It is an actual situation of today that giant oil tankers are commomly equipped with a screw propeller of five propeller blades. In this paper is taken up the problem of blade number and discussed the merits of six-bladed propeller. We, authors, recommend the use of six-bladed propeller on giant oil tankers for their advantages in decreasing vibratory forces and moments induced by propeller without affecting propulsive efficiency. The paper also represents the results of our model propulsion tests on four-, five- and six-bladed propellers, wake pattern data calculated values of propeller forces and an example of a 70,000 DWT oil tanker equipped with a six-bladed propeller.
