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-   -   Flaperons: Up or Down? (https://www.rcuniverse.com/forum/aerodynamics-76/89838-flaperons-up-down.html)

Jazzy 03-28-2002 04:37 PM

Flaperons: Up or Down?
 
I need a info/advice.
I've been setting up my sport and aerobatic models such that when I'm on final, the ailerons drop slightly acting as flaps.
Lately, I've been hearing about raising them, (for highly aerobatic models), to induce washout to help prevent tipstalls when going too slow for aerodynamic efficiency.
My WM SuperChipmunk has inboard flaps which work nicely. Does the fact that they are inboard as opposed to full aileron make a significant difference?
Would dropping or raising them on a 9 lb. .60-.90 Cap 232 have significantly different effects? (I haven't had a chance to try them on it yet.)
A little clarity on this matter would help me understand it much better. (I do understand the aerodynamic basics of washout and flap drag.)

Thanks,
Jeff

Dansy 03-28-2002 05:41 PM

Flaperons: Up or Down?
 
I used to up side of the flaperon on my GT Giles 202 (pattern version Gator)it actually mixed with elevalor, the end product is a slower approach with a fairly high nose attitude and usually require to apply some throttle, I have started using this to shorten my roll out at funfly since there field were quite small....it also work very well on the funfly 3D aircraft by having a approach that is very steep to a smooth landing.

You should tried at altitude first to dial in the elevator, I could look at my programs (JR) but you don't need that much deflection to be effective.

Daniel D.

niccolai_m 03-28-2002 06:09 PM

Flaperons: Up or Down?
 
1 Attachment(s)
I an ideal world you would have flaps and airleron with your transmitter programmed such that...

1. For aerobatic flight the flaps would move in the same direction as the ailerons for roll (to improve roll rate) and the flaps would move in the opposite direction to the elevator (to improve pitch rate). If you were ambitious you could try making the airlerons move in the opposite direction to the elevators too, but you'd probably only want to do this when you've got pretty good airspeed. Doing this at low speed would invite a tip stall.

2. For approach and landing you would have the flaps move in a convetional manner (down) and the ailerons would attend to roll. The flaps going down would in effect give you washout.

3. If you were really ambitious you could dial in some roll control with your elevators too.

This is the sort of thing that modern combat and civil aircraft do but they have sophisticated sensors and computers to handle all this for them. the civil guys do it to reduce fatigue and the combat guys do it more for the reasons that you are. It's one reason that the F18 shown here made it home missing most of one wing. Happens about twice a year, sometimes the damage is much worse.

bob_nj 03-28-2002 06:23 PM

Good Question Jazzy
 
And very eloquently put. My experience is that different designs act differently with the addition of up or down aileron used as flaps. Flaps and flaperons are strange animals, but very interesting nonetheless as you've questioned. What I call Flaperon being a Futaba dude, is the lowering of the ailerons mixed with the raising of the elevator and vise versa. This is an old technique used by the U Control guys to smooth out loops and other looping type maneuvers. It seems to give the wing better lift. In R/C, it can and is often used during flight in general and not just landing. Again, it makes life smooother.
Reflex, or raising of the ailerons is used more and more these days with the advent of 3D and such. It seems to help in Elevator and Harrier type maneuvers to keep wing rocking to a minimum.

I've been hearing about raising them, (for highly aerobatic models), to induce washout to help prevent tipstalls when going too slow
Although is does help as far as washout, remember that a full span aileron is also washing out the root. Use reflex sparingly and after testing different attitudes and flight characteristics.
In my mind flaps create lift, reflex dumps it.

Does the fact that they are inboard as opposed to full
aileron make a significant difference?
My first reaction is yes. This is no longer a flaperon but a true flap. It's doing what flaps do, and that is to keep the root from stalling before the tips. I would NOT raise them unless you had much altitude to play with and they were on a switch as opposed to a function that is on all the time.
The purists may correct some of this, but until then...

Jazzy 03-28-2002 10:25 PM

Geat Answers!
 
Thanks a great deal!
Since I've got three T6XAs I'm right with ya Bob.
Using a mixing switch, I have experimented with my Advance 40 by coupling the elevator with the ailerons, (two servos there). Coupling them such that the ailerons, (which now are working as both flaperons and ailerons), move in the same direction as the elevator. At moderate speeds, vertical tail movement is very evident. With them coupled oppostie, it'll turn and loop like a fun-fly.
When I'm lining up I flip the airbrake switch which drops the flaps about 85% and puts in a touch of down elevator. Good for those days when your plane just doesn't want to come down! (Its like its doing it on purpose.)
Given the illumination from the above posts, I think I'll just stick to what I've been doing. I seems I was doing the right thing.

Thanks again All and thanks for the compliment Bob. I tried to be concise and to the point.

Theres one less thing to worry about...

Jeff

Ed_Moorman 03-28-2002 10:48 PM

Flaperons
 
If you are using a computer radio, you can set your ailerons to reflex upwards slightly at low throttle, after being armed with the Landing Switch, and drop back to the normal position above half throttle. I use this setting on most of my airplanes.

Since you have separate flaps and ailerons, you also can use the Ultra Stick setup and use crow for landings.


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