Measurement and calculation of gate rudder performance

This paper introduces an innovative propulsion system which may not be categorized as a conventional energy saving device and it has not been even fully explored so far. Yet this system, which is called "GATE RUDDER ", has been already applied for the first time on a 2400 GT container ship and full-scale sea trials were conducted successfully in November 2017 in Japan. The new concept stemmed from a new idea of propulsive efficiency, called "Elementary Propulsive Efficiency", that may be exploited by any arbitrary shape and arrangement of propulsor system apart from a conventional propeller-rudder system. The recent full-scale trials with 110m Japanese domestic container vessel have confirmed the superior performance of the GATE RUDDER system which is not only a remarkable energy saving (~14%) achieved over her sister ship fitted with a conventional (flap) rudder-propeller system but also it has other favourable performance characteristics (e.g. superior manoeuvrability, quieter aft end etc.) as discussed in the paper. The Authors believe the innovative GATE RUDDER system might eventually take place of the conventional high lift rudders for steering ships.