船舶復原性より見たる安全示數

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When a ship, which is rolling among waves around the steady heel due to wind, is attacked by a sudden gust, sometimes accompanied by the rudder action, if the work done by the gust and rudder action be greater than the reserve of her stability, she capsi es. The condition, that the capsize may not occur, can be expressed by the following relations : [numerical formula] where S_d : dynamical stability arm, i.e. the area of the stability curve divided by the weight of the ship, D_w : heeling moment arm (the speed of the gust assumed to be 1.4 time of the mean wind speed), θr : range of the stability curve, C_w : reduction coefficient determined from the fact of the reduction of wind speed near the sea level, θ_0 : rolling angle. D_0 : heeling moment arm due to the rudder action, m : metacentric eight. Being given the speed and the rolling period of a ship, the waves (length and height) and wind speed, which cause the severest conditions to her heel, are to be found from the curves given in the paper. C' in (A) should be at least greater than unity, but, considering the other conditions which are not taken into account in the deduction of (A), the permissible lowest value of C′ must be taken much greater than unity. C′ is called in this paper the safety criterion, and can be considered as like the factor of safety in the strength of materials, and its permissible lowest value should be determined from the experiences of actual ships. Values of C′ are calculated with several small-typed vessels, and given in the Table.
社団法人日本船舶海洋工学会の論文

船舶復原性より見たる安全示數

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