Twin-rudder system for large ship

Abstract

In such a high lift twin-rudder system that: a pair of high lift ruddersis arranged behind a single propeller; the respective high lift rudderhas a top end plateand a bottom end plateat the top end and the bottom of a rudder blade; the respective rudder bladeis provided with a reaction fin, protruding from an inboard face of the rudder bladeon a nearly same level with the axis of the propeller, that is originated nearly from the leading edge portion toward the rear and has a fixed chord length; the reaction finof the rudder bladethat faces on the board-side where the propeller blades rotate in the ascending direction assumes a posture that makes such attack angle that the ratio of a forward vectored thrust to a drag, both produced by a propeller slip stream having a stream component in the ascending direction, becomes maximum; and the reaction finof the rudder bladethat faces on the board-side where the propeller blades rotate in the descending direction assumes a posture that makes such attack angle that the ratio of a forward vectored thrust to a drag, both produced by a propeller slip stream having a stream component in the descending direction, becomes maximum, the respective rudder bladeis so constituted that a chord length is of 60˜45% of a propeller diameter.