The scale effect of a waterjet propelled planing boat on its manoeuvring performance

Abstract

There are some differences between model ship and full-scale ship performance due to the ‘scale effect’. For planing boats, in particular, the percentage of the frictional resistance in the total resistance is large in comparison of the conventional vessels, so the scale effect cannot be negligible. In this research, turning and zig-zag tests were performed for two kinds of scale model boats with each model self-propulsion points. As the length of the model boat is smaller, tactical diameters become smaller, roll angles and yaw rates get larger in turning motions. And the overshoot angles increase, initial turning length and time are reduced with decreasing model length in zig-zag motions. For the similarities of manoeuvring characteristics of model and full-scale boat, model nozzle angle correction is proposed under the equilibriums of horizontal forces and moments acting on the boat.