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        Question Eliminating channel mixing

#1 derp express Dec 23, 2012 07:31 PM

Eliminating channel mixing
 
Gents,

I know this probably sounds like a step backward technologically, but would it be feasible to eliminate or mitigate potential pitch sensitivity in a nurflugel or other flying wing type of aircraft by having the elevator and aileron controls on separate, unmixed channels, where the ailerons are still large surfaces with long throws for quick rolling, but the elevator(s) are just tiny surfaces with short throws enough to give the wing smooth pitch control, but not enough to throw it into a tumble with too much control input? I'll admit I have little experience with wings, but this idea occurred to me as something that might theoretically work.

#2 nmasters Dec 23, 2012 09:59 PM

It's not unusual at all for planks to have an elevator in the middle with ailerons outboard. Swept wings can also be configured that way but for smaller sweep angles elevons produce better pitch response.

#3 1967250s Dec 25, 2012 09:49 AM

What about a mechanical mixer? A double swing arm, like the o es used for v tails? Then you'd have best of both worldsnand andnot have to have a fancy mixing radio

#4 Quick61 Dec 25, 2012 11:29 AM

Quote:

Originally Posted by 1967250s (Post 23615981)
What about a mechanical mixer? A double swing arm, like the o es used for v tails? Then you'd have best of both worldsnand andnot have to have a fancy mixing radio

As far as mechanical mixing goes, there area couple of good examples with the Eclipse (V-tail) that slides the servo tray for elevator movement and the Voodoo that has mechanical mixing for elevon. I think the Voodoo is a good example to follow for mechanical mixing on flying wings.

Mark

#5 HerkS Dec 25, 2012 11:32 AM

The radio systems I use allow elevon mixing control, such that I can easily adjust the amount of elevator movement that I want - relative to the amount of aileron movenemt that has been set. Separate surfaces can be used but that means I would need to use more servos. I have both plank and swept flying wing models that use elevons. I almost always want to modify the elevator and aileron movement separately.

Mechanical mixers can do this with somewhat more complexity - though the newer programmable radio systems essentially remove the need for them. They also allow quick on the field changes during a flying session.

#6 slebetman Dec 27, 2012 03:27 AM

These days, if you don't have a computer radio and want to fly a wing or delta, I would suggest getting a V-tail mixer and use it to get elevon mixing. They are cheap these days:

http://www.hobbyking.com/hobbyking/s...tra_small.html
http://www.hobbyking.com/hobbyking/s...ail_Mixer.html
http://www.hobbyking.com/hobbyking/s...200_step_.html

Much less hassle than mechanical mixing.

However, you may just be curious about the feasibility of separating elevator and ailerons on wings. Well, it's been known to work for planks, swept forward wings and deltas. Usually with the elevator set up in the center and ailerons on wing tips. I've built an experimental delta myself with this setup and it works great.

For swept-back wings, both elevator and ailerons want to be at the wing tips. Ailerons wants to be outboard for leverage and elevators wants to be rearward for the same reason. And for a swept-back wing both occupy generally the same space. If I were to try this I'd put the elevators on the wing tips with slightly inboard ailerons. That way, applying up elevator would get me automatic yaw stabilization.

#7 jeff93063 Jan 07, 2013 12:28 PM

This is kind of moot with today's computer radios and cheap mixers, but I always wondered why you couldn't just physically rotate the gimbal in your transmitter 45 degrees. Does anyone know if that was done back in the old days? I did the math and it would work as a crude v-tail or elevon mix. Just curious.

#8 slebetman Jan 07, 2013 02:44 PM

Quote:

Originally Posted by jeff93063 (Post 23740576)
This is kind of moot with today's computer radios and cheap mixers, but I always wondered why you couldn't just physically rotate the gimbal in your transmitter 45 degrees. Does anyone know if that was done back in the old days? I did the math and it would work as a crude v-tail or elevon mix. Just curious.

I actually flew once like that. Before I got my computer radio*. And that was just three years ago. Works but got weird stares from others at the field. Also crashed all the time but that could be because I was a newbie then.


*note: actually, I'm still using the same HK-T4A radio, only heavily modified and wrote my own software so I could have a computer radio.

#9 biber Jan 07, 2013 06:12 PM

You can have separate controls without any mixing in a plank, as already suggested by Norm.
You can aswell have it in a swept wing, using a setup like the Multibumm.
http://www.rcgroups.com/forums/showthread.php?t=504495

biber

#10 slebetman Jan 07, 2013 07:28 PM

One type of control that I've always thought to be natural for flying wings is the kind employed by the Dunne series of flying wing biplanes. It didn't have elevon mixing instead used two control sticks, one on either side of the pilot, to directly control each elevon. The pilot is the elevon mixer.

To do this with RC equipment I guess you'd need to modify your TX and install a spring on the throttle stick. Then employ some other input for throttle control (one of the knobs on your TX?). For a glider, you don't need throttle. And some of my planes I fly on full throttle 100% of the time, those planes could probably be configured with one of the switches as throttle.


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