Marine propeller

Claim 1

A marine propeller having specially configurated blades exhibiting resistance to ventilation and cavitation at high speed operation, each blade including a leading edge, a trailing edge, a face constituting a pressure side, and a back constituting a suction side; said face having a contour consisting of a convex surface extending from said leading edge to a transition zone about 20-25% of the blade chord length toward said trailing edge, and a concave surface extending the remainder of the chord length to said trailing edge; said convex and concave surfaces having curvatures defined relative to reference pitch datum lines at particular radial blade sections, said reference line at any particular radial blade section being a straight line outside of said blade, intersecting said blade trailing edge, and at an angle φ to a plane transverse to the propeller axis, the arc tangent of said angle φ being the blade pitch divided by 2πr, where r is the distance of the particular radial blade section from the propeller axis; said blade having its maximum set back from said pitch datum line at said leading edge, said set back being between about 7% of the blade chord length at the inner radii blade sections to about 1% of the blade chord length at the outer blade chord sections; said blade convex surface having minimum offset from said pitch datum line at about 10 to 15% of the blade chord length from said leading edge, said offset being about 1 to 21/2% of the blade chord length; said blade concave surface having a maximum spacing from said pitch datum line at about mid-chord length, said spacing being about 2 to 31/2 of the blade chord length from said pitch datum line.