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Experimental Cubs & Extreme Stol Devices, Flaps,slats,sl

Barnes McCormick's text, Aerodynamics, Aeronautics, and Flight Mechanics, has information on slots, slats, leading edge flaps, and Kruger leading edge flaps on pages 113-120.

Slots can provide a CL increment on the order of 0.1-0.2
Slats can provide a CL increment on the order of 0.9
Leading edge flaps and Kruger leading edge flaps can also add an increment of about 0.9.
A Kruger leading edge flap combined with a split trailing edge flap can give a total CLmax on the order of 3.0, which is about 0.3-0.4 higher than the leading edge devices acting alone.

JimC
 
In the, "for what it's worth" department...

I flew in Dakota Cub's slotted wing Cub.

2 people
160 hp
Borer 41
EDO 2000 Floats
Slotted Wing

Cruise was 95 mph

(of course we all know how accurate a Cub's airpeed indicator is - but it moved right out)

Brad
 
Stol devises

Jim C,
I have read every book and artical I could get my hands on and have learned a lot.
Everything tested that I read about worked with higher wing loadings than a light cub
and at air speeds above what we are doing. I know this will muddy the water for
some but through testing we found some new laws that work quite different at the
speeds and weight we are dealing with. When you get below 20 mph you can no
longer compress air through a slot / slat very well. The whole mass of air will back
up and go around the out side of the slat. This is all done at very high angle of attack
and with high power as you plow ahead. you will get a lot of lift with the eng.
pointing up fighting the lift and drag of the wing. Wayne
 
Yea... looking back at it again that mighta been a little too basic ...sorry , Rob
 
Steve, CL is a proportionality factor, the coefficient of lift. It is equal to the lift divided by the product of the dynamic pressure and the reference area..
 
Wayne wrote:
> I have read every book and artical I could get my hands on and have learned a lot. <

I wish I could say the same. I'm eaten alive with ignorance.

> Everything tested that I read about worked with higher wing loadings than a light cub and at air speeds above what we are doing.<

You might try the Journal of Experimental Biology. It deals a lot with lower wing loadings and airspeeds than most of the aeronautical journals. And the Journal of Vertebrate Paleontology deals some with animals about the size, wing loading, and speed of our planes. I work mostly on the aerodynamics, flight mechanics, and flapping kinematics of a couple of late-Cretaceous azhdarchid pterodactyls, one of which is about the size of a Cub, though a bit lighter.

> I know this will muddy the water for some but through testing we found some new laws that work quite different at the speeds and weight we are dealing with. When you get below 20 mph you can no longer compress air through a slot / slat very well.<

I agree. Air is usually treated as essentially incompressible below speeds of about Mach 0.4. And low Reynolds number flight performance is quite a bit different than flight performance at higher Reynolds numbers too.

> The whole mass of air will back up and go around the out side of the slat.<

This is to be expected, as the stagnation point shifts down and aftward at high aoa.

> This is all done at very high angle of attack and with high power as you plow ahead. you will get a lot of lift with the eng. pointing up fighting the lift and drag of the wing. Wayne<

I agree re drag. But with the engine pointing up, isn't the downward component of the engine thrust helping some with the lift?

I've always been much impressed with what you and Jerry know about slow flight in small aircraft. My slow flight studies are more oriented toward flapping wings and unsteady flows.
All the best,
JimC
 
Up thrust

Jim C,
Sorry for the miss understanding, you are correct. The point I was trying to make
was that with the eng. pulling up in the front and the wing producing lift and drag
up and back the weight is being divided between the eng. thrust and the wing.
Therefor your wing has a lower weight per sq. ft. when under power. Of the
three 18 type I spoke of the one that is the heavest has the most hp. and fly's the
slowest under power.
By your thoughts I don't beleave any one could say you are ignorant. And I don't
in any way think I have it all together. I just like to play with what I love SLOW
FLIGHT! Thanks for your input. Wayne
 
Books

By the way the books I was talking about were only in the airfoil, slot, slat, or flap
department. I have by no means read every thing avalable. Wayne
 
Wayne
I would be interested in some of your favorite books on this subject. Could you list a few of them.

Eddie
 
Books.

Hi Eddie. Never fear. You have not been forgotten. Wayne has most of his books stored here. And he has read all of mine also. I was digging through boxes, and discovered a lot of my old test data. So I got sidelined trying to figure a way to get some of this stuff posted. I'm working on your request also. Please bear with me. Jerry. :)
 
Thanks Jerry
Please dont go to a lot of trouble. I enjoy reading about our hobby but haven't been able to find very many good text books on the engineering of the wings and STOL devices.
Eddie
 
books and articals

Hi eddie'
Sorry it's been so long in reply on your note. I have been really busy trying to get
a cub out of the shop that got behind. To many add ons, but it flew away yesterday.
Turned out to be a real good performer. On the books as jerry said all of my things
are stored away. But you can get quite a lot out of library's. I have picked out a
particular plane like the Custer Channel Wing CCW 5 and found some really good info.
I,m new with a comp. but I have found a lot with the search mode. I have also
barowed a lot of books and read what I was interested in and gave them back.
There are many stol devices that really work well but very few that can be put on
a cub type aircraft dew to weight and structure. Over the years that I have been
playing with this I have tried to pick out all the things I like on different airplanes and
incorperate them into a single plane. I'm shore I will get to old to do it all, But will
have fun. There will allways be something else. Wayne
 
Gurney flaps.

Wayne or Jerry,

Do you guys have any experience with Gurney flaps? There is an article in "Custom Planes", May 2002 about a slow flying Cub with these high lift devices. It is a 3/4" stip of metal mounted in a downward position on the trailing edge of the wing, outward from the ailerons.

This Cub also has 3/4" tall VGs instead of the normal 1/4".

Hans :D
 
Flaps.

Hi Hans. Talked to people who have used them, they are used mostly for banner towing. Where they want to spend most of the day at 40-45 mph. Can you post the ariticle? Jerry.l
 
experimental cubs

Have you seen the latest issue of Northern Pilot, pretty interesting stuff! Company called Performance Air is putting out a supercub kit dubbed the Copycat Cub. Kit is all inclusive, less engine, prop, n covering materials!It got pretty high praise from the folks at NP. I was intrigued by there use of coil spring suspension in place of the hydro-bungee system on cert. cubs.Sure looks alot cleaner n aerodynamic. Any opinions, better, worse,safety, ? Curious because my newly built cub sits left wing low.New landing gear legs n struts nbungees. Only measurment that is diff. is the hydrosorb assemlys themselves, any insight as to why? they were measured with no weight load n 1 is 5/16 longer!
 
experimental cubs

Nothern Pilot never did get into any #s as far price of the kits n PerformanceAir didn't list a web site, sure be interesting to see what theyre asking. I built my cub from scratch,started with only my paperwork n my engine! Have all receipts n invoices, would be interesting to compare price! This also adds another factor to the question to "buy new topcub, rebuilt SC or now build experimental cub?" If money is no object its pretty simple, but for most of it is, " make house payment or buy fuel for cub" !!
 
experimental

Hi David,
It's good to here about a experimental cub company going after the market. Do you
have the address or phone # for these peaple. Are they offering any options with
the kit, such as large flaps, large baggage, or other stol mods. Thanks for your
imfo and thoughts. Wayne
 
Wayne,

Steve Tubbs:
Performance Air
4919 Aviation Way CALDWELL, ID 83605-8143

208) 455-7400

Tim
 
exp cub

Wayne, from what I read in the article you can get just about any mod you want, with several being standard on every kit. Fusalage strakes, vortex gens., 24 gal. tanks, extended bagage, extended flaps(inboard to fusalage) are standard. Wing mods are also available;ext. ailerons, droop tips, etc.! Worth tracking down the latest issue of Northern Pilot, good read.
 
Performance Air cub

pa12driver, do I see what I think I see on the photo of the PerformanceAir cub (pg. 28,rt. side view). It sure looks as though the tail is twisting enough on take off to wrinkle the fabric just in front of the tail! doesn't look too good what ever is going on there! Whats your take on it ?
 
I noticed that too. Hopefully it's just a reflection, but it really does look like wrinkles.
 
exp. cub

Mark, looking at their fusalage (pg. 27) there doesnt appear to be the weld-in truss or x brace in the tail like Big Lakes or Univairs. With the installation of 180hp wouldnt that present a problem with twist in the tail?
 
Flaps

Looking for info. flaps,
Would like to hear from anybody that has experance with the to part flaps, like on an
Otter. Also the slated flap on the Platus Porter. Any info. or thoughts welcome.
There has been a lot of desighs that worked and some that didn't. I'm allways
looking for more, thanks. Wayne
 
Hans, Gurney flaps usually consist of a vertical dam ventral to the trailing edge that has a height ratio of about 2% of the chord. They are pretty well known and work by increasing the circulation, and can increase lift by up to about 20%, but they don't do so on all wings. There is some drag penalty, but it usually isn't substantial. They are sometimes used with high lift S1223 airfoils. Gurney flaps will substantially increase the nose down pitching moment of the airfoil because they substantially increase the static pressure on the aft underside of the wing. On airfoils where they work, they will work with either vg's or drooped leading edges or both. Because they work by increasing the circulation, I'm not sure they will work with leading edge slats. I would speculate that they do. They could probably be safely installed on the trailing edge of flaps, but not on the trailing edge of ailerons because of the increased risk of catastrophic flutter (not to mention erratic aileron forces).
JimC
 
Flaps

JimC,
Sorry been so long, work. I am putting a plane together now for a fellow and we are
going to use these gurney flaps. It has a Tcraft airfiol on pacer spares and no flaps.
It has a cub trim system so I don't think will have a shortage of trim control do to the
pitching moment. Has small eng. and shouldn't weigh over 800 lbs. Rigging the controls
now and hope to start fabric soon. I will keep you posted on flaps and progress.
My own plane is starting come together now. The fuse. is welded up and I have the
twin rudders installed. Starting on the tailfeathers next.
The 7ac parts that i posted about earlyer are also comeing together. Most of the
parts and peices we now have so the fun begins. My own and the chump will both
have the slats. keep it in the air Wayne
 
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