Abstract
According to sharp rise in bunker prices after the oil crises, there appeared a trend to design large ships with lower-powered engine for lower service speed as measures for energy saving. Such a lower-powered ship is anticipated to show a different operational performance in rough seas from that of an ordinaly higher-powered ship. Model experiments were carried out, therefore, to investigate the effect of the output of main engine installed on operational performance of a ship in rough seas in particular reference to nominal speed loss and course keeping ability. The results obtained from experiments and predictions indicate that in severe waves and wind a lower-powered ship has larger speed loss ratio and poorer course keeping ability than a higher powered ship. From this fact, it is considered that in the design of a lower-powered large full ship the selection of engine output should be made in careful consideration of the propulsive performance and course keeping ability in rough seas.
