6. Model Experiments on Capsize and its Prevention for a Small Fishing Boat in Waves

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Capsizing accidents, often resulting in the loss of human lives, occur frequently among fishing boat in the northern sea area of Japan. These accidents occur more frequently among salmon fishing boats than among any other kind of boat. The purpose of this paper are: first, to determine factors that affect the capsize of a small fishing boat; and second, to test the effectiveness of inflatable bulges in preventing accidents. These aims were accomplished using model experiments. During experimentation, a 1/7 scale model ship was navigated in both regular and irregular steep waves within a model basin. Observation of factors affecting the capsize of the model allowed researchers to predict the conditions of both model and sea when capsize may be expected. Since cargo shifts are often the cause of capsize, the model ship was equipped with a weight shifting device, the purpose of which was to simulate cargo shifts caused by the rolling motion of the ship. Inflatable rubber bulges were attached to both sides of the model hull. The purpose of these bulges was to lend additional buoyancy and righting moment to the ship in emergencies. Many runs under various ship's conditions and sea conditions were carried out during experimentation. Capsizing phenomena were frequently observed when there were poor stability conditions. Through analysis of the experimental results it was determined that: first, a combination of trapped water on deck and a cargo shift was the most effective way of causing capsize in beam and quartering seas ; and second, inflatable bulges were so effective in preventing capsize that, despite trapped water and weight shift, when they were inflated, capsizing did not occur. The theoretical analysis of ship motions such as rolling, acceleration and relative motion in irregular waves can explain the experimental results. Understanding of capsizing phenomena will help to illustrate the danger of navigation in quartering sea, having high steepness.
社団法人日本船舶海洋工学会の論文

6. Model Experiments on Capsize and its Prevention for a Small Fishing Boat in Waves

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