On the Preliminary Design of Semi-Submerged Catamaran from the Viewpoints of Motions in Waves and of Resistance

Abstract

A procedure of preliminary design of semi-submerged catamaran (SSC) is presented, treating the investigation of both characteristics of motions in waves and of resistance as a process of design, the former of which plays a more important role on the design of SSC than on the design of conventional ship. The principal dimensions (breadth of strut, distance between two demihulls) are determined from the survey of the natural periods which lead with little probability to resonant conditions in a seaway, while the dimension and the configuration of lowerhull are given beforehand so that the lowerhull has charge of the required displacement under the restriction of draft. After the determination of the principal dimensions, the shape of strut is determined so as to minimize the wave making resistance caused by the strut and the lowerhull by the use of linear theory of wave making resistance. The motions in regular waves and the resistance are measured with the models which are designed with the procedure proposed here. The interaction between both characteristics of motions in waves and of resistance is shown by changing the principal dimensions. The effect of asymmetric lowerhull with respect to vertical and lateral directions on resistance performance is examined with resistance test. The effect on the flow field near bow is also investigated through the observation of limiting streamline.