Nice Cub Polle!
ORIGINAL: pimmnz
...Cl max can be taken as 1. It don't seem to matter what shape the foil is, at our sizes there is little to choose between them so far a Cl max is concerned. Most of the airfoil data available is for full size sections and does not relate well to model sizes, for example....
While I agree with this in general terms for smaller models (in fact Clmax can be as low as 0.6-0.7 due to low Reynolds numbers) bear in mind that with a span of 43cm at 5m/s the Reynolds number is almost 150k.
I have experimental data from Selig which shows Clark Y acheives a Clmax of 1.3 at Re 100k.
Using Clmax of 1 won't be far off as a conservative starting point, but CL1.2ish may be possible - ie slower still.
I have a feeling that the airfoil on Polle's Cub is not proper Clark Y though? Maybe flat bottomed 13% instead...