Clark-Y airfoil

My Waco has a Clark-Y airfoil. What makes this different from the other wing shapes? Thanks Jeff

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Flat bottom, blunt nose, high lift, easy to build as the ribs lay flat on the table.
Don

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The Clark Y, while being mostly flatbottomed, does have a somewhat rounded entry...

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That big leading edge radius is what tames the stall. Sharpnosed airfoils, whatever the rest of the airfoil looks like, will have abrupt and unforgiving stall behaviors. Cessna started using "drooped" leading edges around 1973 or 1974 on their light airplanes; the droop was necessary to increase the radius and improve low-speed performance. We have both the old-style and new 172s, and there is considerable difference in handling. Makers of STOL kits for various airplanes use the same trick. Some of the models I've seen have really ragged or pointy leading edges, and they must be a stinker to fly. Increasing radius does wonders, and doesn't increase drag noticeably.
Dan
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Just think....... that's the typical airfoil on nearly every 'basic trainer' offered today !
David
On 9 Feb 2004 08:16:52 -0800, Dan_Thomas snipped-for-privacy@yahoo.com (Dan Thomas) wrote:

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#$%^ snipped-for-privacy@yahoo.com (David AMA40795 / KC5UH) wrote in message

Actually, such flatbottomed airfoils are rarely seen anymore. They're too slow, and people want to go fast. The Maule has a relatively highly cambered airfoil, IIRC, as does the Citabria and a few homebuilts, but most, like the 172's, are nothing like the Clark Y. It really isn't necessary to use a fat, flatbottomed wing to get low stall speeds if flaps are available. Those old airfoils were more popular before more powerful engines were widely available to haul around the extra weight of flap mechanisms.
Dan
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I'll add a little more specificity here and say that my favorite airfoils for virtually anything I design are the NACA2412 and NACA2415. The 2415, especially, is a real floater. And with flaps, I personally think it's a much better airfoil than the Clark Y.
MJC

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Dan, The old Ace molded foam wings are very nearly NACA 2415's, which I found out when I decided to start cutting my own when they got so hard to find. Dave
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I would prefer the NACA 24-series over the 22-series. The foil is extremely gentle with monkey-proof stall characteristics down to low Reynolds numbers.
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How many basic trainers really use a Clark Y airfoil, versus a straight line with an LE radius and some curve on top? The Clark Y is only flat from 25% back and is not really overly thick at 11.72%. The Kadet airfoil for example sure ain't a Clark Y. The Clark Y is, in colloquial terminology, a "semi symettrical" airfoil with 3.56% camber.
Mike D.
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On 07 Feb 2004 18:47:44 GMT, snipped-for-privacy@aol.com (RCFlyerNYC) wrote:

The story goes, Clark drew it up when he had a few too many.... The next day, he didn't know when or Y. The airfoil tested in the wind-tunnel to be about the cleanest in 1928, giving the best lift-to-drag ratio for wings of aspect ratio = 6, and having a very forgiving stall. Not only that, it was very simple to construct.
Many airfoils were designed to capture its characteristics, notebly the NACA 4412 and I think the Goettingen 385.
-Fritz
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On Sat, 07 Feb 2004 17:49:37 -0500, Fritz Bien

Whoops, I meant 1922, not 1928, A second source said that the Goettengen airfoil was invented during the same period as the Clark, so it isn't clear whotook it from who.
-Fritz
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Thanks to you all for gettig back to me. Interesting stuff. Jeff
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Also, maybe you have already [or maybe it is what the Waco used but I wouldn't know] but I would verify that it really does have a true Clark Y airfoil. A real Clark Y is only flat from the 25% chord point rearwards. There is a specific set of coordinates for it like any other airfoil. So many times I have seen people refer to an airfoil as a Clark Y when it looks more like it was created by drawing a straight line, a LE radius and some french curve profile on the top. I've even heard the Gentle Lady airfoil referred to as a Clark Y before as an example. Not quite.
I have built a few sport sailplanes and power models using a properly designed Clark Y and it is truly a very well mannered airfoil with a gentle stall. I don't mean to suggest that there are not better airfoils in existence now for many/most applications but the Clark Y is still a good choice for many sport aircraft. Plus it sits nicely on the building board. Dave Thornburg endorses its use for sport sailplanes in his book.
Mike D.
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Ok, guys. Go to
http://www.nasg.com/afdb/list-airfoil-e.phtml
and click on Clark Y to see what it looks like. Not a true flatbottom. Compare that with the Clark Z or the USA 35B to see what a more flatbottomed foil looks like. Check out, too, the difference between the P-51's root foil compared to its tip foil. FS light airplanes often use foils like the NACA23012. Lots of interesting stuff on this site.
Dan
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Dan_Thomas snipped-for-privacy@yahoo.com (Dan Thomas) writes:

IINM, the J3 Cub uses the USA 35B and not a Clark Y as most everyone thinks.
Dan Thompson (AMA 32873, EAA 60974, WB4GUK, GROL) remove POST in address for email
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Boy are they ever close! I just overlayed the two. Thickness almost identical, slghtly more camber in the USA35B. I should try adding a hair of camber to the Clark-Y and see how tightly they match...
Interesting.
Mike D.

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Hi guys,
I have designed a foam profile parkflyer (a stand-way-far-of Spitfire) from 3-view drawings and used templates from CompuFoil Clark Y for hot-wire cut foam wings. The plane flies reasonably wel (even inverted) but, I have been thinking of trying a semi-symmetrica airfoil. On the off-chance that you guys are still being notified o new posts and with the expertise I see in this thread, I would like t solicit some recommendations. Only criterion is a thick (slow) airfoi the foam also gets some of its strength from the cross-section. The plane is electric. It uses a Hacker B20S with a 4:1 gearbox 3-cell Li-Poly battery pack, a 10 X4.7 propeller and the all-up weigh is 13.8 oz. and the wingspan is 34 Any ideas? Thanks, Jac
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If you have Compufoil, use teh NACA generator to make yourself a NACA 2213. I have used this one a few times, Very stable and good stall characteristics.

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http://www.rcgroups.com/forums/showthread.php?threadid 7222
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P.S. Here is a photo of an early version which used an under-cambere
wing, but you get the general idea of what it looks like. Jac
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