Experimental assessment of seakeeping characteristics for non-monohedral planing hull

Since early fifties planing hullforms have been widely used for passenger ships, pleasure boats and naval application. Beside powering performance prediction the seakeeping assessment and the operability evaluation according to the ship service are a fundamental step in the design of such high speed craft. Difficulties in the analysis of hydrodynamic lift do not allow the use of standard procedures based on the strip theory and non linearities in the hull response to hydrodynamic loads do not allow RAO approach for operability evaluation. Beside that the well known Fridsma and Savitsky-Brown empirical formulations refer to simplified prismatic hull form and generally give results not enough accurate to get a meaningful result. Within this frame an experimental program focused on the behaviour of non-monohedral planing hull in regular and irregular head sea has been carried out at the towing tank of the Department of Naval Architecture of the University of Naples. A scale model has been tested at Froude number Fn from 0.9 to 1.4 in regular waves with /L ranging from 1 to 5. Tests in irregular waves described by standard ITTC two parameters spectrum were performed for three different ship velocities. Vertical motions and accelerations have been measured at helmsman position. The results have been analysed and compared with values provided by ISO 12215-5.