Outboard Propulsor Study for a Planing Boat - Propeller Type C

Experiments of self propulsion have been carried out at CNR-INM for a planing hull equipped with a YAMAHA Outboard Type Propulsor (briefly named POD). The objective of the present project is to study the propulsive performances at three trim angles of the lower unit, fitted with the Type "C" propeller. The POD is internally instrumented with a dynamometer for measuring thrust and torque close to the propeller, while the total force of POD, acting on the boat, is measured by a force block fitted between the propulsion unit and the stern of the model. The self propulsion tests have been performed according to the Load Varying Method. Tank tests with the hull model allow that the propulsor operates in a velocity distribution similar to the actual full-scale flow field, but with boundary layer thickness and static pressure field not scaled. In particular, the latter condition do not allow the onset of the cavitation. The measures frequently detected possible air-water mixed flow field. The global complexity of the tests led eventually to perform three campaigns to provide the best estimate of the propulsive factors. These were calculated from the measured propulsive quantities when the latter showed a good consistency with the resistance results, used as a reference.