P/001009 Regulation 3,28 5 AUSTRALIA Patents Act 1990 10 COMPLETE SPECIFICATION FOR A DIVISIONAL INNOVATION PATENT 15 20 Invention Title: FIN ATTACHMENT SYSTEM 25 The invention is described in the following statement together with the best method of performing it known to us 30 35 40 Our Reference: 066011 -2 FIN ATTACHMENT SYSTEM The present invention relates to fins and their attachment to small water craft and, more particularly to 5 a system for attaching a variety of fin configurations to a surfboard. BACKGROUND As with many types of sporting equipment, many variations on the basic article have been developed to tailor the 10 article to the preferences of the user and the conditions of use. So it is with the fins attached to the rear undersides of surfboards. It is an obvious advantage for the owner of a board to be able to interchange the fin or fins both to experiment, 15 with the aim of finding the fin most suited to their body weight and style of riding, and from time to time to suit the conditions in which the board is to be ridden. Interchangeable fin systems are known and comprise of a selection of fins retained in a so-called fin box. 20 Particular examples may be found in US 5830025, US 5975974 and WO 01/70565. The fin box is generally a permanent fixture built into the body of the board during -3 its manufacture and, again generally includes a slot or slots into which the tab or heel of the fin may be inserted. The means for retaining an inserted fin securely in the fin box are many and varied, ranging from 5 relatively simple snap-in systems to arrangements incorporating fasteners requiring the application of tools to install and remove a fin from its fin box. A disadvantage with these systems is that the fin box is designed to take only one configuration of a fin tab, so 10 that the owner of a board who wishes to change or experiment with a variety of fins from manufacturers other than the manufacturer of his or her board, or at least the fin boxes fitted to the board, is restricted in choice. 15 It is an object of the present invention to address or at least ameliorate some of the above disadvantages . BRIEF DESCRIPTION OF INVENTION Accordingly, in a first broad form of the invention, there is provided a fin box for releasable attachment 20 of a fin to the body of a surfboard or the like; said fin including a fin-tab associated therewith; said fin box adapted for insertion into and retention within said body; said fin box further adapted for reception and releasable retention of at least one fin-tab -4 configuration- thereby to releasably retain a said fin in fixed relationship with said surfboard or the like; and wherein said fin box comprises a generally elongate body provided with at least one substantially 5 rectangular section recess open at a first surface of said body; said fin box further provided with a peripheral flange extending outwardly from said elongate body at said first surface; a first portion of said flange defining an area of said first surface 10 around said recess; an outer area of said flange offset from said first surface; said offset arrange so that when said outer area of said flange is flush with a surface of a foam core of a said surfboard or the like, said first surface is substantially flush with a 15 finished exterior surface of said surfboard or the like; said fin box further provided with a pair of buttress portions along at least one side of said elongate body; said buttress portions forming a projecting abutment between a surface of said flange 20 opposite said first surface, and said at least one side of said elongate body, and wherein at least one pair of angled threaded holes extend from said first surface of said elongate body to emerge at points within said recess approximately half way between said first 25 surface and a base of said recess; said angled threaded holes disposed along at least one side of said recess; ~5 each hole of said angled threaded holes coincident with a said buttress portion. Preferably, various ones of said fin box are adapted to form a centre fin box for retaining a said fin in the 5 centre of a said surfboard or the like, a right hand fin box for retaining a said fin at a right hand side of a said surfboard or the like and a left hand fin box for retaining a said fin at a left hand side of a said surfboard or the like; and wherein at least one side 10 wall of said recess of each of said right hand and said left hand fin box is provided with at least a portion of outwardly sloping wall section; said outwardly sloping wall section of said right hand fin box disposed along a right hand side of said recess; said 15 outwardly sloping wall section of said left hand fin box disposed along a left hand side of said recess. Preferably, the length of said recess is equal to or greater than the overall length of dual fin-tabs of one of said plurality of fin-tab configurations; said 20 overall length defined by a leading edge of a front fin-tab and a trailing edge of a rearward fin-tab of said dual fin-tabs; a said fin box provided with a length greater than said overall length adapted to provide for fore and aft adjustment of a said fin 25 mounted in said fin box.
-6 Preferably, said area of said first surface of said fin box is of a length and width sufficient to support a said fin entirely so that no portion of said fin is in contact with said body of said surfboard or the like. 5 Preferably, said outer portion of said peripheral flange is provided with a plurality of apertures distributed at intervals around said recess; said apertures adapted to allow passage therethrough of resin or bonding agent so as to increase retention 10 strength of said fin box in said body of said surfboard when lateral and axial forces act on a fin inserted in said fin box. BRIEF DESCRIPTION OF DRAWINGS 15 Embodiments of the present invention will now be described with reference to the accompanying drawings wherein: Figure 1 is a view of the underside of a surfboard fitted with the fin attachment system for a typical three- fin 20 arrangement according to a preferred embodiment of the invention; Figure 2 is an end view of the surfboard of Fig. 1 showing a centre and left and right fins; -7 Figure 3 shows side views and plan views of four fin and fin-tab configurations able to be fitted to a preferred embodiment of the fin attachment system, or fin box of the present invention; 5 Figure 4 is a perspective view from below of a centre fin-box; Figure 4A is a further perspective view from below of a fin box with a modified form of perforations provided around the flange of the fin box; 10 Figure 5 is a cross section view of the fin box of Fig. 4 with a fin retained in the fin box; Figure 6 is a side cross section view of the fin box of Figs. 4 and 5; Figure 7 is a plan view of the fin box of Fig 6; 15 Figure 8 is a side and perspective view of an insert for use with the fin box of Figs. 6 and 7. Figure 9 is a sectioned end view of the fin box of Figs. 6 and 7 when fitted with fin 3A of Fig. 3; Figure 10 is a sectioned side view of the fin box of 20 Figs. 6 and 7 when fitted with fin 3C of Fig. 3; Figure 112A is a plan view of a left side fin box; -8 Figure 11B is a series of cross sections taken along the length of the fin box of Fig. 11A; Figure 11C is an end view of a side fin with an inline fin-tab; 5 Figure 1ID is an end view of a side fin with a canted fin-tab. Figure 12 is a perspective view of a preferred form fin box according to the invention with an adjustable fin; Figure 13 is a perspective view of an insert for use in 10 the fin box of Fig. 11A; Figure 13A is a perspective view of an alternative insert for use in the fin box of Fig. 11A; Figure 14 is sectioned view of a fin inserted in the fin box of Fig. 11A with the insert of Fig. 13: 15 Figure 14A is a sectioned view of a fin inserted in the fin box of Fig. 11A with the insert of Fig. 13A; Figure 15 is a perspective view of the fin box of Fig. 4 showing a further retaining system for fin 3D of Fig. 3; Figure 16 is a sectioned end view of fin 3D retained in 20 the fin box of Fig. 4; -9 Figure 17 shows plan and end views of a further preferred embodiment of a left, right and centre fin box; Figures 17A, 17B and 17C are sectioned end views of the centre, left and right fin boxes of Figure 17; 5 Figures 17D, 17E and 17F are sectioned end views of an alternative arrangement of the centre, left and right fin boxes of Figure 17; Figure 17G shows plan and end views of a further preferred embodiment of a left, right and centre fin box; 10 Figure 18 is a sectioned side elevation view of one of the fin boxes of Figures 17, and 17A to 17C with a dual fin-tab fin installed together with insert, Figures 18A, 18B and 18C are detailed perspective views of inserts for the centre, left and right hand fin boxes 15 of Figures 17 and 17A to 17C; Figures 18D, 18E and 18F are detailed perspective views of inserts for the centre, left and right hand fin boxes of Figures 17D, 17E and 17F. Figure 19 is a sectioned side elevation view of one of 20 the fin boxes of Figures 17 and 17A to 17C without an insert and with a fin with the fin-tab of Figure 3C installed; -10 Figure 19A and 19B are sectioned views of a fin box with both a recess and base of a fin blade greater in length than the fin-tab of the fin, allowing fore and aft adjustment with the heel or toe of the fin blade 5 extending beyond the fin box recess; Figure 20 shows plan and sectioned end elevation views of a further preferred embodiment of a centre, left and right fin box according to the invention; Figure 21 is a sectioned side elevation view of still a 10 further preferred embodiment of a fin box with a dual fin-tab fin installed; Figures 21A and 21B are sectioned side elevation views of a fin with dual fin-tabs installed in a recess of a fin box wherein the recess is of a length allowing fore and 15 aft adjustment of the fin in the fin box; Figure 21C is a sectioned side view of the fin box of Fig. 21A and 215 provided with two longitudinally aligned recesses; Figure 22 shows plan and sectioned end elevation views of 20 a further preferred embodiment of a fin box. Figures 23A and 23B are sectioned side elevation views of a fin with single fin-tab shorter in length to a recess -11 of a fin box allowing fore and aft adjustment of the fin in the fin box. DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS First Preferred Embodiment 5 In a first preferred embodiment of the invention and with reference to Figs. 1 and 2, a surfboard 10 is fitted with three fin retaining structures 12, 13 and 14, commonly known as fin boxes, embedded into the underside 16 of surfboard 10. Fin box 12 provides for a centre fin 17, 10 while fin boxes 13 and 14 accommodate left outside fin 18 and right outside fin 19 respectively. Fins 17, 18 and 19 are held in retaining structures of fin boxes 12, 13 and 14 by a fin-tab formed at the top edge of the fin, that is that edge of the fin 15 substantially flush with the surface of the underside of the surfboard. Examples of typical fins and fin-tabs commercially available are shown in Fig. 3. Referring again to Fig. 2, it will be noted that while centre fin 17 has its central plane normal to the 20 underside 16 of surfboard 10, the left and right outside fins are canted outwardly relative to that plane. That canting is generally at an angle of 5 degrees. Canting of outside fins may be introduced either by introducing the -12 cant angle within the recess of the left and right fin boxes, or by the canting of the plane of the fin relative to the fin- tab. The fin boxes 13 and 14 of the present invention provide for canting of outside fins which have 5 the fin-tab in-line (that is, no canting of the fin-tab), as well as allowing the use of outside fins canted relative to the fin-tab, as will be explained in more detail below. Turning now to the specific structures of a preferred 10 embodiment of fin boxes according to the invention for centre and outside fins able to accept a multiplicity of commercially available fins, both with in-line and canted fin-tabs. With reference to Fig. 4 a centre fin box 20 is constructed as a generally elongate body 22 provided with 15 a recess 24. Body 22 has a first surface 25 which, when fin box 20 is installed in the body of a surfboard (as shown in Fig. 1 and 5) is generally flush with the fibre glass surface of the underside 16 of the board 10. First surface 25 includes a peripheral flange 26 extending 20 outwardly from the body 22. Peripheral flange 26 is generally flush with the surface of the foam core of the board. Recess 24 extends into the body to a depth sufficient to accept any of the fin-tabs of the commercially available 25 fins shown in Fig. 3. As best seen in Figs. 4 and 5, body -13 22 is further provided with a pair of buttress portions 28 at each side of body 22, extending from the underside of flange 26 to the side surface 31. Angled threaded holes 34A and 34B are provided along each side of recess 5 24, passing from surface 25 to emerge at.inside surfaces of the recess as best seen in Figs.. 5 , 6 and 7. Angled threaded holes 34A and 34B coincide with the buttress portions 28. A further angled threaded hole 35 emerges at the forward inside end wall 36 of recess 24. A vertical 10 threaded hole 37 is also provided as shown in Figs. 4, and 7. The width and configuration of the recess is such as to allow insertion of the fin-tabs shown in Fig. 3. Thus for example, the lateral recesses 23 extending outwardly from the main recess 24 are adapted to accept 15 the projecting elements 30 of fin-tab 29 of fin 3A in Fig. 3. As can be seen in Fig. 9 the fin-tab of fin 3A may be securely retained in recess 24 of fin box 20 by a setscrew 38 driven into the angled threaded hole 34A on one side of recess 24 and engaging with cylindrical 20 portion 40 of the fin-tab. With reference to Figs. 6 and 7, recess 24 is provided with a retention member 32 extending across the width of recess 32 and projecting from the rearward end wall 33 of recess 24. Retention member is adapted for engagement 25 with a rear notch 35 in the fin-tab 34 of fin 3C (shown - 14 in Fig. 3) . As shown in Fig. 10, fin-tab 34 of fin 3C is retained in fin box 20 at the rear by the engagement of notch 35 with retention member 32, and at the front by setscrew 38 engaging front notch 34. Additionally, 5 setscrews 38 (not shown in Fig. 10), may be driven through angled threaded holes 34A and 34B against the sides of fin-tab 34. The fin 3B shown in Fig. 3 has a fin-tab made up of two sections 42A and 42B. To accommodate this fin-tab in the fin box of the present 10 embodiment of the invention, there is provided an insert 44A shown in Fig. 8. Insert 44A is of similar external dimensions as the fin-tab 34 of fin 3C, and is provided with similar rear notch 45 and front notch 46 to enable the insert 44A to be retained in fin box 20 by retention 15 member 32 and the set screw through front threaded hole 35. Insert 44A is further provided with cutout portions 48A and 48B, sized to receive fin-tab sections 42A and 42B. These sections are then secured in fin box 20 by setscrews driven through angled threaded holes 34A and 20 342 with the setscrews driving up against the sides of fin-tab sections 42A and 42B. With reference to Figs. 15 and 16, fin 3D (shown in Fig. 3), has a fin-tab 50 with slot 51 at the interface between the fin and the tab. This fin, once inserted into 25 the recess 24 of the fin box, is retained by a plate 53 - 15 inserted into slot 51 and secured to the fin box by screw 52 screwed into vertically threaded hole 237. The side fin boxes 13 and 14 are of similar configuration to that of the centre fin box thus far described, but 5 have recesses that are somewhat modified. The left and right fin-boxes are of symmetrical configuration and only the left fin box will be described in detail. Fig. 11A shows a plan view of the flanged face of a fin box 13 for the left fin of a three-fin surfboard. The recess 124 of 10 this box has sections 128 of the inside wall of the recess closest to the outside edge of the surfboard (to the left in Fig. 11A) sloping outwardly by 5 degrees as indicated by the sectional views A-A to D-D in Fig. 11B. The opposing end walls 123A and 123B of lateral recesses 15 123 which extend outwardly from main recess 124, slope inwardly so as to be parallel to the modified sloping wall sections of the recess 124 towards the outside edge of the surfboard, as can be seen in section C-C. The outward sloping sections 128 at A-A to D-D are so placed 20 within recess 124 as to accommodate side fin configurations with in-line fin-tabs such as shown in Fig. IIC and canted fin-tabs as shown in Fig. liD. Of the fin-tab configurations shown in Fig. 3, which may be accommodated in the fin box of the present invention, 25 fins 3A and 3B have in-line fin-tabs for both left and -16 right fins, while fin 3C and fin 3D have fin-tabs canted by 5 degrees for the left and right outside fins. It will be seen from the placement of the outwardly sloping sections 128 of recess 124 in Figs. 11A and 112, that in 5 line fin-tab 29 of fin 3A when inserted into recess 124, will be canted outwardly by 5 degrees, since all the vertical faces of that fin tab will slide into those sections at A-A, B-B and C-C which have the side surfaces sloping at 5 degrees. 10 Likewise, the fin-tab configuration of fin 3B will be accommodated at sections B-B and D-D, when combined with the insert 44B of Fig. 13 as previously described, but which, for this insert has a 5 degree cant built into cutout portions 48C and 48D. Fig. 14 shows fin 32 located 15 in recess 24 with insert 44B, and locked in place by a set- screw through angled threaded hole 135. Fin-tab 34 of fin 3C, and fin-tab 50 of fin 3D however need to be retained in the fin box without the 5 degree cant. This is achieved by the remaining sections 126 of 20 recess 124, which retain parallel vertical walls. As well, fin box 13 is provided with one pair of angled threaded holes 134A and 134B only along that side of the recess 124 away from the outside edge of the surfboard (that is to the right in Fig. 11A). Thus the in-line fin- - 17 tabs 29 of fin 3A is driven by the set screws through holes 134A and 134B into the desired canted position within recess 124, against the sloping side surfaces towards the outside of the surfboard. 5 With reference again to Figs. 13 and 14, the in-line fin tabs 42A and 42B of fin 3B are positioned at the 5 degree cant by inserting the fin-tabs into the recess portions 48C and 48 D of insert 44B. The fin-tabs are then secured by setscrews 38 that pass through slots 50 in recesses 10 44C and 44D to drive the fin-tabs against the outwardly sloping side surfaces of recess 24 and so canting the fin towards the outside edge of the surfboard by 5 degrees. Fin-tab 34 of fin 30, and fin-tab 50 of fin 3D, are retained in the normal vertical orientation as previously 15 described for the centre fin box. The centre, left and right fin boxes of the present invention as described above are further able to accept and retain an adjustable fin. As shown in Fig. 12, an adjustable fin 210 is provided with a shortened fin-tab 20 212. Preferably, fin tab 212 is 20mm shorter than recess 224, so that fin 210 may be moved forward or rearward by 10mm from a median position. Fin-tab 210 is still provided with notch 235 so as to allow the fin-tab to be located up against the rear wall 233 and not interfere 25 with the retention member (32 in Figs. 6 and 7) when -18 located in its rearmost position. However, fin-tab 212 does not rely for retention in recess 224 on the retention member, nor on the forward setscrew in angled threaded hole 235. In this embodiment, the fin-tab 212 of 5 fin 210 is provided with recesses 214A and 214B. For a left side fin (as shown in Fig. 12) or right side fin box, both recesses are on one side of the fin-tab, that is, on that side on which the angled threaded holes 234 are positioned. For a centre fin, the recesses are 10 provided one on each side of the tab to correspond with the equivalent angled threaded holes of a centre fin box as described herein above. The length of recesses 214 is such as to permit the setscrews driven through angled threaded holes 234 to engage with the recesses regardless 15 of the user' s preferred position of the fin. Second Preferred Embodiment In a further preferred embodiment of the invention, the fin boxes are somewhat simplified from those described above and shown in Figs. 6 to 8 and Figs. 11 and 12. In 20 this embodiment the left, right and centre fin boxes cater for fins with the fin tab configurations of Figs. 3B and 3C. With reference to Figure 17, a centre fin box 300, right hand fin box 304 and left hand fin box 302 (as viewed in 19 Figure 17) are each formed as before, as an elongate body 306 provided with a central recess 308 and a peripheral flange 310. As can be seen in the sectioned views of each of Figures 17A to 17C, recesses 308 extend from a first 5 outer surface 316 to proximate an opposite inner surface 314. Shown as dashed lines in Figures 17, and as best seen in Figure 18, the recess 308 of this embodiment is also provided with a retaining structure 319 projecting from the rearward end wall 311. 10 First outer surface 316 comprises a first inner portion of peripheral flange 310 around recess 308. An outer portion 318 of flange 310, is offset from first outer surface 316. As can be seen in Figures 17, 17A, 17B and 17C, the offset between first outer surface 316 and the 15 outer portion 318 of flange 310 is such that when the fin boxes are installed in the body of a surfboard, the surface of outer portion 318 is flush with the surface 315 of the foam core 307 of a surfboard and the first outer surface 316 is then flush with surface 322 of the 20 finished outer fibreglass skin 320 of the underside surface 322. The outer portion of the peripheral flange 310 is provided with a plurality of apertures, 301 distributed at intervals around the recess 380 (as also shown in Fig. 4 around recess 24). These apertures are 25 adapted to allow passage through the apertures of resin -20 or bonding agent thereby increasing the retention strength of the fin box in the body of a surfboard when lateral and axial forces act on a fin inserted in the fin box. 5 The length and breadth of first outer surface 316 which, though flush with the surface 322 of the surfboard, remains exposed, is such that no part of a fin. installed in a fin box 300, 302 or 304 is in contact with the underside surface 322. The fin blade is thus fully 10 supported by and within the extent of first outer surface 316. With reference to Figures 17, 17B and 17C, the right hand fin box 304 and left hand fin box 302 of this embodiment are each provided with two outwardly sloping wall sections 309. Outwardly sloping wall sections 309 of 15 fin boxes 302 and 304 slope towards the right hand .side and left hand side respectively of a surfboard. The length and disposition of sloping wall sections 309 conforms to the length and spacing of the dual fin-tabs 42A and 42B of the fin-tab configuration "B" of Figure 3. 20 Provided opposite each sloping wall section 309 is an angled threaded hole 313 passing from first outer surface 316 to the adjacent sidewall of recess 308. The right hand and left hand fin boxes 302 and 304 respectively of the present embodiment are provided with 25 a left hand removable insert 330 and a right hand -21 removable insert 332 respectively as shown in Figures 17, 17B and 17C. Removable inserts 330 and 332 are of a length, width and depth such as to substantially fill recesses 308. With reference to Figures 18B and 18C, 5 removable insert 330 and 332 are each provided with a notch 334 at the rearward end of the insert, adapted to releasably engage with the retaining structures 319 of recesses 308. Removable inserts 330 and 332 are each further provided with a pair of receiving recesses 331 10 and 333 respectively. The length and disposition of recesses 331 and 333 are such that when the inserts are inserted into the respective recesses 308 of right hand fin box 304 and left hand fin box 302, the receiving recesses coincide with sloping wall sections 309. Inner 15 walls 336 of receiving recesses 331 and 333 are provided with slots 338 to allow set screws 339 driven through angled threaded holes 313 to pass through the slots 338 and engage with the dual fin- tabs of a dual fin-tab fin. The inner walls 336 of receiving recesses 331 and 333 20 slope inwardly with the same degree of slope as that of sloping wall sections 309 of recesses 308, so that with the inserts located in recesses 308 the sloping wall sections 309 are parallel to the inner walls 336 of receiving recesses 331 and 333. The separation between 25 these opposing parallel walls conforms to the thickness -22 of the dual fin- tabs 42A and 42B of Figure 3. As can be seen in the sectioned views of Figures 17B and 17C, since these dual fin-tabs are in-line with the median plane 340 of the fins 342, the fins 342 assume an outwardly canted 5 angle relative to the underside surface 322. Thus a dual fin-tab fin inserted into right hand fin box 304 fitted with removable insert 332, is canted towards the right hand side of a surfboard, while an identical fin likewise inserted into the left hand fin box 302 and its 10 associated removable insert 330, is canted towards the left hand side of the surfboard. With reference now to Figures 17 and 17A, the recess 308 of centre fin box 300 is not provided with sections of sloping walls; opposing sidewalls being parallel and 15 vertical relative to the underside 322 of a surfboard. The centre fin box 300 is also provided with two angled threaded holes 317 spaced apart and located along the length of the recess as are the threaded angled holes 313 of the right hand and left hand fin boxes, but disposed 20 one on either side of recess 308. Centre fin box 300 is also provided with a removable insert 350 (shown in Figure 18A) of similar outward configuration and dimensions as the removable inserts 332 and 330 for the right hand and left hand fin boxes 25 described above. Removable insert 350 is also provided -23 with receiving recesses 352 sized and positioned along the length of the insert as are the receiving recesses 333 and 331 of the right hand and left hand inserts. However, the rear walls 354 of these recesses are not 5 sloping, so that when the insert 350 is inserted into recess 308 of the centre fin box, the recesses form parallel sided and vertically disposed recesses. Thus a dual fin-tab fin installed in the centre fin box 300 with its removable insert 350, will be vertical relative the 10 underside 322 of a surfboard. Because of the arrangement of the angled threaded holes of the centre fin box, only the rear wall 354 of the rearward receiving recess need be provided with a slot 356 for a securing set screw to pass through. 15 With the respective inserts 332, 350 and 330 of the right hand, centre and left hand fin boxes removed, the fin boxes can receive a fin-tab configuration of the type shown as "C" in Figure 3, as can be seen in Figure 19. For the right hand and left hand fin to be canted 20 outwardly to the right and left hand sides of a surfboard respectively, fin- tabs canted relative to the plane of the fin as shown in Figure 3D can be used. In an alternative arrangement [refer to 061130 JF-INSERT Change TEXT.D] with reference to Figures 17E, 17D and 25 17F, in which like features are numbered as for Figures -24 17A, 17B and 17C, the right hand fin box 304 and the left hand fin box 302 are each provided with two inwardly sloping wall sections 309. Inwardly sloping wall sections 309 of fin boxes 302 and 304 in this embodiment, slope 5 towards the left hand side and right hand side respectively of a surfboard. The length and disposition of sloping wall sections 309 conforms to the length and spacing of the dual fin-tabs 42A and 42B of the fin-tab configuration "B" of Figure 3. Provided adjacent each 10 sloping wall section 309 is an angled threaded hole 313 passing from first outer surface 316 to the adjacent sidewall of recess 308. Still with reference to Figures 17D, 17E and 17F, the right hand and left hand fin boxes 304 and 302 15 respectively of the present embodiment are provided with a right hand removable insert 332 and a left band removable insert 330 respectively as shown in Figures 17, 17B and 17C. Removable inserts 330 and 332 are of a length, width and depth such as to substantially fill 20 recesses 308. With reference to Figures 18B and 18C, removable insert 330 and 332 are each provided with a notch 334 at the rearward end of the insert, adapted to releasably engage with the retaining structures 319 of recesses 308.
With reference to Figures 1SE and 18F, removable insert 330 and 332, are adapted for the recesses with inwardly sloping sections described above and shown in Figures 17D, 17E and 17F. The inserts are each provided with a 5 notch 334 at the rearward end of the insert, adapted to releasably engage with the retaining structures 319 of recesses 308. Removable inserts 330 and 332 are each further provided with a pair of receiving recesses 331 and 333 respectively. The length and disposition of 10 recesses 331 and 333 are such that when the inserts are inserted into the respective recesses 308 of right hand fin box a& 304 and left hand fin box 302, the receiving recesses coincide with inwardly sloping wall sections 309. 15 The inner walls 336 of receiving recesses 331 and 333 of Figures 18E and 18F, slope inwa-rdly outwardly with the same degree of slope as that of inwardly sloping wall sections 309 of recesses 308, so that with the inserts located in recesses 308 the sloping wall sections 309 are 20 parallel to the inner walls 336 of receiving recesses 331 and 333. The separation between these opposing parallel walls conforms to the thickness of the dual fin-tabs 42A and 42B of Figure 3. As can be seen in the sectioned views of Figures 172 and 17F, since these dual fin-tabs 25 are in-line with the median plane 340 of the fins 342, -26 the fins 342 assume an outwardly canted angle relative to the underside surface 322. Thus a dual fin-tab fin inserted into right hand fin box -3-e- 304 fitted with removable insert 332, is canted towards the right hand 5 side of a surfboard, while an identical fin likewise inserted into the left hand fin box 302 and its associated removable insert 330, is canted towards the left hand side of the surfboard. With reference now to Figure 17D, the recess 308 of 10 centre fin box 300 is not provided with sections of sloping walls; opposing sidewalls being parallel and vertical relative to the underside 322 of a surfboard. The centre fin box 300 shown in Figure 17D, is also provided with a removable insert 330. The configuration 15 and dimensions of this insert shown in Figure 18D differ from those of the removable inserts 332 and 330 of the right and left hand fin boxes described above, in order to reduce the overall depth of the fin box 300. This is desirable for thinner bodied surfboards, because of the 20 central fin being placed further to the rear of the board relative to the two side fins, the central fin box of Figure 17A would be too close to, or even protrude through the upper surface of the board. The external side surfaces of the insert 350, have a pair of offset -217 extensions 356 and 357 which coincide with the location of the pair of recesses 366 and 367 in finbox 300. Removable insert 350 of Figure 18D, is also provided with receiving recesses 354 and 355, sized and positioned 5 along the length of the insert as are the receiving recesses 333 and 331 of the right hand and left hand inserts shown in Figures 18F and 18E. However, for this embodiment, the recesses are disposed towards opposing sides of the longitudinal axis of insert 350, and the 10 overall depth of the insert is reduced to suit the fin box of Figure 17D. Also, the rear walls of these recesses are not sloping, so that when the insert 350 is inserted into recess 308 of the centre fin box, the recesses form parallel sided and vertically disposed recesses. Thus a 15 dual fin-tab fin installed in the centre fin box 300 with its removable insert 350, will be vertical relative the underside 322 of a surfboard, and centrally located relative to the longitudinal axis of recess 308. The right hand, centre and left hand fin boxes of both 20 arrangements of the present embodiment are further able to accommodate and allow fore and aft adjustment of fins with the fin-tab configuration shown in Figure 12. These fins are provided with fin-tabs specific to right hand, centre and left hand fins, with the fin tabs of the right 25 and left hand fins canted relative the blade of the fin -28 so as to set the fin at an outwardly sloping angle relative the underside of the surfboard when the fin-tab is retained between the parallel and vertical opposite walls of the fin box recesses. 5 The fore and aft adjustment of this fin-tab configuration is provided by the length of the fin-tab being some 20mm shorter than the length of the fin box recess. Figures 19A and 19B show a fin 440 with a shorter fin-tab 442 in a maximum forward position and a maximum rearward 10 position respectively. The fin-tab 442 is secured in the fin box by the setscrews previously described. As well it will be noted that, regardless of the fin's adjusted fore-aft position, the blade is fully supported on the surface of inner portion 316 and is not in contact with 15 the surface 444 of the surfboard. Third Preferred Embodiment Turning now to Figures 20 and 21, in this further preferred embodiment of the invention, as for the second preferred embodiment described above, a right hand fin 20 box 404, centre fin box 402 and a left hand fin box 400 are provided, all with the same general external configuration of the fin boxes of the second preferred embodiment shown in Figure 17.
-29 However, in this embodiment, the central recess 408 of each fin box is shortened to a length equal to that from leading edge 420 of the forward fin-tab 421 of a dual fin- tab fin 426, to the trailing edge 422 of the 5 rearward fin- tab 423, as shown in Figure 21. Also, there is no retaining structure projecting from the rearward end wall of the recess. For the right hand fin box 404 and the left hand fin box 400, the central recesses 408 have parallel sidewalls 10 canted at an angle to the underside surface 418 of a surfboard, while the sidewalls of the recess of the centre fin box are parallel and vertical. With reference to Figures 21A and 21B, fore and aft adjustment of a dual fin-tab fin 526 in the fin boxes may 15 be provided by a recess length longer than the distance between the leading edge 520 of the forward fin-tab 521 and the trailing edge 522 of the rearward fin-tab 523. Thus as shown in Figures 21A and 21B, a recess 530, 10mm longer than the overall length of the dual fin-tabs 521 20 and 523 will allow the fin 526 to be adjusted plus or minus 5mm from a median position between the fully forward location of Figure 21A and the fully rearward position of Figure 21B. The overall length and breadth of the surface of first outer surface 516 remains such that -30 no part of fin 526 is in contact with the surface 532 of the surfboard. In an alternative preferred arrangement, the fin tabs of the fin shown in Fig. 3B, may be accommodated in a 5 modified fin box as shown in Fig. 21C. In this embodiment of a fin box according to the invention, the recess is divided into two sections by divider portion 540, effectively forming two longitudinally aligned recesses 530a and 530b. The length of divider portion 540 between 10 recess 530a and recess 530b is such that allowance is made for the fin of Fig. 3B to have a fore-aft adjustment. Thus for example if the length of divider portion 540 is 2mm and the separation between the forward and rear fin tabs of the fin of Fig. 3B is 12mm, an 15 adjustment of 10mm fore and aft is provided for. A further advantage of this particular embodiment of the fin box is that there is a considerable strengthening of the box compared with that of a single continuous recess. Fourth Preferred Embodiment 20 With reference to Figures 22 and 23 in a fourth preferred embodiment of the invention, the right hand, centre and left hand fin boxes 600 are identical. The external configuration of fin boxes 600 is as previously described for the second and third preferred embodiments above, but -31 the recess 608 is further simplified to a rectangular section recess with opposing parallel side and end walls, normal to the first outer surface 612. In this embodiment each fin box is provided with a pair of angled threaded 5 holes 617 at each side of recess 608, and adapted to receive set screws 614 for the retention of one-piece fin-tabs 620. Threaded holes 617 are coincident with buttress portions The fin boxes of this embodiment are adapted for fin- tab 10 configurations where the fin-tab is canted relative to the median plane of the fin for the right hand and left hand fins of a three-fin arrangement. In use The fin boxes of the present invention may be incorporated in the body of a surfboard in accordance 15 with known processes. That is the board may be completely- finished to the glassed stage, after which suitable recesses are machined through the glassed surface and into the foam of the core. The boxes are then inserted and retained with a suitable bonding agent, or 20 another small section of glass clot localised to cover the finbox. Alternatively, a cavity may be for ned in the foam core and the box inserted prior to glassing. For this process the box may be provided with a projecting barrier 240 so -32 as to prevent resin flowing into the recess 224 and angled threaded holes 234 and 235. Fifth Preferred Embodiment A feature particularly of high performance surf boards is 5 that the underside surface of the board is provided with scalloped channels between the centre fin and the two side fins. These concave formations cause the surfaces immediately adjacent the two opposing sides of the central fin box first outer surface 316 (see Figures 17 10 and 17G), and the inside edges of the outer surfaces 316 of the left and right hand fin boxes, to curve into the body of the board. For this type of surfboard, the peripheral flange 310 of the central fin box is angled towards the base of the fin box so as to ensure that the 15 flange remains under the outer skin of the board. Similarly, the inward facing portions of the flanges of the left hand and right hand fin boxes are also angled towards the base of those boxes. The above describes only some embodiments of the present 20 invention and modifications, obvious to those skilled in the art, can be made thereto without departing from the scope and spirit of the present invention.