An investigation into the performance of high-speed catamarans in calm water and waves

The characteristics of fast, displacement catamarans in calm and rough water have been investigated in a systematic manner. Over 50 catamaran models derived from the NPL round bilge series have been tested in calm water. Measurements of total resistance, wave pattern resistance, trim and sinkage have been made up to a Froude number of unity. A summary of the test conditions is as follows: L/∇1/3 range 6.3, 7.4, 8.5, 9.5; B/T range 1.5, 2.0, 2.5; S/L range 0.2, 0.3, 0.4, 0.5 and monohull; Fn range 0.2 - 1.0.An investigation into other calm water drag components has been made. The influence of induced drag, spray and wave breaking have been examined. The effect of scale was also investigated by testing two model lengths for the finest hull form.A slender body method has been developed for calculating calm water wave pattern resistance. The theory has been modified to better describe the flow behind the transom and good agreement has been found with the measurements of far field wave pattern resistance from model tests.A subset of the calm water models has been used for seakeeping experiments in head seas. Models were tested in both regular and irregular waves. Measurements of added resistance in waves, pitch, heave and vertical accelerations at two longitudinal positions were made. A summary of the test conditions is as follows: L/∇1/3 range 7.4, 8.5, 9.5; B/T 2.0; S/L range 0.2, 0.4 and monohull; Fn range 0.20, 0.53, 0.80; ωe range 5 - 20; λ/L range 0.46 - 7.31.A holistic approach to design has been investigated combining the results from both calm water and rough water investigations. Design criteria for such vessels have been suggested and the implied compromises discussed.