Extreme Speed Prop Planes Discuss the need for speed with fast prop planes (Screamin Demon, Diamond Dust, Shrikes or any REAL sound breakin'''' plane)

Outlaw Flutter

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Old 08-23-2004, 06:52 PM
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rightflyer
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Default Outlaw Flutter

I have an Outlaw with a 25FX. I think I have heard mild flutter so have decided to rethink my servos. First, any ideas which surface flutters--Elevons or Rudder? I am current running standard servos with a five cell pack what is the minimum servo torque should i use?
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Old 08-23-2004, 07:43 PM
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evan-RCU
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Default RE: Outlaw Flutter

I've built at least ten Outlaws and we have many more at the field, all fly on .32 or bigger engines with 8+ pitch props(in other words SPEED). none have ever had a flutter problem. All have used standard or better servos on 4.8V. I don't think the servos are your problem. Maybe hinge gap or something else, do you have a camera so you can show us the hinge area of teh elevons and the rudder.... also the servo push rods and control horns...
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Old 08-24-2004, 09:54 AM
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Default RE: Outlaw Flutter

Make sure to seal the control surface gaps. One side only, use either covering material or simple tape.

The servos alone will not cause the flutter, although sloppy linkages can permit its amplitude to get out of hand.

Flutter is caused by rapidly changing pressure differential at the control surface. Sometimes turbulent airflow at the TE or seperated airflow will cause this. More commonly, odd airflow through a control surface gap can cause this condition. Airspeed plays into this, as the speed determines the pressure differential between the upper and lower surface of the wing (in otherwords, lift).

Having good servos will permit you to survive this condition, but it won't prevent it.

There is no racing, aerobatic or speed aircraft I fly which does not have each control gap sealed. It avoids this condition, ensures that the control authority at each elevator/aileron is the same as for the opposite side, and and also results in increased control surface authority (requiring less throw to achive the same aircraft response).

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Old 08-24-2004, 12:28 PM
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Default RE: Outlaw Flutter

is it even possible to get flutter on any 25 aircraft

it might be just the engine noise vibrating through the plane. whats it covered in?
i've got 148's on a 37 with pipe, even full power dives don't phase it.
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Old 08-26-2004, 05:41 PM
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rightflyer
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Default RE: Outlaw Flutter

Thanks for your tips. I do not have my surfaces-not sure why not, I usually do. I tried to upload a pciture of my setp with no luck.
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Old 08-28-2004, 08:36 AM
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Default RE: Outlaw Flutter

If you want to add some strength to the control surface and minimize the chance of flutter or oscillation to even begin, you can make a control horn that extends further out on the control surface.This added leverage increases the support to the control surface and distributes the load further out, rather than having the load all at the hinge line.Check out the picture of my wing on the Speed Models Stinger 21 thread, you will see my home made plywood control horns.These are glassed both sides and are very strong.This in combination with sealing the surface will minimize the chance of any flutter.Regards Chris.
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Old 09-01-2004, 05:13 PM
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Default RE: Outlaw Flutter

Just seal the outer surfaces of the elvons about 3" should do it .
This works on about any aircraft . Is the surfaces made of soft balsa ?
You should use only hard balsa on the control surfaces .
Also use Ultracoat or Monocote hinges this is simple and will head of any flutter in the future .
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