On the Results of Experiments on Model Rudders in the Propeller Race

A theoretical consideration of the effect of the propoller race upon the performance of rudders has already been expounded in the third report. In this fourth report, therefore, the author tries to explain the results of his experiment, concerning the model rudders in the propeller race, which was carried out at the circulating channel. From this rudder experiment, the following results have been secured.1. The increment ratios of the normal force of rudder due to the propeller race are proportionate to the one and a half power of the slip ratio of the propeller.2. The position of the center of pressure on rudder travels forewards due to the propeller race, and its movement gets larger in proportion to the increase of the slip ratio of the propeller.3. If the gap between the propeller and the rudder is changed in the range of 1.02.0 R, it affects slightly upon the rudder force. (R : radius of the propeller) 4. The qualitative tendency of the performance of the rudder, of which positon deviates from the propeller center, or of which height differs from the propeller diameter, can be observed by the following method. First, the total area of rudder be divided into two parts. The one is directly affected by the propeller race, and the other is not affected. Then the open results should be applied to the part not affected by the propeller, and the experimental results in propeller race to the affected part.5. In the propeller race, the effect of the angular velocity of steering upon the performance of rudders was also observed, in the same manner as in the open test.