Originally posted by Goldenhawk1
You guys went from a very complicated description of flutter to a discussion of gap sealing. To set some of this straight. FLUTTER is caused on any surface by something being loose. It could be linkage, hinges, loose servo in it's mounts or broken gears. It is NOT cause by gaps between the moveable surface and the fixed surface. Gaps on fullscale aircraft of the aerobatic type and competition gliders are sealed for two reasons . One is to make the surface more efficient there by resulting in less required deflection and two causing less drag. If you experience flutter for any other reason it is an over speed condition caused by too much power resulting in speed for which the aircraft was not designed.
seeling the hinge line is one way of helping stop flutter.
the reason this is done is that a gap invites airflow between the control surface and the main stab/wing this can cause a vibration like a whistle. this vibration can, at a certain speed create a vibration that matches the resonant frequency of the surface, amplify itself until you have uncontroled vibration, or flutter.
anyone into music, esp speaker/instrument design can tell you that if two peices are closed matched in resonent frequency a small input from an outside source will make those two peices feed each other and you will get a louder sound (more vibration)
sealing the gap eliminates the whistle which is a source of vibration that can change its pitch due to speed, and is more likely to match the resonance of the surface.