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Old 11-16-2014, 12:09 AM   #1
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Default Drooped ailerons

What's your opinion of drooped ailerons for helping with tip stall problem?

Life's journey is not to arrive at the grave in a well preserved body,
but rather to skid in sideways totally worn out shouting, Holy Crap... what a ride.
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Old 11-16-2014, 01:10 AM   #2
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Right idea wrong direction. You want to slightly raise the ailerons. This will simulate washout and it can work well. I use it on small Alfa warbird models with great results. Not much is needed or desired.

Dropping the ailerons actually moves the center of stall more toward the tip, bad. You actually want the stall to occur toward the wing center, thus many wings are designed with some washout to help cause this.

What plane we working on here? It matters as on super aerobatic models may not be totally benefitted by using washout.

Mike
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Old 11-16-2014, 01:25 AM   #3
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It's a 800mm T-28. Sort of squirrely at low speed.

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but rather to skid in sideways totally worn out shouting, Holy Crap... what a ride.
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Old 11-16-2014, 01:40 AM   #4
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Drooping ailerons will accelerate the stall in 99% of cases. There's the rare case where the taper of the control surface makes it actually work for what you want. but your airplane isn't one of those.

try 1 to 2 turns on the clevises pushing both ailerons up instead. it doesn't take much change in aileron to make a large difference in how the plane responds in a stall.
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Old 11-16-2014, 01:48 AM   #5
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OK, thanks. I'll give it a try.

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Old 11-16-2014, 02:15 AM   #6
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Originally Posted by fhhuber View Post
Drooping ailerons will accelerate the stall in 99% of cases. There's the rare case where the taper of the control surface makes it actually work for what you want. but your airplane isn't one of those.

try 1 to 2 turns on the clevises pushing both ailerons up instead. it doesn't take much change in aileron to make a large difference in how the plane responds in a stall.
Interesting:

Back in the mid 1960's, I scratch built a 60 inch wingspan model of my own design with an Enya 60 engine. The model flew like crap. One of my club members flew it, and told me the ailerons are drooping. He was right. Correcting that issue, and the model really flew well.

So, now days we have the ability to program in spoilerons on our models, and I've not really been impressed with them. Seems to me the model gets squirrely at low speeds.

Would this be the same thing???

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Old 11-16-2014, 02:31 AM   #7
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Results vary a lot with wing planform and aileron shape. Also with the airfoil used.

There is a general flying neutral position which will work well for any airplane.

You can be off an amount that is difficult to see without measuring and have adverse effect on the aircraft. Too far up or down.

Most aircraft can tolerate the ailerons being up slightly much better than drooped.
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Old 11-16-2014, 11:30 AM   #8
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If it has full length 'strip' ailerons then setting then 'up' is unlikely to help much, if at all, with alleviating tip stall. It will however increase the stall speed slightly which is only counterproductive. If the model has ailerons which are only on the outer part of the wing angling them up should help much more.


A more effective fix might be to see if you can twist in some washout by twisting the wing and carefully applying some heat.
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Old 11-16-2014, 02:26 PM   #9
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Originally Posted by JetPlaneFlyer View Post
If it has full length 'strip' ailerons then setting then 'up' is unlikely to help much, if at all, with alleviating tip stall. It will however increase the stall speed slightly which is only counterproductive.
+1. Thus my ask on model type.

And flapperons work great on most strip ailerons but not on barn door or outer like the t-28 uses. Again all about moving the center of stall on the wing. The closer stall is to root the better (in most cases).

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Old 11-17-2014, 09:29 PM   #10
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Are you sure its a tip stall and not just flying too slow for the elevator to function? Does the wing have any washout in it now? Have you tried moving the cg back?

I think I need a signature.
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Old 11-17-2014, 09:32 PM   #11
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Dunno Larry. Not tried moving CG.

Life's journey is not to arrive at the grave in a well preserved body,
but rather to skid in sideways totally worn out shouting, Holy Crap... what a ride.
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Old 11-17-2014, 10:40 PM   #12
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You may just be trying to fly too slow

Id start by checking the wing for washout/washin using some story sticks or an incidence meter if you have one. Add washin if needed, then re-fly.

Then I would move the CG back in small steps to see if that helps.

I think I need a signature.
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Old 11-18-2014, 05:27 PM   #13
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Originally Posted by Larry3215 View Post
You may just be trying to fly too slow

Id start by checking the wing for washout/washin using some story sticks or an incidence meter if you have one. Add washin if needed, then re-fly.

Then I would move the CG back in small steps to see if that helps.
??

Onto the subject of strip ailerons and whether a degree or so UP helps ... that really depends on the wing shape ...

If the wing is a straight no-taper wing - then I agree ... all you do is effectively reduce wings net angle of attack overall. But if the wing is tapered - then the change of net AoA as you move outboard increases.

Take a look at the end of wing and then draw a line through centre ... LE to TE. Now deflect aileron up ... the SHORTER chord at tip gives a greater change to the chord line than the longer wider root chord.

Its not just a matter of strip or not ... the wing form has much to do with it as well.

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Old 11-18-2014, 05:43 PM   #14
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If he's having issues with instability in a stall... moving CG back may be a very bad idea.

CG too far back can make the plane act badly in a stall.
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Old 11-18-2014, 06:34 PM   #15
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Originally Posted by fhhuber View Post
If he's having issues with instability in a stall... moving CG back may be a very bad idea.

CG too far back can make the plane act badly in a stall.
Totally agree ... unless model has been setup seriously too far forward CoG and then its a mushy wallowing mess ...

Instability in stall ... if its at onset of stall - then that usually indicates a poor geometry of model ... where a lot of trim has been applied for normal flight, which then loses authority as stall approaches ...

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Old 11-18-2014, 08:43 PM   #16
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We had a beginner many years ago... GP .40 size Cessna 182 as trainer. The thing was an awful beast about snapping into a spin at stall.

I had the guy turn the aileron clevices ONE TURN pushing both ailerons up. Complete cure.

You couldn't see that the ailerons had been moved.

Sometimes its just a tiny setup error...

Ever since then... for planes with dual aileron servos I set up "flaperon" mode at some small % (3% to 7%) and as part of the test flight I do stall tests, adjusting the ailerons to check for BEST position. Then I lock it in and turn off the mix.
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Old 11-19-2014, 03:22 AM   #17
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Originally Posted by Larry3215 View Post
You may just be trying to fly too slow

Id start by checking the wing for washout/washin using some story sticks or an incidence meter if you have one. Add washin if needed, then re-fly.

Then I would move the CG back in small steps to see if that helps.
Sorry for the sloppy typing. As noted - that should have read washOUT.

Although it is possible that you will find one wing has too much washout already and needs to go the other way. So I might have been correct all along


Originally Posted by simibill View Post
It's a 800mm T-28. Sort of squirrely at low speed.
My advice was based on this comment. Sounds like he hasnt actually stalled the model. Its just "squirrely" at slow speeds.

That may or may not have anything to do with stall behavior and may or may not have anything to do with wing twist or aileron droop.

All of us are guessing based on very little data. In the absence of first hand knowledge and seeing how it flys, my guess is its not actually a stalling problem. YMMV as usual

Most models have a recommended CG that is too far forward - especially war birds - and many people start out with the cg even more forward "just to be safe". Add in that it is a war bird that probably doesnt like to be flown too slowly.

This could easily be a combination of things. Investigate first with the story sticks and go from there

I think I need a signature.
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