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If the flaperon cause a pitch down and up elevator can compensate that, that is exactly what I expected on a normal plane (not delta wing). that sounds like would be good for the air brake I want after a fast landing on a runway to stop the plane from over shoot the runway.
jhsa: I was right the 1st time.

flying character is not an issue for this application, it is for after landing. I have a couple EDF with little wings I know it will come in fast, and the run way in my club is not very long. once over shot it is dirt, every time I over shot it bends my front wheel. of course I may have to master high alpha to do this too, but that will take some scary trial and crash for sure, these edf can go 100+mph with little wings.
I was flying planes without wheels and grass landing which has no limit of run way. And I am not a acrobatic flyer either.

kaos wrote: jhsa: I was right the 1st time.

Yeah? ok, then try it
Flaps increase lift as far as I know.. That is why I always been told to retract the flaps right after landing when I learnt to fly 1:1 planes. But if you think the other way is correct, then try it..

João

Flaperons causing pitching might be dependent on the plane. My Tower Hobbies uproar, I can use the ailerons as elevators if I would like. One time I tried experimenting by having both ailerons go down (like flaps) with the elevator up. So maybe I could make faster loops. I was surprised in flight when I enabled it and pulled full back. The ailerons actually had more authority than the elevator and it went nose down instead of up! So really you will just have to test what it does on you particular plane to see what happens. Kaos, can I suggest doing taxi runs to test your ideas, might save a few crashes.
-Gohst

For sure you don't want flaps DOWN to help get stopped on the ground! Spoilerons are called that because they spoil lift while creating drag by going UP. Likewise, air brakes normally go up or sideways.

On several EDF models that I've seen, including my own Habu, the most effective measure was to set up the ailerons to give about 20-30 degrees UP for landing. This increases drag while reducing lift and allows you to fly it safely at a higher angle of attack (lower speed) without tip stalling and while maintaining full aileron control. Anything you do on the ground (short of arrester wires and a hook) will be much less effective than landing more slowly and consistently. Ideal is inboard flaps down and ailerons up (crow on a glider).

gohsthb wrote:Flaperons causing pitching might be dependent on the plane. My Tower Hobbies uproar, I can use the ailerons as elevators if I would like. One time I tried experimenting by having both ailerons go down (like flaps) with the elevator up. So maybe I could make faster loops. I was surprised in flight when I enabled it and pulled full back. The ailerons actually had more authority than the elevator and it went nose down instead of up! So really you will just have to test what it does on you particular plane to see what happens. Kaos, can I suggest doing taxi runs to test your ideas, might save a few crashes.
-Gohst

Definitely. On the delta I mentioned, the ailerons were a long way behind the CG and functioned as elevons in pitch. So down flap means down pitch. Very predictable.

On the other hand, if they are close to the CG, as on a conventional plane, the situation is much less clear. They may have less direct pitch authority and affect the attitude mostly through the change in lift. In other words, down flap increases lift and raises the nose. So it could go either way. There's really only one way to find out -- in the air, carefully!

Regardless of pitch effects in the air, it's predictable that down flap will increase lift. Whether this will cause the model to pitch up when on the ground or nose over, it's not desirable and needs to be compensated with elevator. At the very least, as gohsthb says, some ground testing would be in order.

All are good input. The only thing I am not sure is the 'lift' on ail down. Cause we are not talking about just 30 degree down, it is full ail down with extended limit, which probably won't generate lift after landing while the spd is reducing drastically without any power input. But all this is in theory. A wind tunnel test would be good. but we don't have a wind tunnel. It also depends on the ail to CG and ele to CG which gives different fulcrum to CG. The surface area of ail is much bigger than the ele so how to balance these two counter acting forces is individual plane dependent.
and yes, taxing test run is also on my mind, the only issue with that is to get to the spd of lift off, I will already used up most of the run way. I guess I just have to see when actually trying it.
But every one should agree this is a good brain teaser.

Even 90 degrees of flap will generate lift, especially when you are very much in ground effect territory. It's almost like a hovercraft.

It's for sure you will get lift. The rest is less clear!

if the lift is at the back of CG not the entire plane then it pushes the head down which is good for my purpose and the ele will keep the tail going up and keep wheels on the ground. at least that is the thinking.
the goal is to create a big drag while keep wheels down, especially the front wheel to steer on the ground.

Looking forward to videos or at least an account of how it goes. Good luck!

I think I can find a large parking lot in a near by school yard where during the wk end there is virtually no car in the lot. I had flown in the yard a few times before when the parking lot and the yard was empty. with enough flat surface I should be able to do some taxing run to experiment with different theories. But I need to get my lipo out of my steel bath tub 1st, they have been sitting in there for > 1 month while I was away.

I will do some video when I get to it.