A PROCEDURE FOR THE DESIGN OF TANDEM PROPELLERS

A procedure is outline in this report for the design of tandem propellers. The specific tandem propeller arrangement discussed with be two propellers operating one behind the other, on the same shaft with the same rotational speed and direction of rotation. The specific design procedure discussed will be for the tandem unit operating in uniform inflow but the logic involved would be directly extendable to the wake adapted design case. A tandem propeller unit designed using this method was constructed and evaluated in open-water experiments. The performance data, presented herein, shows that the unit produced the desired thrust at the design revolution rate and that the open-water efficiency was as good as, or better than, a single propeller carrying the same load at the same operating conditions. The ability to design tandem propeller units which meet prescribed performance criteria and which operate at acceptable propeller efficiencies could have considerable impact on ship powering technology. Tandem propellers can be applied to ships with high delivered horsepower, where vibration and cavitation erosion are anticipated problems, and where the physical constraints make a tandem arrangement attractive. (Author)