Rodney

Dirtybird, sorry I have to dissagree with you that static balance helps flutter. It definately does nothing in that catagory. It does take some of the load off the servo; and dynamic balancing would take even more load off the servo. neither has any effect on flutter however.

GPitts

My Feedback: (6)

I just got back from flying a few hours ago and flew 4 flights. If I'm not mistaken I surely did not hear any flutter sounds, so did my buddies that came out with me. I asked them to tell me if the can hear any flutter but they never said anything. The plane seems fine now right after I fixed the right aileron.[8D]

JL1

My Feedback: (93)

Hmmmm, my Midwest extra 300 had flutter until I counter balanced the ailerons. After that, no more flutter.

greg53

mag 52xls can turn up to 15k harmonic vibration?

greg53

also did you balance the prop? at that rpm the vibration on an unbalanced prop gits intense

jaka

Hi again!
Glad you have fixed the flutter on your airplane.
Most of the time there is flutter on a modelairplane it's the ailerons that flutter never the siderudder. The elevator could ofcourse flutter too but long soft balsa ailerons are usually the culprit.
I have seen ailerons flutter many times in pylonracing, especially on airplanes with ailerons that go out all the way to the wing tip.
I have also seen whole stabs that flutter but this is usually easy to see in flight as the whole stab vibrates.
Fixing aileron flutter is easy as you only tape the outer part of the aileron to the wing.....Thats right...you tape them together!
The tape to use is called 3M "Plastic. You tape the upper side and lower side of the aileron to the wing.
This tape is so flexible that the aileron servo has no difficulty moving the aileron...only the outer part of the aileron is slightly hindered to move...but this will not make the airplane sluggish in any way.


It is important that the tape do not go all the way to the aileron trailing edge as it will make the ailerons to tough to move for the aileron servo.

This is how pylonracers all around the world fix their aileron flutter if they have any.....
See pictures of my Q-500 racer!

Regards!
Jan K
Sweden

Propwash in Pa

Wow, this is some transfer of knowledge. Jan, do you also seal the hinge gap? Typically, I seal all gaps from the underside.

John - 373786

TexasAirBoss

My Feedback: (22)

About 1990 I built a twin. Our field was small and surrounded by trees. So I decided I needed flaps. I used torgue rods on the flaps and the ailerons. Imagine a torque rod 14 inches long. I don't know what I was thinking. Well, needless to say, those ailerons fluttered all of the time. So I put ballancers on them. Something like this. And with those stupid torque rods, that plane flew great for 11 years until I sold it. I think it is still flying.

dirtybird

My Feedback: (5)

I am sorry you disagree. I can put you in touch with a Boeing design engineer that disagrees with you if you like and you can explain to him why you disagree.
For your information I cured a flutter problem by static balanceing so I know it works for me.

dirtybird

My Feedback: (5)

You may want to check this out:

http://www.stormingmedia.us/95/9508/A950823.html

fledermaus

Some postings have suggested that the sound might not be due to control surface flutter. One possibility that has not been mentioned is your radio antenna. I could not see where it is from your photo of the Me-109, but if it is possible for the antenna to drum against the covering material you will get a sound very similar to flutter.

I discovered this by experiment, because my plane (not a fast warbird, actually an LT-40 trainer) has the antenna run along the bottom surface of the fuselage outside, retained by an elastic. If the elastic is too loose, the plane buzzes like its about to tear itself apart, but it is just the antenna wire beating on the fuselage surface.

Since you have adjusted, tightened and otherwise tweaked a lot of things relating to your control surfaces, I suggest this for what it's worth. On the other hand, I wouldn't be surprised that at >100 mph a single aileron servo working through torque rods might not hold full-span ailerons rigid.

geritol

Rodney: I would like to know how you dynamic balance an aileron, this is not like balancing your car tires. Also, did you ever read about the elevator flutter problems that the P- 38 (full size) had until they balanced the control surfaces.

Rodney

The reason your fix apparently stopped the flutter was most probably not beacuse of the counterbalance but because you changed the moment of inertia and thus the natural frequency of the assembly. You would most probably have acheived the same results by just making the original assembly of more dense material. I spent quite a few years in instrumentation of real aircraft, lots of it on flutter measurements and changes in structure to prevent said flutter on several military aircraft. Anything can and will flutter given the proper stimulus, the secret is to make sure that area of resonance falls outside your flight spectrum. Counter balance does not, of itself, do anything to prevent flutter but: if you added mass or stifness to any part of the system in the process of adding counterbalance you did change the natural frequency of that structural member. The flutter stopped because of that, not because of the counterbalance functioning as a counterbalance. Flutter and its causes and effect are a very complicated subject and you find much dissagreement amoung even the accepted experts.

Rodney

Geritol, static or dynamic balance is when the weight of the member is balanced on the hinge line; i.e. mass balanced. Aerodynamic balance is when the forces on the surface member is equal in the front and back of the hinge line. In real life, you never want complete aerodynamic balance or you will have problems maintaining a neutral position. Especially on large models, static balance will save many servo gear trains by preventing shock loads caused by hard landings as well as not having the effects of gravity causing undue servo drain when there are no air loads on the surfaces such as when parked or taxing.

dirtybird

My Feedback: (5)

Ah yes there is much disagreement. Kelly Johnson destained "those little weights". I notice that after a certain mod letter all P-38's carried counterweights on their elevators, however.
I agree that the counterbalance fixed the flutter because it changed the moment of inertia and natural frequency of the assembly. That is precisely the reason for adding the weights. In so doing it stops the flutter. Counterbalancing also removes a source of power (gravity) from the resonance equation. Adding weights increases the moment of inertia and can itself power a flutter so adding weights is not the final answer. But it works quite well at the speeds our models fly.
I agree flutter correction is a complex subject. I also noticed that all full scale aircraft balance their control surface. It seems they would rather make sure that is taken care of before trying other things.