The experimental results of model high speed marine vehicles are often affected by  significant scale effect errors in ship-model prediction methods, especially on longitudinal trim angle.

For a good mechanical similarity’s condition, it is necessary to simulate a correct position of center of gravity and longitudinal trim angle.

This paper, after an introduction on characteristics and performance of stepped hull, shows the results on towing tank tests and sea trial tests of stepped hull.

The speed range is from 0 to 60 knots, at sea trial, from 0 to 8 m/s at towing tank tests.

The procedure of experimental towing tank tests and sea trials are shown in details and all tests are carried out in same sea state.

The results are analyzed and compared to find out the optimum experimental procedure for towing tank test on high speed stepped hull.