The aim of this paper is to give some idea of the difficulties which can arise at the design and operation of multi-purpose ducted CP-Propellers.

The most important problems are the contradictory requirements of bollard pull and push forces, but simultaneously the requirements for transit conditions with pull or reduced power, often at constant propeller RPM, must be fulfilled.

In all the cases it is desired that no harmful cavitation phenomena appear (i.e. no erosion and vibration problems and no propeller force reduction.)

Investigations in the SSPA cavitation tunnel and towing tank have been carried out with a number of propeller and duct models to study the influence of geometric parameters on the propeller behaviour at different conditions. Some of the results of these investigations are analyzed and discussed here.

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