Wing warping How?

[Joel K. Scholz]

Can someone point me to some info on a practicle wing warping method?

[BMatthews]

Do you mean to remove or put in fixed full time trimming warps or wing warping as a flight control?

[vintage1]

Big discussion on this in the scale forum.

First requerment is a flexible enough wing.

Then either use pull pull cables as per the full size, or (my suggestion) try a carbon tube throgh all the ribs not glued except at the tip two or three, and use it as a torque rod..

[Ollie]

Monoplane or biplane?

[Joel K. Scholz]

warping as a flight control on a monoplane wing. I may have thought of a way, but would like ideas.

[Ollie]

For a monoplane, the guy wires go to pulleys above (best higher) and below (best lower) the wing such as a king post.

[BMatthews]

Yep, I like the way the full sized ones do it with cables. Especially since the wing needs to be flexible enough to twist easily. And if it's that flexible then it won't be strong enough to take flight loads without the proper bracing.

Although the torque rod idea may work as long as the spar is stiffer than the torque rod so it doens't tend to bind the torque rod.

[vintage1]

Yep, I like the way the full sized ones do it with cables. Especially since the wing needs to be flexible enough to twist easily. And if it's that flexible then it won't be strong enough to take flight loads without the proper bracing.

Although the torque rod idea may work as long as the spar is stiffer than the torque rod so it doens't tend to bind the torque rod.


You could make the spar from one tube and use another inside it that is the 'spar' for the last couple of ribs.

Since you need a thin sectin anyway, a CF spar is probably a Good Thing.
There is no doubt that cables will work, and itf its scale, thats the way to do it...BUT you need the scale thin undercambered section as well, and you will duplicate all the appaling adverse yaw that seems to go with wing warping.

Wing warping was abandoned because it really didn't work that well, and many pre 1914 planes were viciously unstable...

[Joel K. Scholz]

Thanks Vintage, I think this is the way I will go. I am working on an electric Pterasaur.

[vintage1]

Ah!

I like it.

Should do a build thread in the 'scale' forum.

I would LOVE to build one too.

[Sparky Paul]

The CF tube as a torque rod inside another CF tube would be good for simulating
the effect of the digits moving the wing membrane for control.
It might require a hefty servo to rotate the inner tube when the wing bends.

[BMatthews]

The CF tube as a torque rod inside another CF tube would be good for simulating
the effect of the digits moving the wing membrane for control.
It might require a hefty servo to rotate the inner tube when the wing bends.

I agree. Perhaps if you can find a slightly softer inner tube that is still torsionally stiff enough like fiberglass or similar then the load on the servo wouldn't be so high... but this is just a guess. You'd have to set up such an arrangement and test it to see how much it binds and what can be done to fix the binding.

[vintage1]

The CF tube as a torque rod inside another CF tube would be good for simulating
the effect of the digits moving the wing membrane for control.
It might require a hefty servo to rotate the inner tube when the wing bends.


You don't need to warp through many degrees, so you can use a LONG torque arm...if the covering is floppy...and I would say that for a pterodactyl it should be, it might not be that hard at all..in fact a single skin of covering on the correct framework would have almost zero torsional stiffness.

[ghoti]

The Carbon Falcon uses wing warping and I could never make mine work but that reflected my lack of flying skill. You could do a search and have a look a it.

Wilber and Orville had just the right combination: Small enough to warp the wings with muscle power and not too fast so flight loads didn't get out of hand. Then they discovered adverse yaw and the rudder was born.

Show us pics when you can. I would love to have a camera plane that looks like a bird. Bill

[ghoti]

Here is a link to Carbon Falcon info.
http://www.acesim.com/rc/p2/p2.html

[yoyoML]

I'll give you one entirely new method here!

Make a very very flexible (duh...) wing and make sure its only spar lies very close to 25% MAC.

Now attach ailerons, small ones near the tips. Mechanically hook up the ailerons the normal way, but REVERSE the aileron channel.

Now if you push the stick to the right, the right aileron drops and the left aileron raises. But the dropped right aileron brings the rear end of the wing up and decreasing the whole right wing's AoA, and the left wing's AoA is increased. You get a right roll in the end.

This is how NASA built their warping wing F18, if you'll google it. In fact, this is also how trim tabs on full-size planes work.

[lowdive]

if interested: http://www.military.com/soldiertech/0,14632,Soldiertech_AAW,,00.html


looks like ailerons work as usual but the flexible wing design allows the wing to twist, lifting the leading edge to create roll. nifty!

[Sparky Paul]

I'll give you one entirely new method here!

Make a very very flexible (duh...) wing and make sure its only spar lies very close to 25% MAC.
...

.
This will result almost instant flutter.

[steveseibel]

Well, almost--trim tabs push on the trailing edges of the control surfaces to which they are attached. Yes you get what initially appears to be a "backwards" effect (e.g. raising the trim tab attached to the elevator gives a nose-down trim input, and raising the trim tab attached to the right aileron gives a left roll torque) but no twisting of the actual structure is involved. If the wing twisted, the effect of the aileron trim tab could become reversed, but of course then the effect of aileron control inputs would also become reversed (I believe this happened in the thin-winged B-47 in the high-speed part of the flight envelope).

On a full-scale airplane if you hold the elevator rigidly in place with some sort of special (removeable!) device that prevents the control yoke from moving fore-and-aft, thus holding the elevator rigidly in place, then the effect of the trim tab is reversed--raising the trim tab then gives a nose-up trim input. Something handy to remember if the controls ever jam. This has nothing to do with anything flexing, the trim tab is now just acting like a miniature elevator. The same would be true in the roll axis but I haven't attempted to experiment with this first-hand.

By the way all flexible-wing weight-shift-controlled hang gliders rely on a passive form of wing-warping--when I shift my weight to the left to initiate a rolling (banking) motion toward the left, as the aircraft starts to roll toward the left, the aerodynamic damping effect increases the angle-of-attack of the left wing, which increases the lift-per-unit-area generated by the left wing, which tends to oppose the rolling motion. This is true of all aircraft. But in the flexible-wing hang glider the increased aerodynamic loading on the descending wing (the left wing in this example) causes it to flex in a way that tends to decrease its lift-per-unit area, and the increased loading on the right wing causes it to flex in a way that tends to increase its lift-per-unit-area, all of which helps overcome the aerodynamic damping effect. The net effect of the aerodynamic damping plus the wing-flexing still ends up being an increase in lift-per-unit-area on the descending wing--that's why I need to keep my weight shifted to the left just to maintain a constant roll rate to the left--but much less so than if the wing surface were not flexible. If the wing were not flexible the aerodynamic damping effect would be much more powerful and the maximum achievable roll rate would be much lower.

I'll give you one entirely new method here!

Make a very very flexible (duh...) wing and make sure its only spar lies very close to 25% MAC.

Now attach ailerons, small ones near the tips. Mechanically hook up the ailerons the normal way, but REVERSE the aileron channel.

Now if you push the stick to the right, the right aileron drops and the left aileron raises. But the dropped right aileron brings the rear end of the wing up and decreasing the whole right wing's AoA, and the left wing's AoA is increased. You get a right roll in the end.

This is how NASA built their warping wing F18, if you'll google it. In fact, this is also how trim tabs on full-size planes work.

[yoyoML]

Well, almost--trim tabs push on the trailing edges of the control surfaces to which they are attached. Yes you get what initially appears to be a "backwards" effect (e.g. raising the trim tab attached to the elevator gives a nose-down trim input, and raising the trim tab attached to the right aileron gives a left roll torque) but no twisting of the actual structure is involved. If the wing twisted, the effect of the aileron trim tab could become reversed, but of course then the effect of aileron control inputs would also become reversed (I believe this happened in the thin-winged B-47 in the high-speed part of the flight envelope).

Yes yes you're right. But just imagine the rigid wing and the freely deflecting aileron as a whole flexible surface, and the aileron trim tab as a small aileron attached to the flexible surface. See the analogy here? No twisting to the original wing+aileron+trim tab combo, but still the same effect as a flexible wing+small aileron.

It also happened to a WWII Soviet fighter I-16: its horizontal stab would flex so much that pitch control reverses at some high speeds.

[steveseibel]

Yes I get the analogy. Interesting thread...

Yes yes you're right. But just imagine the rigid wing and the freely deflecting aileron as a whole flexible surface, and the aileron trim tab as a small aileron attached to the flexible surface. See the analogy here? ...