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Old Mar 07, 2012, 07:22 PM
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Fixed leading edge slats, examples

I am just looking for examples of fixed slats on RC aircraft. Links to threads and such. Find a lot of attempts at retractable LE slats, but not much on fixed.

In this case it's going on an Eagle 2, for hopefully STOL like take-offs and landings.
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Old Mar 08, 2012, 10:52 AM
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"In this case it's going on an Eagle 2, for hopefully STOL like take-offs and landings. "

At our Reynolds numers, they are not likely to be at all effective.

Les
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Old Mar 08, 2012, 02:28 PM
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I have heard that before, however wouldn't airflow separation be more significant at our numbers?
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Old Mar 08, 2012, 05:15 PM
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oooooooh snap! my fifth R/C plane in the mid 1990's (and my first 3D/Funfly) was a crazy ungodly light weight design called an eliminator. It had optional fixed slats (made of 1/8" balsa sheet you wetted & curved to follow the wing). what you did was glue 1/4" balsa stand off blocks onto the top portion of the leading edge * the slats started just above that. roughly like this



the slow flight was absolutely crazy. all funflys will fly slow. frankly they're all only 3-4 pounds with thick, high lift wings & tons of airflow over them. and you always hear stories about planes flying backwards. but that plane at idle no joke would fly backwards in very little wind. not even gusty it had so much lift.
plane was destroyed after several WOT, 90* straight down wall pullouts. nobody had informed me that it was a plane that couldn't fly that fast & the G's made the wing explode into balsa & covering pieces. fuse lawn darted with such impact it buried passed the engine.
kept one of the slats. only part of the wing that survived.





they work very well. however:
1) flaps work better with no drag penalty
2) why would anyone need slats on an eagle 2 (which normally builds light weight for trainers in that size class making them even more floaty!). in fact. MORE lift at low speed is EXACTLY what you don't want on a trainer. it makes them harder to land as they want to keep flying way too much. mixing in spoilers makes trainers handle much better at low speed. you can pull the throttle back & the loss of lift will actually let the plane have a sink rate.


slats are not used simply because the airframes that could benefit from them, you can simply mix in flaps for no weight/drag penalty
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Old Mar 08, 2012, 11:32 PM
TigreJohn
United States, CA, Corona
Joined Aug 2008
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If you want STOL performance with a minimum of construction grief, stick with flaps. Here is a good example of what can be done with them.

Alaska bush pilot (1 min 0 sec)


Other than that, if your still want fixed LE slats, look for airfoil data on the Feisler Storch.
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Old Mar 09, 2012, 10:58 AM
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"I have heard that before, however wouldn't airflow separation be more significant at our numbers? "

Not from my research has indicated.

Les
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Old Mar 09, 2012, 12:25 PM
Zor
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A fascinating project

Quote:
Originally Posted by RCB1 View Post
I am just looking for examples of fixed slats on RC aircraft. Links to threads and such. Find a lot of attempts at retractable LE slats, but not much on fixed.

In this case it's going on an Eagle 2, for hopefully STOL like take-offs and landings.
RCB1,

I have not seen as yet any fixed slats on a model airplane.

It would be fascinaing to build a model airplane with slats huilt in (built on ?).

Some full size airplanes have slats that open automatically when the stalling angle is approached.

Even that (automatic) would be a nice challenge for a model builder.

I certainly encourage you to have fun experimenting with its design, construction and flying results.

There is still a few of us modelers who enjoy this kind of activity.

Perhaps they could be shaped from cabon fibers to give them more rigidity in the event of landing in stiff growths.

Let us know of any decision you make and pictures of any construction. It would not be too difficult to make. The importance would be their cross section shape and the location in relation to the leading edge.

By all means, enjoy a challenge.

Zor
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Old Mar 10, 2012, 08:20 AM
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As stated above, the Fiesler Storch has fixed slats. Here are a few pics of my friend Glenn McIntosh' 1/5 scale model.

Glenn took 3rd place at the Toledo Show with this model, and it was also featured in High Flight magazine.
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Old Mar 10, 2012, 08:48 AM
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Here we go again! I LOVE it! There are those who ask "Why in the WORLD'? and then there are those of us who say -yeah-why not??
Made slats years ago,on a Piper cub.Finally got the illusion of scale speed with them. Whatever they did to the airflow was nothing compared to what they did to the aileron response. It slowed the aircraft to where it became rudder only.
You think they have no effect ,then say why would you need to go slower with an Eagle?
No effect? You try putting them on the bottom of the leading edge ,and tell me that! It stalled as if the wheels hit a wire!!!

Slats are the equivalent of a bi-plane wing,but they only work in short chords,close to the wing surface.,at the leading edge...exactly like a 'Jib' sail feeding wind into the Main'sl.,on a sailboat.
Is it clearer now? Still wanna know why? It's because they work...up to a point.
I only wanted to go slower,with more control and that worked.except the airflow was spoiled over the ailerons at very high alpha.1/4 " crepe paper streamers never touched the ailerons at very slow speeds.(on top)
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Old Mar 10, 2012, 09:08 AM
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Quote:
Originally Posted by LesUyeda View Post
"In this case it's going on an Eagle 2, for hopefully STOL like take-offs and landings. "

At our Reynolds numers, they are not likely to be at all effective.

Les
A leading edge slat is effectively the size of an elevator on the tail....is an elevator effective at our reynolds numbers?
sorry-just thinking out loud.lol
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Old Mar 10, 2012, 09:20 AM
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oh wait. you said slats. (which extend from the leading edge of the wing down & forward & are a part of the AIRFOIL) i was talking about fixed SLOTS. they help keep air attached to the wing at high AOA. couldn't find the actual one remaining slot i was talking about. (it's somewhere im sure... always the last place you look!)

but look what i did run across no telling what decade this plane was from (70s-90s), but other than being... not suited for high speed and blowing into a gabillion bits, it was a nice little funfly for the time. altho i still say the slots were gimmicky. typical full length barn door ailerons it had a high roll rate (so ive no comment on aileron effectiveness. they worked but they were huge with big throws. it was something everybody ooo'd and ahhhh'd over (and they looked great being florescent orange on front of a black wing hah), but flap/spoileron mixing woulda done much better.










by that the Fiesler Storch example above does not have SLAT's it has SLOT'S!



slat (note it is extending the airfoil. flaps in reverse if it were)


slot (not it is only keeping air attached to the airfoil at high AOA)
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Old Mar 10, 2012, 10:33 AM
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"A leading edge slat is effectively the size of an elevator on the tail...."

Elevator on the tail is more akin to the tail feathers on an arrow. As in horizontal and vertical "stabilizers".

Les
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Old Mar 10, 2012, 07:07 PM
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Quote:
Originally Posted by LesUyeda View Post
"A leading edge slat is effectively the size of an elevator on the tail...."

Elevator on the tail is more akin to the tail feathers on an arrow. As in horizontal and vertical "stabilizers".

Les
Don't correct me out of context.....I was comparing "reynolds" numbers.....if they'll affect an elevator,they'll affect a leading edge slat of the same size....
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Old Mar 10, 2012, 09:22 PM
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<3. .
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Old Mar 10, 2012, 11:02 PM
Zor
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Quote:
Originally Posted by TomCrump View Post
As stated above, the Fiesler Storch has fixed slats. Here are a few pics of my friend Glenn McIntosh' 1/5 scale model.

Glenn took 3rd place at the Toledo Show with this model, and it was also featured in High Flight magazine.
Hello Tom,

I am trying to understand what are all these black (dark) pieces distributed along the length of the slat seen in the picture to the right.

I cannot think of curve guages as not that many would be needed.

Anticipating your response. Thanks.

Zor

Edited by Zor 11 March 2012 at 00:58 EST
I ma guesssing they are the parts that will hold the slat in place and keep the gap after they are relocated.

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