Behaviour and performance of compact frigates in head seas1

Abstract

This report describes an experimental investigation into the motions and powering of a so-called Compact Frigate in waves. Special attention was given to the measurement of the relative motions, with respect to the wave surface along the length of the ship, bearing in mind that not the available power but mainly deck wetness and slamming are governing its sustained sea speed. For that reason, two models having the same main dimensions, weight distribution and underwater cross sections, but different forebody section shapes above water, were tested in regular and irregular head seas, in order to study the effect of flare upon motions and propulsion. In this analysis the deformation of the waves, when traveling along the hull, has been accounted for since the models were also run in restrained condition. The applicability of the linear superposition principle is examined, whereas the model motion measurements are compared with strip theory calculations.