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 . A fin arrangement for a surf craft, comprising:
 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.   
     
     
         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 
 to 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. 
     
     
         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 at least the central fin comprises a projecting lobe extending rearwardly from a base of the central fin.   
     
     
         10 . The fin arrangement of  claim 9 , wherein the projecting lobe defines at least part of a trailing edge of the central fin. 
     
     
         11 . The fin arrangement of  claim 10 , wherein the trailing edge along the projecting lobe has a convex curvature. 
     
     
         12 . The fin arrangement of  claim 10 , wherein the trailing edge has a sharp inflection point at a location adjacent the projecting lobe. 
     
     
         13 . The fin arrangement of  claim 10 , wherein the trailing edge of the central fin has multiple inflection points along its length. 
     
     
         14 . The fin arrangement of  claim 9 , 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. 
     
     
         15 . The fin arrangement of  claim 14 , 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°, and   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.   
     
     
         17 . The fin arrangement of  claim 2 , wherein each of the first and second side fins comprises a projecting lobe extending rearwardly from respective bases of the first and second side fins. 
     
     
         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 .