The paper explains the stabilization principle of slanting rudders and proposes that higher lift coefficient can be obtained by using high-efficient flap type rudder.

Research of the hydrodynamic performance of flap rudder on open water and behind propeller;

In this paper, a nounal test with table L9(34) has been ed for a new type of flap rudders, and put forward some regression formulae of hydrodynamic performance,such as rudder normal force derivahve fa, the critical angle of attack ah and rudder nounal force coefficient CN, these formulae had been validated by the flap rudder in 9000t cement - carrier ship.

A new method for predicting the hydrodynamic performance of the flap rudder behind a propeller is presented.

Basedon the analysis of the energy saving principle of rudder ball and the specificity of the flaptype rudder mounted with rudder ball,the paper introduces firstly the research results of theflap-type rudder mounted with rudder ball and discusses the influences of the clearance between rudder ball and propeller, and the influences of the ratio of ball diameter and propellerdiameter and so on.