ORIGINAL: hllywdb
I have experienced this with not enough rubber bands on the wing on a couple of planes. The lift of the wing lifts the front of the wing high, causing a temporary incidence issue, followed by the fuselage snapping back UP to the wing, changing angle of attack and the whole thing just snowballs. It sounds crazy and took me a while to figure out what was going on, but check that first.
Thanks, that was not one I had thought of. I was using 10 #64s, but I will recheck to see if that is enough. I was taught to hold the wing dowels with your index fingers and press the wing up with your thumbs, and if you can move the wing, it was not enough rubber bands.