On the Analysis of Steering Quality of Ship by the Z Maneuvering Test, and Its Application

Abstract

We are convinced that the Z maneuvering test should be used to evaluate steering quality of ship quantitatively, and we have performed these tests on many ships built by Kawasaki Dock Yard in last few years. Now we have analysed the results by the method of Mr.K.Nomoto and his colleague, and have evaluated the parameters K,p and (-pK) quantitatively which represent turning, course keeping and quick response abilities of ship, respectively. Then we have reached to the following conclusion: 1. If rudder area ratio (RA)/(L・d) is constant, improvement of turning ability is incompatible with that of course keeping ability. Therefore, alteration of the form of fore and aft parts of ship means only to shift a compromise point between the above both abilities. However, if (RA)/(L・d) increased, both turning and course keeping abilities are improved, but quick response ability is determined only by (RA)/(L・d) approximately. 2. We may consider however that the possibility of some improvement of both the turning and course keeping abilities are still left in alteration of the form of fore and aft parts of ship. 3. The K,p expression is useful to express the requirements of ship handler for ship maneuvering, and to supply ship designer with suitable means which can satisfy these requirements. But, in order to complete the above mentioned method, it is necessary to carry out various model tests together with ship tests.