On the Index-Numbers of Directional Stability and Course Stability

Abstract

In the analysis of turning movements of a ship, the moment of inertia of the ship's virtual mass about the pivoting point cannot be used as that of the ship when she is turning, because the moment of inertia varies according to turning conditions, and is the same in value as the centrifugal force exerted on the ship. By the help of this idea the index-numbers of directional stability and course stability can be explained as follows respectively m_2Mr<OG>^^^-ω^2/P_δV_<1∞>^2cosδ<OA>^^^-<^^=5.25 m_2Mr<OG>^^^-ω^2/0.555(I_0+m_2Mr<OG>^^^)ω^2<^^=0.84 where m_2=0.9+0.1(L/B)