[secant0give]

Here's a link to the airfoil polars for the MH 33
It was designed by a German proffessor, who obviously has a love for aeromodeling

http://www.mh-aerotools.de/airfoils/mh33koo.htm

Very thankfully, he's published a bunch of stuff that would have taken quite a bit of time and resources to put together!!

If you look at the calculated polars, this foil does a little better than most at Renalds numbers around 400,000. probably not suprisingly it's about the thinnest too. But is has quite a constant velocoty gradient accross the top surface and doesn't seem to suffer detached flow at the Re I want to use it for. Mind you the stall looks like it might get a bit sudden when it slows up, you can't have it all can you. the trick is to keep it as light as possible then when it slows up it won't need to opperate at a CL where it's likely to stall suddenly .........................that's the plan.

All those polars are just calculated by computer models and probably don't match the real world all that well any way. At least it's a method of comparison I guess.

Matrin Hepperle also has the nicest explanation of how to read airfoil polars as well. see link below

http://www.mh-aerotools.de/airfoils/index.htm

There is also a great deal of other technical info on his web site !!

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... Because weight also increases drag ...

I'm with you on all the bits of your post - except this bit.

Certainly there's a non-linear relationship between the power transferred to whatever is providing the thrust (propeller, impeller, turbine, whatever ...) and the velocity of the airframe - but in level flight the drag and weight vectors are orthogonal and therefore independent?...

They are at 90 degrees to one another that is true but to balance that force you need lift and that means angle of attack and that causes drag. especially in a tight turn when the model is pulling 30Gs ie weighs 30 times its static weight

......edtied to fix some of the spelling