warped

The trailing edges of both my FT Flyer (elevators) and my FT Delta (elevons) have become too warped to fly. The servos can't move the control surfaces enough anymore. The FT Delta had a coat of Minwax on it but maybe I didn't do it well enough? Both have been flown on dewy, wet mornings. Is...

I wasn't sure which area to post this in but ... I just visited a local Dollar Tree for the first time and bought several sheets of white and black foamboard. I had to really sort through many sheets to find some that were not badly warped. I couldn't find any that were ideal and the 2 black...