The Choice of the Propeller

In this paper the four main requirements for a propeller are dealt with. These requirements concern efficiency, cavitation, propeller-excited forces and stopping abilities. In a propeller diagram the characteristic efficiency curves for different conditions are explained. A comparison of the optimum efficiencies for various types of propulsors is given, and the applications on a 130,000-dwt tanker are considered. Cavitation-inception curves both for a specific propeller and for systematic propeller series are discussed. Predicted torque and thrust fluctuations, based on model-test data, and the results of measurements on the full-size ship are compared. Finally a quasi-steady testing technique, developed to analyze different types of stopping maneuvers, is described.