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Old 11-16-2008, 09:16 AM   #11
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Re: Dragging tail....why?

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Differential aileron!!! What is required on all trainers is differential aileron, Like twice as much up as down. ALL Real A/C have it. On my shoulder wing A/C I drilled two more holes in the servo arm (disk) so they produce a 60 degree angle with the pivot point. If you have the same amount of up and down aileron, most A/C will produce "negative yaw", in other words the nose will tend to go in the opposite direction to the turn. I worked on a Navy A/C that has a 12' spoiler that comes up with the aileron to help drop and slow down the inside wing. You might have to change the control horns on the wing or reposition them so they do not counteract the 60 deg. bell crank. Also the balance point should be at 25% to 30% back on the wing cord. The stab and wing should have "zero" incidence to each other. Look at the A/C from the back and check for warps and alignment.


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Old 11-16-2008, 01:28 PM   #12
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Re: Dragging tail....why?

Keya: If you dont crash, you dont fly.

Kip Im not sure I fully get how to do this. All I have is the typical servo with push rods strait tp the ailerons.

I built an incidence meter and it worked great!! In order to have 0 (zero) incidence I had to build up a little over a quarter of an inch on the leading edge.(seems like a lot doesnt it?)
I measured 10 times and dry fitted everything first. it looked good. there is still 1/16th to go for 0 degree decalage. Ill add more if I need later.
Ill fly tuesday if possible,see if this is any better.
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Old 11-16-2008, 01:56 PM   #13
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Re: Dragging tail....why?

If I can get this to work! I took two pictures of the servo and one at each wing tip so you could see the difference in full left aileron. You see it is more important to slow down and drop the inboard wing, this makes for a better turn.

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Old 11-16-2008, 02:40 PM   #14
Gary Maker
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Re: Dragging tail....why?

I may very well get bitten by makeing this statement but if you consider the way it was described that the plane was origionally flying... lots of down trim needed with high power and lots of up trim with little or no power, ( see post # 1 ) drouping and pitching in a turn etc.. I doubt that it has much to do with whether or not the plane is utilizing differential ailerons.

I think you're definitely on the right track with the incidents shimming. THAT will make a world of difference in the way it flys! This suggestion will help if you want to try it later, but I think you should concentrate on doing what your doing..first!

Don't get me wrong! On any flat bottomed wing, differential ailerons do make a difference and do help for the good, ie: eliminates adverse yaw, especially for a scale type aircraft, like a J3 Cub for example. But you never hear of any instructions in the setup for a trainer, at least that I've seen, advise or recommend that the builder/assembler should setup for differential ailerons. I've personally built and flown many many different trainer aircraft w/o differential ailerons: PT40, 3 X Eagle II, 2 X Tele 40, Kadet Sr., 2 X Wiz 40, etc. and never encountered the problem(s) listed above. Unless you need to be concerned with absolutely precise turns, I personally doubt that you will notice much difference anyways with a slow flying trainer type airplane - in MHO!

That being said, nothing wrong with learning how to setup and take advantage of differential ailerons. With my 1/4 scale Cub, I wouldn't fly it without using them!

Actually on a full scale Cub, anti yah is built in by the way the aileron pivots back from the leading edge of the aileron. The aileron itself is used to prevent adverse yah by causing the leading edge of the aileron to drop below the bottom of the wing when that aileron is deflected upwards, which causes drag to counter act the opposite ailerons drag when deflected downward. Hope this make sense to you?? Man, what a drag...

Most newer computer radios have built in programming to do this for you. W/O one, then you'll need to do a mechanical setup as has been described or similar! Something new to consider once you get it handling properly and you think/feel that differential ailerons might be something you want to try!
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Last edited by Gary Maker; 11-16-2008 at 02:56 PM.
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