prop efficiency

Try here, there is a neat thrust calculator there. Some limited testing in the real world tends to support the results.

You have asked a question that has interested me for many years, in fact when I took a propeller design course at Georgia Tech in 1956. What are the ranges of propeller efficiencies and what is the optimal design for model airplane designs? Over the years I have built computer codes to solve for the design of and efficiency for model props. From my work, that takes into account the higher drag at the lower Reynolds Numbers, I have concluded there is an optimum propeller design for a given set of operating conditions. For these optimal designs it is difficult to achieve efficiencies higher than 80%. So the answer to your question is that the best efficiency for a model propeller is somewhere between 65 to 75%. Contrast this with 93%+ for full-scale propellers. FYI, a 10% increase in propeller efficiency produces a 10% increase in thrust.

My designs are based on the work of Theodore Theodorsen of NACA. An excellent prop design site is at

where Martin Hepperle has done some great work on this subject. Another link is for a group in Australia that makes custom designs; they have some good data too. I believe that the results I have calculated are consistent with Hepperle's work, although I think we use different design methodologies. It is interesting that we both come up with designs that have wider blades at the 30% radius station and the blade chords taper down to zero at the tips. Most manufactured prop designs have narrower 30% chords and generally have wider chords at the tips.

If you go to the APC web site at

there is a discussion of APC's design process. I don't see any specifics on propeller efficiency but they might give some answer to that question if you contact them.

Marlowe