抄録
The large vessls are treated as the wall sided ships, so the equation of motion in waves is in general as follows (Ix+Jx)θ+f_1(θ)+f_2(θ)=Fcos(wt+φ) but, as for the smalller coasters, the effects on the stability of the non-wall sided should be considered, as the parallel body is very short as compared with the large vessels. The smaller coasters have the short period of rolling and have easy resonance in the sea sea waves with the period of waves or gust, therefore some of them has been upset in the ligh condition notwithstanding the sufficient freeboard. When the wall angle of the non-wall sided smaller coaster is φ, the increase of the lever of statical stability is 4(1+2Cw)/3(1+Cw)cot^2φ・θ^3 and the virtual increase of GM is approximately 4(1+2Cw)/3(1+Cw)cotφ・θ^2. The rolling period of the smaller coasters considered above results show the better results.
