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Old Feb 07, 2004, 07:01 PM
RCFlyerNYC
Guest
n/a Posts
Clark-Y airfoil

My Waco has a Clark-Y airfoil. What makes this different from the other wing
shapes?
Thanks
Jeff
Old Feb 07, 2004, 07:01 PM
Don Hatten
Guest
n/a Posts
Re: Clark-Y airfoil

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

Don



"RCFlyerNYC" <rcflyernyc@aol.com> wrote in message
news:20040207134744.13001.00001934@mb-m02.aol.com...
> My Waco has a Clark-Y airfoil. What makes this different from the other

wing
> shapes?
> Thanks
> Jeff



Old Feb 07, 2004, 07:01 PM
Bill Fulmer
Guest
n/a Posts
Re: Clark-Y airfoil

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


"RCFlyerNYC" <rcflyernyc@aol.com> wrote in message
news:20040207134744.13001.00001934@mb-m02.aol.com...
> My Waco has a Clark-Y airfoil. What makes this different from the other

wing
> shapes?
> Thanks
> Jeff



Old Feb 07, 2004, 07:01 PM
Fritz Bien
Guest
n/a Posts
Re: Clark-Y airfoil

On 07 Feb 2004 18:47:44 GMT, rcflyernyc@aol.com (RCFlyerNYC) wrote:

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


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
Old Feb 07, 2004, 07:01 PM
Fritz Bien
Guest
n/a Posts
Re: Clark-Y airfoil

On Sat, 07 Feb 2004 17:49:37 -0500, Fritz Bien
<fritzbien@CASTOROILcomcast.net> wrote:

>On 07 Feb 2004 18:47:44 GMT, rcflyernyc@aol.com (RCFlyerNYC) wrote:
>
>>My Waco has a Clark-Y airfoil. What makes this different from the other wing
>>shapes?
>>Thanks
>>Jeff

>
>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


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
Old Feb 08, 2004, 04:00 AM
RCFlyerNYC
Guest
n/a Posts
Re: Clark-Y airfoil

Thanks to you all for gettig back to me. Interesting stuff.
Jeff
Old Feb 09, 2004, 07:01 PM
Dan Thomas
Guest
n/a Posts
Re: Clark-Y airfoil

"Bill Fulmer" <grafix01@cox.net> wrote in message news:<gIbVb.16295$Ii2.999@lakeread03>...
> The Clark Y, while being mostly flatbottomed, does have a somewhat rounded
> entry...
>


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
Old Feb 09, 2004, 07:01 PM
M Dennett
Guest
n/a Posts
Re: Clark-Y airfoil

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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"RCFlyerNYC" <rcflyernyc@aol.com> wrote in message
news:20040207212055.19241.00001198@mb-m26.aol.com...
> Thanks to you all for gettig back to me. Interesting stuff.
> Jeff



Old Feb 10, 2004, 04:00 AM
David AMA40795 / KC5UH
Guest
n/a Posts
Re: Clark-Y airfoil

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_nospam@yahoo.com (Dan Thomas)
wrote:

>"Bill Fulmer" <grafix01@cox.net> wrote in message news:<gIbVb.16295$Ii2.999@lakeread03>...
>> The Clark Y, while being mostly flatbottomed, does have a somewhat rounded
>> entry...
>>

>
> 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


Old Feb 10, 2004, 07:00 PM
Dan Thomas
Guest
n/a Posts
Re: Clark-Y airfoil

#$%^ham2405@yahoo.com (David AMA40795 / KC5UH) wrote in message news:<402841af.11144168@netnews.comcast.net>...
> Just think....... that's the typical airfoil on nearly every 'basic
> trainer' offered today !
>
> David
>


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
Old Feb 10, 2004, 07:00 PM
M Dennett
Guest
n/a Posts
Re: Clark-Y airfoil

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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"David AMA40795 / KC5UH" <#$%^ham2405@yahoo.com> wrote in message
news:402841af.11144168@netnews.comcast.net...
> 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_nospam@yahoo.com (Dan Thomas)
> wrote:
>
> >"Bill Fulmer" <grafix01@cox.net> wrote in message

news:<gIbVb.16295$Ii2.999@lakeread03>...
> >> The Clark Y, while being mostly flatbottomed, does have a somewhat

rounded
> >> entry...
> >>

> >
> > 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

>



Old Feb 11, 2004, 07:00 PM
Dan Thomas
Guest
n/a Posts
Re: Clark-Y airfoil

"M Dennett" <dennett@cesaroni.net> wrote in message news:<sdOVb.1235$sO4.323310@news20.bellglobal.com> ...
> 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.



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
Old Feb 11, 2004, 07:01 PM
Dan Thompson
Guest
n/a Posts
Re: Clark-Y airfoil

In article <43cbd38a.0402110806.647d2c8d@posting.google.com >,
Dan_Thomas_nospam@yahoo.com (Dan Thomas) writes:

> 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
>


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

Old Feb 11, 2004, 07:01 PM
M Dennett
Guest
n/a Posts
Re: Clark-Y airfoil

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.



> 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
>



Old Feb 11, 2004, 07:01 PM
M Dennett
Guest
n/a Posts
Re: Clark-Y airfoil

I found this on the Taylorcraft.org site while searching for "Piper Cub
airfoil".:

"What airfoil did Taylorcraft use that has less drag than the Piper Cub?
The Taylorcraft uses the NACA 23012 airfoil, it is a semi-symmetrical
airfoil. The Taylor Cub wing had a flat bottom surface, which continued to
be used by Piper for the J-3."

Another site mentions that the Piper Cub used "NACA designed airfoils". I
realize that the above sentence does not say that the Piper Cub used the
23012 airfoil.

What is odd to me though is that if I ring up a NACA 23012 on Compufoil it
looks nothing like a light plane airfoil, but a 28012 is not too different
from the Clark-Y or USA35B. Is the NACA airfoil generator out of whack or
was it not a 23012?

Not that I will lay awake at night about this or anything..

Mike D.





"Dan Thompson" <wb4guk@aol.comPOST> wrote in message
news:20040211134206.05957.00000422@mb-m26.aol.com...
> In article <43cbd38a.0402110806.647d2c8d@posting.google.com >,
> Dan_Thomas_nospam@yahoo.com (Dan Thomas) writes:
>
> > 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
> >

>
> 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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