On the Theory of the Characteristics of Propellers with Contrarudders

In order to increase the propulsive efficiency of ship, we often use the contrarudder. The effect of the contrarudder has been often experimented in tanks. If we can solve theoretically on this problems, we can design the most suitable propller-contrarudder series of the ship.Then in this papers, the author solved for the effect of the contrarudder theoretically, and calculated the gain of the propeller thrust for some examples.In conclusion it has been verified that the gain of the propeller thrust is about 1-3% for some examples in comparison with ordinary streamlined rudder, and this percentage is nearly the same as in tanks.