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In spite of remarkable developments about the research of the ocean wave, the properties of the waves in the closed sea area which are closely concerned with designing small ships are yet unknown.In this paper, the authors calculated the spectrum of the waves, and reduced the statistical properties of the waves nearly the course of small ships in The Seto Inland Sea.The observations were carried out with a pressure type wave recorder hanging under the buoy.And the objected area is about 25 miles square in size, and is almost isolated from open sea. So it may be affimirative that the waves are generated only by the window blowing over the area..The results are represented in Table 4, Fig. 6, Fig. 7 and Table 9.

The so-colled “KIHANSEN”, a small wooden cargo ship whose length is about 20 meters or more, operates mainly on the Seto Inland Sea, a typical Archipelago in Japan. In the previous papers, the authors studied its safety with regards to its loading conditions, its particular ship form and construction, and complicated sea conditions under which the ship must navigate. And concluded that the causes of its casualties were 1) extraordinary length-breadth ratio (L/B), namely, about 3.8 2) undesirable loading conditions which are unsuitable with ship nature especially in case of carring heavy cargos, and 3) the unfavorable hold arrangements for seaworthiness, which allow shipping sea water easily.In this paper, to confirm above conclusions, with deta of 164 serious ship casualties, the situations of affairs are examined and studied severally, and furthermore some designing problems are discussed in connection with the safety of this sort of ship.

In this paper, the authors studied the wooden cargo ship disasters on the Inland Sea with the aid of 621 materials presented to the Regional Maritime Bureau, and obtained an approximate equation which shows the relation between cargo weight and freeboard.Nextly they examined the rolling of the type ship in the waves whose nature readily estimated with the Darbyshire's method, and confirmed the conclusions of the previous paper about their safety at sea.

The KIHANSEN-a wooden sailing vessel with an auxilary propulsive engine which developed uniquely in Japan during the last half century-operates mainly on the Inland Sea and its neighboring area ; and suffered many shipping causualities in every wintertime.While little attention has turned to the causes of their disasters beacuse of the following reason : 1) poor informations about their loading conditions. 2) almost lacks of accurate lines of ship. 3) particular nature of the sea under the influences of the surrounding lands and islands.With a view to studying their safety, as a first step, the authors examined the reports of the damaged ships presented to the Regional Maritime Bureau, and obtained the charts which show some relations between cargo weight and freeboard ; and it was found that both the excessive cargo weight in case of carrying heavy cargo and the excessive wind force in case of carrying light cargo, such as timber, paper and miscellanious goods are the causes of the disasters.