KenLitko

Paul,

What you are describing is adverse yaw. The lift side will get a dramatic increase in drag due to the increase in lift from the flap.

Maybe what Joojoo is seeing is a very dramatic adverse yaw due to the likely very high lift from the morphing wing. If I was looking at the pictures in the PDF file correctly, it looked like the non-lifting wing of the aircraft would go to a near-zero angle of attack, which of course will give you the least drag on that side.

One way to cure this is to create a non-lift-induced drag on the non-lifting side of the aircraft. Sometimes you can do this by programming in a large negative throw in the non-lifting aileron (non-proportional to the positive throw on the opposite side). I'm not sure how you would do this on this morphing craft though?!

Spoilers may be another option.

Joojoo

My Feedback: (2)

Spoilers? Is that another word for homework?

I think both of you are correct in that the morphing does in fact generate some amount of adverse yaw. However, by the response of the airplanes, I would be inclined to say that the morphed wing surpasses critical alpha and fully stalls that wing section.

For small deflections, all the airplanes are really fun to fly. Whether using torque tubes or tentioned lines, the roll axis feel is very nice. I didn't have any problems trimming out the airplanes or flying aerobatics. For large deflections... especially at slow speeds, the airplanes will occasionally start the turn in the commanded direction, then roll violently in the opposite direction and enter a very pretty spin. If it wasn't so surprising, I'm sure I would admire the spin a lot more, but it does precisly opposite to what I tell it to.

Looking at the flight data, there are some instances where relatively large yaw rates are built up during strictly morphing commands. We had discounted those as excitations of the dutch roll oscillation, but it may very well be adverse yaw.

As for the tailerons, we've had a recent shift here in the lab back to tailerons (elevons really). We seem to go through mood shifts where we design for rudder elevator, then back to elevon, then wherever else the wind blows.

Tall Paul

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ADD drag?
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Sometimes you can do this by programming in a large negative throw in the non-lifting aileron (non-proportional to the positive throw on the opposite side). I'm not sure how you would do this on this morphing craft though?![/QUOTE]
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WAY too much complexity for a problem that is eliminated by proper flight technique
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Spoilers may be another option.

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Elminating any hinge lines and having a smooth surfaced wing is the goal.
Unless the spoiler is inflatable, you get hinge lines and surface edges.
[/QUOTE]

Tall Paul

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I'd couple the rudder to the wing.
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I've been flying this thing for a couple weeks. A sloper ala ZAGI™. it's not supposed to have verticals. Iniital flights showed it could fly withou them, but if the speed dropped, so did directional control. It would sail off in any direction, any side in the direction of flight... like totally sideways!
I've been scabbing on foam and balsa verticals to see what works best..
And flying ZAGI™s with and without verticals. As long as speed is kept up, it's not an important surface.

KenLitko

I'm not sure what you are trying to say. Are you saying that you do not get an increase in drag with an increase in lift? That is not possible. With increased lift, you always get increased drag (induced drag). This slows that wing down and yaws the aircraft.

That is not to say that the other side -can't- have a decrease in drag, it very much can. But adverse yaw is generally attributed to the increase in lift-induced-drag on the flapped side.

You can't easily get rid of lift-induced-drag, so a common solution is to increase the drag on the other wing. In-flight, the rudder can usually compensate for adverse yaw, but under certain circumstances the solution is to add drag on the opposite wing.

Tall Paul

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????????????????????????????????????
For the stated example, flaperons at full deflection, the surface is as far -down- as iit can go!
"Nothing changes on the side with the flaperon full down." when a roll command is issued. The flaperon on one side CAN'T go down any further!
Nothing changes on that side!
Neither the lift or the drag.
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For a morphing wing however, which may be capable of deflecting past the local alpha of the stall, the wing may stall, but the lift merely diminishes, while the drag increases.
This pulls the plane in the opposite direction to that commanded.
Disconcerting and disorienting when it's actually experienced.
For conditions where the flaperon is extended less than full travel, a lessening of roll authority will be noted.

KenLitko

Sorry TP, I was referring to Joojoo's experience in flight, I wasn't paying attention to the example you set for flaperons at full down.

a088008

It's Mr Q. to you! (just kidding The letter Q is the first letter of my first name, but that's all I'm going to disclose. Those who know me know who Q is, and to those that don't, I hope we meet some day to indulge in my favourite pastime - fly and discuss others/my designs.)

I loved the paper. Thanks for letting us read it.

I'll certainly be looking out for wierd spin behaviour, and trying to avoid it at first. This brings up an idea I had. I'd like to setup the tiperons as flaperons on my computer radio. This way (with 2 servos) I can control the AoA of each tiperon. I could then setup a landing mode where the tiperons deflect downward a few degrees. This would create a kind of washout that can be adjusted at will. It should help prevent snap rolls on low speed, high AoA aproaches when sygnificant roll control inputs are being fed to the plane.

-Q.

a088008

This shape reminds me of a military, or NASA, prototype that was used to investigate VTOL. It was a yellow thing with two very large props at the end of a lifting body in the shape of a "D". The front was the flat side of the "D". By all accounts it flew very well, but had gearbox problems that prevented it from being a viable solution. Also, the jet age overtook it's simple prop design.

-Q.

Tall Paul

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That's the Vought V-173 which flew, and the fighter generated from those flights, which didn't (F5U).
I've built the missing wingtip, and ever cautious, decided on a real horizontal for the first tries.
The fragility of the tiperons is still a botherment.
I need a long high grassy slope. Ain't none in California! The one I have in mind is on the road from DC to Pax River.
Tad expensive to get there from here just to toss a toy airplane.

a088008

I think that the wintip will be fine, if you don't land on it - which is a real possibility. I have the same concerns about my design. I even considered an axle for the tiperon to rotate around and then place a wingtip on the tip of the wing. This would give a little protection from dragging the tip on landings.

It's still a work in progress, so who knows where the design will end up.

On a similar note, I have been considering another design with inboard all-moving wing sections that act as flaperons. The motors (2 of them - one for each section) would be mounted at the front of these all-moving sections. This would give a serious VTOL capability with the ability to thrust vector if the sections were mixed as true flaperons. Roll rates would be insane! And, 3D manouvers woud be limitless.

-Q.

a088008

Here is a picture of the V-173.

Tall Paul

Check out the Freewing shown in "scale modeling", guess the plane thread.

a088008

I found a picture. Is this what you meant by the Freewing? It's awsome plane. I love the concept. I fell in love with the plane when I saw it some years ago. You can see another example at http://www.freewing.com/.

My design would be similar, except that it would have 2 inboard wing mounted motors on moveable wing sections that do not go all the way to the wingtip.

-Q.

paccamura

Hi to everybody,
I've read with great interest this discussion. I'm looking for someone that has experience with all-moving wing tips for roll control.
I'm designing homemade UAVs (around 3m wing span) and I'm interested in this control device as a possible solution.
I've already flown a prototype that behaved relatively well (though I have to increase the tiperons dimension as the maximum roll rate was a bit poor)

I would be interest in this paper, but the link doesn't seem to work anymore and the title is not clear. does anybody can help me with this?

Of course I would like to know if Q finally build his tiperon aircraft and what is his opinion about it.

if there is anybody interested in the topic that would like to share information with me I'll be very happy

thanks

Tall Paul

You're putting a major control surface at the end of the wing.
What keeps it on?
Where will the actuating servos be?
How will they pivot the surface?
Will the lift/drag loads jam the pivot?
Will the pitching moment of the tiperon section overload the tiperon servo?
In a cartwheel landing, will the tiperon mechanization be damaged?
Other than being different, I don't see any real advantage.

BMatthews

The major POSSIBLE gain in performance for such a tiperon control is in the quickness and magnitude of the response as would be needed for aerobatic flying.  Clearly a UAV does not require this sort of performance level.  So you end up trying to include a solution where a problem doesn't exist.  Add in the extra structural complexities associated with this form of control surface installation and you really get a solution that was made from a surplus of belly button intospection time...

Seriously, this is not a solution for any sort of UAV build other than if the craft has an extremely odd planform such as the old ARUP airplane from the 30's which used tiperons for roll control.  Conventional hinged surfaces have done well for subsonic aircraft for literally 100 years.  The all flying tails used on fighter jets are there for various reasons.  Some of which involved response at supersonic speeds.  Something UAV designers and model flyers don't need to consider.

Rick.

worth adding here, - i had an idea for a wing warping mechanism for use on thin wing foamy planes - never actually built it (yet), but essentially my idea was to thread a cf tube right through each wing half, root to tip and epoxy the cf spar ONLY inside the last couple of inches of wing. When rotated the tip would angle with the tube and the rest of the wing would warp to a gradually lessening extent as the root was approached. Only suitable for thin foamy wings i must stress, but makes a great 'invisible' way to get roll control on something like a flying model of a bird (hint)....Rick.