Generally, semi-submerged propellers are considered useful for planning and SES hulls. But their value for displacement hulls is explored in this document. Two attributes make this concept attractive: the good propulsive coefficient demonstrated by semi-submerged propellers and the possibility of minimizing hull appendage drag by deleting propeller shafting, hub and struts.
This investigation includes analysis of semi-submerged propeller designs suitable for a twin screw DD 963 Class destroyer. The performance is estimated for various diameters, amount of submergence and other parameters. An analysis of the merits of a cavitating versus fully-wetted blading is described. The analysis concludes that the aforementioned attributes are valid and the concept is attractive. A fully-wetted blade design is selected based on this study as well. Propeller channel tests are described which confirm propeller performance and a propulsive efficiency of 60 percent to 65 percent. All results are tabulated and discussed. The fully-wetted design. is determined as the best approach.
Fully self-propulsion tests for a DD 963 destroyer hull with twin semi-submerged propellers are reported. A 5 percent reduction in SHP at 20 knots is measured. All results are tabulated and discussed. A 10 percent reduction can be expected for an optimized propeller design. Noise tests have not been carried out yet, but they are proposed for future investigation. In conclusion, the work to date indicates that the concept is attractive for an energy-conserving propulsor design and should be further evaluated for monohull configurations.
