Propulsive Performance Analysis of a Stepped Hull by Model Test Results and Sea Trial Data

n recent years, advanced materials and manufacturing technologies have allowed the construction of boats of lighter weight and more powerful, smaller and lighter engines. Consequently, the reduction of the weight/power ratio leads to an increase of the maximum speed. Designers when making the performance prediction for marine vehicles, they know that the power delivered by the engine is a function of hull and propeller efficiencies. The non-linearities of the hydrodynamics of planning hull, the high speeds and the dimensions of the ship and model hulls, especially for the stepped hulls, lead to complicated analytical and experimental solutions. However, model tests and full-scale trials are still the primary source of scientific investigation into the behavior of planning hulls. In this regard, while the results of resistance tests are wide and varied, more limited are those of the self- propulsion tests. In particular, in the literature there is no wide evidence of propulsion tests carried out on hull model of small and fast boats with outboard engine. Recently in (Clement E.P., 2006) the authors have develop a method to estimate propulsive performance for planning craft with outboard engines simulating the propulsion tests. The authors, in (Clement & Pope, 1964) proposed a set-up for a new experimental methodology to obtain good results for the measure of total model resistance on stepped hull by comparing the results of model tests and sea trials of a stepped planning craft. In this paper the authors continue the investigations and analyse the propulsive pe rformance of a stepped hull and make an estimation of the values of the propulsion factors by using the results of the model resistance tests, screw propeller open water test and seat trial data.