Last time we got into flutter. This time, let's look at a couple of things which can prevent it. Just about everyone knows that "springy" controls may let the control surface flutter. I always use a servo in each wing with a straight shot for the pushrod to the aileron. I have seen too many guys have flutter with sloppily set up belcranks. Hey, don't get me wrong, belcranks will work. There are just more places for slop which promotes flutter. I also like cables for rudder. My rudders always have the maximum throw, so a little slop at the servo or any play in the servo gears is multiplied at the rudder. With cables, you can tighten everything up. I have never had a cable operated rudder flutter. I take that back, I did, too. I remember one time that I rushed a test and forgot to tighten up the cables. The rudder had about an inch of play and it had minor flutter, not the violent buzz, but a slow wiggle back and forth. I noticed it on a low fly by, landed and found the loose cables. I tightened up the cables like I should have done before the test and the flutter went away. I have used both single and dual pushrods and also cables on my elevators and haven't noticed any flutter with either setup.

The place I get flutter, when I get it, is on the ailerons, so I always take precautions with them. Flutter occurs at high speed, so if you have a slow plane, you probably won't get flutter. Watch it, however, you may pick up enough speed in a diving turn. Remember last time I mentioned the Fly Baby which got bad elevator flutter in a diving turn. In addition to giants, I fly some 40 sized fun fly aerobatic planes. These little guys use max control throws and can get going pretty fast in a full power, vertical dive, so the conditions for flutter are present all the time. I can say that I have gotten flutter and cured it (boy, that sounds like a disease) and here are my prevention and cures.

From my observations and experiments (crashes), I have found that flutter on ailerons occurs at the end of the aileron out at the wing tip. I also found that if I move them in about 3 to 4 inches from the tip, any flutter tendency goes away. Take a look at the drawing and you'll see what I mean by moving them in.

If you are building a non-scale plane like a giant stick with strip ailerons, cut off the last 3-4 inches and glue it to the trailing edge of the wing. This "fixed" portion of the aileron won't flutter. I used to do this to 60 powered Ugly Sticks.

If your wing and ailerons are already built and you are getting flutter, try cutting off the last 3-4 inches of aileron on a diagonal as shown in the photo. Sorry that I don't have a giant with this mod, but the diagonal cut offs are illustrated on this original, 40-50 sized, twin-tailed design of mine called the Scrambler. I am drawing up a giant Scrambler with plug in wings. I think 80 inches and a G-62 ought to be just right.

Another thing you can do on all control surfaces is to keep all the edges sharp and all lines straight. Look at the drawings of control surface cross sections and notice which are good for preventing flutter.

A and B are the ones I used for years until I started having flutter with pattern planes. After a little research, I started doing a better carving and sanding job like drawing C. On all of my giants which have tail surfaces built from 3/8 square, l use elevator and rudder cross sections like D. You got it, flat with square corners and sharp edges. Saves time, easy to cover, and looks like drawing E. That's right, don't bother tapering the balsa sheeting. Glue it together and sand it square. Remember, flutter loves nice rounded edges and curving surfaces, but it hates straight lines and sharp edges.