freakingfast

My Feedback: (3)

What are these little fences on the wings and stab for? Do they actually work?

BMatthews

I think that they are there to avoid airflow through the gap which would occur when the controls are deflected. But they'll add some drag on their own which is permanent. So it's a tossup if they help or hurt pending some actual testing in a wind tunnel to determine if they are a good thing or not.

da Rock

They probably come under one of two categories:

1. Baffle the competition with something incomprehensible and you'll gain a edge, especially if that something doesn't hurt your performance.

2. Anything you think works for you does, whether or not it does.

combatpigg

My Feedback: (3)

Tape little crepe paper streamers to the wing tips and stab tips, then go do some flights with and without the fences.
You might need to get pretty good [zoomed in] video to be able to observe any difference in the streamer's behavior.
The only other thing I can imagine doing on those test flights would be to record the model's speed and handling while doing pylon laps.
Problem with my idea is it might be difficult to find a clean way to mock up the experiment.

Yak 52

It's a bit odd. It's obviously a fast model with a lot of attention being paid to drag, by the look of the planform. But the planform and partial span control surfaces would be more about reducing induced drag at low speed. And yet the fences surely add parasite drag at high speed...?

da Rock

Hey, just discovered that they are on the full scale Alley Cat. That's certainly interesting, if not really very informative as to the value.

da Rock

BTW, one would guess they would work for the surfaces they border as tip plates work for wings. They might increase the effective span/aspect ratio of the surface making it more effective.

speedracerntrixie

My Feedback: (29)

Yes, they make the surface more effective by not allowing airflow to spill off the surface tip. This means less deflection, less drag created by deflection, more speed.

rmh

In the real world fences,dams and spades DO work -on even tiny 2 ounce indoor aerobatic models
in some cases they stop all wing wobble in high alpha flight Ialso used tip plates on a 33% EDGE Very effective.

AmishWarlord

My Feedback: (5)

Looks like mass balancers to me. Can you tell if they are weighted "full of lead"?

da Rock

Looking closely at the pictures, they appear to be part of the wing.

AmishWarlord

My Feedback: (5)

Ah I see that now. I couldn't tell on the cell phone.

freakingfast

My Feedback: (3)

Thanks for all the responses guys. I was guessing that they were there to help stop a stall propagating down the wing or control surface under hard maneuvering at high speed. Then again they may be there to induce conversation, in that case they are functional.

rmh

Fly more - cogitate less-

Sport_Pilot

Faster roll rate less time in turn.

speedracerntrixie

My Feedback: (29)

I set up my pylon airplanes to be a bit slow on roll rate. The easiest way to kill airspeed is overfly the airplane. Slow bank to knife edge, carve a nice turn. Too tight and you drop alot of speed. If running a 2 stroke, it takes a lap or two to get the engine unloaded again.

vasek

My Feedback: (4)

^+1 and why does that creepy pilot wear a "chainsaw" mask ?

Sport_Pilot

In full scale they tend to wait till the last second and roll to the required bank as fast as possible. But probably easier to do and roll rate less in full scale.

Simul8R

My Feedback: (1)

They look like the equivalent of winglets for the end of the control surface.

They will control a tendency for air to move spanwise into the reduced air pressure over the deflected control surface. They will probably reduce the adverse aileron yaw noticably so you'll get a drag reduction due to better coordinated turns.

I can't imagine there will be a significant increase in parasite drag but there will be some, probably be offset by the reductions in deflected control surface drag by making the control surface deflections more efficient thereby reducing the deflection needed to get the desired effect.

Just my best guess.

HoundDog

My Feedback: (49)

Wouldn't flying a true Ellipse, Close to the Pylons be the fastest way around a 2 Pylon Race Course? Just Asking. It seems the smoothest pilot comes out on top more often than an erratic pilot.


Edited to remove a lot of format coding.- bmatthews

rmh

The actual flight path really depends on th e type of model in the race - a slow event requires the minimum distance -a really fast -high wing loading model on a short course -may fly almost a round path.
(I have flown both types)

BMatthews

Hounddog, if you're composing your text in some other application and then cut and pasting it here do so as "text only" to avoid a lot of formating baggage. Thanks.

For model pylon racing where the planes are so light and the course relatively short compared to the speed a tight turn is what they want. But if they try to turn TOO tight then it generates too much drag and bleeds off too much speed. So like most things in life there's a compromise to be found which results in the fastest way around the course instead of the shortest.

flycatch

My Feedback: (26)

Bingo!!!

HoundDog

My Feedback: (49)

[quote]ORIGINAL: BMatthews

Hounddog, if you're composing your text in some other application and then cut and pasting it here do so as "text only" to avoid a lot of formating baggage. Thanks.

Where's the Flippen Spell Checker for the RCU word processors ...

Rotaryphile

Control surface fences are intended to reduce leakage of air at the ends of the surface, increasing control effectiveness, and reducing drag and yaw. Somewhat similar to gap sealing.

Evidently, they have been considered to be worthwhile on some competition sailplanes, improving low-speed aileron effectivness, and more than offsetting their slight additional drag in straight flight. Nice conversation piece at the field, too.

It would be relatively easy to tape temporary fences to a wing for a quick low speed handling test, taking care to ensure that they won't come adrift and jam an aileron.