Surfcraft Fin Arrangement

Abstract

A fin arrangement for a surf craft includes a base coupling portion to couple the fin arrangement to the surf craft; a central fin having a central fin base portion, the central fin coupled to the base coupling portion to extend substantially perpendicularly away from an underside of the surf craft; a first side fin coupled to the central fin base portion and extending away from the central fin and the surf craft at a first acute angle to the central fin; and a second side fin coupled to the central fin base portion and extending away from the central fin and the surf craft at a second acute angle to the central fin, the second acute angle being substantially the same as the first acute angle, and a projecting lobe extending rearwardly from the base of the central fin.

What is claimed is: 
     
         1 . (canceled) 
     
     
         2 . A fin arrangement for a surf craft, comprising:
 a central fin to extend substantially perpendicularly away from an underside of the surf craft;   a first side fin coupled to one of:
 a central fin base portion of the central fin, and 
 an underside of the surf craft 
   
       at a position closely adjacent to the central fin base portion, the first side fin extending away from the central fin and the surf craft at a first acute angle to the central fin; and
 a second side fin coupled to one of:
 the central fin base portion, and 
 the underside of the surf craft 
 
 
       at a position closely adjacent to the central fin base portion, the second side fin extending away from the central fin and the surf craft at a second acute angle to the central fin, the second acute angle being substantially the same as the first acute angle,
 wherein the first side fin and second side fin each comprise a projecting lobe extending rearwardly from respective bases of the first and second side fins. 
 
     
     
         3 . The fin arrangement of  claim 2 , wherein the first and second acute angles are between about 35° and about 65°. 
     
     
         4 . The fin arrangement of  claim 3 , wherein the first and second acute angles are between about 40° and about 60°. 
     
     
         5 . The fin arrangement of  claim 4 , wherein the first and second acute angles are between about 45° and about 55°. 
     
     
         6 . The fin arrangement of  claim 5 , wherein the first and second acute angles are between about 48° and about 52°. 
     
     
         7 . The fin arrangement of  claim 2 , wherein the central fin has a lateral width of about 9 mm to about 15 mm at a base of the central fin. 
     
     
         8 . The fin arrangement of  claim 2 , wherein a lateral width of the first side fin and the second side fin is non-uniform in a fore-aft direction and in a base-to-tip direction. 
     
     
         9 . A fin arrangement for a surf craft, comprising:
 a base portion to couple the fin arrangement to the surf craft;   a central fin coupled to the base portion to extend substantially perpendicularly away from an underside of the surf craft;   a first side fin coupled to the central fin and extending away from the central fin and the surf craft at a first acute angle to the central fin; and   a second side fin coupled to the central fin and extending away from the central fin and the surf craft at a second acute angle to the central fin, the second acute angle being substantially the same as the first acute angle,   wherein the central fin comprises a projecting lobe extending rearwardly from a base of the central fin, and   wherein the first side fin and second side fin each comprise a projecting lobe extending rearwardly from respective bases of the first and second side fins.   
     
     
         10 . The fin arrangement of  claim 9 , wherein the projecting lobes each define at least part of a trailing edge of each respective fin. 
     
     
         11 . The fin arrangement of  claim 10 , wherein the trailing edge along each projecting lobe has a convex curvature. 
     
     
         12 . The fin arrangement of  claim 11 , wherein the trailing edge of each fin has a relatively sharp inflection point at a transition between the projecting lobe and the rest of the fin in comparison to a curvature of a tip of the fin in a same plane as the inflection point. 
     
     
         13 . The fin arrangement of  claim 10 , wherein the trailing edge of the central fin has multiple inflection points along its length. 
     
     
         14 . (canceled) 
     
     
         15 . The fin arrangement of  claim 2 , wherein the projecting lobe of each of the side fins has a plan form surface area less than a plan form surface area of the central fin. 
     
     
         16 . A fin arrangement for a surfcraft, comprising:
 a central fin,   a first side fin and   a second side fin,   wherein a cant angle of each side fin is between 30° and 65°,   wherein a leading edge of a base of each side fin is positioned at a distance from a base axis of the central fin,   wherein the distance is less than 30% of a base to tip distance of the central fin, and   wherein the first side fin and second side fin each comprise a projecting lobe extending rearwardly from the respective bases of the first and second side fins.   
     
     
         17 . (canceled) 
     
     
         18 . The fin arrangement of  claim 2 , wherein inner faces of the first and second side fins are at least partially concave. 
     
     
         19 . The fin arrangement of  claim 2 , wherein a leading edge of each of the central and first and second side fins has a convex curvature along its length. 
     
     
         20 . The fin arrangement of  claim 2 , wherein a trailing edge of each of the central and first and second side fins has a concave curvature along at least part of its length. 
     
     
         21 . A surfcraft comprising the fin arrangement of  claim 2 . 
     
     
         22 . A surfcraft comprising the fin arrangement of  claim 1 . 
     
     
         23 . A surfcraft comprising the fin arrangement of  claim 16 .