Using Single Propeller Performance Data to Predict the Performance of a Counterrotating Pair

The question of using off-the-shelf model boat propellers in a counterrotating-pair configuration was addressed. A number of candidate propellers were performance tested in a water tunnel. Both open-water single-propeller tests and counterrotating-pair tests were performed. A model based on momentum theory was devised to predict the performance of the counterrotating pair from the individual single-propeller performance curves. Unknown coefficients in the model were determined by minimizing the deviation of the model from the counterrotating performance data. Excellent agreement between the model and the data was found over the entire range of the counterrotating pairs tested. The model can now be used to predict the thrust, net torque and efficiency of two off-the-shelf model boat propellers operating as a counterrotating pair.