Section profiles for planing hydrofoils and hydrofoils operating close to a free water surface

Abstract

A hydrofoil section ( 401 ) comprising upper ( 4014 ) and lower ( 4015, 4018, 4017 ) cambered profiles and a reference line in which: the reference line is drawn between the trailing edge ( 307 ) of the section and the leading edge ( 304 ) or a point close to and below such leading edge, and both profiles have a positive camber, and a substantial part of the lower profile lies above such reference line, and the area bounded by such reference line and by such lower profile lying above such reference line is greater than any area lying below such reference line.

1 . A hydrofoil section comprising upper and lower cambered profiles and a reference line in which:
 the reference line is drawn between the trailing edge of the section and the leading edge or a point close to and below such leading edge, and   both profiles have a positive camber, and   a substantial part of the lower profile lies above such reference line, and   the area bounded by such reference line and by such lower profile lying above such reference line is greater than any area lying below such reference line.   
     
     
         2 . The hydrofoil section according to  claim 1  comprising a point of maximum camber of the lower profile measured from the reference line which is situated at a point not exceeding 50% of the length of the reference line measured from the trailing edge of the section. 
     
     
         3 . A hydrofoil section according to  claim 1  in which the lower profile has a camber exceeding 1% of the length of its reference line. 
     
     
         4 . A hydrofoil section according to  claim 1  in which a significant part of the lower profile extending from a point close to the leading edge of the section is made up of a generally straight or slightly curved line which is generally parallel to the reference line. 
     
     
         5 . A hydrofoil section according to  claim 4  in which the generally straight portion extends over a length exceeding 10% of the length of the reference line. 
     
     
         6 . A hydrofoil section according to  claim 1  which comprises at least one conic such that the section pressure and velocity characteristics may be varied by adjusting the position of such conic or conics and by adjusting the weight assigned to any vertex or curve point thereof. 
     
     
         7 . A hydrofoil section according to  claim 6  entirely created from conics and straight lines. 
     
     
         8 . A hydrofoil section according to  claim 7  in which lines are arranged to be tangent continuous other than at any vertex or curve point of any conic section and at the trailing edge. 
     
     
         9 . A hydrofoil section according to  claim 7  in which the section shape and hydrodynamic characteristics are optimised by alteration of the points and conic vertex or curve point weights within a computer programme.