AU2017201742A1 - Adjustable Fin System - Google Patents

Abstract

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.

Description

1 2017201742 14 Mar 2017

Adjustable Fin System

Technical Field [0001] The present invention relates to an adjustable fin for a surfboard. More particularly, the invention relates to a surfboard fin having a fin section that can be adjusted relative to a base in a direction towards the leading edge or trailing edge of the fin.

Background Art [0002] The following discussion of the background art is intended to facilitate an understanding of the present invention only. The discussion is not an acknowledgement or admission that any of the material referred to is or was part of the common general knowledge as at the priority date of the application.

[0003] A surfboard, stand-up paddleboard (SUP), or similar type of board for use in water sports and other activities can be viewed in one sense as a summation of hydrodynamic surfaces. The surface of the bottom of the board in contact with water generates lift and affects speed. More importantly though, it is the fins working in collaboration with rail and bottom contour that most influence the feel of the board when changing direction. Since the form shape of surfboards including the rails and bottom surface has undergone finer and finer adjustments over the past few decades, the largest gains that can still be made to a board’s performance is in fin modification.

[0004] Predominant factors that influence the effect of the fins include (i) foil shape, and the curve from leading to trailing edge as it changes from base to tip; (ii) template shape, which is the combination of depth, width, and rake that make up the profile of the fin; (iii) stability and flex, which can depend on the materials from which a fin is made; and (iv) fin placement, which comprises tow and camber of the fins, the distance between the fins, and the distance of the fins from the rear of the board. 2017201742 14 Mar 2017 2 [0005] Foils comprise surfaces which affect lift and drag. Where one surface of a foil is curved and the other, predominantly flat (a ‘flat foil’), it takes less effort (drag) for liquid to flow past the flat surface as the path of least resistance than the curved surface. As a result, more water will flow past the flat surface of the foil creating an area of high pressure. Conversely, an area of low pressure is created adjacent to the curved surface of the foil. This difference in pressure creates lift towards the curved side of the foil. The more curve a foil has, the more drag it induces over the curved surface which means that a foil with greater curvature will have more lift at lower speeds. The problem is at higher speeds that additional drag will develop turbulence and stall the flow across the foil. Side fins on a surfboard are usually flat foils which are oriented with the flat face of the foil facing towards the centre or stringer of the board. The resulting pressure differential assists to pull the board fins and rail of the surfboard down into the water. Therefore, thicker, more curved foils are preferred by surfers for slow waves, and flatter, finer foils for faster waves.

[0006] Template shape affects stability and control. As an example, fins that are deeper, with a wider base and more rake provide greater stability and control as a result of a relatively large surface area. However, more surface area causes greater drag and slows a board down. As a generalisation known amongst surfers, fins with a greater surface area are more preferred for steep and heavy waves, choppy and irregular conditions, for heavier surfers, and/or surfers with a flowing style. Alternatively, fins with less surface area are more preferred for sloped, clean and glassy waves, for lighter surfers, and/or surfers that exercise extreme and radical manoeuvres.

[0007] The flex of a surfboard fin can affect stability in turns. For example, a flexible tip on a fin can dampen or smooth out some of the bite when a surfer changes direction on a surf board. But a stable fin base is crucial to prevent or minimise turbulence which can generate drag and disturb the lift causing loss of fin control, making the board slow and out of control. Less flex can make turns more off a pivot. 3 2017201742 14 Mar 2017 [0008] ‘Toe’ can be considered in terms of the angle the base of the side fins are pointed in towards the centre of the board relative to the leading edge and trailing edge at the base. ‘Cant’ can be considered in terms of the angle the body of a fin is set at relative to the bottom surface of the board in a plane perpendicular to the direction of the stringer. Both toe and cant affect the ‘angle of attack’ of fin foils in their movement through the water. A greater angle forces more water flow around the outside curved surface of the foil at lower speeds making it easier to initiate turns on slower waves. However, too much angle at higher speeds increases turbulence and drag slowing down the board.

[0009] Since the introduction of removable fins about two decades ago by FCS®, there has been a greater interest from surfers and particularly professional surfers in fin placement in addition to the other factors described above. While fin placement is often left to convention, for example, with many board shapers following the benchmark for approximate location set by Simon Anderson more than thirty years ago, many other board shapers have their personal preference for each surf board model they shape. There are, however, subtle differences in most boards and in all riders. An adjustment of the position of a fin as small as a 4 mm fin movement fore or aft in either or both the centre fin or side fins can have a profound effect on the performance of a board, similar to a change of fin size or template. In general terms, moving a fin towards the rear of the board will stiffen the board, allowing it to handle greater speed and irregular water conditions. Moving a fin forward will loosen the board allowing it to turn on a tighter radius for easier changes in direction, and is preferable in glassy water conditions and short beach surf breaks.

[0010] Removable fin arrangements and systems have therefore been designed, with some available for purchase, which allow a surfer to adjust the position of a fin on their surfboard, and in some cases, even the tow and cant of the fin. However, these removable and adjustable fin arrangements commonly attach to their own unique and custom fin box or plug requiring a new board or modifications to an existing board. Many of these adjustable fin 4 2017201742 14 Mar 2017 arrangements also require tools to be carried by the surfer to adjust the position of the fins on the board. As a result, there has been a relatively small uptake of these adjustable fin arrangements by the millions of surfers and other board riders around the world.

Summary of the Invention [0011] First Aspect of the Invention [0012] In a first aspect, the invention provides an adjustable fin for use on a surfboard, the adjustable fin comprising: a base comprising: at least one mounting means for mounting the adjustable fin on to a surfboard; and an adjustment member; a fin section comprising: two outer fin surfaces which meet at a leading edge and a trailing edge; an opening to an internal cavity, the internal cavity configured to house the adjustment member and enable slidable movement of the adjustment member in a direction towards the leading edge or the trailing edge; and a locking means which can releasably couple to the adjustment member at one of two or more locking positions thereby preventing slidable movement of the adjustment member; wherein the fin section can be adjusted relative to the base by uncoupling the locking means from the adjustment member at a first locking position, slidably moving the adjustment member through the internal cavity, and releasably coupling the locking means to the adjustment member at a second locking position. 2017201742 14 Mar 2017 5 [0013] In a preferred embodiment, the base is coupled to the fin section by at least a portion of a sliding joint. The at least one sliding joint preferably 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. The at least one sliding joint more preferably comprises at least the walls and a portion of the base of a tongue adjacent to each wall, slidably engaged with at least the walls of a groove and a portion of the base of the groove adjacent to each wall of the groove. The sliding tongue and groove joint, or portion of the sliding tongue and groove joint, are preferably complementary in shape and form to couple and allow slidable movement of the tongue or a portion of the tongue, in the groove or at least a portion of the groove.

[0014] According to the first aspect of the invention, the base preferably comprises at least a wall and a portion of the base of a groove on either side of the adjustment member, and the fin section comprises at least the walls of the tongue and a portion of the base of the tongue. More preferably, the base preferably comprises at least a wall of the groove and a portion of the base of the groove adjacent to the wall, on either side of the adjustment member, and the fin section comprises at least the walls of a tongue and a portion of the base of the tongue adjacent to each wall. Even more preferably, the fin section comprises a wall and at least a portion of the base of the tongue adjacent to the wall, on opposing sides of the internal cavity and preferably within an indentation adjacent to, or at the opening to the internal cavity. Preferably the wall of a tongue does not extend beyond the opening to the internal cavity.

[0015] In a more preferred embodiment, the sliding joint comprises at least the walls or, more preferably, at least the ‘cheeks’ of a dovetail tongue slidably engaged with at least the walls of a sliding dovetail groove. A cheek of a dovetail tongue comprises at least a wall and a portion of the base of the dovetail tongue which may form a wedge shape. Preferably, the sliding joint comprises at least the walls or ‘cheeks’ of a dovetail tongue slidably engaged with at least the walls and, preferably, part of the floor adjacent to a wall, of a sliding dovetail groove. 6 2017201742 14 Mar 2017 [0016] The sliding joint preferably comprises a sliding dovetail joint, and the base comprises at least a wall, and preferably a portion of the base adjacent to the wall (which may be referred to as a cut-away), of a sliding dovetail groove on either side of the adjustment member, and the fin section comprises at least the walls and a portion of the base (‘cheeks’) of a dovetail tongue. The wall of a sliding dovetail groove preferably comprises the angle of the dovetail and at least a portion of the base (which may be referred to as a floor or bottom face) of the dovetail groove creating a dovetail corner through which a dovetail, or cheeks thereof, may slidably move. The cheeks of a dovetail tongue preferably include the wall or part of the wall of the dovetail, and a portion of the bottom surface or base of the dovetail which can slidably engage with the dovetail groove. The dovetail cheek may resemble a wedge shape extension, and the wall of a sliding dovetail groove may be in a form to slidably engage with the wedge-shaped extension. The fin section preferably 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 opening to the internal cavity.

[0017] In a preferred embodiment, the base is releasably coupled to the fin section by at least one sliding joint. Preferably, the at least one sliding joint comprises at least the walls of a groove having at least one gap, and the base can be uncoupled from the fin section by slidable movement of at least the walls of the tongue into the gap. That is, 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. Conversely, the base may be coupled to the fin section by passing the at least walls of the tongue through a gap in the at least walls of the groove and slidably moving the at least walls of the tongue along the at least walls of the groove. There is preferably two gaps through which two of at least walls of a tongue may pass through, following which the at least walls of the tongue may be slidably engaged with the at least walls of the groove.

[0018] The locking means can preferably be manipulated from an outer fin surface. In a preferred embodiment, the locking means comprises at least one 7 2017201742 14 Mar 2017 knob which is accessible for a user at an outer fin surface of the fin section for manipulating the locking means, and wherein turning the knob uncouples the locking means from the adjustment member, or recouples the locking means to the adjustment member.

[0019] The adjustment member is preferably substantially planar, comprising a flat or substantially flat surface, and extends in a direction substantially contrary to the mounting means. Preferably, the planar adjustment member is between approximately 1 mm to 2 mm thick. This can allow the construction of a relatively thin adjustable fin of the invention which is preferable for reducing fin drag. The internal cavity of the fin section preferably comprises a slot configured to house the substantially planar adjustment member and through which the adjustment member can slidably move, or be removed from inside the internal cavity when separating the fin section from the base. More preferably, the adjustment member comprises three or more teeth, and a valley between two teeth forms a locking position. The peaks of the teeth may comprise a variety of shapes including pointed teeth peaks, or peaks rounded in shape or asymmetric in shape. Preferably, the three or more teeth point in a direction contrary to the mounting means. The adjustment member preferably comprises a first and a second end, wherein the first end is attached to the mounting means, and the three or more teeth are located at the second end of the adjustment member. The three or more teeth preferably point in a direction substantially contrary (that is in a substantially opposite direction) to the mounting means.

[0020] The opening to the internal cavity is preferably situated between the two outer fin surfaces. The length of the internal cavity within the fin section, measured from an end closest to the leading edge to an end closest to the trailing edge, and the length of the adjustment member measured along the same plane, will determine the maximum distance the fin section may be adjusted by slidable movement of the adjustment member towards the leading edge or the trailing edge, within the internal cavity. Preferably, the internal cavity permits up to approximately 10 mm to 30 mm of movement of the fin section relative to the base in a direction towards the leading edge or the 8 2017201742 14 Mar 2017 trailing edge. More preferably, the internal cavity permits up to approximately 20 mm of movement of the fin section relative to the base in a direction towards the leading edge or the trailing edge. The length of slidable movement will depend on the size and shape of the fin section which will limit the length of the internal cavity possible within the fin section, and the shape and length of the adjustment member. Means for showing the user the position of the fin section relative to the base are also within the scope of the invention, for example, to enable a user to adjust two or more fins on a board equally.

[0021] The locking means preferably comprises a locking portion which is received at a locking position in a valley thereby coupling the locking means to the adjustment member and therefore the fin section to the base, and turning the knob moves the locking portion out of the valley and the locking position, thereby uncoupling the locking means from the adjustment member and enabling slidable movement of the adjustment member through the internal cavity. The locking portion is preferably a cam and even more preferably, the cam is not circular but is wedge shaped or of a shape wherein turning the locking means and therefore the cam approximately 90 degrees can move the portion of the cam that is in a locking position in a valley completely out of the valley. Following slidable movement of the adjustable member through the internal cavity, re-turning the knob can move the locking portion into the same or a different valley and a locking position, thereby recoupling the locking means to the adjustment member. Thus, a user can turn the knob and adjust the position of the fin section relative to the base when the adjustable fin is mounted to a surfboard. The knob and locking means may be constructed from a variety of materials. The knob may be constructed from the same material as the fin section or from other materials. For example, the locking means may additionally comprise rubber rings, and/or one or more screws or rivets to hold the mechanism or assembly together.

[0022] In one preferred embodiment, a portion of the knob protrudes form at least one outer fin surface and means the at least one knob can be finger turned by a user. Preferably, the portion of the knob protruding is in the form of a ridge. 9 2017201742 14 Mar 2017 [0023] In another preferred embodiment, the knob comprises a slot and an object partially inserted in the slot can be turned to turn the knob. The slot is preferably between 1.5 mm to 1.8 mm wide, and more preferably approximately 1.7 mm wide. The object preferably comprises a coin or other disc shaped object, a portion of which can be accommodated in the slot. This may be a coin such as an American dime, an Australian 10 cent piece, or another similarly shaped object. The knob comprising the slot may sit flush or not flush to an outer fin surface.

[0024] Other forms of the knob are considered to be within the scope of the invention comprising, for example, a foldable wing-type nut which can be unfolded from a position flush or almost flush to an outer fin surface, then turned by a user to turn the knob, and then refolded. In another example, a key can be inserted in a key hole in the knob to turn the knob.

[0025] Following slidable movement of the adjustment member through the internal cavity, re-turning the knob preferably can move the locking portion into the same or a different valley and a locking position, thereby recoupling the locking means to the adjustment member.

[0026] In a preferred embodiment, the outer fin surfaces adjacent to the base are flared. It is preferable that these flared sides contact the external bottom surface of a surfboard to which the adjustable fin is mounted to reduce any drag or other effect from the almost right angled corner usually created between most fins known in the art and the surfboard on which it is mounted.

[0027] In another preferred embodiment, the fin section comprises a ridge protruding from at least one outer fin surface, and preferably a substantially matching ridge on either outer fin surface, the ridge substantially parallel to the external bottom surface of the surfboard on to which the fin is mounted. The ridge preferably comprises flat, flared or curved sides above and below the ridge, and even more preferably, the knob of the locking means is substantially aligned with the ridge when the locking means is coupled to the adjustment member. In addition, a portion of the ridge is shaped to prevent the knob from being turned more than 180 degrees, and more preferably 90 10 2017201742 14 Mar 2017 degrees. A benefit of incorporating the shape of the locking means into the ridge is to enable a user easy access to the locking means extending from the outer fin surface while reducing drag which would otherwise be caused by the locking means if it extended from an outer fin surface without such a ridge.

[0028] A further preferred embodiment provides an independent bottom portion of an adjustable fin of the invention as herein described, to which an upper portion of the fin section is attachable at an upper fin portion attachment surface. Preferably, the bottom portion of the adjustable fin comprises the locking means and the internal cavity. The upper fin portion attachment surface preferably comprises an upper fin portion attachment means for attaching the upper portion of the fin section to the bottom portion of the adjustable fin.

[0029] The upper fin portion attachment means in one embodiment comprises at least one biscuit joint for attaching the bottom portion of the adjustable fin to the upper portion of the fin section. At least a portion of the joinery ‘biscuit’ is preferably incorporated into the form of the bottom portion of the adjustable fin of the invention. The upper portion of the fin section may be attached to the biscuit joint with screws or rivets, or may be formed over the biscuit joint in a mold.

[0030] A benefit of a separate bottom portion of the adjustable fin of the invention is for manufacturing purposes wherein the same bottom portion of the adjustable fin of the invention can be formed into a wide variety of different complete fins by attaching an equally wide variety of upper fin portions of, for example, amongst others, different shapes, sizes, templates, and of different materials. The upper portion of the fin section may comprise at least one part. In one, non-limiting example, the upper fin portion may comprise three parts including two upper portion outer fin surfaces, and an internal honeycomb structure to produce rigidity and strength while reducing weight.

[0031] In another embodiment, the upper fin portion attachment means comprises one or more surfboard fin plugs and/or fin boxes forming a cavity or cavities in the upper fin portion attachment surface. In one, non-limiting 11 2017201742 14 Mar 2017 example, the one or more surfboard fin plugs and/or fin boxes are preferably compatible with, and capable of attaching to commercially available fin mounting blocks including commercially available FCS® fin and/or Futures® fin mounting blocks. In one non-limiting example, a commercially available FCS® fin, preferably a quad fin which is shorter than a thruster fin, with the FCS® dual mounting blocks could comprise the upper fin portion and be attached to a bottom portion of the adjustable fin of the invention to complete the adjustable fin of the invention. Two screws, for example, amongst others, hex or ‘Grubscrews’ could be used to secure the, for example, FCS® quad fin to the bottom portion of the adjustable fin of the invention, accessed through screw holes in the bottom portion of the fin section.

[0032] In a further embodiment, the upper fin portion attachment means comprises one or more cavities for accommodating tabs on the upper fin portions. Adhesive is preferably used to attach the tabs within the cavities. In one example, five cavities in the upper fin portion attachment surface accommodate five asymmetrically shaped tabs.

[0033] The attachment of the upper portion of the fin section to the bottom portion of the adjustable fin completes the adjustable fin for use on a surfboard. Thus, the invention further provides manufacture of an adjustable fin as described herein comprising attaching the bottom portion of the adjustable fin to the upper portion of the fin section.

[0034] Second Aspect of the Invention [0035] The first aspect of the adjustable fin of the invention comprises a slidable joint for coupling the base to the fin section, wherein the fin section comprises at least a portion of the tongue of the joint, and the base comprises at least a portion of the groove of the joint. Alternatively, according to a second aspect of the adjustable fin of the invention, the fin section comprises at least a portion of the groove, and the base comprises at least a portion of the tongue, of a sliding joint for coupling the base to the fin section.

[0036] According to the second aspect of the adjustable fin of the invention, the fin section comprises at least a wall and a portion of the base of the 12 2017201742 14 Mar 2017 groove on opposing sides or either side of the internal cavity, and the adjustment member comprises at least a wall and a portion of the base of the tongue of a sliding joint. The sliding joint preferably 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 adjustment member comprises at least a wall and a portion of the base of the dovetail tongue either side of the adjustment member. The fin section preferably comprises at least a wall of the groove on opposing sides of the internal cavity. More preferably, 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 base comprises at least a wall and a portion of the base of the tongue of a sliding joint.

[0037] In a preferred embodiment, the sliding joint preferably 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, that is, either side, of the internal cavity, and the adjustment member comprises at least a wall and a portion of the base of the dovetail tongue either side of the adjustment member. More preferably, the fin section comprises at least a wall of a sliding dovetail groove and a portion of the base of the dovetail groove adjacent to the wall, on opposing sides of the internal cavity, and the base comprises at least the cheeks of a dovetail tongue.

[0038] The base according to the second aspect of the adjustable fin of the invention may comprise a mounting means as described herein.

[0039] However, in a preferred embodiment according to the second aspect of the adjustable fin of the invention, the mounting means comprises: a base attachment plate comprising a substantially flat base attachment surface which contacts the external bottom surface of a surfboard on to which it is mounted.

[0040] The base attachment plate is preferably attached to the external bottom surface of the surfboard with adhesive and/or screw type fasteners including screws. 2017201742 14 Mar 2017 13 [0041] In this respect, the base attachment surface preferably comprises at least one cavity in the substantially flat surface. More preferably, the at least one cavity can be filled with an adhesive for attaching the base attachment surface to the external bottom surface of a surfboard. The base attachment plate comprises at least one conduit which passes through the base attachment plate and one end of the conduit opens into a cavity.

[0042] The adhesive is preferably introduced into a cavity through a conduit. More preferably, adhesive is injected through a conduit into a cavity and a second conduit with an end also opening into the cavity enables air in the cavity to escape to avoid the formation of air bubbles which could prevent the complete filling of a cavity with adhesive.

[0043] Before or after the adhesive has set or ‘cured’ in a cavity, the conduits may be used as screw holes when attaching the base attachment plate to the external bottom surface of the surfboard with screw type fasteners, for example, screws, or rovings. Thus, in a preferred embodiment, the base attachment plate is attached to the external bottom surface of the surfboard with both adhesive and screws.

[0044] In a second preferred embodiment of the base according to second aspect of the invention, the base attachment plate and adjustment member comprise separate components of a base assembly. In a preferred embodiment, the base attachment plate is pivotably engaged with the adjustment member, wherein: the base attachment plate comprises a half or semi cylindrical rod shaped projection extending in a direction substantially contrary to the base attachment surface; and the adjustment member comprises a saddle, the saddle comprising a portion of a cylindrical shell extending at least a portion of the length of the adjustment member which can pivotably engage with the semi cylindrical rod shaped projection. 14 2017201742 14 Mar 2017 [0045] The saddle can be secured to the semi cylindrical rod shaped projection, and preferably, the saddle is secured to the semi cylindrical rod shaped projection with screw type fasteners, for example, screws. Securing the saddle of the adjustment member to the semi cylindrical rod shaped projection sets the angle of the adjustment member relative to the base attachment plate. This angle may be selected by a surfboard shaper setting an angle for a desired surfboard fin cant when the adjustable fin is mounted to a surfboard.

[0046] After the saddle of the adjustment member is secured to the semi cylindrical rod shaped projection at a selected angle, a base cover plate is preferably secured to at least the base attachment plate and/or a portion of the adjustment member, wherein the base cover plate covers at least the outer surface of the base attachment plate that does not comprise the base attachment surface, and covers the saddle of the adjustment member. Preferably, the base cover plate comprises a hole through which the adjustment member can extend through, and through which the adjustment member passes when placing the base cover plate onto the base attachment plate. Screws can be passed through the base cover plate and base attachment plate to secure together the base assembly.

[0047] Alternatively, the saddle of the adjustment member may be additionally secured to the rod shaped projection at a selected angle, for example, with screws. The selected angle, for example, amongst others, is approximately 3.5 degrees off 90 degrees, wherein 90 degrees is measured between the adjustment member and the surface of the base attachment surface.

[0048] Securing the base cover plate onto the base attachment plate completes assembly of the base according to the second aspect of the invention. The fin section can then be coupled and secured to the base as described herein to complete the adjustable fin of the invention.

[0049] The front profile of the fin section according to the second aspect of the adjustable fin of the invention is preferably rounded, ‘bulbous’, or 15 2017201742 14 Mar 2017 ‘submarine-shaped’ towards the bottom of the fin section adjacent to the mounting means. This shape is possible due to the configuration of the components of the sliding joint according to the second aspect. The benefit of this shape is that it allows a variety of different cants for the fin section relative to the surfboard on to which it is mounted, which is not possible when the adjustable fin according to the first aspect comprises flared surfaces adjacent the mounting means.

[0050] The fin section according to the second aspect may also comprise other cut-outs which are necessary in the production of the fin section. Such cut-outs may allow water to pass through into the internal cavity, or the cutouts may be filled with material, for example, flexible polymer or polycarbonate, amongst other materials.

[0051] Third Aspect of the Invention [0052] According to a third aspect, the invention provides a dual fin comprising a fin section, a second fin section and a base, the base comprising a mounting means for attaching the dual fin to a surfboard.

[0053] In preferred embodiments of the third aspect of the invention, a second fin section is attached to a fin section according to either the first aspect of the adjustable fin of the invention or the second aspect of the adjustable fin of the invention, the second fin section comprising two outer fin surfaces which meet at a leading edge and a trailing edge, and an underside surface meeting both outer fin surfaces.

[0054] The second fin section is preferably attached to the fin section by one or more attachment means. Attachment means may, in some non-limiting examples, comprise rods, plates, pins, bars, and/or be formed from a portion of either the fin section or the second fin section. More preferably, the one or more attachment means comprise one or more ribs, and even more preferably, three ribs. The one or more attachment means preferably preserve a minimum distance between the fin section and the second fin section of between approximately 0.1 mm and 5 mm. The one or more attachment means preferably preserve a minimum distance between the fin section and 16 2017201742 14 Mar 2017 the second fin section of between approximately 0.25 mm and 1.5 mm. The one or more attachment means more preferably preserve a minimum distance between the fin section and the second fin section of approximately 1 mm. The attachment means preferably reduce or remove any ‘fluttering’ effect on either fin section caused by water passing around and between the fin section and the second fin section.

[0055] The second fin section is preferably positioned substantially parallel to the fin section and offset such that the leading edge of the second fin section is not aligned with the leading edge of the fin section. Alternatively, the leading edges of the fin section and the second fin section may be substantially aligned. The fin section preferably comprises a flat foil having a substantially flat outer fin surface, and a curved outer fin surface. The second fin section also preferably comprises a flat foil having a substantially flat outer fin surface, and a curved outer fin surface. In a preferred embodiment, the substantially flat outer fin surface of the fin section and substantially flat outer fin surface of the second fin section substantially face the same direction, and the leading edge of the fin section is in a position forward of the leading edge of the second fin section. Preferably, the leading edge of the fin section is forward of the leading edge of the second fin section by approximately 5 mm to 25 mm, and more preferably by approximately 10 mm.

[0056] The second fin section preferably comprises at least one passage through which water can pass. The passage comprises an opening on each outer fin surface of the second fin section through which water can enter and exit. The passage preferably comprises an opening on the substantially flat outer fin surface, and an opening on the curved outer fin surface, and the opening on the curved outer fin surface is located between the trailing edge of the second fin section and the minimum distance between the fin section and the second fin section. Preferably, the opening of the passage on the substantially flat outer fin surface of the second fin section is located closer to the leading edge of the second fin section than the opening of the passage on the curved outer fin surface of the second fin section. This will mean that when in normal use on a surfboard, water will preferentially enter the opening on the 17 2017201742 14 Mar 2017 substantially flat outer fin surface, pass through the passage, and exit through the opening on the curved outer fin surface. A passage and an opening to a passage through the second fin section is preferably not round or another shape that would cause water passing through the passage to form a vortex. The openings and passages may be created from drilling or cutting holes or perforations through the second fin section or from the shape of a mold used to make the fin section.

[0057] An adjustable dual fin according to the third aspect of the invention is preferably mounted in the position of a side fin on a surfboard wherein: at least the second fin section comprises a flat foil having a substantially flat outer fin surface facing the centre line or stringer of the surfboard, and a curved outer fin surface facing the adjacent rail of the surfboard; the fin section is in a position closer to the adjacent rail of the surfboard than the second fin section; and the leading edge of the fin section is positioned closer to the front of the board than the leading edge of the second fin section.

[0058] Two or more adjustable dual fins according to the third aspect of the invention may be mounted to a surfboard.

[0059] In a preferred embodiment, the second fin section comprises at least one passage comprising an opening on the substantially flat outer fin surface, and an opening on the curved outer fin surface of the second fin section through which water can pass. When the adjustable dual fin of the third aspect of the invention is mounted to a surfboard which is moving in a substantially forward direction through water during normal use, the at least one passage in the second fin section is preferably configured to: enable water to enter an opening on the substantially flat outer fin surface of the second fin section, pass through the passage, and exit through an opening on the curved outer fin surface in a location 18 2017201742 14 Mar 2017 between the trailing edge of the second fin section and the position of the minimum distance between the fin section and the second fin section; and substantially prevent water passing in the reverse direction through the passage.

[0060] The openings preferably comprise holes or perforations on the surface of the substantially flat and curved outer fin surfaces of the second fin section through which water can enter and exit, respectively. Preferably, the opening on the substantially flat outer fin surface of the second fin section is positioned closer to the leading edge than the opening on the curved outer fin surface.

[0061] In an alternative embodiment of the third aspect of the adjustable dual fin of the invention, both the fin section and the second fin section are attached to the base. The fin section may be an adjustable fin according to either the first aspect or second aspect of the invention. The second fin section may be an adjustable fin according to either the first aspect or second aspect of the invention.

[0062] The second fin section may be the same size or a different size to the fin section. The second fin section may have a different fin template to the fin section. Preferably, the size and template of the second fin section is similar or the same as the size and template of the fin section.

[0063] Portions of the fin section and/or the second fin section preferably comprise a titanium alloy as described herein. The remainder of the fin section and/or the second fin section is preferably an overmolding, for example, a flexible polymer overmolding.

[0064] Without wanting to be limited by any one theory, it is believed that the adjustable dual fin according to the third aspect of the invention provides a benefit of increased thrust and therefore speeds in a direction substantially towards the front of a surfboard it is mounted to when in normal use, for the following reasons. 19 2017201742 14 Mar 2017 [0065] The distance between the flat outer fin surface of the fin section and the curved outer fin surface of the second fin section is nearest at the peak of the curved outer fin surface of the second fin section. This distance is preferably between approximately 0.1 mm and 5 mm, more preferably between approximately 0.25 mm and 1.5 mm, and even more preferably approximately 1 mm. The proximity and position of the fin section and the second fin section forms a V-shaped channel between the peak and the leading edge of the fin section and the leading edge of the second fin section, the V-shaped channel extending along the curved length of the fin sections to their tips. On the other side of the peak is a rear chamber formed between the peak and the trailing edge of the fin section and the trailing edge of the second fin section.

[0066] During normal use when mounted on a surfboard, water passes into the V-shaped channel but only a small amount of this water can pass between the thin gap between the fin section and the second fin section. The majority of the water is forced along the length of the V-shaped channel towards the tip of the fin sections at a higher velocity than the normal speed that water is passing the fin sections. This higher velocity is generated due to the higher pressure behind the water forced into the channel than the pressure of the water in front of the water leaving the channel adjacent to the tips of the fin sections according to Newton’s 2nd law. In accordance with Bernoulli’s principle, the increase in the velocity of the water occurs simultaneously with a decrease in pressure. Therefore, a region of low pressure is created in this V-shaped channel.

[0067] Conversely, some water passes through the thin gap between the fin section and the second fin section, and passages direct water through the second fin section from the side of the substantially flat outer fin surface into the rear chamber. The effect of forcing all of this water into the limited space of the rear chamber results in the creation of a region of high pressure.

[0068] The pressure differential between the area of low pressure in the V-shaped channel and the area of high pressure in the rear chamber results in a lift force acting perpendicular to the direction of the fluid flow in the V-shaped 20 2017201742 14 Mar 2017 channel. That is, in a direction towards the front of the fin on a slight downward angle. The thrust provided by this lift force acts to increase the overall speed of the fins in this direction, and therefore, the board through the water.

[0069] The adjustable dual fin according to the third aspect comprises a mounting means as herein described. If the dual fin comprises a fin section according to the second aspect of the invention and the mounting means comprises a base attachment plate, the cant of the dual fin may be set off ‘centre’ (90 degrees), for example at approximately 3.5 degrees off centre.

[0070] Fourth Aspect of the Invention [0071] According to a fourth aspect, the invention provides a fin for use on a surfboard, the fin comprising: a leading edge, a trailing edge, and a base, the base comprising at least one mounting means for mounting the fin onto a surfboard; a first and a second outer fin surface which meet along the leading edge and the trailing edge and abut the base; a first ridge protruding laterally from the first outer fin surface, and a second ridge protruding laterally from the second outer fin surface.

[0072] In a preferred embodiment, the first and second ridges are substantially parallel to the base. When the fin is attached or mounted onto a surfboard, the first and second ridges are preferably substantially parallel to the adjacent bottom surface of the surfboard.

[0073] In a preferred embodiment, the first outer fin surface either side of the first ridge comprises first ridge sides. Ridge sides which are present either side of the first ridge are preferably contiguous and merge in with the first outer fin surface. That is, the first ridge preferably forms out of the first outer fin surface connecting without a break. Likewise, the second outer fin surface either side of the second ridge comprises second ridge sides. Ridge sides 21 2017201742 14 Mar 2017 which are present either side of the second ridge are preferably contiguous with the second outer fin surface.

[0074] The first ridge preferably protrudes laterally from the first outer fin surface by less than 30 mm, more preferably, by less than 15 mm. The second ridge preferably protrudes laterally from the second outer fin surface by less than 30 mm, more preferably, by less than 15 mm.

[0075] The ridge sides or at least a portion of the ridge sides of the first and/or second ridge are flat in one embodiment. In another embodiment, the ridge sides or a portion of the ridge sides of the first and/or second ridge comprise a curve. Where they comprise a curve, preferably, the ridge sides or a portion of the ridge sides are concave. Alternatively, where they comprise a curve, preferably, the ridge sides or a portion of the ridge sides are convex. A ridge side on one side of a ridge on the fin of the invention may comprise a different shape to the ridge side on the other side of the ridge. For example, amongst others, a ridge side on one side of a ridge on the fin of the invention may comprise a concave portion, while the ridge side on the other side of the ridge may comprise a flat or convex portion, amongst the multitude of possible combinations.

[0076] In a preferred embodiment, the first and second ridge are located adjacent or close to the base. Therefore, when the fin is mounted to the bottom surface of a surfboard, the first and second ridge and associated ridge sides will be located close to the surface of the surfboard. Preferably, the first and second ridge is located within 25 mm of the base. In another embodiment, the first and second ridge is located within 20 mm of the base. In a further embodiment, the first and second ridge is located within 15 mm of the base.

[0077] The first and second ridge are preferably located equidistant from the base, or located equidistant from the tip of the fin, wherein the tip is at the top of the fin at the opposite end to the base where the leading and trailing edges meet.

[0078] The length of the first and second ridges are preferably most or all of the length between the leading edge and the trailing edge of the fin, though 22 2017201742 14 Mar 2017 they may also be smaller than this length. That is, each ridge preferably comprises a front end adjacent to the leading edge of the fin, and a rear end adjacent to the trailing edge.

[0079] The ridge may comprise a sharp edge where the ridge sides meet, or may comprise a rounded edge, or a combination of both a sharp and rounded ridge edge along the length of the ridge.

[0080] In a further embodiment of the fin of the invention according to the fourth aspect, the fin comprises a third ridge protruding laterally from the first outer fin surface, and a fourth ridge protruding laterally from the second outer fin surface. The third and fourth ridges are preferably smaller than the first and second ridges. The third and fourth ridge are preferably located equidistant from the base, and are preferably the same size and shape. The third and fourth ridges are preferably substantially parallel to the base. That is, when the fin is attached or mounted onto a surfboard, the third and fourth ridges are substantially parallel to the bottom surface of the surfboard.

[0081] The third and fourth ridges are preferably substantially parallel to the first and second ridges, or may have a slight acute angle of attack towards the base. The first outer fin surface either side of the third ridge preferably comprises third ridge sides. The first outer fin surface either side of the fourth ridge preferably comprises fourth ridge sides. Ridge sides either side of the third ridge are preferably contiguous and merge in with the first outer fin surface, and ridge sides either side of the fourth ridge are preferably contiguous and merge in with the second outer fin surface.

[0082] The third ridge preferably protrudes laterally from the first outer fin surface by less than 30 mm, more preferably, by less than 15 mm. The fourth ridge preferably protrudes laterally from the second outer fin surface by less than 30 mm, more preferably, by less than 15 mm.

[0083] The ridge sides or at least a portion of the ridge sides of the third and/or fourth ridge are flat in one embodiment. In another embodiment, the ridge sides or a portion of the ridge sides of the third and/or fourth ridge comprise a curve. Where they comprise a curve, preferably, the ridge sides or 23 2017201742 14 Mar 2017 a portion of the ridge sides are concave. Alternatively, where they comprise a curve, preferably, the ridge sides or a portion of the ridge sides are convex. A ridge side on one side of a ridge on the fin of the invention may comprise a different shape to the ridge side on the other side of the ridge. For example, amongst others, a ridge side on one side of a ridge on the fin of the invention may comprise a concave portion, while the ridge side on the other side of the ridge may comprise a flat or convex portion, amongst the multitude of possible combinations.

[0084] The third ridge is preferably smaller and located further from the base than the first ridge on the first outer fin surface. The third and fourth ridges are preferably located equidistant from the base. The fourth ridge is preferably smaller and located further from the base than the second ridge on the second outer fin surface.

[0085] In a preferred embodiment, the fin is an adjustable fin comprising: the base comprising an adjustment member; and a fin section comprising: the first and the second outer fin surfaces which meet along the leading edge and the trailing edge; an opening to an internal cavity within the fin section, the internal cavity configured to house the adjustment member of the base and enable slidable movement of the adjustment member in a direction towards the leading edge or the trailing edge; and a locking means which can releasably couple to the adjustment member at one of two or more locking positions thereby preventing slidable movement of the adjustment member; wherein the fin section can be adjusted relative to the base by uncoupling the locking means from the adjustment member at a first locking position, slidably moving the adjustment member through the internal cavity, and releasably 2017201742 14 Mar 2017 24 coupling the locking means to the adjustment member at a second locking position.

[0086] The means or mechanism for the fin section to be adjusted relative to the base may be any of those means or mechanisms already described herein in relation to an aspect of the invention.

[0087] In a preferred embodiment, the adjustment member is preferably substantially planar and extends in a direction substantially contrary to the mounting means. The adjustment member preferably comprises three or more teeth, and a valley between two teeth forms a locking position. The three or more teeth are preferably located at an end of the adjustment member, and the three or more teeth preferably point in a direction substantially contrary to the mounting means.

[0088] The locking means preferably comprises a locking portion which is received at a locking position in a valley thereby coupling the locking means to the adjustment member, and turning the knob moves the locking portion out of the valley and the locking position, thereby uncoupling the locking means from the adjustment member and enabling slidable movement of the adjustment member through the internal cavity. Following slidable movement of the adjustable member through the internal cavity, re-turning the knob can move the locking portion into the same or a different valley and a locking position, thereby recoupling the locking means to the adjustment member.

[0089] The locking means is preferably manipulated from the first and/or second outer fin surface. More preferably, the third and/or fourth ridge incorporates the locking means.

[0090] The locking means preferably comprises at least one knob accessible for a user at the first and/or second outer fin surface for manipulating the locking means, and turning the knob uncouples or recouples the locking means from the adjustment member. Preferably, the knob can be finger turned by a user. 2017201742 14 Mar 2017 25 [0091] In a preferred embodiment, the knob is located within the third and/or fourth ridge. Preferably, the knob has an exterior surface, and a portion of the exterior surface of the knob lies flush with the third and/or fourth ridge and ridge sides of the third and/or fourth ridge when the locking means is coupled to the adjustment member.

[0092] A side fin according to the fourth aspect of the invention for use in a thruster or quad or similar arrangement on a surfboard, is preferably asymmetrical from a front view. Preferably, a portion of the ‘inside’ side of the fin (facing toward the middle, centreline or stringer of the board onto which it is mounted) is substantially flat and a portion of the ‘outside’ side of the fin (facing toward the rails and edge of the board onto which it is mounted) is curved similar in configuration to a flat foil standard existing side ‘thruster’ fin, but also both outer fin surfaces comprise main and minor ridges (although not necessarily symmetrical to each other).

[0093] The fin according to the fourth aspect of the invention comprises one or more mounting means as described herein in relation to any one of the other aspects of the invention. Preferably, the one or more mounting means are mounting blocks capable of attaching to commercially available fin plug and fin box systems. In another embodiment, the base comprises: a base attachment plate comprising a substantially flat base attachment surface which contacts the external bottom surface of a surfboard on to which it is mounted.

[0094] Locking Screws [0095] In a preferred embodiment, the adjustable fin of the invention according to any of the herein described first, second, third, or fourth aspects, or the fin of the invention according to the fourth aspect, further comprises locking screws that can be housed in screw holes in the fin section and can be screwed into the internal cavity to contact the adjustment member and provide further means of coupling the fin section to the base. 26 2017201742 14 Mar 2017 [0096] The locking screws may comprise, for example, amongst others, socket screws (may also be referred to as Allen screws or Grubscrews) having a hexagonal socket in the head which require an Allen key or hex key to tighten or loosen them. In another preferred example, the locking screws comprise a slot and may be turned using an object placed in the slot and turned by a user. A coin such as an American dime and Australian 10 cent piece can preferably be used to turn the locking screws. The screws may be turned by other means known in the art including foldable wing nut-type screws wherein the wing nut can be unfolded to turn the screw and then refolded.

[0097] The locking screws may be screwed into the adjustment member or another part of the base which may or may not comprise indents, cavities or holes for the locking screws to be screwed into to contact with the base and provide an additional means of securing the adjusted fin section to the base of an adjustable fin of the invention. Preferably, two locking screws are located either side of the fin section.

[0098] The locking screws can be beneficial where the adjustable fin of the invention is used on, for example, kite boards, wake boards, wind surfers, big wave surfboards, and other such boards where the adjustable fins will be exposed to considerably greater forces than those faced during regular shortboard surfing and aim to prevent or minimise fin ‘wobble’.

[0099] Alternatively, one or more locking screws may be used with the adjustable fin of the invention as the locking means to couple and uncouple the base to the fin section to enable slidable movement of the fin section relative to the base. f001001 Safety [00101] For the purpose of maintaining the safety of users of one or more adjustable fins of the invention on a surfboard, the adjustment member preferably comprises a weak portion. The weak portion comprises a portion of the adjustment member that can more easily be broken than the remaining portion of the adjustment member. More preferably, the weak portion is 27 2017201742 14 Mar 2017 adjacent to the mounting means. Under strong forces acting on an adjustable fin of the invention, for example, heavy contact of: a reef, the surfer, another surfer, another board, or rocks, amongst others, the adjustment member can break at the weak portion. The purpose of the breakage is to reduce the potential damage to the person the adjustable fin comes into contact with, or reduce or minimise damage to the board to which the fin is mounted which can occur if a fin gets torn out of the board due to catching on a reef or rock, as some non-limiting examples.

[00102] The weak portion may comprise a portion of the adjustment member that is thinner than the preferably 1 mm to 2 mm thickness of other portions of the adjustment member. In another embodiment, the weak portion may comprise perforations in a line that is substantially parallel to the mounting means and teeth.

[00103] A further safety feature is the overmolding of flexible polymer over titanium alloy fin portions, when used, to prevent sharp leading and tailing edges from being a danger to the surfer or other nearby persons in the water.

[00104] Mounting Means [00105] The mounting means for an adjustable fin of the invention according to any of the first, second, third, or fourth aspects, or the fin of the invention according to the fourth aspect, as herein described, may comprise a variety of means known for mounting or attaching a fin to a surfboard or another board.

[00106] In a preferred embodiment of an adjustable fin of the invention according to the first, second, third, or fourth aspect described herein, or the fin of the invention according to the fourth aspect, the mounting means comprises one or more mounting blocks for attaching to one or more surfboard fin plugs and/or fin boxes. The one or more mounting blocks are preferably compatible with, and capable of attaching to commercially available fin plug and/or fin box systems. Preferably, the one or more mounting blocks can be mounted to commercially available FCS® fin plugs and/or Futures® fin boxes. 28 2017201742 14 Mar 2017 [00107] In another preferred embodiment, the mounting means comprises a base attachment surface which is directly and fixedly secured to the external bottom surface of the surfboard with adhesive and/or screw type fasteners as described herein. The adhesive is preferably Araldite®, marine silicon, or another epoxy or non-latex construction silicone adhesive that can maintain an adhesive connection between an adjustable fin of the invention and a surfboard or another board, particularly when exposed to water. The marine silicon may provide up to, or greater than 600% elongation ability thereby providing a bond between the adjustable fin of the invention and a surfboard on to which it is mounted, which will unlikely break even under the forces of a heavy surfer turning sharply and quickly on a heavy wave. The base attachment surface preferably provides recesses of a size sufficient to accommodate the adhesive to provide such a bond between the surfboard and the adjustable fin or fin.

[00108] Preferably, one or more screws or screw type fasteners secure a base attachment plate comprising at the base attachment surface to the surfboard and preferably in combination with adhesive. The one or more screws may be secured to the surfboard at a variety of different positions through the base attachment plate. Preferably, the screws are placed at least in front of the leading edge of the adjustable fin or fin, behind the trailing edge, and adjacent to each outer fin surface. The screws may be secured to the surfboard through holes in the base attachment plate through which adhesive is injected. The screws can preferably be turned with a hex or Allen key and screw plugs, for example, plastic screw plugs, may be pre-set in the surfboard into which the screws can be driven and embedded to secure the base of the adjustable fin or fin to the surfboard.

[00109] In another embodiment, the base attachment surface may be ‘fiberglassed’ onto the surfboard using traditional ‘glassing’ methods known in the art. For example, comprising placing ‘rovings’ around the outer edge or border of the base attachment surface.

[00110] Adjustment Indicators 29 2017201742 14 Mar 2017 [00111] Means for showing the user the position of the fin section relative to the base are also within the scope of the invention. Such means may include adjustment indicators, markings or numbering on the fin section, cut outs of the fin section, ‘windows’ or transparent portions of the fin section, or a combination of these, as some non-limiting examples. These means would, for example, enable a user to determine whether two or more adjustable fins mounted as side fins on a board have been adjusted equally. In another example, a user could identify by these means the position of a fin section relative to its base when an adjustable fin of the invention is mounted to a board, without having to manipulate or even touch the adjustable fin.

[00112] Elevated Fin Section [00113] In preferred embodiments of the adjustable fin of the invention as herein described, a portion of the fin section, preferably adjacent to the opening to the internal cavity, contacts, abuts or aligns flush to the external bottom surface of the surfboard on to which the adjustable fin is mounted.

[00114] In an alternative embodiment of the adjustable fin of the invention according to an aspect as herein described, the adjustable fin comprises an extended base which forms a gap between the fin section and the external outer surface of a surfboard on to which it is mounted. The length of the gap between the fin section and the external outer surface of the surfboard is preferably between approximately 5 mm and 25 mm. The length of the gap is more preferably approximately between approximately 10 mm and 20 mm. The length of the gap is more preferably approximately 15 mm. Without wanting to be limited by any one theory, a benefit of elevating a fin section from the outer surface of a surfboard on which it is mounted is to reduce drag, when compared to a fin section which abuts or aligns flush with the outer surface of a surfboard.

[00115] Board Type [00116] The adjustable fin of the invention according to the first, second, third, or fourth aspect, or the fin of the invention according to the fourth aspect, as herein described, may be mounted to any one of the boards in the group 30 2017201742 14 Mar 2017 comprising: surfboard, shortboard, kneeboard, longboard, minimal, soft board, kiteboard or a board used for kite surfing, wind surfer, stand up paddleboard, wakeboard, rescue board, bodyboard, or another board used in surface water sports or activities. Reference herein to a surfboard can also include reference to any one of these other boards.

[00117] Fin Arrangement [00118] More than one adjustable fin of the invention according to an aspect the first, second, third, or fourth aspect, or the fin of the invention according to the fourth aspect, as described herein may be mounted to a surfboard. For example, a thruster fin setup on a surfboard may comprise up to three adjustable fins of the invention as described herein. Alternatively, a single fin or a quad fin setup comprising adjustable fins of the invention may be mounted on to a surfboard. In some non-limiting examples, a fin arrangement may comprise:

Three adjustable fins according to the first or second aspect of the invention and the three adjustable fins are in a ‘thruster’ arrangement;

Two adjustable side fins at a 3.5 degree toe according to the second aspect of the invention and a centre fin according to the first aspect of the invention;

Two adjustable dual side fins according to the third aspect of the invention and a centre fin according to the first or second aspect of the invention;

Three adjustable or non-adjustable fins according to the fourth aspect of the invention; or

Two non-adjustable side fins according to the fourth aspect of the invention and an adjustable fin according to the first or second aspect of the invention, in a thruster arrangement.

[00119] Various combinations are therefore possible for using various embodiments and/or aspects of adjustable fins of the invention, or non- 31 2017201742 14 Mar 2017 adjustable fins according to the fourth aspect, as described herein, exclusively, or in combination with existing non-adjustable or other types of fins on a surfboard.

[00120] Process for Mounting a Fin of the Invention [00121] The present invention further provides a process of mounting an adjustable fin of the invention according to the first, second, third, or fourth aspect, or the fin of the invention according to the fourth aspect, as herein described, 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. The present invention also provides a process of mounting an adjustable fin of the invention according to the first, second, third, or fourth aspect, or the fin of the invention according to the fourth aspect, to a surfboard by mounting the adjustable fin or fin using a mounting means as described herein.

[00122] Process for Manufacturing a Fin of the Invention [00123] The present invention also provides a process of manufacturing an adjustable fin of the invention or a bottom portion of an adjustable fin of the invention according to the first, second, third, or fourth aspect, or the fin of the invention according to the fourth aspect, as described herein. The adjustable fin of the invention according to the first, second, third, or fourth aspect, or the fin of the invention according to the fourth aspect, is preferably constructed from common materials known to be used to make surfboard fins and/or from materials described herein. In one embodiment of the invention, part or the entire base and/or bottom portion of the adjustable fin is constructed from, or comprises, a metal or a metal alloy. In another embodiment, the entire adjustable fin or fin of the invention is made of metal. The metal is preferably strong, light weight, and incapable of rusting or significant corrosion.

[00124] In a preferred embodiment, the metal is titanium. Preferably, the metal is a titanium alloy. More preferably, the titanium alloy comprises between approximately 3.5% to 4.5% vanadium, and between approximately 5.5% to 32 2017201742 14 Mar 2017 6.75% aluminium. Most preferably, the titanium alloy comprises approximately 4% vanadium and approximately 6% aluminium. In a preferred embodiment, a portion of the fin section and any second fin section comprises a titanium alloy. In another embodiment, only plates of titanium alloy are used adjacent the base to provide strength to fins or fin sections of the invention constructed of other materials such as resins or plastic. In a further embodiment, the base is constructed from titanium alloy. This titanium alloy can provide beneficial flex characteristics for a surfboard fin constructed wholly or almost wholly from this material. The titanium alloy in the fin section preferably comprises holes or cut outs of the same or various sizes which can further reduce the weight of the fin and increase the flex characteristics of the upper fin section. The titanium or titanium alloy is preferably encased within a flexible polymer overmold by the process of overmolding. The overmolding may be molded to cover the shape of the titanium alloy fin, or may form a larger portion of a fin section which contains within it a titanium alloy fin portion.

[00125] Use of the titanium alloy in the adjustable fin or fin of the invention enables a thinner fin to be constructed. Where a commercially available shortboard fin may be 7 mm to 8 mm thick at its thickest point on the fin section, the titanium alloy fin section is preferably between approximately 1.5 mm and 3 mm thick, and more preferably between 2 mm and 2.5 mm thick, at its widest point. With the overmolding over the titanium alloy, the fin section is preferably between approximately 2.5 mm and 4 mm thick, and more preferably between 3 mm and 3.5 mm thick at its widest point.

[00126] In another embodiment, the whole fin, part or the entire base and/or bottom portion of the adjustable fin or fin comprises dust or flakes of: titanium, or titanium alloy comprising approximately 4% vanadium and approximately 6% aluminium.

[00127] Alternatively, the metal is aluminium. The fin section may be formed from two halves joined together or from more components.

[00128] Similarly to the large number of different fins currently available for mounting to a surfboard or another type of board described herein, an 33 2017201742 14 Mar 2017 adjustable fin according to the first, second, third, or fourth aspect of the invention, or the fin of the invention according to the fourth aspect 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; 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 or 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.

[00129] In developing the present invention, the inventor addressed many issues that have prevented successful uptake of adjustable fin systems by surfers and other board riders.

[00130] A first benefit is that no tools are required to adjust the position of the adjustable fin on the surfboard. This means that a surfer or another board rider can easily adjust the position of one or more adjustable fins of the invention on their board without even leaving the water. This allows the ‘fine tuning’ of their board to adjust to a much greater range of swell sizes and conditions without paddling in to the beach to swap fins and/or surfboards, and no need for tools or equipment.

[00131] A second benefit is that the adjustable fin of the invention can incorporate mounting blocks that attach to existing fin plug and fin box arrangements such as FCS® fin plugs or Futures® fin boxes. As a result, surfers and other board riders do not have to purchase a new board having a specific fin plug or box arrangement but can use one or more adjustable fins of the invention in their current boards, and without any modifications to their boards.

[00132] A third benefit is that one or more base of the adjustable fin of the invention can be left attached to the surfboard and the fin section removed, either for transport (for an adjustable fin of the invention according to the 2017201742 14 Mar 2017 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 34 second aspect), or to swap different fin sections without tools as the user requires or desires.

Brief Description of Drawings

Figure 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.

Figure 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.

Figure 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.

Figure 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.

Figure 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.

Figure 6. 2017201742 14 Mar 2017 35 according to the second aspect of the adjustable fin of the invention. Figure 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. Figure 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. Figure 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. Figure 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. Figure 11. is an illustration showing (A) an exploded front view, and (B) an exploded perspective view, of the embodiment shown in Figure 10. Figure 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. Figure 13. is an illustration showing (A) an exploded front view, and (B) an exploded perspective view, of the embodiment shown in Figure 36 2017201742 14 Mar 2017

Figure 14.

Figure 15.

Figure 16.

Figure 17.

Figure 18.

Figure 19.

Figure 20. 12; and (C) an underside perspective view of the base of the embodiment. 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. 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. 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. 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. 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 Figure 17. 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 Figures 10 to 15. is an illustration showing (A) a side view, (B) the alternative side view, (C) an exploded perspective view (excluding the upper fin 37 2017201742 14 Mar 2017

Figure 21.

Figure 22.

Figure 23.

Figure 24.

Figure 25.

Figure 26. portion), of an embodiment according to the second aspect of the adjustable fin of the invention. 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. is an illustration showing (A) a side cutaway view, and (B) an exploded perspective view, of the embodiment shown in Figure 21. matching rendered and black and white illustrations showing (A) a port side view, (B) a starboard side view, (C) a front view, and (D) a rear view, of a preferred embodiment of a non adjustable centre fin according to the fourth aspect of the invention, the fins comprising mounting blocks which can be secured within FCS® fin plugs. matching rendered and black and white illustrations showing (A) bottom perspective view, (B) top perspective view, (C) bottom view, and (D) top view, of the preferred embodiment of the non adjustable centre fin shown in Figure 23. rendered illustrations showing (A) a perspective view, and (B) a front view, of a preferred embodiment of a three-fin thruster arrangement of non-adjustable fins according to the fourth aspect of the invention, the fins comprising mounting blocks which can be secured within FCS® fin plugs. illustrations of (A) front and side views, and (B) a side view, of preferred embodiments of a non-adjustable centre fin according to the fourth aspect of the invention with a mounting block which can be secured within a Futures® fin box. 38 2017201742 14 Mar 2017

Figure 27.

Figure 28.

Figure 29.

Figure 30.

Figure 31. matching rendered and black and white illustrations showing (A) front view, (B) top perspective view, (C) port side view, (D) top view, and (E) bottom view, of a preferred embodiment of a nonadjustable centre fin according to the fourth aspect of the invention with a base attachment surface for mounting the fin to the bottom surface of a surfboard. illustrations showing a (A) front view, (B) a rear view, (C) top view, (D) bottom view, (E) right or starboard side view, and (E) left or port side view, of a non-adjustable port side fin (left side fin) according to the fourth aspect of the invention for use in a thruster or quad arrangement, with mounting blocks that can be secured within FCS® fin plugs. illustrations showing a (A) front view, (B) a rear view, (C) top view, (D) bottom view, (E) right or starboard side view, and (E) left or port side view, of a non-adjustable port side fin according to the fourth aspect of the invention for use in a thruster or quad arrangement, with a mounting block that can be secured within a Futures® fin box. illustrations showing a (A) front view, (B) a rear view, (C) top view, (D) bottom view, (E) right or starboard side view, and (E) left or port side view, of a non-adjustable port side fin according to the fourth aspect of the invention for use in a thruster or quad arrangement, with mounting blocks that can be secured with a base attachment surface for mounting the fin to the bottom surface of a surfboard. illustrations showing (A) a port side view, (B) exploded port side view, (C) exploded front view, and (D) exploded top perspective view, of a preferred embodiment of an adjustable centre fin according to the fourth aspect of the invention with a base attachment surface for mounting the fin to the bottom surface of a surfboard. 2017201742 14 Mar 2017 39 Figure 32. (A) Graphical representation of a sectional component of a conventional modern surfboard coupled with either the Inventive fins or Standard fins, and showing the two geometries modelled; illustrations of: (B) the simulation domains at the Waterline 1 for the fins modelled, and (C) a front view of the geometry with inlet flow moving into the paper (as denoted by crosses). Figure 33. Graphical representation of a mesh distribution on the rear Inventive fin (15.7 million faces, such as those appeared on the fin, are used in the simulation at Waterlevel 1). The overall mesh cell thickness on the board is 0.4 mm and on the fin is 0.06 mm, leading to y+ in the range of 30 ~ 100-300 to allow wall function to be used. Figure 34. Secondary velocity vectors (Ux, Uz) comparison between right (a) Inventive fins and (b) Standard fins (at 10m/s). (c) shows the position of the cutting plane through the lateral fins. Figure 35. Secondary velocity vectors (Ux, Uz) comparison between right (a) Inventive fins and (b) Standard fins (at 10m/s). (c) shows the position of the cutting plane aft of the lateral fins. Figure 36. Secondary velocity vectors (Ux, Uz) comparison between central Inventive fins and Standard fins (at 10m/s). (c) shows the position of the cutting plane through the aft central fin. Figure 37. Flow field comparison showing lateral velocity Ux [m/s] on a cut-plane located at the gap height under the lateral Inventive fin immediately adjacent to the board surface. Figure 38. Streamlines generated besides the Inventive fins and Standard fins (at 10m/s) showing the formation of a longitudinal wake vortex behind the lower ridge’. Figure 39. The comparison on the geometry of Inventive fin (inner side fins) and the Standard fin (outer side fins), with inlet flow moving out 40 2017201742 14 Mar 2017 the paper (as denoted by dots), where ‘right’ fin is the starboard fin and ‘left’ fin is the port fin in the thruster arrangement.

Description of Preferred Embodiments [00133] 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.

[00134] 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.

[00135] 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.

[00136] 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.

[00137] Features of the invention will now be discussed with reference to the following preferred embodiments.

[00138] First Aspect of the Invention [00139] 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 Figure 1. The fin section 100 in Figure 1A comprises a leading edge 102 and a 41 2017201742 14 Mar 2017 trailing edge 104 and outer fin surfaces 106 of which only one is visible in Figure 1A.

[00140] 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 Figures 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.

[00141] A biscuit joint 114 shown in Figure 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.

[00142] 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.

[00143] 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 42 2017201742 14 Mar 2017 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.

[00144] A preferred embodiment of the base 200 according to the first aspect of the adjustable fin of the invention is shown in Figure 2. The base 200 comprises 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.

[00145] The base 200 comprises a substantially planar adjustment member 204 which extends in a direction contrary to that of the mounting blocks 202. At the end of the adjustment member 204 furthest from the mounting blocks 202 are teeth 206. Between the teeth are valleys 208.

[00146] 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 adjustment member 204.

[00147] Figure 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 adjustment 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 ‘0’ 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.

[00148] An assembled bottom portion of the preferred embodiment of the adjustable fin of the invention according to a first aspect is shown in Figure 4A. An exploded view of the same bottom portion is shown in Figure 4B. Four wedge-shaped extensions 116 project from within an indentation 118 in the 43 2017201742 14 Mar 2017 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.

[00149] In the coupling of the base 200 with the fin section 100, the adjustment 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 adjustment 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.

[00150] 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 44 2017201742 14 Mar 2017 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.

[00151] 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.

[00152] Figure 5 shows a side view (Figure 5A), a side view showing locking screws 802 (Figure 5B), and a bottom view (Figure 5C) of the embodiment of the bottom portion of the adjustable fin of the invention. Figure 5C shows an embodiment of a side view of a complete adjustable fin of the invention.

[00153] Second Aspect of the Invention [00154] Figure 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.

[00155] 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 Figure 7A, the base 400 comprises wedge-shaped extensions 402 from the adjustment member; and the fin section 100 shown in Figure 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. 45 2017201742 14 Mar 2017 [00156] 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 adjustment 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 adjustment 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.

[00157] In Figure 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.

[00158] 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 Figure 6A: the base 400, a base attachment plate 420, and a base cover plate 440. Screws 450 secure the base assembly together as shown in Figure 6B.

[00159] 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 (Figure 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 46 2017201742 14 Mar 2017 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.

[00160] An exploded view of the base 400 and base attachment plate 420 in Figure 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 adjustment member 404. The saddle portion 410 pivotably engages with a semi cylindrical rod shaped projection 422 extending longitudinally on the base attachment plate 420.

[00161] 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 2017201742 14 Mar 2017 47 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.

[00162] 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.

[00163] 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 Figure 9B, the base cover plate 440 comprises a centre hole 442 through which the adjustment 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.

[00164] 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. 48 2017201742 14 Mar 2017 [00165] Further preferred embodiments of the adjustable fin of the invention according to the second aspect are shown in Figures 10 to 15.

[00166] Figures 10 shows collapsed views and Figure 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 (Figure 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.

[00167] Figure 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. 49 2017201742 14 Mar 2017 [00168] The upper fin 500 shown in Figure 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 Figure 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.

[00169] The upper fin 500 shown in Figure 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.

[00170] 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.

[00171] 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 2017201742 14 Mar 2017 50 edge of the fin section which decreases in thickness with closer proximity to the trailing edge.

[00172] In the embodiment of the adjustable fin shown in Figures 10 and 11 and as shown in Figure 11 A, the base 400 and mounting blocks 202 form one piece and do not comprise separate components that have been attached.

[00173] A further preferred embodiment of the adjustable fin of the invention according to the second aspect is shown in a collapsed form in Figure 12, and an exploded form in Figure 13. This embodiment is the same as the embodiment of the adjustable fin in Figures 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 for mounting onto the external bottom surface of a surfboard with adhesive and/or rovings, screws or other mechanical attachment means.

[00174] The underside of the base plate is shown in Figure 13C showing the base attachment surface 424 and large cavities 426 for accommodating adhesive.

[00175] The holes 515 in the upper fin 500 can be seen in Figure 13B but they are not visible in Figure 12A due to the opacity of the overmold in this embodiment of the adjustable fin of the invention.

[00176] When mounted to a surfboard, the base of the embodiment of the adjustable fin of Figures 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 Figures 12 and 13, the base of the embodiment of Figure 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. 51 2017201742 14 Mar 2017 [00177] A further preferred embodiment of the adjustable fin of the invention according to the second aspect is shown in Figure 15. This embodiment is similar to the embodiment shown in Figures 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.

[00178] Figure 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 Figure 10 to 14, but the base comprises a similar base assembly to the embodiment shown in Figures 6 to 9. A key difference between the base of the embodiment shown in Figure 15 and the embodiment shown in Figures 6 to 9 include different shaped and larger volume cavities 426 for accommodating adhesive.

[00179] A further preferred embodiment of the adjustable fin of the invention according to the second aspect is shown in Figures 17 and 18. This embodiment is similar to the embodiment shown in Figures 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.

[00180] 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 Figure 19. The locking means comprises a cam 304 of a squarer configuration than the cam in the embodiment shown in Figure 3.

[00181] A further embodiment of the adjustable fin of the invention according to the second aspect is shown in Figure 20. This embodiment is similar to the embodiments shown in Figure 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 52 2017201742 14 Mar 2017 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.

[00182] The second key difference is that the embodiment shown in Figure 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.

[00183] Third Aspect of the Invention [00184] An embodiment of the upper fin portion of the adjustable fin of the invention according to the third aspect is shown in Figures 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.

[00185] 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 53 2017201742 14 Mar 2017 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.

[00186] 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.

[00187] The titanium fin portions may contain 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.

[00188] Fourth Aspect of the Invention [00189] A preferred embodiment of the fourth aspect of the invention is the non-adjustable fin shown in a variety of views in Figure 23 and Figure 24. This is the centre fin of a thruster (three-fin) arrangement though could also be used as a side fin. The fin comprises a leading edge 602, a trailing edge 604, and a base 606, the base 606 comprising mounting blocks 608 which can be secured into FCS® plugs in a surfboard to mount the fin onto a surfboard.

[00190] The fin further comprises a first outer fin surface on the ‘port’ or ‘left’ side of the fin (the port side outer fin surface 610), and a second outer fin surface on the ‘starboard’ or ‘right’ side of the fin (the starboard side outer fin surface 612), when considered from the rear or trailing edge 604 of the fin looking towards the front or leading edge 602. The port side outer fin surface 610 meets the starboard side outer fin surface 612 along the leading edge 602 and the trailing edge 604. Both the port side outer fin surface 610 and the starboard side outer fin surface 612 abut the base 606 by meeting along separate edges of the base 606 as shown in Figure 24C.

[00191] Protruding laterally from the port side outer fin surface 610 adjacent the base 606 is a port side main ridge 614 from leading edge 602 to trailing edge 604. Protruding laterally from the starboard side outer fin surface 612 adjacent the base 606 is a starboard side main ridge 616 from leading edge 602 to trailing edge 604. The port side main ridge 614 and starboard side main 2017201742 14 Mar 2017 54 ridge 616 lie substantially parallel to the base 606 and equidistant to the base 606. When the fin is mounted to a surfboard with mounting blocks 608 secured in FCS® plugs in the board, the port side main ridge 614 and starboard side main ridge 616 also lie substantially parallel to the bottom surface of the surfboard, at least at the location the fin is mounted.

[00192] The port side outer fin surface 610 either side of the port side main ridge 614 comprises a port side main ridge upper side 618 and a port side main ridge lower side 620.

[00193] The starboard side outer fin surface 612 either side of the starboard side main ridge 616 comprises a starboard side main ridge upper side 622 and a starboard side main ridge lower side 624.

[00194] In this embodiment, the port side main ridge lower side 620 and starboard side main ridge lower side 624 comprise a slight curve; however, they may also comprise more curvature, or less curvature, or comprise at least a portion that is flat.

[00195] In this embodiment, the port side main ridge upper side 618 and starboard side main ridge upper side 622 comprise flat and curved portions; however, they may also comprise curved portions with no flat portions, and the curved portions may have more or less curvature.

[00196] The ends of the port side main ridge 614 and starboard side main ridge 616 meet at the leading edge 602 and trailing edge 604.

[00197] A port side minor ridge 626 protrudes laterally from the port side outer fin surface 610 above the port side main ridge 614. The port side minor ridge 626 is smaller than the port side main ridge 614 and is positioned further from the base 606. The port side minor ridge 626 does not extend to the leading edge 602 or the trailing edge 604. In the embodiments of the fin that are adjustable and contain a knob, the port side minor ridge 626 can comprise the knob. 55 2017201742 14 Mar 2017 [00198] A smaller, starboard side minor ridge 628 protrudes laterally from the starboard side outer fin surface 612 above the starboard side main ridge 616. The starboard side minor ridge 628 is smaller than the starboard side main ridge 616 and is positioned further from the base 606. The starboard side minor ridge 628 does not extend to the leading edge 602 or the trailing edge 604. In the embodiments of the fin that are adjustable and contain a knob, the starboard side minor ridge 628 can comprise the knob.

[00199] The port side minor ridge 626 and starboard side minor ridge 628 may be parallel to the main ridges, but in this embodiment, the port side minor ridge 626 and starboard side minor ridge 628 have a slight angle of attack towards the base at the ends closest the leading edge 602 as shown in Figure 23A and 23B.

[00200] This embodiment of the non-adjustable fin is made in a mould constructed in one part, though could be constructed from more than one part.

[00201] Figure 25 shows in 25A and 25B a three fin ‘thruster’ arrangement similar to how the fins would be positioned once mounted to a surfboard. The centre fin 630 is set back from the side fins, and the side fins positioned with a slight inwards toe towards the centre of the arrangement and on a slight outward cant. The right or ‘starboard’ side fin 632 of the thruster arrangement and left or ‘port’ side fin 634 of the arrangement may be identical to the centre fin 630 or may be configured differently and asymmetrically as shown in Figure 28.

[00202] Figure 26 shows a fin according to the same embodiment in Figure 23 and 24 except the mounting means at the base comprises a single mounting block 636 which can mount the fin into a Futures® fin box in a surfboard. Figure 26A shows a mounting block 636 with one shape of mounting block holes 638 and Figure 26B shows a mounting block 636 with another shape of mounting block holes 638. Other mounting block hole shapes or cut outs, including triangles or circles, amongst others, are also within the scope of the invention. Alternatively, there may be no cut outs, or holes in the mounting 56 2017201742 14 Mar 2017 block 636 though the benefit of such holes is to reduce weight and the amount of material required to manufacture the fin which can be a cost saving.

[00203] Figure 27 shows a fin according to the same embodiment in Figure 23 and 24 except the mounting means at the base comprises a base attachment plate 640 as a further means for mounting the fin to a surfboard, as already described herein. The base attachment plate comprises a substantially flat base attachment surface 642 for contacting to the external bottom surface of a surfboard to which it is to be mounted (Figure 27E). Cavities 644 (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 fin can be attached to the external bottom surface of a surfboard. Preferably, the adhesive is injected into each cavity 644 through an injection conduit in the form of a tunnel or injection hole through the base attachment plate 640 (not shown) once the base attachment plate 640 is placed in the desired position on the surfboard to which it is to be mounted. A second injection conduit (not shown) in each cavity 644 would enable air to be released from the cavity 644 as the adhesive is injected into a first injection conduit and spreads throughout the cavity 644. Thus, the formation of air bubbles and therefore weaknesses in the adhesive attachment can be avoided. Once the cavity 644 is full of adhesive, excess adhesive will exit the second injection conduit indicating that the cavity 644 is full, and the excess adhesive can be wiped away before it dries. Preferably, screws are driven through injection conduits and into the surfboard prior to, or after the adhesive has dried, to provide additional strength in the attachment of fin to the surfboard to which it is mounted.

[00204] The portion of the fin relative to the base attachment surface 642 may be created at a specific cant for use as side fins in a thruster set up.

[00205] Figure 28 shows a left or port side fin 634 as shown in the thruster arrangement of Figure 25 with mounting blocks which can be secured into FCS® plugs in a surfboard in the port side position of a thruster or quad arrangement. Front the front view, the port side fin 634 is asymmetric as opposed to the centre fin of Figure 23 and Figure 24. This asymmetric 57 2017201742 14 Mar 2017 configuration aims to benefit from both: (i) the effect of having both the main ridges and minor ridges on both sides of the fin to reduce the size of trailing vortices to reduce drag; and (ii) a substantially flat portion on the starboard side outer fin surface 612 of the port side fin 634 (that is, facing towards the centre line or stringer of the surfboard) and a curved port side outer fin surface, which can generate the known thrust experienced with flat foil side fins in a thruster arrangement on a surfboard as already described herein.

[00206] Figure 28 shows the port side minor ridge 626 and starboard side minor ridge 628 are of a similar size and equidistant to the base. However, the starboard side main ridge 616 and starboard side main ridge upper side 622 and starboard side main ridge lower side 624 are all smaller than the port side main ridge 614 and port side main ridge upper side 618 and port side main ridge lower side 620, respectively. The starboard side main ridge upper side 622 merges into the substantially flat starboard outer fin surface 612.

[00207] Support plates 645 have been attached in this embodiment to the port side main ridge lower side 620 and starboard side main ridge lower side 624 to provide additional strength to this portion of the fin. Such support plates 645 may, or may not be part of the fins of the invention. Support plates 645 may be a metal or metal alloy including those already described herein. In a preferred embodiment, the support plates are made from titanium alloy.

[00208] A starboard side fin (not shown in Figure 28) will be the mirror image of the fin shown in Figure 28.

[00209] Figure 29 is the same as the port side fin of Figure 28 but with a mounting block which can be secured into a Futures® fin box in a surfboard in the port side position of a thruster or quad arrangement. A starboard side fin (not shown in Figure 29) will be the mirror image of the fin shown in Figure 29.

[00210] Figure 30 is the same as the port side fin of Figure 28 but with a base attachment surface for mounting the fin to a surfboard as described herein in the port side position of a thruster or quad arrangement. A starboard side fin (not shown in Figure 30) will be the mirror image of the fin shown in Figure 30. 58 2017201742 14 Mar 2017 [00211] Figure 31 shows an adjustable version of the fin of Figure 27. Similarly to other aspects of the invention, a base portion 646 engages a fin portion 648 to form the adjustable fin, wherein a planar member 650 attached to the base attachment plate 640 to form the base portion 646 is located within an internal cavity within the fin section 648. The planar member 650 is secured to the fin section 648 within the internal cavity by screws 652 that are accessible from the outer fin surfaces and pass through the fin section 648 into the internal cavity and can engage with the planar member 650 at locking cavities 654. To adjust the positon of the fin section 648 relative to the base portion 646, screws 652 are unscrewed out of a set of locking cavities 654 at a first locking position, thereby un-securing the fin section 648 from the base portion 646, the fin section 648 is slidably moved toward the leading edge or trailing edge, and the screws 652 are screwed into locking cavities 654 at a second locking position, thereby re-securing the fin section 648 to the base portion 646 at the second position. The more locking cavities 654 on the planar member 650, the more locking positions are available for adjusting the fin section 648 relative to the base portion 646.

[00212] Initially, the purpose of the main ridges either side of the fin section according to the second and fourth aspects of the invention was to increase the width of the fin section to accommodate the internal mechanism for adjusting the fin section relative to the base. The minor ridge was formed to accommodate the locking mechanism in order to reduce drag created by the protruding knob. Flowever, during testing of the fins by expert surfers, surfing waves on surfboards to which fins according to these embodiments of the invention were mounted, unusually high speeds were observed as well as maintenance of speed during turning when compared to standard flat fins. Upon further analysis, it was considered that the shape of the fins was causing the increase of speed due to reduction of drag forces by affecting vortices adjacent where the fin is mounted onto the board. It is understood that where large vortices are created behind an object moving through water, or air, these large vortices create drag or a ‘sucking’ effect, therein reducing velocity. Thus, by disrupting large vortices from forming and instead creating smaller vortices around the base of the fin either sides of the main ridges, a reduction of drag 59 2017201742 14 Mar 2017 forces behind the fins was predicted to be causing the observed effect. Thus, computational fluid dynamics modelling and analysis was performed to confirm the benefits provided by these fin configurations when compared to standard flat fins.

[00213] Computational Fluid Dynamics Modelling and Analysis [00214] Background [00215] Comparative computational fluid dynamics (CFD) modelling of a three-fin ‘thruster’ arrangement of: fins of the invention (the “Inventive fins” or “INV”), compared to standard, commercially available fiat fins (the “Standard fins” or “STD”) as shown in Figure 32, was conducted by Aurora Offshore Engineering (Aurora). The modelling software used was the widely documented, validated and accepted open-source numerical modelling fool OpenFOAM®, which is a general-purpose CFD modelling code for solving the Reynolds Averaged Navier-Stokes equations for fluid flow.

[00216] The geometries modelled are shown graphically in Figure 32A featuring a sectional component of a conventional modern shortboard surfboard coupled with either the Inventive fins or Standard fins. Two waterlines have been considered as shown in the Figure 32A. The flow velocity combinations are given in Table 1. The flow direction is always parallel to the waterlines as given in Figure 32A. INV Fins STD Fins Waterline 1 10 m/s 10 m/s Waterline 2 7 m/s 7 m/s 4 m/s 4 m/s [00217] Table 1. Flow velocity combinations modelled.

[00218] The numerical model of the fluid flow was constructed using a rectangular domain containing the relevant board and fin sections as shown in Figure 32B. The position and orientation of each fin system is shown in Figure 32C and a view of the surface mesh on the base of the board, the main ridge 60 2017201742 14 Mar 2017 (comprising the first and second ridges), and the minor ridge (comprising the third and fourth ridges) shown in Figure 33.

[00219] Results [00220] The analysis of the results focuses on investigation and identification of the flow fields around the different fin systems and differentiation of their resulting performance. Figure 34 gives the velocity vector field normal to the board velocity and located on a cut-plane down through the side fins as shown in Figure 34c. The secondary velocity field as generated by (Ux, Uz) shown in this figure demonstrates how the influences of the Inventive fin features on the local flow field compared to the Standard fins, showing (1) that both fins generate a similar trailing wake vortex around the fin tip, while (2) the Inventive fin main ridge and minor ridge also generate division of the longitudinal flow near the base of the fin. These rotational flows appear to be more apparent at the locations of geometry change along the Inventive fin, as shown in (3).

[00221] Figure 35 gives the velocity vector field norma! to the board velocity and located on a cut-plane down just aft of the side fins as shown in Figure 35c. The secondary velocity field as generated by (Ux, Uz) shown in this figure demonstrates how the influences of the inventive fin features on the local flow field compare to the Standard fins, showing (1) that both fins generate a trailing wake vortex around the fin tip, while (2) the Inventive fin main ridge and minor ridge also generate a significant change in the flow behaviour against the board surface adjacent to and inboard of the fin. Comparing the flow at (3) in Figure 35(iii), the Inventive fins cause changes in not only the direction of the flow, but also in the magnitude of the velocity.

[00222] The effect of flow past the rear central fin is shown in Figure 36 which gives the velocity vector field normal to the board velocity and located on a cut-plane through the aft fin as shown in Figure 36c. The secondary velocity field as generated by (Ux, Uz) shown in this figure demonstrates how the influences of the Inventive fin features on the local flow field compare to the Standard fins, showing (1) that the prevailing flow at this location is upwards 2017201742 14 Mar 2017 61 towards the free water surface and board, while (2) the Inventive fin main ridge and minor ridge also generate division of the longitudinal flow near the base of the fin, which are similar to those features in Figure 34.

[00223] Differentiation of the flow behaviour between the Inventive and Standard fins is also investigated by considering a cut-plane parallel to and slightly below the board surface as shown in Figure 37c at the elevation of the gap between the Inventive main ridge and the board. As can be seen by comparison of the lateral velocity (Ux) between figures (a) and (b), the flow immediately adjacent to the board differs significantly between the inventive and Standard fins, with (1) the Inventive fin frontal gap under the main ridge enabling significant inboard flow, followed by (2) the rear gap enabling significant outboard flow which is not possible with the Standard fin which has continuous contact with the board surface. The downstream wake behind the fins (3) shows significant continuation of the wake from the Inventive fin which is much stronger than for the Standard fin.

[00224] To further assist in understanding the response of the flow to the presence of the key design elements of the Inventive fin, streamlines are generated down either side of each fin system as illustrated in Figure 38, looking forwards from behind the lateral fin. The streamlines demonstrate the formation (1} of a persistent downstream longitudinal wake vortex with its axis of vorticity centred around the longitudinal axis of the main ridge (which is predicted by the inventor to act in a manner similar to a caudal keel of some fast fish). This wake vortex is located adjacent to the board surface and is therefore anticipated to have a significant influence on the flow past the board downstream of the fin.

[00225] Forces in Tables [00226] The hydrodynamic forces extracted from the CFD model for each of the fins are presented in Table 2. 62

Board Speed [m/s] Waterline (Figure 32A) Fin Lateral Force on Fin /μ [N] Af(x) INV STD Port -2.71 -3.98 -32% 4 2 Centre 0.09 0.18 -50% Starboard 2.63 4.55 -42% Port -17.86 -12.03 48% 7 2 Centre 0.24 0.52 -54% Starboard 17.87 13.72 30% Port -11.84 6.72 -276% 10 1 Centre -0.54 1.65 -133% Starboard 13.27 -3.76 -453% 2017201742 14 Mar 2017 [00227] Table 2, The ratios of change in lateral forces of inventive fins compared to Standard fins. Note: The sign convention is that the forces are the water force on the fin, which is oriented so that (for 4 and 7 m/s) the forces are towards the inner side of the board as shown in Figure 39.

[00228] The key observations from this are that: • The lateral fin forces are considered as giving the best indication of how much of an effect the fins are having on the flow over the board; • The centre fins have very low forces and therefore are expected to have very little effect since they are aligned with the flow; • The lateral fins (both types and at all speeds) produce roughly equal and opposite forces - this is expected since the board is travelling straight ahead. There are subtle differences in the geometries which can be seen in the differences between left and right forces; and • The lateral forces increase as speed increases for waterline 2, but the change in waterline and velocity results in a change in the direction of the forces on the Standard fins.

[00229] In general, lateral forces increase greatly on the Inventive fins, compared to the Standard fins, which is anticipated to be important in the observed speed increase with Inventive fins. It will also be very important in 2017201742 14 Mar 2017 63 the performance and stabiiity of the board during turning manoeuvres, one of the most frequent actions needed to be taken during surfing.

[00230] Conclusions [00231] The results of the CFD modelling show a significant change in the flow of water immediately adjacent to the board and downstream of the fins of the invention when compared to the standard fins in a thruster arrangement. These flow changes are potential causes for the observed speed and stability increases observed for boards using the fins of the invention.

Claims (20)

1. The Claims Defining the Invention are as Follows

   1. A fin for use on a surfboard, the fin comprising: a leading edge, a trailing edge, and a base, the base comprising at least one mounting means for mounting the fin onto a surfboard; a first and a second outer fin surface which meet along the leading edge and the trailing edge and abut the base; a first ridge protruding laterally from the first outer fin surface, and a second ridge protruding laterally from the second outer fin surface.
2. 2. A fin according to claim 1, wherein the first and second ridges are substantially parallel to the base.
3. 3. A fin according to claim 1 or claim 2, wherein when the fin is attached to a surfboard, the first and second ridges are substantially parallel to the adjacent bottom surface of the surfboard.
4. 4. A fin according to any one of the preceding claims, wherein the first outer fin surface either side of the first ridge comprises first ridge sides, and wherein the second outer fin surface either side of the second ridge comprises second ridge sides.
5. 5. A fin according to claim 4, wherein at least a portion of the first and second ridge sides are flat, curved, convex, and/or concave.
6. 6. A fin according to any one of the preceding claims, wherein the first and second ridge is located adjacent the base.
7. 7. A fin according to any one of the preceding claims, wherein the first and second ridges are located equidistant from the base.
8. 8. A fin according to any one of the preceding claims, wherein the first and second ridges comprise a front end adjacent to the leading edge.
9. 9. A fin according to any one of the preceding claims, wherein the first and second ridges comprise a rear end adjacent to the trailing edge.
10. 10. A fin according to any one of the preceding claims, wherein the first and second ridge is located within 25 mm of the base.
11. 11. A fin according to any one of the preceding claims, wherein the fin comprises a third ridge protruding laterally from the first outer fin surface, and a fourth ridge protruding laterally from the second outer fin surface.
12. 12. A fin according to claim 11, wherein the third and fourth ridges are smaller and are located further from the base than the first and second ridges.
13. 13. A fin according to claim 11 or claim 12, wherein the third and fourth ridges are substantially parallel to the base, and wherein when the fin is attached to a surfboard, the third and fourth ridges are substantially parallel to the bottom surface of the surfboard.
14. 14. A fin according to any one of claims 11 to 13, wherein the third and fourth ridges are substantially parallel to the first and second ridges and are located equidistant from the base.
15. 15. A fin according to any one of claims 11 to 14, wherein the first outer fin surface either side of the third ridge comprises third ridge sides, and wherein the first outer fin surface either side of the fourth ridge comprises fourth ridge sides.
16. 16. A fin according to claim 15, wherein at least a portion of the third and fourth ridge sides are flat, curved, convex, and/or concave.
17. 17. A fin according to any one of the preceding claims, wherein the fin is an adjustable fin comprising: the base comprising an adjustment member; and a fin section comprising: the first and the second outer fin surfaces which meet along the leading edge and the trailing edge; an opening to an internal cavity within the fin section, the internal cavity configured to house the adjustment member of the base and enable slidable movement of the adjustment member in a direction towards the leading edge or the trailing edge; and a locking means which can releasably couple to the adjustment member at one of two or more locking positions thereby preventing slidable movement of the adjustment member; wherein the fin section can be adjusted relative to the base by uncoupling the locking means from the adjustment member at a first locking position, slidably moving the adjustment member through the internal cavity, and releasably coupling the locking means to the adjustment member at a second locking position.
18. 18. A fin according to any one of the preceding claims, wherein the one or more mounting means are mounting blocks capable of attaching to commercially available fin plug and fin box systems.
19. 19. A fin according to any one of the preceding claims, wherein the base comprises a base attachment plate comprising a substantially flat base attachment surface which contacts the external bottom surface of a surfboard on to which it is mounted.
20. 20. A fin according to any one of the preceding claims, 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.