A Contrarotating Propeller Design for a High Speed Patrol Boat with Pod Propulsion

A contrarotating (CR) propeller design with a tractor pod for a high speed patrol boat is addressed. In the current arrangement, a CR propeller is placed at the forward end of a pod which is aligned with the local inflow. The powering and cavitation experiments show the performance prediction agree well with measurements. Compared to the existing controllable pitch propeller with shaft and struct configureation, the pod-mounted CR propeller show a 28% reduction in power consumption at design speed with a 7 know improvement in cavitation inception speed. At full power, a larger pod is required, which will reduce the gain in power consumption.