Development of a New Hull Form with Semi-Submerged Bow for High Speed Craft

Abstract

To improve seakeeping quality some advanced high speed crafts have been developed and in service. However, in view of total performance including building cost, operation and maintenance cost, they are not satisfactory in commercial use. Under this circumstance, a new type of high speed craft having a submerged torpedo-shaped body under the bow bottom of conventional monohull high speed craft was developed. This new type of craft with Semi-Submerged Bow (SSB) has improved seakeeping quality with comparable total performance of conventional monohull type high speed craft. In this present paper, procedure in developing this new type of craft are explained.First, as a preliminary study, theoretical calculations were made before tank tests to confirm effect of a submerged body for the reduction of ship motion in waves.Next, preliminary tank tests were carried out in waves with two small models of 1. 4 m in length (SSB and Conventional monohull) towing at the same time in parallel position to compare directly the seakeeping quality of SSB and conventional monohull and hull resistance of two models were also measured to evaluate propulsive performance.Based on this preliminary study, an initial design of a large high speed passenger craft of SSB hull form was made.Then, applicability of this type of hull form to actual ship was confirmed with some additional experiments by use of small models.Finally, tank tests were carried out by use of a 3. 8 m self-running model to evaluate quantitatively both seakeeping quality and propulsive performance.It was found from the test results that the bow acceleration in waves was reduced considerably and the effective horse power was almost comparable to conventional monohull in the speed range of conventional use.