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Aileron flutter Fliton Inspire 60, what now?

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Aileron flutter Fliton Inspire 60, what now?

Old 04-11-2007, 10:31 PM
  #1  
JoeyCoates
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Default Aileron flutter Fliton Inspire 60, what now?

I just finished building a Fliton Inspire 60 about two weeks ago, but due to weather/being out of town have only flown it three times. The first two flights were short due to tuning the engine (deadsticks) but on the second flight I thought that I heard some flutter but was not sure. I flew it again today and it definatly has some severe aileron flutter, I really cannot believe that the wings did not come apart! I am talking not only hearing but seeing the flutter, the whole wing was just starting to get into the oscillation but I had chopped the throttle so the airplane slowed before it could really get going. all of the hinge lines are sealed, the aileron servo's are JR DS821's, and I used Nelson Hobby 4-40 heavy duty ball links with 4-40 rods. The servo horns are Du-Bro Super Strength JR servo arms. I am posting some photo's so that you can see the linkage setup and see if there is something obviously wrong with the installation. Oh, the control horns are World Model horns which I have always cosidered to be pretty good.

The airspeed was not very high when it began to flutter, about mid throttle, YS91ac, 15x8 APC, all up aircraft weight 6.5 lbs.



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Old 04-12-2007, 01:54 AM
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alan0899
 
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Default RE: Aileron flutter Fliton Inspire 60, what now?

G'day Mate,
I believe your problem may stem from the 15x8 prop you are using, go for a lower pitch, probably no more than 6"pitch, that should help keep the speed down a bit & use your throttle, these planes are not designed for high speed or high pitch props.
You already have it way overpowered, with the 91.
Another problem would be the ball links on your ailerons, take the ball links off, & use clevises, the way it is now, it is pushing & pulling on the side of the horns, & they will twist, if you use clevises, the chance of twist will be reduced, if not eliminated, as the push rod will be in line with the horns.
Old 04-12-2007, 09:32 AM
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RCVFR
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Default RE: Aileron flutter Fliton Inspire 60, what now?

alan0899 has the right idea. Rule #1 for designs with oversized control surfaces is thet "speed kills". 8 pitch is way too much, and even 6 might be too much. Try a 4" pitch and see how much better it is for your type plane.
Old 04-12-2007, 10:20 AM
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JohnBuckner
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Default RE: Aileron flutter Fliton Inspire 60, what now?

Simple mass balance works with a known problem surface


John
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Old 04-12-2007, 12:00 PM
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Default RE: Aileron flutter Fliton Inspire 60, what now?

I would leave the ball link on but take out that spacer between the ball link and the control horn. Definitely go to a lower pitch prop and fly slower, speed killed alot of Funtana 90's
Old 04-12-2007, 12:49 PM
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scratchonly
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Default RE: Aileron flutter Fliton Inspire 60, what now?

Is your aileron LE thinner than the wing trailing edge? This has been known to cause flutter. As stated speed kills.
Old 06-26-2008, 12:14 PM
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Zippi
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Default RE: Aileron flutter Fliton Inspire 60, what now?

JoeyCoates,

Everyone has hit all the credical points and I might add one more. I always seal the control surface gaps. I'm flying a GP Reactor with a Saito .82 spinning an APC 14X4W prop to keep the speed down and at the same time it creates a lot of low end torque for hovering.
Old 06-26-2008, 12:52 PM
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Rodney
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Default RE: Aileron flutter Fliton Inspire 60, what now?

I dissagree on the ball links, they are very good (much better than clevises). Check your hinges, are they slop free and inline? Are the materials in the ailerons stiff (no soft wood or easily flexed material)? The flutter may not be in the ailerons, it could be the wing itself fluttering. Is the wing easily twisted or flexed.
Old 06-26-2008, 02:01 PM
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krossk
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Default RE: Aileron flutter Fliton Inspire 60, what now?

It looks to me like the combined use of the ball link and the threaded control horn allow for movement.
If the tab on the horn rotates even a couple of degrees, the ball joint can flex and allow the control surface to deflect slightly.
My suggestion is to use one or the other, but not both.
Old 06-26-2008, 02:16 PM
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jaka
 
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Default RE: Aileron flutter Fliton Inspire 60, what now?

Hi!
The problem is speed and large flying surfaces!
15x8" is way too much pitch!
Go with a 16x4 or 17x4 instead!
The Fliton is a 3D airplane not an aerobatic F3A airplane!

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