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.