We've just posted online some of the propeller data that we've been collecting in wind tunnel tests here on campus. All of the data is here:

http://www.ae.illinois.edu/m-selig/props/propDB.html

So far there's data for about 80 propellers. We've tested over 100 and we'll be adding that soon.

The results show a significant drop in efficiency relative to full-scale propellers. The reduced performance is a Reynolds number effect as well as in some cases non-optimal designs (chord, twist, airfoil selections). Also the results show significant differences in performance between different prop manufacturers and styles.

I hope this is useful to designers trying to optimize aircraft performance of UAVs and models (SAE and DBFplanes also).

We just presented this at a conference. The link above includes a paper that describes the methods.