A Study on the Characteristics of Self-Propulsion Factors of Planing Craft with Outboard Engine

The purpose of this study is to develop a method to estimate propulsive performance for planing craft with outboard engines. In order to understand the characteristics of this form of propulsion, a fully captive model test system with propulsion was developed and tested. And the effects of the changes in hydrodynamic forces and moments acting on hull due to the interaction with the lower-hull of the outboard engine and its propeller, as well as the effective wake fraction and the relative rotative efficiency, is presented. Based on the experimental results, an estimation method is proposed. By using the proposed method, running attitude (or trim and rise), thrust (or THP; Thrust Horse Power), crank shaft torque (or BHP; Braking Horse Power), maximum forward speed and fuel consumption of a real craft are estimated. It was found that the effective wake fraction and the relative rotative efficiency have significant impact on the estimate of maximum forward speed of the craft.