自由落下式救命艇の新しい離脱方式について

抄録

This paper describes a new skid-launching system of free-fall lifeboats. In a conventional free-fall lifeboat system, a set of guide rails on port and starboard sides of the boat touch the rails of a skid arrangement. Thus a forward motion is given to the lifeboat during the boat glides on the skid. In the system, when the center of gravity of the boat passes the edge of the skid, a reaction force and the weight of the boat form a couple. Rotating motion (i.e., pitching) is exerted to the boat by this couple. The boat holds the same rotating rate while it falls freely through the air until it comes into contact with the sea surface. Therefor, if a fall height increases, water entry angle of the boat increases as well, and the entry angle has a tendency to come close to a right angle (i.e., vertical entry). This may cause a very dangerous situation by the effect of extreme buoyancy that makes the boat to run backward or even to stumble on the water surface. In this paper, therefore, a new double-skid launching system is proposed. By this system, rotation of the boat does not occur at the edge of the skid with a simple combination of the launching rails and the guiding apparatus of the boat. A series of performance simulations of the conventional system and the proposed one is carried out by using the numerical simualation method of free-fall lifeboats that the authors have developed. Experiments that utilize a small lifeboat model are also conducted. From the analysis of the numerical simualations and model experiments, the superiority of the proposed system in the boat motion is shown.