Chapter 10 - Intact Stability Regulations II

Abstract

The regulations of the German Navy take into account the influence of waves on the righting arm. Therefore, for some cases the righting arm to be used is the mean of the cross waves in wave trough and on wave crest. The free-surface effect is considered as a heeling arm and is plotted as such in the statical stability diagram. The wind heeling arm is calculated with a formula that does not yield zero for 90-degree heel and is plotted from the free-surface arm up. In other words, the heeling arm that intersects the curve of the righting arm is the sum of the free-surface and wind arms. After finding the intersection, that is the first statical angle, it is necessary to go to a reference angle given by a formula and measure there the residual arm, that is the difference between the righting and the heeling arm. Another formula indicates the minimum acceptable value of the residual arm. The chapter explains also the criterion in turning. The chapter ends by describing a MATLAB function that carries on the calculations and draws the required curves.