Marine propulsion and constructional details thereof

Abstract

A fin for use on a propeller, the fin comprising a lift generating section having a leading edge and a trailing edge, and a pair of surfaces extending between the leading and the trailing edges thereby defining a tip and a root having a root chord; and a dihedral section integrally formed with the root of the lift generating section and having a rotation axis about which, in use, the lift generating system can be rotated to vary the dihedral of the fin, the axis being generally parallel to the root chord of the lift generating section.

1 . A fin for use on a propeller, the fin comprising:
 a lift generating section having a leading edge and a trailing edge, and a pair of surfaces extending between the leading and the trailing edges thereby defining a tip and a root having a root chord; and   a dihedral section integrally formed with the root of the lift generating section and having a rotation axis about which, in use, the lift generating system can be rotated to vary the dihedral of the fin, the axis being generally parallel to the root chord of the lift generating section.   
   
   
       2 . A fin according to  claim 1 , wherein the axis of dihedral rotation is within a 15 degrees deviation from the root chord. 
   
   
       3 . A fin according to  claim 2 , wherein the axis of dihedral rotation deviates by no more than 3 degrees from the root chord. 
   
   
       4 . A fin according to  claim 3 , wherein the axis of dihedral rotation is parallel to the root chord. 
   
   
       5 . A fin according to  claim 1 , wherein the dihedral section comprises a front boss adjacent the leading edge and a rear boss adjacent the trailing edge. 
   
   
       6 . A fin according to  claim 5 , wherein each boss is provided with a through hole which is splined for engagement with a corresponding spline on a shaft, in use. 
   
   
       7 . A fin according to  claim 6 , wherein the axis of rotation passes through the centres of the through holes in each boss. 
   
   
       8 . A fin according to  claim 1 , wherein the front boss blends smoothly into the leading edge such that no re-entrant form is created between the boss and the leading edge. 
   
   
       9 . A fin according to  claim 1 , wherein the fin has a pitch axis and a stack axis, wherein the stack axis is offset from the pitch axis. 
   
   
       10 . A fin according to  claim 9 , wherein the pitch axis is closer than the stack axis to the leading edge. 
   
   
       11 . A fin according to  claim 9 , wherein the stack axis does not pass through the axis of rotation. 
   
   
       12 . A fin according to  claim 9 , wherein the stack axis is angled relative to the pitch axis. 
   
   
       13 . A fin according to  claim 1 , wherein the centre of pressure of a fin is located forward of the pitch axis. 
   
   
       14 . A fin according to  claim 1 , further comprising a stop element mounted on either or both of the front and rear bosses for limiting rotation of the fin about the axis of rotation in at least one direction. 
   
   
       15 . A fin according to  claim 1 , wherein the surface between the front and rear bosses at the root of the fin is shaped such that, when the fin is mounted on a yoke, the surface at the root of the fin acts, during rotation, to remove marine growth, sediment or other unwanted material from the yoke.