Vortex Generators or Turbulators ...Huh???

[satdave]

Guy's

I need some help with my Comp-Arf 3.3 YAK , It's new with a pretty potent power package ( DA-170 w/ RE-3's). I have experienced flutter on the elevators several times , something none of my 40%'ers has ever done. It only does it at higher speeds . I know it's destructive so the plane is grounded now.
I talked to my old buddy Mark Trent who has advised me to use these 3/16" PVC "L's" to effect a remedy to the aerodynamic flutter. Any one have advice, experiences or comments on a fix. I'm running Futaba 9156's x 2 with SWB Arms. Desperate to fix it because it fly's so well.

[hpapilot]

Are the elevators properly mass counterbalanced? I.E., do they have enough weight in the counterbalance so that they sit neutral with no linkage connected? Also, are your linkages/servo geartrains pretty tight?

[satdave]

One Droops, the other stays put, everything feels tight. Servos are new ( 4 Flights).

[Mithrandir]

It is possible the STAB is fluttering and not the ELEVATOR.....

I am not sure (aerodynamically) what the trailing edge drag'r'vators do. I have seen these employed on the rudder of the 3.0 extra as people have suggested the counterbalance was too big and it wandered in yaw.

If this was my plane, I would use a dremel to open a hole on the inboard face of the counterbalance... what you might think of as the root rib on the counterbalanced part of the elevator.... the region ahead of the hinge line.....
I would open about a 1/2 dia hole, and then mix about 3 ounces of lead birdshot with 30 minute epoxy into a lead shot/epoxy slurry and then pour half into the left elevator leading edge and half into the right elevator leading edge.... this is simply Mass Balancing to increase the flutter speed.

As a test, you can externally tape some lead to the leading edge and see if that fixes the problem.

[hpapilot]

Do you know if both elevators fluttered or just one? They dont necessarily have to be perfectly balanced, but if only one fluttered, that may be a good culprit to examine.

T-strips on the trailing edge may or may not help. I've seen this more on the rudder, but usually for tracking, not flutter.

[satdave]

	Quote: Originally Posted by Mithrandir
	It is possible the STAB is fluttering and not the ELEVATOR..... I am not sure (aerodynamically) what the trailing edge drag'r'vators do. I have seen these employed on the rudder of the 3.0 extra as people have suggested the counterbalance was too big and it wandered in yaw. If this was my plane, I would use a dremel to open a hole on the inboard face of the counterbalance... what you might think of as the root rib on the counterbalanced part of the elevator.... the region ahead of the hinge line..... I would open about a 1/2 dia hole, and then mix about 3 ounces of lead birdshot with 30 minute epoxy into a lead shot/epoxy slurry and then pour half into the left elevator leading edge and half into the right elevator leading edge.... this is simply Mass Balancing to increase the flutter speed. As a test, you can externally tape some lead to the leading edge and see if that fixes the problem.

Looks like you have one.....ever did it to you?

[satdave]

	Quote: Originally Posted by hpapilot
	Do you know if both elevators fluttered or just one? They dont necessarily have to be perfectly balanced, but if only one fluttered, that may be a good culprit to examine. T-strips on the trailing edge may or may not help. I've seen this more on the rudder, but usually for tracking, not flutter.

First time was the right side ( the one that droops) last night they both did it. I had 6 pairs of eyes watching.

[hpapilot]

I would suggest first of all ensuring that both are well mass-balanced. Besides that I'm not sure what to suggest. You could try a small T-strip, I can't see it hurting much.

[Mithrandir]

	Quote: Originally Posted by satdave
	Looks like you have one.....ever did it to you?

My old SX would occasionally flutter at high speed....
you might also consider putting the little nylon bushings from McMaster Carr on the short hinge plates that stick out of the trailing edge of the stab and inside the leading edge of the elev's...... without the bushings, over time, the holes wear and get bigger causes some sloppyness to develop

If you go the mass balance route, prolly you don't need full mass balancing.... this can cause other issues as mass will increase the rotational inertia of the elevator and that is a whole different set of problems

[Bill Clark]

Gurney flap
http://en.wikipedia.org/wiki/Gurney_flap

[satdave]

	Quote: Originally Posted by Mithrandir
	My old SX would occasionally flutter at high speed.... you might also consider putting the little nylon bushings from McMaster Carr on the short hinge plates that stick out of the trailing edge of the stab and inside the leading edge of the elev's...... without the bushings, over time, the holes wear and get bigger causes some sloppyness to develop If you go the mass balance route, prolly you don't need full mass balancing.... this can cause other issues as mass will increase the rotational inertia of the elevator and that is a whole different set of problems

OK, the bushing thing is done. Where do you suggest the lead be added..........on the inside right ? of the counter balance.

[satdave]

Took Right side apart , tightened the mini tray up again. Might get a chance to use the self adhesive weight for a test on Sunday.

[Wojcigitty]

Subscribed, I'm interested in your results.

[Mithrandir]

you got it... on the root-leading edge rib on the counter balance..... drill or grind a hole near the leading edge.... and just slurry an ounce of epoxy-lead shot in the hole, set it leading edge down during the cure so it goes as far fwd as possible.

Yes... keep us posted on the results.....

[satdave]

Will fly it tonight. I added some sinkers I had for a total of 1.42 oz on each side. Fingers crossed.