Two British triple screw cross-channel ferries have been equipped with Escher Wyss controllable pitch propellers of the fully feathering type on the center shaft. Due to the highly skewed blades the fully feathering position is achieved by gradual pitch increase rather than by the hitherto applied pitch reduction. The performance of the system was predicted on the basis of the model tests and monitored during prototype trials, mainly with regard to spindle torque characteristics. The results of the model and full scales measurements are reported and analyzed. In addition, the propeller blade forces are determined analytically for the fully feathered condition, applying finite aspect ratio wing theory and advanced viscous flow foil section analysis.

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