Fin system

Abstract

A fin collar including a body having a proximal region locatable adjacent to an underside of a water craft. The fin collar also including a distal region, the body including a longitudinally extending slot adapted to receive a watercraft fin, the slot extending through the body between the proximal and distal regions. An outer surface of the body includes a fluid flow modification surface which extends around a perimeter of the body.

1 . A fin collar comprising:
 a body having a proximal region locatable adjacent to an underside of a water craft, and a distal region, the body including a longitudinally extending slot adapted to receive a watercraft fin, the slot extending through the body between the proximal and distal regions,   wherein an outer surface of the body includes a fluid flow modification surface which extends around a perimeter of the body.   
     
     
         2 . The fin collar of  claim 1 , wherein the fluid flow modification surface is a fillet curve, such that when the collar is located on a fin, a tangent of the fillet curve at the distal region of the collar adjacent to the slot is substantially coincident with an adjacent region of the fin, and a tangent of the fillet curve adjacent to the underside of the water craft is substantially coincident with the underside of the water craft. 
     
     
         3 . The fin collar of  claim 1 , wherein the proximal region is laterally thicker than the distal region, such that when a fin is located in the slot, and the fin collar is located adjacent to a base of the fin, the fluid flow modification surface adjacent to the distal end is substantially coincident with an adjacent surface of the fin. 
     
     
         4 . The fin collar of any one of the preceding claims, wherein the body is made from an elastically deformable material. 
     
     
         5 . The fin collar of any one of the preceding claims, wherein one or more projections extend away from the proximal region, the projections being engageable with a fin box. 
     
     
         6 . The fin collar of any one of the preceding claims, including one or more tabs located at the proximal region, the tabs being adapted to be positioned under a base surface of the fin such that when the fin is fitted to a watercraft, the tabs inhibit the fin collar from being removed from the fin. 
     
     
         7 . The fin collar of any one of the preceding claims, wherein the outer surface of the body at the proximal region includes one or more recesses adapted to provide access to a fastener for securing or removing the fin. 
     
     
         8 . The fin collar of any one of the preceding claims, wherein a trailing end of the collar is open, such that the slot can be enlarged to permit a fin to be located within the slot. 
     
     
         9 . The fin collar of  claim 8 , further comprising a clasp defined by a first projection formed on a first side of the body, and a second projection formed on a second opposing side of the body, wherein when a fin is in engagement with the collar, the first and second projections each extend beneath a base of the fin and project away from the underside of the watercraft, to define a pair of fingers, each finger being located on an opposing side of the fin. 
     
     
         10 . The collar of any one of the preceding claims, wherein the fluid flow modification surface is one of a chamfer, concave, convex, sawtooth, undulating, bulbous and stepping surface or combination of surfaces. 
     
     
         11 . The collar of any one of  claims 1  to  4 , wherein the collar is manufactured by co-moulding or shrink fitting, and the collar is securable to a groove or channel formed in the fin. 
     
     
         12 . The collar of  claim 11 , wherein one or more holes are locatable in the fin to assist adhesion. 
     
     
         13 . A fin system including a fin box adapted to be fitted to a watercraft and a fin,
 the fin including a body with a base portion mountable to an underside of the watercraft, and a fin tip located at an opposing end of the fin, the base portion including a mounting tab and a skirt which extends away from the fin tip generally around a perimeter of the base;   the fin box including a longitudinally extending body having a receptacle adapted to receive the mounting tab, the body having an upper surface, a groove being formed in the upper surface, the groove being adapted to receive the skirt, and the groove being deeper than the skirt.   
     
     
         14 . The fin system of  claim 13 , wherein the fin includes a fillet curve profile, which defines a reduction in thickness of the fin between the base portion and the body. 
     
     
         15 . The fin system of  claim 13  or  14 , wherein the fin box includes a lower surface, the lower surface being generally parallel to the upper surface, and extending around the perimeter of the fin box, wherein a step extends between the upper surface and the lower surface. 
     
     
         16 . The fin system of  claim 15 , wherein the step is chamfered. 
     
     
         17 . The fin system of  claim 13 , wherein one or more breaks are formed in the skirt to provide access to a fastener receiving hole formed on the upper surface. 
     
     
         18 . The fin system of any one of  claims 13  to  17 , wherein a recess is formed in a wall of the receptacle, the recess being adapted to receive a projection of a fin collar. 
     
     
         19 . A fin system including a fin box adapted to be fitted to a watercraft and a fin,
 the fin box including:
 a longitudinally extending receptacle having first and second fin box side walls and an opening, a first plane extending across the opening of the fin box and being generally coplanar with the surface of the watercraft in the vicinity of the fin box; 
 a longitudinally extending first rib located on the first fin box side wall; and 
   the fin including:
 a body having a leading edge, a trailing edge, a first side face and an opposing second side face, the side faces extending between the leading and trailing edges, a second plane defined by and including the leading and trailing edges, 
 a base portion having a first side having a longitudinally extending first slot and a second side having a shoulder, a thickness of the base being greater than the thickness of the body, a fastener receiving hole extending through the base portion from the first side face to the second side face; 
 wherein the base portion is insertable into the receptacle in a first position in which an acute angle is defined between the first and second planes, and the first rib is located in the first slot; and 
 further wherein the fin is pivotable to a second position in which the first and second planes are generally perpendicular, the first rib remains located in the first slot and the shoulder is located in the receptacle; and 
 a fastener is insertable into the fastener receiving hole to engage the shoulder and inhibit removal of the base portion from the receptacle. 
   
     
     
         20 . The fin system of  claim 19 , wherein the fastener receiving hole extends diagonally, such that an entry to the hole is closer to a fin tip than an exit to the hole. 
     
     
         21 . A fin system including a fin box adapted to be fitted to a watercraft and a fin, the fin box including:
 a receptacle having a receptacle opening; and   the fin including:
 a fin body having a leading edge, a trailing edge, and opposing hydrodynamic surfaces extending generally between the leading and trailing edges, and 
 a mounting tab having a proximal portion adjacent to the fin body and a distal portion extending away from the fin body, the mounting tab being insertable within the receptacle opening and having a first surface and an opposing second surface, a fastener receiving hole extending through the mounting tab, the fastener receiving hole having a first opening located on the first surface and a second opening located on the second surface; 
   wherein the fastener receiving hole is diagonally oriented such that the second opening is closer to the distal end than the first opening.   
     
     
         22 . The fin system of  claim 21 , wherein a side wall of the receptacle includes a recess adapted to receive a leading portion of a fastener projecting from said second opening. 
     
     
         23 . The fin system of  claim 21  or  22  wherein a portion of the fin box adjacent to the receptacle opening includes a fastener access channel. 
     
     
         24 . The fin system of any one of  claims 21  to  23  wherein the fastener receiving hole is threaded.