The results of PRS studies up to date on the stability of freely floating ships, primarily led by Prof. Maciej Pawłowski, are important, therefore we wish to bring them to the attention of ship building and shipping communities.
Study results are presented in the PRS Technical Report No. 72, of July 2013. This report provides further development of the theory presented in the PRS Technical Reports No. 34/99, 46/02 and the Prof. M. Pawłowski’s publication “Some inadequacies in the stability rules for floating platforms”, Naval Architect No. 2, 1992.
The Report presents the problem of calculating the righting arms (GZ-curve) for a freely floating ship, longitudinally balanced at each heel angle. In such cases the GZ-curve is ambiguous, as it depends on the direction of the heeling moment. Three cases are discussed: when the heeling moment is normal to the trace of water in the midships, when it is parallel to the trace of water in the ship plane of symmetry (PS), tailoring the direction of the wind-heeling moment, and when it performs the least work, i.e. when it is parallel to the principal axis of the waterplane. Angular displacements (heel and trim) are the Euler\'s angles related to the relevant reference axis. Exemplary calculations illustrate the GZ-curves for these three cases. The most important features of the GZ-curve for a freely floating ship are discussed.
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