elevator flutter
 

Hello. I've recently built a Spad version of the Edge 540. It has a 48" wingspan with 600 sq. in. of wing area. I've put a couple of test flights on it, but I'm getting elevator flutter when I start to build speed. I have a .40LA on it with a mousse can muffler and intend to put something larger on it like a .46FX, but would like to get this flutter issue solved first. You can actually see the elevator flutter when flown over the runway. It appears that the whole elevator is fluttering, not just the moveable portion. I stiffened the fixed portion with a couple of bamboo skewers and it helped a little, but it still flutters. Can anyone help? Would flying wires help, or would that just be a waste of time and weight? Thanks for any comments.

RE: elevator flutter
 

Clip the elevator tips back at a 45 degree or greater from the hinge area inboard. It takes the tip out of the air flow. Works for airlerons too. What happens is, the tips start oscilating when that increased airflow hits it. I also had a problem when I used round PVC for a SPAR and had that big opening at the wing tip. Increases in speed would cause a vacuum to form in that tube and would cause the plane to sound like an A-10 on a straffing run. Cool, but the resonance caused the whole plane to shake in flight. A little expansion foam in the tips fixed that.

RE: elevator flutter
 

It might also pay to fix a correx doubler to the fixed stab with the flutes going the other way. That will stiffen the tailplane with minimal wieght gain.

RE: elevator flutter
 

On the hinge, I've been just making one cut on the moving side and bending the fixed side up slightly. that seems to keep the wind out of the hinge line and may help a little.

RE: elevator flutter
 

I haven't done this on spads, but it worked great on other (balsa) 3D planes. The hobby store has airfoil shaped aluminum struts that can be cut to length, flatten the ends with pliers, make a short flattened piece for the opposite side, and use small nuts and bolts to connect each horizontal stab to rudder. Next suggestion is to slow down. After a while the coroplast does weaken and must be replaced. Be sure it is not creased in any way. Maybe the push rod linkage has too much play, or the pushrod is connected to close to the elevator hinge or too far from the servo center of output shaft. May be servo gears are too worn out.

RE: elevator flutter
 

What prop are you using?, an edge is made to fly slow, it is built lightly and fly slow with liberal amounts of throttle management. a low (approx 4") pitch prop is a must.

with a 40 use a 10-3 (la 4o),10x4 10.5x4.5W,11x3 or 11x4
with a 46 use a 11x4, 11x5 ,12x4 (my favorite), 12.25-3.75.

make thrust and not speed and a 3d plane will be happy


or stuff your elevator flutes with 4mm (or 3/16) carbon tubing ;)[>:]