Originally Posted by dave1993
there are few actual naysayers. in fact ive never heard a single contradiction to the true advantages (wing strength and improved stall). it is also untrue that rigorous studies are lacking. numerous government and academic evaluations were done although it does take time to dig the data out.
as i mentioned before the fellow who got me started in this hobby built dozens of kf wings, top and botton, of varied percentages with careful measurments of lift-to-drag/glide-ratio. i was there. in ALL tests kf exhibited increased drag over flate plate and other common airfoils and no major improvement in lift. on the other hand kf improved stall characteristcs big time.
i built a few myself and found the plane much more fun to fly. my kf wings were significantly stronger too. however getting to altitude on a given mah were slightly inferior to flat plate and markedy less efficient than the famous 4-40 uc.
its unfortunate that religious zeal often overshadows real world benefits of this wonderful wing configuration.
You might want to view these videos of a side by side comparison between a KFm3 airfoil and a conventional airfoil. The results were surprisingly similar.