Propeller Including a Blade Back Flow Guide

Abstract

THIS invention relates to a propeller and more particularly but not exclusively, to a propeller for use with inboard and outboard boat engines. The propeller includes a hub, and a plurality of blades, each blade having a blade face, a blade back and a blade peripheral zone comprising a leading edge, a trialing edge and a blade tip zone extending between the leading edge and the trialing edge. The propeller is characterized in that a flow guide is provided on the blade back of each blade.

1 - 11 . (canceled) 
     
     
         1 - 12 . (canceled) 
     
     
         13 . A propeller including:
 a hub; and   a plurality of blades, each blade having a blade face, a blade back and a blade peripheral zone comprising a leading edge, a trialing edge and a blade tip zone extending between the leading edge and the trialing edge;   wherein the blade face is substantially smooth, and a flow guide is provided on the blade back of each blade in order for incoming water to flow across a part of the blade back before it is redirected towards a blade face of an oncoming blade.   
     
     
         14 . The propeller of  claim 13 , wherein the flow guide is in the form of a single elongate ridge protruding from a surface of the blade back. 
     
     
         15 . The propeller of  claim 14 , wherein the flow guide is spaced apart from the leading edge of the blade at a distance of between 40% and 60% of the width of the blade, with the blade back surface between the flow guide and the leading edge being substantially smooth. 
     
     
         16 . The propeller of  claim 13 , wherein the flow guide is linear. 
     
     
         17 . The propeller of  claim 16 , wherein the flow guide is angularly offset relative to a radially outwardly direction of the propeller blade. 
     
     
         18 . The propeller of  claim 17 , wherein the flow guide is at least partially parallel to a trailing edge of the blade. 
     
     
         19 . The propeller of  claim 13 , wherein the flow guide is located closer to the trialing edge of the blade than the leading edge of the blade. 
     
     
         20 . The propeller of  claim 13 , wherein the flow guide is of a tapering profile when viewed in cross-section. 
     
     
         21 . The propeller of  claim 20 , wherein a side of the flow guide disposed towards the trialing edge of the blade is higher than a side disposed towards a leading edge of the blade. 
     
     
         22 . The propeller of  claim 21 , wherein an upper surface of the flow guide is disposed at an angle of between 10 and 40 degrees relative to the surface of the blade back. 
     
     
         23 . The propeller of  claim 22 , wherein an upper surface of the flow guide is disposed at an angle of between 25 and 35 degrees relative to the surface of the blade back. 
     
     
         24 . The propeller of  claim 13 , wherein the flow guide extends from the blade root towards at least half the distance to the periphery of the blade.