Some aspects in designing shaft brackets for high-speed vessels

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Some aspects in designing shaft brackets for high-speed vessels

Jonk, A. / Hackett, J.P.

Many modern high speed vessels, such as containerships, ferries, and Ro-Ro (roll-on-roll-off) vessels have an open shaft arrangement. In cases where the speed of these vessels is larger than about 26 knots, there is a risk of bracket cavitation. At model basins, test-techniques have been developed to determine the correct alignment of the brackets with the flow. In spite of these techniques, bracket cavitation still occurs on full scale. Therefore, improvement of the existing test techniques was necessary. At MARIN, methods have been developed to improve the accuracy of the alignment tests. In addition investigations have been carried out to study parameters, which influence bracket alignment. This paper reviews the test methods used; describes the implications of model instrumentation, model appendage construction, and installation procedures to the measurements; and shows results of some measurements. It is concluded that bracket location is an important parameter; therefore, a better understanding of the flow field in the region of the bracket is required.