GB340000A - Improvements relating to screw propellers - Google Patents

Abstract

340,000. Kristofersen, E. L. June 14, 1929. Drawings to Specification. Screw propellers. - In screw propellers with combined variable radial and axial pitch the pitch of the pressure surface at the leading edge varies from tip to root in accordance with the varying average axial velocity of the inflow water in the annular zones about the centre of the propeller. Single screw propellers have a decreasing pitch and outboard twin propellers have an increasing pitch and in combination the pitch is altered axially across the blade until the pitch at the following edge is approximately constant but where there is a decrease or increase in pitch this is dependent upon the thickness or thinness of the axial sections. The angle of deflection of the water between the leading and following edges increases from the tip to the root in accordance with a hyperbolic law. For laying out such a screw surface the template rotates about the centre outside the propeller axis and the following edge coincides with a line through the moulding centre and with a line connecting this centre and the propeller centre.