normal surfing conditions, a surfer of approximately 85 kg surfing a shortboard with a thruster fin setup, wherein the surfboard is travelling at approximately 7 m/s and turning sharply will exert approximately 400 N of force over the surface of the three fins. The titanium alloy upper fin 500 at a thickness of 2 mm to 2.5 mm is sufficient to handle such forces without breaking or permanently deforming, while providing some beneficial flex to provide additional power for the surfer as they come out of the turn.

(56) The upper fin 500 shown in FIG. 11B comprises upper fin attachment members 520 which are received and restrained in cavities 525 to attach the upper fin 500 to the bottom portion of the adjustable fin. Adhesive may be used to restrain the upper fin attachment members 520 in the cavities 525. The embodiment shown in FIG. 11B comprises 5 upper fin attachment members 520 and 5 matching cavities 525. However, more or less than 5 upper fin attachment members may be used, and they may comprise a variety of different shapes and sizes with matching cavities that can receive and restrain the members.

(57) The upper fin 500 shown in FIG. 10A also comprises circular holes 515 or cut outs of various sizes. These cut outs reduce the weight of the upper fin 500 further and assist in providing the beneficial flex characteristics for the adjustable fin of the invention. While the cut outs are circular in this embodiment, they may comprise a variety of different shapes. Furthermore, where the adjustable fin of the fin is in a dual fin arrangement, there will be no cut outs present in the position where the ribs or other attachment members attach the two fin sections.

(58) In use, however, a thin titanium alloy upper fin 500 constitutes a potential hazard for persons if they came into contact with its sharp edges. In addition, three or four silver metal fins flashing through a wave on a sunny day has the potential to act as a lure for large ocean inhabitants. To address these potential hazards, the titanium alloy upper fin 500 is covered in a protective safety polymer by a method known as overmolding. The polymer overmold 510 covers the sharp edges of the upper fin section therein protecting surfers from being cut by the metal in the upper fin 500, and is preferably of a colour or level of opacity which prevents the silver of the titanium from acting as a lure. The polymer overmold 510 increases the thickness or width of the fin at its widest point to approximately 3 mm to 3.5 mm.

(59) Across the profile of the upper fin section is varying thickness to create a single or double sided fin foil as is known in the art and common to the shapes of surfboard fins, with a thicker section 505 toward the leading edge of the fin section which decreases in thickness with closer proximity to the trailing edge.

(60) In the embodiment of the adjustable fin shown in FIGS. 10 and 11 and as shown in FIG. 11A, the base 400 and mounting blocks 202 form one piece and do not comprise separate components that have been attached.

(61) A further preferred embodiment of the adjustable fin of the invention according to the second aspect is shown in a collapsed form in FIG. 12, and an exploded form in FIG. 13. This embodiment is the same as the embodiment of the adjustable fin in FIGS. 10 and 11 with the exception that instead of mounting blocks attached to the base, the base 400 is attached to a base attachment plate 420 which comprises the mount in this embodiment for mounting onto the external bottom surface of a surfboard with adhesive and/or rovings, screws or other mechanical attachment means.

(62) The underside of the base plate is shown in FIG. 13C showing the base attachment surface 424 and large cavities 426 for accommodating adhesive.

(63) The holes 515 in the upper fin 500 can be seen in FIG. 13B but they are not visible in FIG. 12A due to the opacity of the overmold in this embodiment of the adjustable fin of the invention.

(64) When mounted to a surfboard, the base of the embodiment of the adjustable fin of FIGS. 12 and 13 points away from the surfboard at an angle of approximately 90 degrees when measured from the external bottom surface of the surfboard on to which it is mounted. While being otherwise the same as the embodiment of FIGS. 12 and 13, the base of the embodiment of FIG. 14 points away from the surfboard at an angle of approximately 86.5 degrees (or approximately 3.5 degrees off centre or 90 degrees) when measured from the external bottom surface of the surfboard on to which it is mounted. That is, the base 400 is 3.5 degrees off pointing in a direction perpendicular to the base attachment surface 424.

(65) A further preferred embodiment of the adjustable fin of the invention according to the second aspect is shown in FIG. 15. This embodiment is similar to the embodiment shown in FIGS. 12 to 14 with a key difference that side shut-off cavities have been replaced with front and rear facing shut-off cavities 160. Another key difference is the presence of injection conduits 428 for injecting adhesive into the cavities or releasing air from the cavities as the adhesive fills the cavities 428, and/or for use as screw holes for attaching the adjustable fin to a surfboard with screw-type fasteners such as screws.

(66) FIG. 16 shows a further embodiment of the adjustable fin of the invention according to the second aspect wherein the fin section is the same as the fin section of the embodiments shown in FIGS. 10 to 14, but the base comprises a similar base assembly to the embodiment shown in FIGS. 6 to 9. A key difference between the base of the embodiment shown in FIG. 15 and the embodiment shown in FIGS. 6 to 9 include different shaped and larger volume cavities 426 for accommodating adhesive.

(67) A further preferred embodiment of the adjustable fin of the invention according to the second aspect is shown in FIGS. 17 and 18. This embodiment is similar to the embodiment shown in FIGS. 12 to 14 (and with corresponding numbering) with key differences that side shut-off cavities have been replaced with front and rear facing shut-off cavities 160, and alternative shapes and volumes of the cavities 426.

(68) An exploded view of the parts of the locking means used in some preferred embodiments of the adjustable fin of the invention is shown in FIG. 19. The locking means comprises a cam 304 of a squarer configuration than the cam in the embodiment shown in FIG. 3.

(69) A further embodiment of the adjustable fin of the invention according to the second aspect is shown in FIG. 20. This embodiment is similar to the embodiments shown in FIG. 15 with two key differences. The first key difference is that the knob 300 of the locking means is in the form of a plate 320 comprising a slot 322. The slot 322 can accommodate part of a coin or another similarly shaped object, and the plate 320 and therefore the locking means and cam 304 can be turned by turning the coin in the slot 322. The range of rotation of the plate 320 is approximately the same as for the herein described knob. While the knob provides the benefit of not requiring tools or other implements to adjust the fin, for example, in the water, the plate 320 comprising the slot 322 for a coin has a benefit of being able to sit almost flush against the side of the fin section resulting in less drag, and some users may find it easier to turn the locking means with a coin than with their fingers.

(70) The second key difference is that the embodiment shown in FIG. 20 comprises four locking holes 802 (two per side) in the bottom portion of the outer fin sections, the locking holes 802 accommodating locking screws 804 which can be screwed in by a user to further lock the adjustable fin into an adjusted position, or unscrewed to enable normal adjustment of the fin relative to the base as described herein.

Third Aspect of the Invention

(71) An embodiment of the upper fin portion of the adjustable fin of the invention according to the third aspect is shown in FIGS. 21 and 22. This upper dual fin comprises an upper portion 900 of a fin section comprising a first titanium fin portion 902. The upper portion 900 is attached to a second fin section 904 with three ribs 910 as attachment means. The second fin section 904 comprises a second titanium fin portion 906. The two ribs 910 closest to the base are attached to the first titanium fin portion 902 and the second titanium fin portion 906 with screws 920 driven through screw holes in the titanium fin portions and the two ribs 910 to provide a strong attachment of the fin sections. The upper portion 900 and the second fin section 904 comprise flat foils and may be used as side fins on a surfboard.

(72) The screws 920 may be removed to separate the upper portion 900 from the second fin section 904 and the ribs 910 so that the upper portion 900 (attached to a bottom portion of a fin section and a base) may be used as a single adjustable fin. Alternatively, an adjustable fin comprising the upper portion 900 may be purchasable separately to the second fin section 904, ribs 910, and screws 920, with the dual fin formed by a user by screwing on to the upper portion, the ribs 910 and the second fin section 904.

(73) Passages 930 in the second fin section 904 direct water passing through them into the region between the flat foils to increase the water pressure in this region as described herein.

(74) The titanium fin portions may contains cut-outs, for example, holes as described herein. However, these cut-outs will preferably not be in close proximity to the rib screws so as to not potentially weaken the titanium fin portion near the dual fin attachment sites.