摘要：The single-propeller/twin-rudder system composed of single propeller and two high-lift rudders of fish-tail type has been installed on many vessels in Japan. With this system, a ship can be maneuvered at any mode including going astern, hovering, dead slow forwarding and turning by means of various rudder angle combination, with propeller revolution being kept in the forward direction. To improve propulsive efficiency of the single-propeller/twin-rudder system, a pair of reaction fins is attached between two rudders where the propeller slip stream passes. Form, size and setting angle of the fin affect propulsive performance a great deal.A method to determine of the setting angle of fin is discussed in this paper. Fundamentally the setting angle is determined by doing model experiment in model basin. As the second method we propose to estimate the setting angle based on fluid pattern of stern. A concept of the datum line for evaluation of lift of fin is introduced. A method to determine the repres ntative inflow angle to the fin by the datum line and to determine the optimum setting angle of fin is discussed.
