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"double" elevon mixing?

Old 12-28-2011, 03:03 PM
  #1  
earthsciteach
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Default "double" elevon mixing?

I'm playing around with a scratchbuilt foamy driven by a 50 mm edf. I'm going to configure it as a canard and am wondering if I can (and if its worth) mixing both main wing and canard control surfaces as elevons. I am thinking that I can use a y harness from both channels 1 and 2 to connect to four servos (two on channel 1-canard and main wing) and two on channel two (other control surfaces on canard and main wing). I know I can't simply link the canard and main wing surfaces by control rod. In my head, it should work. But, A LOT of things work in my head that don't in the real world!
Sound reasonable?
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Old 12-28-2011, 03:49 PM
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constantCrash
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you would need 4 separate channels with elevon mix + canarderon mix (i just made up a word)

elevon both sides go up when you pull back on the stick. canard both sides need to go DOWN when you pull back on the stick.

BUT when you roll right you want both the left elevon and canarderon to go down and both the right elevon and canarderon to go up. vise versa for roll left.

So using Y harnesses and elevon mixing ether your roll will be wrong, or your elevator will be wrong.

See the incompatibility now? It's possible to do, but you need 4 channels and i think 4 mixes.

L aileron -> left canard
R aileron -> right canard
negative Elevator -> left canard
negative elevator -> right canard
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Old 12-28-2011, 03:53 PM
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earthsciteach
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Ah, so I'd still have the same problem if I did it with a mechanical linkage. I can make the pitch work, but not the roll.

This will give me something to play around with for a while!
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Old 12-28-2011, 04:07 PM
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JetPlaneFlyer
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This is not a problem to do, no need for four channels or fancy double mixing. You can do it with two y leads and a standard elevon mix. One elevon channel goes (via Y lead) to left canard and right elevon. The other elevon channel goes to right canard and left elevon. Arrange so that up elevator command makes the canards go down and elevons go up. Because of the diagonal cross linking aileron command now makes both canard and elevons produce synchronise roll command.. Pretty straightforward to do.

You can do it mechanically by the same cross linking of left canard to right elevon, but that gets bit more tricky in practice.

Steve
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Old 12-29-2011, 03:55 PM
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Dereck
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Having seen the pictures of the model, I humbly suggest you admit to an outburst of normalcy and rig the controls as boring ol' elevators on the canard and equally boring ailerons on the main wing.

Once the model's proved itself to be a superbly safe and responsive flier and your clubmates are treating it as something normal , then consider messing with lots of mixing.

Taking things one step at a time is a good plan

D
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Old 12-29-2011, 04:13 PM
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earthsciteach
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Haha! Already met you half-way. I still have elevons programmed, but regular elevator on the canard. I'll dial in some expos just in case.

I'm NEVER going to be normal! LOL!
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Old 12-29-2011, 05:34 PM
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JetPlaneFlyer
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FWIW i will add a +1 to what Derek said. Although it's simple enough to mix the canard with elevons I'm not sure you would really want to do it for most applications. The problem with elevons is that when you pull up elevator you need the wing to produce maximum lift. Having the elevons reflex upward only serves to reduce the lift that the wing can make before it stalls which is the last thing you really want.

You have no choice with a tailless 'flying wing', so you just have to live with it, but having a canard elevator means you don't need to accept the disadvantage that elevons inherently impose.

Steve
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Old 12-29-2011, 05:39 PM
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earthsciteach
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I'll defer to those more experienced than me! Its just a programming thing, anyway.
Thanks, guys!
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