Model Test of Influence of Propeller Arrangements Aboard a Four Propeller Boat

Abstract

Although it is not uncommon to employ four propellers on a high speed displacement vessel, there is a lack of literature on this subject. This paper presents the propulsive performance of a fourpropeller craft and gives the influence of propeller arrangements on the propulsive performance. According to the rotation direction, the transverse and longitudinal positions of four propellers, five factors are designed as the possible influential factors and 18 propeller arrangements are selected depending on the Taguchi orthogonal array. In fact, there are only 15 selfpropulsion tests because the outer and inner propellers are overlapped in the same longitudinal position. The results of the model tests indicate that the influence of the hull form is negligible for highspeed craft because the frictional wake is small. In order to solve the problem of three missing selfpropulsion tests, an unbalanced analysis of variance (ANOVA) is adopted. The propulsive efficiency, propeller thrust, and torque are considered as response variables in order to explore the importance of each factor. The order of importance is also obtained to provide designers with valuable guidance information.