US Patent 8696318 Stepped surface propeller

A marine surface propeller, and blade therefore, which is surface piercing and partially submerged, and includes a blade geometry that improves distribution of pressure and control to wetted and ventilated regions. Preferably, the feature has a positive step (ramp, cup, interceptor, indent or other geometric addition or intervention) between one fifth and four fifths chord length so as to create a high pressure peak or zone in what is now a low pressure zone on either the blade face or back or both and to create speed controllable wetted and ventilated regions.