flutter problem
 

ok i got a funtana 90 and i have a flutter problem on my downlines... i have a saito 150 on it hitec digital metal gear servos. 200 oz
why does it flutter so bad and what do i need to do to fix it..

RE: flutter problem
 

4 things come to mind.

1. Seal the control surface gaps.
2. Ensure that the servo/control surface linkage is slop-free.
3. Ensure that the servos are set up with the proper advantage. Ie, the servo arms must NOT be longer than the control surface arm geometry.
4. Control your speed.

Safe Flying!

RE: flutter problem
 

I've lost a plane to flutter that was a chronic problem with it.

The older Funtana 90 ARFs were known to have problems with the wings breaking if you flew too fast. I think they have fixed that in the last year or so. Funtanas do have critical speed limits.

The problem with gaps isn't the gap itself in regards to flutter. It is a combination of gap and uneven control surfaces such as an elevator installed with one side higher than the other. This means that you have an uneven amount of that surface up into the air stream and the imbalance starts the fluttering. Sealing the gaps does give a smoother flying plane.

Control linkage slop may be where your problem lies. My plane only had elevator flutter when it was balanced correctly. Having it nose heavy would stop the problem, but the plane flew badly then. How fast are you going on those downlines? Are your push rods stiff and secure?

RE: flutter problem
 

Viper,
Does it flutter on the ground or in the air, and what exactly do you mean when you say "downlines"? Reason I ask about the ground is because I have a Flip with digitals in it and sometimes it flutters on the ground. I think the reason is, the digitals are so precise any movement and the servos immediately correct. Its kinda hard to describe. It stops immediately when you move the control surfaces (on the ground) in the air you have, of course, air pressure on the surfaces, so no problems.

RE: flutter problem
 

Viper,

Does the flutter happen in all DL's or only WOT DL's? Oh, and BTW if it was 'BAD', you would have a much more travel-friendly airplane by now.

RE: flutter problem
 

sealing the gap wouldn't do anything to stop flutter
metel gears have more slop then nylon so you really need tight control connections
too much speed can do it also
there no one answer

RE: flutter problem
 

In most cases, the speed only aggravates another existing problem. It isn't the problem without another contributing factor, like slop in the linkage, uneven control surface alignment, or structural weakness that sets up vibrations. I had a Major Hobbies Fantasy that had chronic problems with elevator flutter. Skyshark RC took over the kit and redesigned the rear of the fuselage to stop flutter. The owner listed the changes somewhere here on RCU.

The original Funtana problems were related to too little structure in the wings. I think they added an extra rib near the servo to help. It wasn't flutter. The wings would break off.

RE: flutter problem
 

Right on the money Skiman. All sealing the gaps will do is change the conditions under wich the sufface will flutter, but they will still flutter. Find out where the slop is comming from at all deflection angles and correct it. That's your problem.

Rrragman