Wing tip stalls and flaperons?  
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Wing tip stalls and flaperons? - 8/10/2003 3:33:31 AM   
Wings-RCU



Posts: 695
Joined: 1/5/2002
From: Green Bay, WI, USA
Status: offline 		I have my flaperons mixed with elevator on my Sledge and it seems to fly better especially in 3D. In fact I leave it on all of the time except in elevators, and then I use spoilerons. I'm thinking of adding flaperons to my 29% Edge. My 29% does have a habit of dropping the right wing with enough elevator so I'm a little leery of adding a flaperons to elevator mix. Does any one have experience with this? What can I expect?
       Post #: 1

Re: Wing tip stalls and flaperons? - 8/10/2003 4:20:35 AM   
Tall Paul



Posts: 4664
Joined: 6/23/2002
From: Palmdale, CA, USA
Status: online 		[QUOTE]Originally posted by Wings
I have my flaperons mixed with elevator on my Sledge and it seems to fly better especially in 3D. In fact I leave it on all of the time except in elevators, and then I use spoilerons. I'm thinking of adding flaperons to my 29% Edge. My 29% does have a habit of dropping the right wing with enough elevator so I'm a little leery of adding a flaperons to elevator mix. Does any one have experience with this? What can I expect? [/QUOTE]
.
Depending on the altitude, either a rebuild or a complete toss into the local land fill.

(in reply to Wings-RCU)
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Wing tip stalls and flaperons? - 8/10/2003 8:03:49 AM   
Wings-RCU



Posts: 695
Joined: 1/5/2002
From: Green Bay, WI, USA
Status: offline 		Tall Paul, Why? Many of the TOC guys are using this setup on 40% planes? I'm pretty sure they are not regular contributors to the land fill. Have you tried this? Did you plant one because of this, or is this a guess? Why would it work on some but not others?

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Wing tip stalls and flaperons? - 8/10/2003 8:43:58 AM   
Tall Paul



Posts: 4664
Joined: 6/23/2002
From: Palmdale, CA, USA
Status: online 		Flaperons or flaps?
Seperate flaps, inboard of the ailerons would present no problem.
Using ailerons for flaps does.
The downgoing surface becomes a flap in essence. The stall angle of attack for a flapped surface is lower than that of the surface with no flap or the flap retracted.
Deflecting a surface down then, on a wing already close to stalling, results in a stall on the downgoing side... the classic "tip stall".
When one side stalls, the plane yaws/rolls over towards the stalled side.
The instinctive response is to try to raise the downgoing wing. The instinctive response keeps that wing stalled, so the situation just gets worse.
Wolfgang Langewiesche examines this thoroughly in "Stick and Rudder" BTW.
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Another problem is with both surfaces deflected down, roll authority diminishes.
Again, it's the surface that is going down, or is as far down as it can get, while the surface on the other side is going up that's the culprit. Drag on the downgoing side increases, or stays the same, while both lift and drag on the upgoing side diminishes.
The result is adverse yaw... at times to the extent the airplane turns -against- the commanded direction.
TOC guys surely know this, and don't go into the deflection ranges where it becomes a problem.
.
Encountering it unexpectedly is both disconcerting, and disorienting.
"Something's wrong! I'm pushing right, but the airplane is going left! INTERFERENCE!!!" ... Nope! Aerodynamics.
.
For me, seperate flaps are a safer way to get the same results.

(in reply to Wings-RCU)
       Post #: 4

Flaperons - 8/10/2003 12:52:33 PM   
Mike James



Posts: 2441
Joined: 1/19/2002
From: Anchorage, AK, USA
Status: offline 		This is meant to be honest and constructive, not "mean"...

I'm a relative amateur at 3D, because it's not my main interest in RC, but have done some, and have been flying otherwise for about 35 years. This issue of flaperons and spoilers keeps coming up here on RCU and elsewhere, and here's my opinion... Buy a different plane, made to take advantage of those devices.

With a typical, lightly-built 3D plane, you should never need flaps for landing. These planes are great at low speeds, if built properly. The "up elevator/up aileron" mix used for aerobatics is good, and when I have a plane with that mixing setup, I just leave it on all the time....but these planes land so slowly anyway it really doesn't seem to matter enough to mention.

Separate, inboard flaps are one thing, but these fixes on planes that don't really need them is typically just asking for more ways to create an accident. Usually that accident is a tip stall.


_____________________________

Mike James
RC Design and Building - www.nextcraft.com

(in reply to Wings-RCU)
       Post #: 5

Wing tip stalls and flaperons? - 8/10/2003 8:50:27 PM   
Wings-RCU



Posts: 695
Joined: 1/5/2002
From: Green Bay, WI, USA
Status: offline 		I'm not interested in slowing the landing, getting rid of the wing drop or even thinking about inboard flaps. I want positive control in stalled conditions. No stick & rudder stuff here. I.e. tighter stalled loops (flops), walls, waterfalls etc. Adding flaperons linked to the elevator (up elevator/down aileron) on my Sledge gives me climbing flat spins, better tumbles, great waterfalls and easier hovers. My question is: will I achieve any of this or just make for a snappier plane if I add this to something a little larger?

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       Post #: 6

Wing tip stalls and flaperons? - 8/10/2003 10:01:35 PM   
Tall Paul



Posts: 4664
Joined: 6/23/2002
From: Palmdale, CA, USA
Status: online 		Those low-to-zero airspeed manuvers are relying on prop blast on the control surface for any turning effect.
Unless the ailerons extend inboard enough to be in the prop blast then using them as flaperons will be kinda useless, for those conditions.

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       Post #: 7

Wing tip stalls and flaperons? - 8/10/2003 10:34:04 PM   
Wings-RCU



Posts: 695
Joined: 1/5/2002
From: Green Bay, WI, USA
Status: offline 		Tall paul, It looks like the Sledge ailerons are certainly in the prop blast. On the Edge the ailerons come to about 2 in from the fuse sides or about the same width as the cowl.
What do you think?

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Wing tip stalls and flaperons? - 8/11/2003 5:22:12 AM   
Tall Paul



Posts: 4664
Joined: 6/23/2002
From: Palmdale, CA, USA
Status: online 		With the Sledge configuration, flaperons should be OK for the low speed stuff.
But at normal flight speeds, the adverse yaw will overcome the expected response..
The image is Tony Frackowiak's "Hovering Cobra" in a very slow climbing right turn. Note ALL the down aileron on the right side! Should be rolling left... .
The prop blast and thrust is doing more of the flying than the wing is..

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