Leading edge slot

[mulwyk]

Anyone have experience with a leading edge wing slots? (Like Stinson, Zenair, maybe others) Opinions, please.

[VictorBravo]

Re: Leading edge slot

Anyone have experience with a leading edge wing slots? (Like Stinson, Zenair, maybe others) Opinions, please.

I have some amateur research experience, but no field experience.

The slot is something that needs to be designed into the wing from a clean sheet to have the most effectiveness... it's not like stick-on VG's that can be added at any time and have most of the effect.

Fixed slots (Fieseler Storch, Zenair 701/801) make a very significant amount of drag 90% of the time, and (according to Heintz) only at one AOA can be made to produce a lower amount of drag.

Retractable slots (Helio Courier, Morane-Saulnier Rallye) allow a wide speed range and no drag penalty at cruise, but are complex to design and build correctly. There is also a potential flaw with "automatic" airflow operated slats where gusty winds near the ground at minimum speed can snap one shut and leave the other one open. So maximum STOL operations carry some risk with the simplified "automatic" slats (which are effectively slots).

The ideal way in terms of having the best of both worlds might be to have some lightweight method of positive actuation (manually operated slats) that do not open and close by themselves.

For two REALLY great resources, go to :

www.zenithair.com and find the series of technical design articles by Chris Heintz on the 701 and 801 designs.

www.heliocourier.net and on the right side of the homepage halfway down there is a 1960's era promotional film on the Helio showcasing the slats.

The Stinson guys will be knowledgable, but the Swift guys will be able to give you some data before/after the wing slots. The Swift had fixed slots in the outer wings, and many of them have been covered over with an STC.

[Forrest Barber]

Re: Leading edge slot

and the Taylorcraft 20 used them. C.G. Taylor also used a device on the Taylorbird that created a positive flow down around the nose of the ailerons. I would grit my teeth and use aileron to bring up a wing during a stall, IT worked.

[dewhitaker]

Re: Leading edge slot

Hey Forrest, speaking of the Taylorbird, where is it? If I could find a picture of it I would post it so others could see it.

[barnstmr]

Re: Leading edge slot

Somewhere in my stuff, I have an old NACA report which compiled the results of tests done on a Taylorcraft BC12D at Texas A&M in the 1950s. In the tests, they looked at the effects (on lateral stability) of changing the degree of washout and also the effects of different sizes and locations of slots or slats (i cannot remember which). If I can get a ROUND TUIT, I will try to post the report number here. Or you might be able to download the report from the internet like I did if you can put in the correct key words into google.

[Dick Smith]

Re: Leading edge slot

This link gives you an idea of what is possible with leading edge slot on a SuperCub.

http://s252.photobucket.com/player.swf?refURL=/&file=http://vid252.photobucket.com/albums/hh11/mscubs/20071228092926.flv&fs=1&os=1&ap=1

Watch the elevator during the approach sequences...guy's got the touch.

Dick

[mulwyk]

Re: Leading edge slot

This is why I love the T-Craft website. Great information, minimum BS.

Dick, The cub guys are absolutely nuts about wing slots. Check out the discussion on www.supercub.org or the wing kits on www.dakotacub.com Some of their claims are really unbelievable.

Terry, I've downloaded some NACA reports from the 1930's when they were testing our beloved 23012 airfoil with leading edge (and center!) slots. Great information and some explicit/practical recommendations for slot size and location. (I'll bet the dakotacub folks are using the NACA 30's windtunnel reports on slots in the Clark Y airfoil for their developments) I'd love to see the 50's Texas reports if you can pull them up.

Forrest, a Taylorcraft 20 with wing slots? Wow. Do you have more info? Drawings?

Bill, very thoughtful observations, as usual. Automatic or manually actuated slots would certainly be the best, of course. But, I hate to admit it, are beyond my skill level, and way beyond what my pocketbook will bear. I wonder, do you think it would be possible to do some sort of modification to the stock leading edge..a simple, fixed leading edge slot?

[tawadc95]

Re: Leading edge slot

Wow!!!!!!!
Is That An Approach Attitude Or What!!!

[VictorBravo]

Re: Leading edge slot

But, I hate to admit it, are beyond my skill level, and way beyond what my pocketbook will bear. I wonder, do you think it would be possible to do some sort of modification to the stock leading edge..a simple, fixed leading edge slot?

There is a way to do a fixed slot, but on a stock 23012 I would have doubts that it would do what that Cub video clip shows. It would definitely help but it would also put your T-craft into the super-STOL Cub's cruise speed range instantly.

Easiest on the pocketboook would be the VG's. Based on hearsay and flight reports and my gut feel, they will give the most bang for the buck by far far far. They are indeed in my future. Build an experimental set out of beer cans and scissors and double stick tape. See if you like them. Then if you do, pay the $700 and buy the STC'd kit.

There are Taylorcraft wing ribs available (D&E) that have sort of a slotted flap capability. Building a set of wings with those AND the VG's would probably make a huge difference. While you're at it build wingtips that don't give away a bunch of lift like our round ones do. Make a swept wingtip. Trailing edge straight or even swept back 10 degrees. Leading edge swept back about 45 degrees. Put these tips on with about 5 degrees of "dihedral" (tips raised) and you will see another noticeable jump in low speed handling, climb and stall performance. Run the VG's out to the very tips too.

The sneaky part (pay attention here) is that the VG's work very hard to prevent (delay) tip stall. Prevention of tip stalls in flight is why the designers rarely droop the ailerons down along with the flaps... they don't want the tips making a lot of lift because a tip stall near the ground is fatal. BUT...

If you have VG's that are working right, the wingtips and ailerons are flying and controllable a lot slower. SO the usual safety problem of lowering the flaps and the ailerons is delayed or minimized. So if you have the VG's helping the air stick to the wingtips, you can droop the ailerons (only about half as much as the flaps for safety), which means you are getting a lot more lift out of the wing at low speed, which means you can make some very big jumps in STOL performance.

To maximize safety while doing this, you need to have the VG's end about two feet from the root (SWAG), so the inboard end of the wing will not have the benefit of the VG's. THIS means your wings will almost guarantee to stall at the root first under all conditions, which is of course what you want.

So you could use existing, off the shelf wing ribs and aileron/flap ribs to build a flapped T-craft wing. Your biggest expense would be designing an appropriate control "mixer" to mechanically move the controls the way you want. But this, in combination with the VG's and the swept tips, would IMHO make an enormous difference... you'd be getting into the BALLPARK of what the Monster Cubs are doing.

The Zenair 701 and 801 have the fixed slot and "full s-pan flaps". The flap/aileron is all one piece. So you have full span ailerons (better control at low speed) and full span flap (maximum lift at slow speed). Start looking at zenithair.com and look at Heintz' articles on airfoils, slots and flaperons... and then look at his control system functions in the free online drawings section.

You can look into what's called a Krueger Flap, which many airliners have. This is not a slot but a leading edge flap that dramatically increases the camber of the wing. It is easier to build than a slat (movable slot).

I have it on reasonable authority (significantly higher knowledge than mine own) that slots/slats versus VG's is an "either - or" choice. Meaning you choose either VG's or slots but not both because both would not give you much more than either one by itself.

Bottom line, there is a LOT of improvements you can make. The only ones that are certified (or even easily certifiable) are the VG's and regular flaps (because later T-crafts had them). Everything else is experimental.

If you want to try the flaps and the drooping ailerons, build a set of aluminum experimental D&E wings with all this stuff and be able to remove them and put your old wings back on. If the wings work that well, build an experimental fuselage for them and have a purpose built STOL airframe that does not "cut up" a classic. If the wings don't work, sell them to some other T-craft experimenter and recoup your money without cutting up your classic.

[taylorcraftbc65]

Re: Leading edge slot

Hey Bill,
I can see it now. A pre-war Taylorcraft with Krueger flaps, V.G.s, full-flying full span flaperons, spoilers for glideslope control, AND, while we are at it, a
PT-6 for rocketship climbout. A Helio courier for a third the price.
Too bad I don't even have one TENTH the price of a Helio Courier, I'D give it a shot. Brie

[VictorBravo]

Re: Leading edge slot

Hey Bill,
I can see it now. A pre-war Taylorcraft with Krueger flaps, V.G.s, full-flying full span flaperons, spoilers for glideslope control, AND, while we are at it, a
PT-6 for rocketship climbout. A Helio courier for a third the price. Too bad I don't even have one TENTH the price of a Helio Courier, I'D give it a shot. Brie

The Zenair 701 with 100HP on car gas will climb out at the same deck angle and angle over the ground as a turbine Helio / Pilatus, etc. There's a fantastic video clip on the "Canyon Surfing" DVD put out by STOLadventures.com . I have this DVD and can verify that the standing start and climbout is very very impressive.

If you are clever, thrifty, and dedicated to it, you can scratchbuild one of these CH701's (airframe) for about six or seven thousand dollars from the plans they offer. I'm about to start one of these projects myself, because the 701 is more of a knock around off-road beater than a classic Taylorcraft.

But the general idea is that the 701 allows a sport pilot to fly in the same environment and get into the same kinds of places as the Monster Cubs do but at a quarter the cost. And a tenth the cost of the Helios, Storches, Porters, and Dorniers.

Brie, if you are competent with a hand drill and a pop rivet gun, you can actually build one of the 701's. Better yet you can order any individual part that you don't feel comfy scratchbuilding.

Only downside is that the airplane is not quite as pretty as a mule.... or its droppings

Bill

[taylorcraftbc65]

Re: Leading edge slot

Bill,
I have flown my friend's, the four seat model with an O200 and the Lasar ignition system. I am REALLY impressed with the way it flies.
I helped build a 701 in 1986 at Sun-N-Fun. The Company brought a kit down, and a bunch of us built it all the way up, ready to fly, in one week.
As far as building one goes, I'm building the next T Hanger for the next plane, and am getting ready to put the wings on an ultralight legal S-1 Pitts replica that I am building, so I have to build THAT first.
Brie

[flylo]

Re: Leading edge slot

Bill,I flew a CH701 a couple years ago. It was fun to pull it up into a power on stall & let it hang there with zero airspeed,it will just hang there & never break. It was slow & ugly as sin,but a hoot to fly. Have you been to the factory yet? They have an open hanger day in the spring I believe. They seem like good people to deal with. I have a set of plans & a 912 Rotax, maybe after the float plane is done.Good luck on your project & keep us posted on the progress.

[Hank Jarrett]

Re: Leading edge slot

Terry, If you find the NACA report give me a buzz and I will hit the Langley Research Center tech library. All of the originals are archived there and they have been scanned into the publicly accessable computer. Unfortunatly they are numbered in the computer files in the order they were scanned and there aren't any titles scanned yet (work in progress). If I can get a look at the front page I can see if I can find it and I will pass the scanned search location on to the group.
Hank

[tim]

Re: Leading edge slot

hey guys there is a guy that is doing this he is the same guy with the skylight stc mr gregory claton up in north pole ak we traded stc for some wing parts i asked him what he was going to do with them and he told me he was building an xwing to see how a drooped leeding edge will work for the tcraft he went on by saying the new leading edge comes out some 2 or 3 in and droops 3 in but after he got the parts and i got my stc i have not heard from him in some time tho