I consider myself fairly knowledgeable but I now find myself stumped. I outfitted my SlowPoke with flaperons and maidened her today. I got some altitude, deployed the flaps and she dove hard. I almost did not have time to turn them off and recover. Why did this happen? I was thinking it is due to the ail. being mounted on the outbound section of the wing. I know I did not need them with such a wide wing but I thought with the flaps I could get zero ground speed in a slight breeze.
Anyone have any thoughts?

Flaps always cause a pitching moment. Most planes pitch up when the flaps go down, but some, like yours, pitch down. I'm thinking the planform of your plane is such that things happen a little differently than with a more conventional plane.

The slowpoke is a VERY short coupled arplane with a wide chord... The flaperons acted more like elevons on a flying wing and overpowered your elevator.

The CaffeenMan is correct, it's pitching moment.
An airfoil's pitching moment can easily change by an order of magnitude with down flap.
The camber change is the culprit.
But now that you are aware of the potential problem, try say less deflection.. or try the spoileron direction.
For a surface at the tip, moving up is safer in terms of tip-stall, than going down, which enhances the chances.
Also the return to flying trim is less extreme when the additional deflection is removed.
On a plane with no tail, the pitching moment of the surface does the control thing... reflexing up for up elevon, which creates a positive pitching moment, and when moving down increases the negative pitching moment.

Thank you all for your input. Your comments have cleared up this problem considerably. I will attempt to deflect them upwards and see how the plane reacts. If anything it should increase the AOA that she will fly. Roger

Flaps down = increased angle of attack.

Flaps up = decreased angle of attack.

The angle of attack is a straight line from the center of the trailing edge to the center of the leading edge. When the flaps go down, so does the center of the trailing edge.

Ok now I am a bit confused again. Since the plane has a short coupled airframe and a wide cord the flaps were overpowering the elevator, essentially working opposite of what they should. I thought I understood that if I deflected the flaps up on the outbound portion of the wing it would essentially add "Wash Out" to the wing. reducing the possibility of tip stalling. Therefore you could increase the AOA. Where did I go wrong reading the posts? Feel free to educate me as now I am lost.

OK, read my last post again. Draw an airfoil if you have to. Draw a centerline through it.

Now draw it with the flaps down and draw a centerline as I indicated in the last post.

Wash-out is reduced incidence at the tips. If you have separate ailerons and flaps and deflect only the ailerons up, then you have wash-out.

The aileron version slowpoke .40 size have the ailerons go to the wingtips? I had the Lil' Poke... same design... but smaller the aileron version uses center section control surfaces. (oddball setup... no control surfaces from the polyhedral break out )

If its like the Lil' Poke... Deflect the ailerons up (as flaperon/spolerons...) and you wash out the center section of the wing... but not the tips. That would GUARANTEE that the tips stall before the root. (lets spin an airplane.)

If its got a single dihedral break at center... and full span control surfaces... you would not be guaranteeing the tips would not stall... but you'd be better off than trying it with the small version.

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The design is ideal for use without flaps or spoilers though... It should do a "Harrier" type landing (see the 3D/Fun-Fly forum) with no problem. Short coupled... relatively large elevator compared to the horiz stab... If it had a full symetrical airfoil... it would be a Fun-fly design.

A trick... couple the ailerons to elevator so both go the same direction... and it should do REALLY tight loops. (the little one did... Loop dia was almost down to its wingspan.) Makes the elevator touchy... have it a program mix that you can turn off.

If you have separate ailerons and flaps and deflect only the ailerons up, then you have wash-out.
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Ok I understand your definition of AOA, totally clear on that. Now I am confused as to the above statement. If I am not dropping an inboard flap what does it matter if they are there? Would not raiseing the Ail. give the same affect on any plane (separate flap or not) in that case?

Deflection of a control surface on a trailing edge alters the camber.. Down, increases the camber, and the pitching moment.
And for a surface such as an aileron, this means the wing ahead of the surface has "wash-in".
Deflect the surface up, the camber changes, but the pitching can be decreased... and the wing ahead of the surface has "wash-out".
Wash-in makes the plane more susceptible to tip-stalls, as the angle of attack, AOA, as the Caffeeman mentions increases. If the plane is already near the stall angle of attack, the change is frequently enough to push the AOA past the stall point. The wing on that side stalls.. and the plane rolls over... as the wing on the other side is not stalled, it lifts, and the plane rolls -opposite- the command direction. towards the stalled side. This leads to confusion, as more aileron in the same direction doesn't fix the problem.
Wash-out OTOH reduces the chance of a tip-stall, as the AOA for that part of the wing is decreased, and the center section will stall first, which is a "good" condition.
For outboard mounted surfaces, therefore, spoilerons are better than flaperons..
When used -with- flaps, flaps down and spoilers/ailerons up is commonly used on high performance gliders, in the "CROW" mode. Adds LOTS of drag, without increasing speed, for precision landings.
Flaperons have another problem.. When both are down as far as they can go, they lose the "aileron" mode. Turning now must be done with the rudder, if the flaperons are really down. When commanding a right turn, say, with flaperons, the right aileron goes up, as it should. The left aileron -should- go down, but it's already as far down as it can get. The result is the drag on that side doesn't change.
On the other side though, both the drag and lift decrease as the surface goes up. The result is much like a tip-stall; the plane turns -opposite- the commanded direction. Disorienting and confusing when it's first experienced.
The spoileron situation though is benign.. the spoiler that's as far up as it can go on the right stays up when a turn is commanded .. the drag doesn't change.
The spoileron on the other side now moves down, decreasing drag on that side, and the plane turns into the expected direction.

Ok I understand your definition of AOA, totally clear on that. Now I am confused as to the above statement. If I am not dropping an inboard flap what does it matter if they are there? Would not raiseing the Ail. give the same affect on any plane (separate flap or not) in that case?
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Washout is a twist in the wing. If you have strip ailerons and you raise or lower them both then you have simply changed the camber, but you have not twisted the wing. If you have barndoor ailerons and your raise them, then yes, you have wash-out regardless of whether you have flaps or not.

Basically wash-out means the tips are flying at a lower AOA than the root. So strip ailerons won't do it unless you actually build a twist into them.

Hmmm flaps on a slow poke? Thats an interesting one! Well, the lovely slow poke was designed to be what originally was ment to be, that is, a slow flying low-winger with basic aerobatic abillities. How could you possibly want an even slower flying speed from that massive wing area??

Sorry, Left out that important bit of info, they are barn door type ail. Essentially if I get what you are all telling me is it would be better if they deflected up not down to get the desired effect.

FHHuber
FYI The .40 has ail. from the polyhedral break to the tip. there is not a lot of polyhedral on this airplane just a couple of degrees, it does have a flat bottom wing however.

Sorry, thats just me never satisfied with the stock configuration on anything. I was happy with the way it flew out of the box. Just looking for something more I suppose

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Yes, up is safer...

I made my maiden flight in my GP Big stick 40 ARF today and the same thing happens... Not to much of a dip but it did... My CG was at the recomended 3 3/4", but I think it may be a bit nose heavy... I guess the farther away your CG is from the flaps or center of lift, the more likely the aircraft will pitch down when flaps are applied. I am going to move my CG aft a little for better 3D, flat spins etc. and I bet it won't pitch down as much when the flaperons are applied... I hope that this works because it sure comes in hot on landing and I either NEED the flaperons or moving the CG aft in itself will make for a slower approach... Is my theory correct?

Forgot to add the noticeable mushyness of my ailerons in flaperon mode... I almost dropped a wing into the deck on one landing because of the lack of response...

The "drop the wing" is the problem with flaperons... the wing stalls -sooner-!
It may be developing more lift, but the stall angle is now less than it was, so the wing on the side with the downgoing aileron stalls.
The plane then will roll towards that side as the other wing is still flying.
The felling of mushiness goes along with this.
The aileron that is already down has more effect on the plane in terms of drag on that side than the aileron which is going up when a turn is commanded, to the extreme situation where the plane turns -opposite- the command.

Scott, I do not think that the CG has much to do with my problem, because I set mine aft before I flew. I set it closer to the recommended CG range and I wanted to get out today to try it out but that didn't happen. As a general rule I thought that having the CG forward = longer glide more stable. CG Aft = steeper glide angle more aerobatic. Of course I have been wrong with just about everything in this thread.

A more forward CG will require you to fly faster. Nose heavynessrequires more up elevator at slow speeds which you need more power to compensate for (my theory)... I also know that flaps, when lowered will make a plane pitch down... It is science as far as I'm concerned... I have just learned to use rudder for direction and roll control for landing with full flaperons... My Big Stick has little to no aileron control when doing a slow full flaperon approach... I flew today on my way off base and there was no wind!! NO WIND IN OKLAHOMA!!!!!!! It was a rarity so I pulled up to the field (had all my stuff in the truck anyhow)... With no wind I started approaching with no flaperons slower, and slower until I was able to land at a reasonable speed and not roll off the end of the runway... I guess it is just the fear of stalling... Well happy flying to all, and who ever prayed for no wind in Oklahoma, do it again... haha