Naca

[Zephyr]

I recently downloaded NACAWin and to be frank I am stuggling.
I thought it might have a wizard or a library or something like that.
Anyway, my question's are- What do each of the four digits equate to?
-Does anyone know of a list of numbers for different types of model, a library of numbers that people have tried before?

Cheers for any help

[Martin Irvine]

NACA 2412
2: 2 degrees camber
4: maximum camber at 40% chord
12: 12% thick

These are mathematically derived so there isn't a specific library.

Try looking for Profili, a free plotting programme with 1800 airfoils included.

Cheers,

Martin

[uscra112]

Try finding the "Plotfoil" program on the net. It's available from a number of sources. Use your browser to search for the single word "plotfoil" and you'll find a bunch. When I downloaded it a year or so ago there was a big library of coordinates files with it.

[feihu]

Zephyr -

NACA technical report # 824 "Summary of airfoil data" was written in 1945 and contains data on just about every airfoil in use today. If you can't find a copy at your library, you might try writing NASA Langley Research Center, Langley Field, VA.

By the way, Martin is right on the meaning of the NACA 2412 airfoil, and that is a very popular airfoil with modelers.

feihu

[Tom Hunt]

Originally posted by Martin Irvine
NACA 2412
2: 2 degrees camber


Uh... slight correction Martin....

2% camber, not degrees...

Tom

[Sail 'n Soar]

NACA technical report # 824 "Summary of airfoil data" was written in 1945 and contains data on just about every airfoil in use today. If you can't find a copy at your library, you might try writing NASA Langley Research Center, Langley Field, VA.

You can learn a lot from the old NACA reports about relative characteristics, but be careful how you interpret the data. The Langley wind tunnel in which that data was taken is not considered a low turbulence level tunnel by more recent standards. With the tunnel turbulence, the foil boundary layers transition from laminar too turbulence prematurely, so that the effective speed/Reynolds Numbers are higher.

The smaller your cord or slower your speed, the more you need to worry about the effect. I designed my first RC glider decades ago based on the NACA 4409 published low speed characteristics (Reynolds Numbers ~40,000). Glider flew fine. But this was probably due to all the little construction imperfections and not because it was approaching the NACA test performance.

[Sparky Paul]

824 is available online!
http://naca.larc.nasa.gov/reports/1945/naca-report-824/
I have a copy from the GPO which I treasure.

[Sail 'n Soar]

Turns out NACA report 824 wasn't the report I was thinking about. The performance charts in this report are all for higher speeds and scales than we see - unless you're flying large scale model turbo machinery.

Ira Abbott and Albert Von Doenhoff's "Theory of Wing Sections including a surmmary of airfoil data" captures much, if not all, of the info and charts from the NACA TR 824, including the conformal mapping techniques for determining pressure distributions around arbitrary shaped foils. Amazon.com has it for $13.97 http://www.amazon.com/exec/obidos/ASIN/0486605868/102-3012554-5056962

For you math nuts, I actually programmed the NACA and Abbott, etc., equations in an old DOS program for my 8088 vintage PC a while back. Results match the NACA predictions perfectly. Added a few boundary layer bells and whistles since and use it to aid my airfoil selections. Helps me to understand why a foil behaves as it does. Frustrated program manager did one of those "left to the student" exercises from college. The info is there if you wish to tackle it.

I've also programmed the material in "Theory of ..." to be able to design wings with ideal taper and wash out. You can define a geometry with excellent stall characteristics and still approach very closely the ideal minnimum induced drag performance. This, too, is a very handy design tool. Sense then I've found a web site, which has the tools on line. I think it is from some Boston area RC glider club. If anyone is interested I'll see if I can find it again.

In any case, if you are really into the theory, spend the $14 + shipping.

[Sparky Paul]

Originally posted by Sail 'n Soar


Sense then I've found a web site, which has the tools on line. I think it is from some Boston area RC glider club.
In any case, if you are really into the theory, spend the $14 + shipping.
.
Here 'tis..
http://www.charlesriverrc.org/articles.htm
.
I did a NACA program some years ago also. It did a nice job with transitional profiles root to tip, added leading edges and spars...
Better stuff available online now.