High Speed Small Craft Aerodynamic Resistance

High cruising speed, at present commonly achieved by small size pleasure and working boats highlights the importance of aerodynamic drag and suggest to consider also aerodynamic lift. To this aim an experimental research program has been jointly carried on at Department of Naval Architecture of Universita’ di Napoli Federico II and at Department of Mechanics of Politecnico di Milano A 1:10 scale model of a planing pleasure boat, decked and GRP built, has been tested in towing tank to assess bare hull resistance, running trim and hull raise at Fn range 1.1-2.1. In the wind tunnel the same model has been connected to a six DOF. dynamometric balance; a set of wedges has been used to set the scale model at trim angles and hull raises previously assessed in towing tank and a flat plane to simulate the water surface. Aerodynamic drag has been assessed at the same speed values used in the towing tank to evaluate the aerodynamic contribution to the total resistance. Then in order to check Reynolds number effect on the aerodynamic coefficients, further tests at higher wind speed values up to 16 m/s have been performed. The obtained results allow the assessment of scale models aerodynamic resistance and represent a contribution for a sound application of the experimental procedure used for planing craft resistance evaluation.