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Old Oct 25, 2004, 08:49 PM
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Polyhedral with ailerons/no rudder, - OK?

I'm half way through building a non specific e-glider about 1.8m span with polyhedral and ailerons. At this stage I am considering ommiting the rudder and retaining just the vert stab with the intention of using ailerons and elevator only. Any comments or suggestions as to how this control arrangement without rudder might handle?
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Old Oct 25, 2004, 09:52 PM
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Why?

Is it a weight issue???

You will keep the stability of dihedral/poly but you will lose
the ability to do a low energy loss turn using the rudder.
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Old Oct 28, 2004, 10:04 PM
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Depending on how steep the angle is on the outer panels of the wing, and where you have the ailerons, you might get adverse yaw from the ailerons. I don't have any experience personally, but have read articles and books that explain why you Don't put ailerons on the outer sections of a poly wing. They start to act more like a Vtail rudder system than ailerons and don't give you the response you want.

I saw a different approach which has a poly wing, R/E and flaps on the inner panels. He has the flaps set up as flapperons so they work like ailerons and are mixed with the rudder to help turn the plane. Since they are horizontal, and not angled like ailerons on the other panels, he gets no adverse yaw. He claims he gets the turning authority of ailerons and the stability and easy flying of a R/E poly wing.

Something to thing about.
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Old Oct 29, 2004, 01:25 AM
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Thanks for the replies. I've decided now to go with a V tail. I will keep in mind any possible adverse effects with the ailerons on the poly tips. If they prove to be a problem I might have to disable them and just use rudder for turns.
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Old Oct 29, 2004, 05:58 AM
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Ailerons aren't need or very effective on a properly designed poly ship.
..a
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Old Oct 29, 2004, 06:38 AM
xtc
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ailerons are not always as friendly with sailplanes at lower speeds [thermaling] and poly is not always friendly with speed!

which do you want??

xtc
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Old Oct 29, 2004, 07:25 AM
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Again, it all depends on how much poly you have in the wing. If this looks like a Spirit or a Gentle lady, you are likely to be disapponted in the response. However if you are talking 5 degrees on the inner section and another 5 degrees on the outer section, then it will probably work fine.

Assuming the larger angles typical of R/E poly ships, if you have not put the ailerons on yet, take the suggestion to move them to the inner section IF you have a computer radio. Set them up as flapperons. Set up for Aileron Rudder mix, but set rudder at 100% of ailerons and set the ailerons at very small throws. Use them to assist on the turn, not make the turn.

That should give you excellent turning authority while not creating excessive drag. And since they will be in the prop wash during climb out, they should be very responsive under power.

This will also give you flaps for landing assistance.

Whatever you do, I would love to see some photos and hear about your flying results. Everything is theory untill you launch the plane!

edit: See correction on mix on later post.
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Old Oct 29, 2004, 12:04 PM
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i built a sobox plane [similiar to art hobby] with a slight amount of poly and dihedral but both are very moderate,i did this hoping to allow the glider to do a little more of the flying on its own at higher altitudes when my eyes start to fail

it performs just as expected but i wouldnt have wanted to add much more!
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Old Oct 29, 2004, 12:15 PM
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another example of poly and dihedral
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Old Oct 29, 2004, 12:18 PM
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For what its worth, Airtronics Legend has a little dihedral in the outer sections, but not much. The tips are up, but the ailerons are only at a slight angle to the fuselage.


Don't know if these photos are of any use, but they will give you an idea of how other planes have implemented some dihedral with ailerons.
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Old Oct 29, 2004, 12:26 PM
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I just want to correct a post earlier about setting up a mix.

Take a look at this thread, starting at post 49. Guy talks about using flaps
as ailerons on a R/E sailplane. Pretty cool idea.
http://www.rcgroups.com/forums/showt...6&page=4&pp=15

Here is the note he sent me about the mix.

"Just set it up the same as any unlimited 6 servo plane, but you are using
aileron channel to control the rudder, NOT rudder. I fly JR, and any of them
will give you butterfly, which has all the flap to elevator, flap travel, etc.
The mix is a standard JR aileron to flap. I use about 20-25% mix. As long as
you plug the rudder into the aileron channel, you have no problem, just assign
dual flap in the set up. I can fly it on the old 347,388,783, 8103, and my new
9303. Most computer radios will do dual flap, and mix aileron and flap. Don't
plug into rudder then try to mix it to the aileron channel, a very common
mistake. It really makes sweet flying with a poly . "
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Old Oct 31, 2004, 06:33 PM
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Thanks everyone for taking the time and effort to comment on my query. Much appreciated. The wing on this one has flown before and seemed OK for the short time before other "factors" entered and led to the demise of the original fuse. A new fuse and V tail are on the bench now. It will probably be a few weeks before flight testing due to other commitments. So I think the approach from here will be "suck it and see"!
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