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Eliminating flutter with more servos?

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Old 11-07-2005, 12:47 PM
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kevinbell
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Default Eliminating flutter with more servos?

I have a 30% Extra 300 that I'm building and have made the control surfaces a little larger for it to be capable of 3D.
It's an I.A.D model designs Extra. I was thinking of putting in two servos per aileron to try to eliminate flutter and gain reliability. The ailerons are full wing length and a bit deeper than standard, I wanted to know if it's worth putting in a second servo? I have two 9202 futaba servo's that produces 7.1 kg/cm @ 6V, are these enough?

Any suggestions?
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Old 11-07-2005, 01:07 PM
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redfox435cat
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Default RE: Eliminating flutter with more servos?

With putting 2 srevos per side your going to have to spend alot of time setting the linkages up perfect so the two servos are not working against each other with unsinked movments. With two servos per side if one dies it will just hinder the other one. one servo perside will have the just as much a reliability factor as 2 per side. I recommend getting a stronger servo for each side. Even up to a coreless high speed if it is that much of an issue.
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Old 11-07-2005, 01:52 PM
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Default RE: Eliminating flutter with more servos?

The size of the servo has little or no effect as to whether or not you get flutter. Everything will flutter if given the right input (perhaps I should say if the wrong input happens, as you do not want the flutter). The way to eliminate flutter (in the dynamic region you are flying) is to have the natural frequency fall outside the range of the inputs which cause flutter. This is done by having very stiff surfaces (raises the frequency above that of the stimulus), having no slop in hinges or linkage and haveing very stiff linkages (can't bend or bow under load). If you have to have two servos per surface, you would be better off cutting the surface in half and driving each half with its own servo. This would also eliminate the need to make each servo track each other perfectly.
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Old 11-07-2005, 02:54 PM
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Default RE: Eliminating flutter with more servos?

If you have to have two servos per surface, you would be better off cutting the surface in half and driving each half with its own servo. This would also eliminate the need to make each servo track each other perfectly.
If I read this correctly, turn each aileron into a ron and flap. Would you use a Y or seperate channel for each servo?

kevin, what is the new surface area dimensions of the ailerons? How much torque per sq inch? ( Futaba 9202 6.0V 98.5 oz-in. 0.21 sec/60° )
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Old 11-07-2005, 03:42 PM
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Default RE: Eliminating flutter with more servos?

kevin, what does the designer recommend???

taking several of the above suggestions.... if the linkage is tight, the hinges are tight and sealed, and the surface is well built... one servo could be enough, (something like a 5955 or even 5945) but it all depends on how the plane is designed.....

Which plane is it, who designed it? who kitted it or is it scratch....

2 servos per aileron are the norm on 40% and similar...but if you do multiple, then you are adding the weight of servos, matchboxes (if needed), linkages and hardware, and potnetially more batteries to power to servos...
not a problem, just things to think about
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Old 11-07-2005, 04:12 PM
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kevinbell
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Default RE: Eliminating flutter with more servos?

I calculate the ailerons surface area to be 159.8 in squared, each. They are tapered as well. 38 3/4" x 4 3/4" at the root and the tip is 3 1/2"
Hope this makes sense.
Thanks for the info.
The name of the designer is I.A.D model designs that's a kit build.
http://www.iadmodeldesigns.co.uk/extral.htm
He recommends 1 servo per aileron but I've made the surfaces slightly bigger. I'll be using ball joints and two horns so it's mounted double sheer and film for hinging.
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Old 11-07-2005, 04:21 PM
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Default RE: Eliminating flutter with more servos?

Good looking plane!
notice that the decals are upside down on the rudder??

Hmmm... tough call... honestly I think you could go either way......
but I do not claim to be an expert
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Old 11-07-2005, 06:07 PM
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Default RE: Eliminating flutter with more servos?

S9153 High Speed/High Torque
FUTM0213
Volts Torque Speed
6.0V 208 oz-in. 0.15 sec/60°

torque area in oz/ sq in
98.5 159.8 0.62 9202 Futaba servo


208 159.8 1.30 S9153 Futaba

Agree with Rodney, but I would still like the extra holding power of a larger servo. Nice looking model.
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Old 11-07-2005, 08:12 PM
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Don M.
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Default RE: Eliminating flutter with more servos?

I have a bunch of 9202 servos and always swore buy them, until recently when I put them on the ailerons on a Balsa Nova 120 with a 26CC gas engine. In about 10 flights I stripped one and then 10 flights later I stripped another. I pulled them and installed Hitec 5625's, much better control and no more stripped servos. This is the first time I have been able to evaluate digitals alongside of analogs and all I can say is that all of my 150 + powered planes will now have digitals and probably will be MG's also.
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