Structural improvement of long board of swim fin

Abstract

An improved structure of a long board of a swim fin does not use a plate in gradually changing thickness, but rather uses a fiberboard in fixed thickness. The fiberboard is provided with at least a first opening and at least a second opening arranged in line from small size to large size. The first opening can be triangular, and the second opening can be n-shaped, so that the mechanical strength of fiber flat plate changes gradually from one end to the other end. The plate effective thickness is changed gradually without time consuming processing technique. As such, the manufacturing time and cost are reduced, and consistent manufacturing quality is maintained.

I claim: 
     
         1 . An improved structure of the long board of a swim fin, comprising a flat plate, wherein the flat plate has at least a first opening and at least a second opening. 
     
     
         2 . The structure defined in  claim 1 , wherein the first opening and the second opening are arranged in alignment. 
     
     
         3 . The structure defined in  claim 2 , wherein there is a first spacing between the first opening and the second opening. 
     
     
         4 . The structure defined in  claim 3 , wherein the first opening is triangular. 
     
     
         5 . The structure defined in  claim 2 , wherein there is a plurality of second openings, and there is a second spacing between every two second openings, the second openings are arranged in ascending order of size. 
     
     
         6 . The structure defined in  claim 5 , wherein the second opening is n-shaped.