Wingerons and Junker Flaps???

In an earlier post, someone gave me some links on Wingerons. It was most interesting reading, and I thank you very much for the links.

All of the applications that I read about for the Wingerons used direct control via the servos. However, I had this interesting question. What if you wanted to control the Wingerons indirectly with junker flaps (JF)? Would it work? Seems like it should, but the control "direction" would be 180* out of phase, i.e. the JF nose down would cause the Wingeron (wing) to pivot nose up. My gut tells me that the aerodynamic forces would balance out and the wingeron would find a stable angle of attack, being sure to keep it in the range below the the stall angle, that is. It might seem more complicated than necessary, but it is an interesting idea, and I'm wondering if anyone can see any obvious and/or severe problems with using Wingerons with JF's.

I got the idea from Charlie Kaman's control scheme for his relicopter rotor system. He used a small aileron on the rotor to "fly" it into the desired angle of attack. As a result the control forces were so low, that hydraulics were not required. The stick is directly, mechanically coupled to the rotors' ailerons, and stick shake is, virtually non-existent; in fact, I saw a video, one time, that showed him using "fingertip control" of the stick to fly one of his intermeshing rotor helicopters. The collective also operated these ailerons on the rotors.

Thoughts?

Is this just a totally stupid idea, or is there truly not anyone with a clue about if and how this might work?

Not stupid. I just don't have much in the way of thoughts on it, so I figured to let more knowledgible people write. So, here are my meager thoughts.

Servo tabs to fly surfaces have been around a long time.

Usually, the tab flies the surface and the surface is in the flow off of a forward surface. Typical is a tab flying an aileron which flies in the flow off of the forward three-quarters of the wing.

When you get to a flap flying a wing, well, I get concerned about self-righting. Wings tend to have negative pitching moments about the .25 C point. If you pivot them there, they will be trying to pitch nose down. If the two wings are linked (opposite pitch) as ailerons are, the pitching moment must be carried by the linkage. Stay with that and just hold the right position with tab, and it becomes a zero pitching moment foil. If instead you use zero pitching moment airfoil, then it might work.

Then comes the fact that you do not have the centering effect of the flow coming from the rest of the wing. It sounds like it could be very fussy.

On most all flying tails, the low resistance to pivoting is countered by having an anti-servo tab to give it some "feel".

A simple wind tunnel and some experimentation would give you alot of knowledge. As long as we have been flying airplanes, this has to have been thought through and written about once already. Get thee to a search engine!

Billski

Originally Posted by wsimpso1

A simple wind tunnel and some experimentation would give you alot of knowledge. As long as we have been flying airplanes, this has to have been thought through and written about once already. Get thee to a search engine!

Billski

Thanks for the reply, Billski. I did do some searching, before I originally made the post. Please note that I stated "All of the applications that I read about for the Wingerons used direct control via the servos. However, I had this interesting question. What if you wanted to control the Wingerons indirectly with junker flaps (JF)?" I have not been able to find anything about wingerons that are not using direct mechanical linkages for control of the pivoting wing. If you happen across some info about this, I would appreciate a link or other directions to said source.

Thanks again!

Hi, Kugel--

I agree with Billski, especially the "not stupid" part. Junkers flaps belong to a group of control surfaces called "stabilators", as Billski implied by comparing it to an all flying tail (also a stabilator). I suppose wingerons are related to stabilators because they pivot about an axis that passes through, or very near to, the aerodynamic center although the root word is a hint that stabilators are pitch control surfaces. What you're asking sounds fine considering that any trailing edge surface can be used as a servo tab. There have been several flying wings (mostly Russian) that used Junkers flaps as the only control surfaces. The major problems are that adverse yaw can be a bit higher than with plain ailerons and the flap tends to get ripped away from the wing in an uncoordinated landing. To keep a free floating wing stabile you need to have stops in the control circuit to prevent the doppelflugel (prof. Junkers name for such a wing) from developing a negative pitching moment. I don't think the pitching moment of the lifting surface is all that important with this setup. Basically what you're designing is a slotted, reflexed, wing with the slot at the elevon hinge line like in the attached drawing. This shows a doppelflugel composed of RAF-34 sections drawn inside a NACA M-6 airfoil. The flap will provide enough moment to control the pitch of the lifting surface so the wing can be based on a -Cm airfoil within reason. The flap needs to be a zero Cm airfoil to avoid trim problems. An anti-servo tab would also be a good addition to the flap for the reason Billski mentioned. The tab linkage could be made adjustable in-flight so it could serve double duty as both an aerodynamic balance and a trim tab.

I wrote an article about Junkers flaps for a newsletter a few years ago. I also put together a bibliography with links to all of my source material including the relevant NACA reports but some civil service genius decided to move everything to another server so all of those links are broken but the report numbers are listed so you should be able to find them on the new server if you want them.

Disclaimer
I am not an engineer nor do I play one. According to my college transcript I was an art major most of the time. Although most of my classes were in the computer science building and the machine shop (the blueprint reading and geometric tolerancing classes were taught by machinists)