CATAMARAN WAVE RESISTANCE

A first iteration computer program developed by Drs. Pien and Strom-Tejsen of N.S.R.D.C. for determining the wavemaking resistance of conventional and catamaran hull forms is updated, consolidated, documented and exercised to produce results of immediate interest to catamaran hull designers. The effect of demihull geometry, design Froude number and hull spacing on wavemaking resistance is demonstrated. Within the constraints used in the investigation, it appears that the range of design Froude numbers from 0.30 to 0.35 in association with non-dimensionalized demihull spacings of 0.26 to 0.34 results in minimum wavemaking resistance. However with the aid of the computer program the designer can obtain information for a wide range of design Froude numbers, hull spacings, and hull geometry (represented by singularity distributions) of his own choosing. Design waterlines showing hull form geometry at six different design Froude numbers are drawn using Michell thin ship theory. The importance, first stressed by Pien, of asymmetric demihulls in producing symmetric wave patterns for maximum wave cancellation is discussed. Finally, the difficulties found at Froude numbers slightly below the design Froude number where the favorable interference factors occur are pointed out.