ON THE MANOEUVRABILITY OF SHIP HAVING SMALL LENGTH BEAM RATIO (SCALE EFFECT AND CONFIRMATION FOR APPLICATION)

The radical growth in the transportation of crude oil has brought forth increases in the size of crude oil carriers, and systematic studies on the economic potential have proposed the possibility of changing the hull form by reducing length-to-beam ratio (L/B). As a consequence, it has become necessary to investigate the manoeuvrability of large tankers at an early stage in the design process. Under such circumstances, one of the greatest concerns of the authors is the manoeuvrability of a newly designed ship which is characterized by the stocky hull form with a small L/B ratio of 5,0. In order to find out the scale effect upon manoeuvrability and to confirm the accurate performance, two large 30m models, one for a conventional V.L.C.C. now in service and the other for a newly designed U.L.C.C., have been subjected to various tests at sea. Systematic model tests by geosim small models have been conducted in an experimental tank. The results of these tests results of these tests reveal that the performance of the newship was superior to that of the conventional one, mainly due to the larger rudder fitted on the former. In addition, the scale effect on the normal force of rudder has been examined, and also the flow around the rudder has been analyzed from the records of rudder force generated by steering. These data contribute to refine a simulation program which has been developed so far for the prediction of the manoeuvrability. The whole aspect of the research is outlined in this paper.