A PERFORMANCE DEPOWERING INVESTIGATION FOR WIND POWERED CARGO SHIPS ALONG A ROUTE

Paper i proceeding, 2020

For a sailing yacht, depowering is aset of strategies used to limitthe sail forcemagnitudeby intentionally moving away from the point of maximum forward driving force, potentiallyreducing theship speed. The reasonsfor doing this includes among others; reduction of quasi-staticheeling angle, structural integrityof masts and sails and crew comfort. For a wind powered cargo ship,time spent onaroute is of utmost importance. Thisleads to the question whether there is a performance difference between different depowering strategiesand if so, how large.In this research, a wind-powered cargo vessel with rigid wings is described in a Velocity Prediction Program (VPP) with four-degrees of freedom, namely surge, sway, roll and yaw, with a maximum heel angle constraint. The resulting ship speed performance for different depowering strategiesare investigated and the implications in roll and pitch-moments are discussed. The wind conditions when depoweringis needed are identified. Astatistical analysis on the probability of occurrence of these conditionsand the impact of the different depowering strategies on the required number of days for a round-trip ona Transatlantic routeis performed