[link=http://jimsrc.com/t2.html#flutter]definition of flutter.[/link] just wiggle the control surfaces (all of them) and make sure they are fairly solid and are hinged properly. also, make sure the hinge line gap is as small as it possibly can be. I'm sure someone will chime in on how to tape the joints I personally, never have done this nor needed to. but still is good to know I suppose.