Fin box assemblies for windsurfers

Abstract: A windsurfer board (12) is formed, towards the tail end thereof, with a slot in which a box (11) is fitted. The box (11) provides a mounting for a fin (10) which is movable, while in use, relative to the board (12) in such manner as to permit simultaneous adjustment of the inclination of the fin (10) relative to the board (12) and of the extent by which the fin (10) projects downwardly beneath the board (12). The mounting for the fin (10) includes a bracket (14) pivotally connected to the box (11) and to the fin (10).

Description: Field of the Invention This invention relates to fin box assemblies for windsurfers. Background of the Invention A fin box assembly as defined in the first part of Claim 1 is described in European Patent Specification No. 0 088 430. This prior art fin box assembly includes a box which is located towards the rear of the board and provides a pivot mounting for a fin which projects downwardly below the board and can be fixed in any one of a plurality of selected angular positions. The degree of adjustability of the fin is, however, limited, the mechanism is complex and the commercial success of this fin box has accordingly been rather limited. It is an object of the present invention to provide an improved form of fin box assembly for a windsurfer which is compact, permits ready adjustment of the position of the fin and is more effective than the prior art fin box design. A further object of the invention is to provide a windsurfer including a fin box assembly having an adjustably mounted fin, which windsurfer can be sailed more effectively in a variety of wind conditions than other windsurfers. Summary of the Invention The present invention provides a fin box assembly and a windsurfer board having the features defined in the appended claims. Brief Description of the Drawings Figure 1 is a perspective view of the rear portion of a windsurfer board fitted with a fin box assembly and showing the fin in its lowermost position, Figure 2 is a perspective view similar to Figure 1 but showing the fin in its raised position, and Figure 3 is an exploded perspective view of the fin and its mounting means. Description of the Preferred Embodiment The fin 10 shown in the drawings is of aerofoil configuration and is formed of a carbon fibre or mesh-reinforced polyester resin or other equally strong and durable semi-rigid plastics material. It is located within a rectangular box fixed within an elongated slot formed in the windsurfer board 12 towards the rear or tail end 13 of the board 12. The box 11 has walls formed either of metal plate or of a glass-fibre-reinforced polyester resin and is bonded in position within the slot in the board 12 so that the upper surface of the box 11 extends just above the upper surface of the board 12 and the lower surface of the box 11 is spaced upwardly a short distance from the lower surface of the board 12. The mounting for the fin 10 includes a U-shaped bracket 14 which has a pair of parallel arms 15 which fit one on each side of the fin 10 and are pivotally connected to the fin 10 by means of a pin 16 which passes through aligned apertures 17 formed in the arms 15 adjacent the ends thereof and an aperture 18 formed in the fin 10. The fin 16 has an enlarged head portion 19 to facilitate removal of the pin 16 if, for example, it is desired to replace the fin 10 by one of greater or lesser length. In practice, the overall length of the fin 10 which is chosen will depend on the area of sail carried by the windsurfer board and this will depend not only on the wind conditions but also on the weight and sailing ability of the person using the windsurfer board. For a larger area of sail, a longer fin will be used. As shown in the drawings, a small number of spaced apertures 18 may be formed in the fin 10 so that, by appropriate selection of the aperture 18 in which the fin 16 is to be fitted, a degree of adjustment of the effective fin area can be achieved. Such adjustment will be effected out of the water and will depend on the individual user and on the wind and wave conditions. The fin 10 has a leading edge 20 and a trailing edge 21 and, although the design of the fin 10 may be varied significantly, the leading edge 20 may comprise an upper straight portion followed by a relatively short lower curvate portion 22, whilst the trailing edge 21 again comprises an upper straight portion followed by a somewhat longer lower curvate portion. The fin 10 is formed, adjacent its upper edge, with a pair of transverse bores 24 and 25 in which stop plugs 26 and 27 respectively are fitted so as to project beyond the adjacent surfaces of the fin 10 and on each side of the fin 10. The plug 26 which is closer to the trailing edge 21 of the fin 10 is a simple cylindrical plug whereas the plug 27, which is closer to the leading edge 20 of the fin 10, is provided at each end with a raised projection 28 of square cross-section positioned so that, when the fin 10 is in its raised position as shown in Figure 2, each projection 28 engages the associated arm 15 of the bracket 14 to limit the extent of movement of the bracket 14 and hence of the fin 10. Spacers 29 and 30 are fitted within the box 11, one adjacent each of the side walls 31, 32 of the box. The spacers 29 and 30 are formed of a material having a low coefficient of sliding friction with the fin 10, the preferred material being ultra high molecular weight polyethylene, though other low friction materials, for example polytetrafluoroethylene, could also be used. Each of the spacers 29, 30 is in the form of a generally flat plate of the configuration shown in Figure 3. The upper edge of each spacer 29, 30 is thus provided with a pair of spaced rebates 33, 34 which are aligned with corresponding rebates 33, 34 formed in the side walls 31 and 32 of the box 11. The spacings between the rebates 33, 34 correspond to the spacing between the plugs 26 and 27. Thus, when the fin is in its lowermost position as shown in Figure 1, the plugs 26 and 27 sit in the rebates 33, 34 in the spacers 29 and 30 and in the aligned rebates 33, 34 in the box side walls 31 and 32, which rebates act as locating elements for the fin 10. Each spacer 29, 30 and each box side wall 31, 32 is also formed with a cut-out 35 which acts (as described below) as a locating formation when a fixed fin is used (as shown in Figures 4 and 5) in place of the fin 10 of Figures 1 to 3. In production, there will inevitably be variations in the transverse spacings of the side walls 31 and 32 of the box 11 and in the thickness of the fin 10. The spacers 29 and 30 may thus additionally act as shims and, as appropriate, two or more spacers will be used to ensure that the fin 10 is a close sliding fit between the walls 31 and 32 of the box 11. As an alternative to using different numbers of spacers 29, 30, it is also possible to provide spacers of different thicknesses or to provide separate shims. This will be of advantage if, for example, a fin box assembly is provided which includes a plurality of alternatively usable fins which are of different lengths and of different thicknesses. One of the arms 15 of the bracket 14 is formed with a seating 36 in line with the through aperture 17 which receives the pin 16. the pin 16 can be a drop-nose pin and the seating 36 will then receive the drop-nose formation of the pin 16 to receive and locate it in position. The upper surface 39 of the fin 10 is formed with a pair of spaced recesses each of which receives a tag 37 attached to a lifting loop 38 which projects above the fin 10. The tags 37 are fixed in position by suitable pins (not shown). The lifting loop 38 may comprise a tube of polyvinyl chloride with a fabric covering of, for example, polyethylene terephthalate. The upper surface 39 of the fin 10 is of a non-slip nature and this may be afforded by, for example, bonding a layer of non-slip material to the upper edge of the fin 10. The upper surface 39 is proud of the box 11 when the fin 10 is in its raised position as shown in Figure 2. When the windsurfer is being sailed up-wind, the fin 10 will be in its lowermost position as shown in Figure 1. The fin 10 will project downwardly a substantial distance below the board 12 and will accordingly provide substantial transverse reaction in respect of the transverse forces to which the sail and board are subjected while sailing up-wind. The area of the fin 10 which is in the water and the depth of downward projection of the fin 10 provide additional lift and enhance the pointing ability of the board 12 to enable the board to be sailed up-wind more efficiently than would otherwise be the case. At the end of the up-wind leg, the windsurfer will bear off slightly to reduce the pressure on the fin 10 and bend down to grasp the lifting loop 38. An upward lifting action will then serve to move the fin from its lowermost position as shown in Figure 1 into its raised position as shown in Figure 2 in readiness for sailing the board along the down-wind leg. As shown in Figure 2, the fin 10 is not only displaced bodily upwardly but is also raked rearwardly as compared to its Figure 1 position thereby effecting a very substantial reduction in the extent by which the fin 10 projects downwardly below the board 12 and in the degree of lift arising from the presence of the fin. At the end of the down-wind leg, the person sailing the board will apply foot pressure to the non-slip upper surface 39 and, by pressing downwardly, will move the fin 10 from its raised position back into its lowermost position. The increase in the effective area of the fin 10 which is then achieved by pivoting the fin 10 back into a substantially vertical position as well as displacing the fin 10 bodily downwardly is considerably greater than would be the case if the fin 10 were merely pivoted forwardly into a generally vertical position. As shown in the drawings, the fin box assembly is located centrally of the board 12 just to the rear of the foot straps 40. The upper edges of the walls of the box 11 will be sanded or ground away so that they lie either flush with the upper surface of the board 12 or project just above the upper surface of the board 12. In this respect, a small degree of projection above the upper surface of the board 12 is to be regarded as "substantially flush" with said upper surface. The box 11 includes a boss 41 which fits between forwardly extending stubs 42 and 43 of the bracket 14 with a pin 44 extending through aligned bores in the boss 41 and the stubs 42 and 43 to provide for the pivotal mounting of the bracket 14. In a typical construction, the axis of the pin 44 is located approximately 8 mm. above the upper surface of the board 12. The front and rear walls 45 and 46 of the box 11 can be inclined rearwardly so that, when the fin 10 is moved into its rearwardly raked position as shown in Figure 2, the leading and trailing edges 20 and 21 of the fin 10 will lie in substantial contact with the walls 45 and 46. The walls 45 and 46 will thus act as stops. In addition, the close spacing between the leading and trailing edges 20 and 21 of the fin 10 and the walls 45 and 46 will reduce the tendency for the generation of a downward flow of air through the box 11 during the high-speed down-wind leg. This downward flow of air is further prevented by means of a sealing gasket 47 which is bonded to the downwardly facing surfaces of the walls of the box 11 and is formed of a resiliently deformable foamed plastics material, such as a foamed polyurethane or a foamed silicone rubber. The sealing gasket 47 is shaped so that it is a close fit around the fin 10 whilst the resilient nature of the gasket material enables the gasket 47 to flex and maintain its sealing action during movement of the fin 10 between its lowermost position as shown in Figure 1 and its raised position as shown in Figure 2. The walls of the box 11 and the spacers 29 and 30 have a height which is slightly less than the thickness of the board 12. The lower surfaces of the walls of the box 11 are spaced upwardly from the lower surface of the board 12 by a distance corresponding to the thickness of the gasket 47 and a flush-fitting arrangement is thus provided.

Claims: A fin box assembly for mounting towards the rear of a windsurfer board (12), said fin box assembly comprising a box (11) and a fin (10), the box (11) defining a chamber within which the fin (10) is mounted so as to depend downwardly from the chamber, said fin (10) having a leading edge (20) and a trailing edge (21), and the fin (10) being adjustably mounted relative to the box (11) so as to be movable between a first limiting position in which the leading edge (20) of the fin (10) extends substantially vertically and a second limiting position in which the leading edge (20) of the fin (10) is raked rearwardly, characterised in that a link (14) is pivotally mounted on the box (11) and is pivotally connected to the fin (10) such that the fin (10) is displaced bodily upwardly during movement of the fin (10) from its first into its second limiting position. A fin box assembly according to Claim 1, characterised in that the link (14) is a substantially U-shaped element (14) having a base and a pair of parallel arms (15) arranged so that they embrace the upper portion of the fin (10), the base of the U being pivotally connected to the box (11) and the arms (15) being pivotally connected to the fin (10). A fin box assembly for mounting towards the rear of a windsurfer board (12), said fin box assembly comprising a box (11) and a fin (10), the box (11) defining a chamber within which the fin (10) is mounted so as to depend downwardly from the chamber, said fin (10) having a leading edge (20) and a trailing edge (21), and the fin (10) being adjustably mounted relative to the box (11) so as to be movable between a first position in which the leading edge (20) of the fin (10) extends substantially vertically and a second limiting position in which the leading edge (20) of the fin (10) is raked rearwardly, characterised in that the box (11) is open at its top and bottom and by the provision of a pair of spacers (29 and 30) which fit one on each side of the fin (10) and a seal (47) which surrounds the fin (10), said spacers (29 and 30) being formed of a low friction plastics material and the seal (47) being formed of a resiliently deformable foamed plastics material which acts between the fin (10) and the walls (31, 32, 45 and 46) of the box (11) to prevent the flow of air through the box (11), the fin (10) being connected to the box (11) by means of a pivotally mounted link (14) which is so arranged that the fin (10) is displaced bodily upwardly relative to the box (11) during movement thereof from its first into its second limiting position, said spacers (29 and 30) acting to facilitate sliding of the fin (10) relative to the box side walls (31 and 32) and the seal (47) flexing to maintain its sealing action during such movement of the fin (10). A fin box assembly according to Claim 3, characterised in that a loop (38) which can be grasped manually is attached to the fin (10) adjacent the upper end thereof so that a user of the windsurfer board (12) can grasp the loop during sailing to move the fin (10) from its first position into its second position, the link (14) pivoting relative to the box (11) and relative to the fin (10) so that such movement of the fin (10) comprises a lifting component and a tilting component. A fin box assembly according to Claim 4, characterised in that the upwardly facing portion of the fin (10) has a non-slip surface (39) so as to facilitate the application of foot pressure thereto so that, when it is desired to move the fin (10) from its second position into its first position, such movement can be effected during sailing by the application of foot pressure to the upper surface (39) of the fin (10). A fin box assembly according to Claim 4, characterised in that the link (14) comprises a U-shaped bracket (14) having a base and a pair of arms (15), the base being pivotally connected to the box (11) by means of a pin (44), the arms (15) being arranged so that they are pivotally connected to and embrace the fin (10), and the fin (10) being provided with stop means (27) for engagement with the bracket (14) when the fin (10) is in its second position. A windsurfer board (12) having upper and lower surfaces and provided, adjacent the rear thereof, with a fin box assembly, said fin box assembly comprising a box (11) and a fin (10) which extends a significant amount downwardly below the lower surface of the board (12), the box (11) defining a chamber within which the fin (10) is mounted, the fin (10) having a leading edge (20) and a trailing edge (21) and being movable relative to the box (11) between a first limiting position in which the leading edge (20) of the fin (10) extends substantially vertically and a second limiting position in which the leading edge (20) of the fin (10) is raked rearwardly, characterised in that the box (11) is open at top and bottom, that the mounting for the fin (10) comprises a bracket (14) having spaced pivotal connections to the box (11) and to the fin (10), and that the pivotal connections between the bracket (14), the box (11) and the fin (10) are so arranged that the fin (10) is displaced bodily upwardly during movement of the fin (10) from its first into its second position. A windsurfer board according to Claim 7, characterised in that renewable plastic spacers (29 and 30) are located between the fin (10) and the side walls (31 and 32) of the box (11), and in that a sealing gasket (47) of a resiliently deformable material is fitted around the fin (10) to provide a seal between the fin (10) and the walls (31, 32, 45 and 46) of the box (11). A windsurfer board according to Claim 8, characterised in that the fin (10) is provided with stop plugs (26 and 27) for limiting the extent of movement of the fin (10) relative to the board (12), at least one stop plug (26, 27) being arranged for engagement with the box (11) when the fin (10) is in its first limiting position and at least one stop plug (27) being arranged for engagement with the bracket (14) when the fin (10) is in its second limiting position.

Inventors: KINNAIRD ANDREW THOMAS, KINNAIRD, ANDREW THOMAS
Applicants: KINNAIRD ANDREW THOMAS, KINNAIRD, ANDREW THOMAS
Application year: 1992
Main classification: B63B35
IPC codes: B63B35