<div style="margin: 0in 0in 0pt">I have an E-Flite Eratix 3D 25e and I&rsquo;m have a problem with aileron flutter, I&rsquo;m using the recommended Hitec HS-225MG servos at 5 volt and the E-Flite 32 motor. Does any one have any idea&rsquo;s ?</div><div style="margin: 0in 0in 0pt"></div><div style="margin: 0in 0in 0pt">Thanks</div><div style="margin: 0in 0in 0pt">Jim</div>

Check all your connections for slop, you don't want any. Check your hinges and make sure they are tight. Then if you still have a problem try sealing the hinge lines. ENJOY !!! RED

How fast are you flying?

IF-all else fails simple mass balance will stop the problem. These would be made smaller for the small electric.

John

Good question, especially since this plane was designed for 3D.

How wide is the hinge gap? Quick test is to use some scotch tape and seal the hinge gap and go for a test flight.

Do check your linkage and make sure that there is no slop.

Carefully check the aileron servo mounting brackets. A friend of mine had your airplane seals the hinge line but a few flights later the aileron sevo came out od the wing on landing..with the wood it was screwed to

There's another thread about flutter on a great planes model. They replied with an instruction sheet showing set-up for linkages. basically, the best setup has the link rod connected to the outermost hole on the aileron horn and the innermost hole on the servo arm.
Next best is to have the link-rod on the outer hole of the aileron horn and outer hole of the servo arm.
Completely undesirable is to have the link-rod on the inner hole of the control horn.
Unfortunately, most 3D setups need monster control throws and this is how people achieve them!

If all else fails a simple mass balance will solve the problem.

Often servos that won,t stay screwed down or servos that mysteriously strip gears, pushrods that seem to fail, one or more hinges keep failing clevis keeps failing are actually just symtems of ongoing flutter that you may not even be aware of.

Yes these items will need to be fixed but that in itself is not going to stop the problem. I have never run across a case ever that sealing hinge gaps has actually stopped the problem. The one thing that will is mass balance.

Flutter analysis is a horribily complex subject and a dedicated engineering discipline in itself and its not all that uncommon to run across a design that is subject to the problem. Every problamatical design that I have had this situation with and became aware of it by constantly stripping servos or the classic maching gun sound and happened to survive the flight has been cured completely with confidence simply by mass balance either with the little guy I pictured or by imbedding a bit of lead in the forward ends of aerdynamic balances of some control surfaces.

I have taken to doing the imbedded mass balance on a number of other folks airplanes which happen to be airplanes known to be flutter problems and this does eliminate the problems at any speed at which the airplane may be capable of reaching.

Perhaps more designers should go ahead on many of these designs with the giant and flexable control surface should plan for this with imbedded mass balance.

John

This bares repeating so the "sealing the hinge" myth is not repeated!.

I sealed the hing gaps with tape and it did not help. Does anyone know if I increase the BEC volts to 6 will that help, it will give me more servo torque. I would also like to here more about balancing the aileron.

Thanks
Jim

Exactly what does the plane do to make you think there is flutter? And did you go over all the linkage to check for slop, including the servo?

I'm not familiar with your aircraft but I've seen some build videos where the push rods where just made from flimsy material and would be susceptible to this problem. They put the push rod through something like a tiny eyebolt attached to the plane to stop the flexing of the pushrod.

Often in larger airplanes installing higher torque servos will not help. Low servo torque is not what causes flutter so uping your servo power is not really going to help.

For a small foamy or a small electric and forgive me I am not familiar with your airplane just roughly scale down the simple device I pictured in an earliar post.

The idea is in a perfect world if you disconnect the aileron or perhaps the elevator from the pushrod and it will tend to drop at the trailing edge. Now what we want to do is balance some of this weight by applying a bit of lead forward of the hinge line as you can see in the picture.

What we do not want to do and thats a good thing is to completely balance the surface so that if there were no hinge friction it would sit level or wherever you released it. Agine that is not what we want to do. Its been in my experiance that it only takes perhaps 5 to 10% of the weight of the control surface.

What that will do is not stop futter but it will push the onset of the flutter threshold to a higher speed that your airframe cannot acheve.

The actual weight you see or the distance forward of the hingeline is not critical it only needs just a small percentage of 100% balance to get that threshole up there where you will never fly. So do not be afaid to experiment a little.

Here is a photo of a fellows simple little eighty dollar airplane that had already cost him around 300 bucks in four servo's each time destroying the aileron servo(s) and each time he keep throwing more money at expensive servos that would not help the real problem i.e. flutter likely caused by excessive aeroelasticity of the surface.

I gave him one of the little balances that I had in my box and he finally was talked into poking into the airlerons and bingo. That airplane never had the problem agine after flying a hard life now perhaps four years.

John

I hesitate to disagrees with Mr. JohnBuckner as he is most often correct. Now, while mass balancing is a big aid in many cases, it rarely corrects a flutter problem but does help in many other ways. Flutter is when a surface continues in oscillation once energized by some external force and a mass balance can remove some of this external stimulation. However, it has not changed the resonant frequency of the surface so, if it gets stimulated by some other force like wimpy push rods, sloppy hinges etc. it will still flutter. The ideal surface that will never flutter is one that has zero mass and infinite stiffness (an unobtainable condition) but you strive for that by building the surface as light and stiff as you can and make sure you have very stiff control rods (or push-pull lines) and zero slop in all pivot points. On ailerons, you can often stop a flutter problem by laminating a very thin layer of material over the top of the existing surface. This makes it stiffer and also, if the leading edge of the aileron is slightly thicker than the trailing edge of the wing surface it is mounted to, you remove a lot of the stimulus that caused flutter in the first place.

The "Myth" about "Sealing hinges" is that people believe that air flows through the small hinge gaps we use and that thereby causes flutter.

All too often the very first suggestion given to cure flutter is to "seal the hinges".

This is poor advice as it does not eliminate the resonance developing in the surface that causes flutter to begin with.

If sealing the hinges has any effect, it is due to the relatively minimal stiffening benefits it has, to help cure lateral movement along the entire hinged surface.

However having one part of the control surface moving out of plane with the other part ( e.g. a twisting force ) is rarely ever the cause of flutter that we see in our models and if it were a CF rod inserted in the surface is a much better solution.

Typically the entire surface tends to vibrate.

As you suggested a first line defense is to make sure all the linkages are tight, and if possible maybe even use multiple servos to hold the entire surface stiff.

Mass balancers are however used even in large aircraft to help reduce or eliminate flutter. Assuming lateral stiffness, they can indeed help eliminate flutter problems and can be so effective that they often appear to be a magical fix. I've used John's technique to make flutter "dissappear"

Ultimately the real "fix" is to fly the plane within the design parameters that it was built for.

Thick winged planes with large control surfaces are not designed to fly as fast as I often see people doing on their overpowered aircraft running at constant full power!

Gentlemen......I agree sealing the hinge line is not a cure for flutter...no more than a cough drop is for a cold.....in my post I said that my friend sealed his hinge line.....and later his aileron servo came out of the wing with the wood that it attached to still screwed to the servo.....you must have slop somewhere to have flutter......and an aileron servo not properly attached to a wing would do it....all I am suggesting is to take a careful look at your aileron mounting bracket in the wing....as there is a history of at least one servo coming out of the wing.....Good Luck

Many, if not most, of the electrics have very thin and almost flimsy linkage to control surfaces. This is to keep things light but often, if the linkage is not installed correctly, it will flex and bend when pushed to a point where it will bend and flex.

Reading the above, two primary causes are very clear, at least to me. One is, as I mentioned, linkage. Either sloppy, loose, or lacking strength. The other is speed. And, speed will force linkage to bend, flex, or oscillate (ie. flutter).

As opjose said, this is a 3D style aircraft and if you fly it as if it were a racer, well, you're going to get flutter.. but consider the reason. The cause may be because of the "flimsy" linkage rods that bend and flex under stress, stresses caused by higher than normal speeds.

If you are not flying it faster than it was designed to fly, then consider the other reasons it may be fluttering, mainly linkage either not strong enough for that plane (if it came with that linkage then it should be appropriate for that style of aircraft) or it's just plain loose.

Check everything that has to do with linkage and make sure that there isn't even a slight bit of slop in the connections. If you have some, do your best to remove.. tighten up the connections so that any and all slop is removed. You can also get stronger linkage that is not a weight issue, or reinforce the path for the linkage by installing light-weight supports for the piano wire to pass through.

CGr.

Here we go again, the cause of flutter is a never ending debate.

And finally (?)
Even if the linkages are all tight and stiff and not bendy at all, the surface can STILL flutter if it can be flexed away from the point of attachment of the horn (ie the surface itself is not stiff)
IMAC models sometimes use 3 servos per surface.
Ailerons with torque rods into the fulselage can twist considerably (and flutter).
The dead certain cure is not to fly so fast.

True, but this is VERY RARELY the cause of flutter on these small 3D planes the OP is talking about.

And even then if this does occur a better fix is to re-inforce the flexy area with an inbedded CF rod or other similiar technique, that is actually effective.

I had problems with "flutter" on my Nexstar. Seeing this thread gave me ideas to check out. I found that the push rods had "wobbled out" the holes in the servo control horn. ( This wing has seen a few crashes.) The rods into the airlerons were still nice and tight. I moved the control rods in one hole on the control horn, and will check out my work the next time I fly. The controls are tight again, so hopefully the problem is cured.

Art
AMA 915882

I had a plane that developed elevator flutter, and when it happened a second time, it cost me the airplane. The elevator servo gears had stripped. That is how I learned about flutter.

This plane was designed to go fast. Next time, I used a counterbalance, or mass balance, on the elevator. I had no further flutter problems.

I also had an overpowered Ugly Stik that had aileron flutter, and a small mass balance on each aileron tip, outboard, solved the flutter problem.

Sealing the control surfaces will result in a more responsive surface, but I agree - in most cases, that will not affect flutter. A stiffer, heavier control surface will tend to reduce flutter, though.

What I would like to know, is if a control surface is made a bit thinner than the airfoil profile would dictate, will this minimize a flutter potential? Or is the opposite true - a control surface that is slightly thicker, that protrudes into the airstream at the leading edge of the control surface, would that minimize flutter? Put another way, will sanding the forward edge of a control surface, so that it is flat, and a bit thinner than the wing section that it is hinged to, will that minimize flutter?

Next question - will a rough surface on a model, like a rough fiberglass cloth surface (much like the dimples on a golf ball, which allows it to travel farther), permit a model to fly faster? (As one can tell here, I like to fly fassst!).


Jim

I can not answer the other questions with any degree of authority but: as to having the leading edge of the aileron slightly thicker than the trailing edge of the wing where the aileron attaches has often been shown to be beneficial in minimizing the onset of flutter, maybe by increasing stiffness as well as helping reestablishing airflow. Another thing often not considered is where the aileron horn is attached. It should always be at an add division of the span of the aileron, i.e. 1/3, 2/3, 2/5, 3/5 etc. as this minimizes the chance of inducing flutter due to the harmonics caused by span wise flexing of the aileron. You still need to shoot for the impossible, as stiff as can be without adding mass. While a counterbalance is usually beneficial, it has little or nothing to do with reducing flutter except for the fact that adding it probably changed the mass (and subsequent resonant frequency).Mass balance does minimize the forces required on the servo though, especially under high G loads as the effects of momentum balance out relieving the servo of having to overcome that force.

Oh no it isn't

Better than eliminating the cause of the flutter?
You're writing rubbish man.