著者

二村 正 石田 茂資 渡辺 巌 Tadashi NIMURA Shigesuke ISHIDA Iwao WATANABE 船舶技術研究所運動性能部 船舶技術研究所運動性能部 船舶技術研究所運動性能部

出版者

運輸省船舶技術研究所

雑誌

船舶技術研究所報告 (ISSN:0495775X)

巻号頁・発行日

vol.32, no.5, pp.233-264, 1996-02

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Capsizing and re-righting performance of three types of sailing yachts, IOR racer type, conventional type and intermediate type, was experimentally investigated in beam transient waves with various wave heights. The effect of CG height, existence of mast and flooded water volume on the critical wave height for capsizing and for re-righting was examined. It was characteristic in the capsizing motion of the models with mast that the rolling motion almost stopped just after the mast plunged into the water because of the hydrodynamic impulsive force on the mast. The stopping heel angle was almost independent of hull forms and model conditions. As a result the static stability vanishing angle, θv, was crucial for capsizing even in flooded conditions. As for re-righting motion θv was also crucial. It was clarified that the IOR racer type yacht is easier to capsize and harder to re-right because of its small θv value even if it has large GM. The way of improving the capsizing resistance was discussed. Lowering the center of gravity or attaching a small float on top of the mast could be an easy and effective way to prevent capsizing disaster because that leads to a large θv value. The flooded water, in general, enlarged θv, that made the models capsize-resistant. But for re-righting motion the relation between the critical wave height for re-righting and θv was complicated, because the water prevents the motion of the models at the same time. The probability of capsizing and re-righting in a sea state with ISSC spectrum was examined. Moreover the capsizing duration time was calculated as a safety index. It was reconfirmed again by the probabilistic approach that θv is very important for the safety of sailing yachts. θv of 120 degrees was proposed as an safety criteria.