An Experimental Method to Evaluate Resistance and Attitudes of Planing Craft Using Very Small Models

Abstract

In order to establish an experimental method to evaluate resistance and running attitudes of planing craft using a very small-scale model, the scale effects on hydrodynamic forces (drag, lift and trim moment) acting on two model ships, a 0.45m model and a 0.9m model, are experimentally investigated by fully captured towing tests. The results demonstrate that the lift and the moment acting on the smaller model are smaller than those on the larger model. The predicted results of running attitudes using the modified hydrodynamic forces obtained for the smaller model, in which the scale effects on the lift and the moment are taken in to account, are in fairly good agreement with the measured running attitudes of the larger model. The residual resistances predicted for the two models based on Froude's hypothesis using Blasius and Plandtl-Schlichting formulae in the prediction of frictional resistance are in fairly good agreement with each other.