Method of making surf fin including injection molded pre-impregnated composite fiber matrix inserts

Abstract

A method of forming a fin configured for use with a water sports board. The method includes providing a mold having a mold cavity and a first insert pre-preg sheet each including structural strands bonded by a first resin material. The method further includes placing the first insert pre-preg sheet within the mold cavity. The method further includes injecting a third resin material under pressure into the mold cavity. The method further includes injecting a core substance only in the form of a gaseous material into the third resin material to form a unitary hollow volume within the third resin material.

1 .- 24 . (canceled) 
     
     
         25 . A method of forming a fin configured for use with a water sports board, the method comprising the steps of:
 providing:
 a mold having a mold cavity at least partially defined by a pair of opposed mold cavity faces; and 
 a first insert pre-preg sheet including a plurality of first structural strands bonded by a first resin material; 
 placing the first insert pre-preg sheet within the mold cavity; and 
 injecting a third resin material under pressure into the mold cavity; and 
 injecting a core substance only in the form of a gaseous material into the third resin material to form a unitary hollow volume within the third resin material. 
   
     
     
         26 . The method recited in  claim 25 , wherein the core substance is nitrogen. 
     
     
         27 . The method of  claim 26 , wherein the core substance has a pressure less than atmospheric pressure. 
     
     
         28 . The method of  claim 25 , further comprising the step of heating the first insert pre-preg sheet prior to the injecting of the third resin step. 
     
     
         29 . The method of  claim 25 , further comprising the step of cooling the injected third resin material to harden the third resin material around the first insert pre-preg sheet while the first insert pre-preg sheet is stretched. 
     
     
         30 . The method of  claim 29 , wherein the step of cooling the injected third resin material causes the third resin material to contract.