One of the math geniuses can chime in on this. I am only going by what I have been told by people smarter than I.

That was a great find.  I do not think the traditional measure of prop efficiency have much for us to usehowever.  Most discussions of prop efficiency are steady state, trying to get the maximum cusing distance out of a drop of fuel.  about 1/2 of a stunt flight is spent in level flight cruise, and I swag about 1/4 of the flight is spent climbing and 1/4 is spent diving.  Its the climbing and diving parts that we need to worry the most about!  WHile a highly efficient cruise prop is likely a fairly high pitch and low RPM, the climb or dive prop will be best spinning fast(er) to maintain speed.  The thought porcess that wnt into the high RPM stunt set-ups applies.

The author mentioned other dissertations forthcoming on Take-off Performance and Climb performance.  I think THOSE are the discussions that might be more adaptable to us.

Lots of prop artists spent lots of time refining their IC props to maximize performance.  When you look at it, IC engines tend to lose RPM under load (climbing) and gain RPM when the load is reduced (diving) so what the prop artists were REALLY doing was adjusting the responses of the IC powerplant to varying loads.  WIth an electric motor, especially one that is governed the RPM is more nearly constant so all that changes climbing & diving is the battery power (current) needed to maintain that constant RPM.

For people conditioned to spending $75 on a wonderful CF prop - that they then hacked & whacked to maximize the performance on their IC engine, it is SCARRY to think that the $7.50 prop on their electric works better - no one wants to believe such a thing is possible!

Most folks who have tried other electric props usually come back to the APC's, but even there we know that some APC's (the thin blades) seem to perform different than others (the thick blades); thus that points the way to some kind of super prop.  Personally I would really like to see lighter alternatives to the APC's to help reduce bearing stresses.  However lighter means either wood (too variable) or the elusive thin CF (however, I value my hands too much to use one)   

When that super prop comes along I suspect it will be judged superior by the usual criteria- if its expensive it MUST be better, right?

Hi Greg,
So there is a fundamental tug of war here: the bigger diameter/lower pitch prop you use, the better the grunt and braking, but at some combination of diameter and prop weight the plane starts to lose groove and or corner. No two airpolanes are the same. In the 60 ounce neighborhood, I know some folks who are exstatic with their 13-1/2 X 4 props, and others with similar sized airplanes that have to drop down to a 12 X 6 to get "the lock" back.
Your mileage will vary!
Sorry, no single pat answer.
Hope that heped,
    Dean P.

yes yes ... 3blade 11x5

you say "IF" ... means not yet??? 

reasons for what? 3bl? or carbon? or something else?

3bl. especially because it is kind for bearing and carbon because I can have 5 the same without risk that it will change pitch like plastic - that is first thing and secon because it survive easier flying on bad surface (did you read report from bulgaria? :- ))) ) ... and last, because I can use arfoil I wish to use (and pitch I want)

Thanks Igor.  One question you say you can use the "airfoil of your choice", does this mean you are making these props yourself?  It all makes sense what you say.
Thanks Again
Andy

Maybe one day Igor, when all my PA engines die.

Derek

those my are probably dead ... because they are hinging by neck on wall in models