The paper deals with an experimental and numerical research carried out on a high speed symmetric catamaran operating in the Gulf of Naples, whose main dimensions at the design load line are : length L = 35.867 m, breadth B = 11.334 m (demihull B = 3.30 m), draugth T = 1,58 m, displacement Δ = 137 t; separation – length ratio s/L = 0.224. The experimental research was jointly carried out on three geosims (model scale λ = 7; 13 and 26) at the Rome towing tank (453 m x 13.5 m x 6.5 m), where the largest model was tested and at the towing tank of Naples (140 m x 9 m x 4.2 m) where the other two models were tested. The experimental research was undertaken with the goal to obtain indications on scale effects on the resistance components, on the influence of the towing line position on the resistance model tests, on the most suitable ship – model correlation and on the power prediction scale effect. A theoretical wave pattern analysis was also carried out by means of the application of a numerical panel methodology based on Rankine sources. The results of the numerical wave pattern were compared with the corresponding experimental results obtained by the longitudinal cut method proposed by Sharma (1966). The comparison was carried out in terms of wave resistance, wave pattern and free wave spectra. The results of this research may give indications on the power prediction for high speed catamarans by model tests and by numerical wave pattern analysis.
