Airfoil coordinate format question
 

I found some airfoil coordinates I downloaded and stored in 1994, and they have an SOF file extension. It is the classic top coordinates on the left and bottom coordinates on the right, nose to tail, as seen in the below excerpt from the Eppler 197. I can't find any references to SOF, so if anyone happens to know what it is, please pass it on. Thanks,

- Erik

E197
31
0 0
.00318 .00789
.01104 .01683
.02335 .02633
.03996 .036
.06075 .04556
8.550999E-02 .05478
.11402 .06345
.14599 .07139
.18112 .07844
.21902 8.442001E-02
.25933 .08918
.30159 .0925
.34551 .09413
.39085 .09394
.43735 .09191
.48474 .08806
.53282 .08246

RE: Airfoil coordinate format question
 

Typically the horizontal coordinate is on the left and the vertical on the right. So that means you've only got about 1/4 of the coordinates here for what appears to be the upper surface since it peaks at 9'ish percent. The left column only goes to .53282 or 53.282% so that's why I'm sure you're missing 75% of the coordinates. If that's all you've got then this file is corrupt.

As for the extension there were no lack of airfoil plotting software solutions a few years back. But often the files were interchangeable just by changing the file extension to make the next program see it as being compatible. I think it's fair to say that these days, and thanks to Selig and his coworker's efforts, the "standard" is the Eppler format.

RE: Airfoil coordinate format question
 

Hi Erik,

Check this link for the E197 coordinates:

http://www.ae.illinois.edu/m-selig/ads/coord/e197.dat

At this place, you can find how to plot the airfoil for any size:

http://www.profili2.com/eng/default.htm

RE: Airfoil coordinate format question
 

The 197 coordinates are incomplete, as you noted. I just took a partial clip to show what I have and it is typical of the 100 or so SOF airfoils files.

It would be nice to know what the SOF means. Maybe it belongs to a particular airfoil plot program. Might even be an old DOS program.

The Eppler system is now the most common format, so the smart thing to do would be convert the SOF to a DAT format. I see several programs out there that claim to do that.

The Selig and UUIC database is absolutely awesome and certainly the ultimate airfoil data source for the serious modeler. Gee, why would anyone want to create a 'new' model airfoil considering what we have in our hands?

My goal is to organize all of this data I have downloaded over the years and eliminate the duplicates.

Thanks for the input!

- Erik

RE: Airfoil coordinate format question
 

Thanks, but I don't need E-197 coordinates, and I don't need a program to plot an airfoil.

RE: Airfoil coordinate format question
 

You are welcome, Erik.

Posts #1 and #2 made me believe you did not have the full coordinates.

RE: Airfoil coordinate format question
 

Not a problem. The UUIC collection, which can be downloaded as a single ZIP file, contains more airfoils than I could possibly use. I consider the coordinates like a library that you go to when you need something. I did input the SOF, or whatever they really are, coordinates into Excel and played around with the graphing capabilities. It wasn't good for the nose, and scaling up and down is a real chore. I also drew profiles in my CAD program by entering the points and then connecting the dots with Bezier curve lines. That is labor intensive, but allows for total rescaling as needed. That was before I found airfoils posted in DWG and DXF format.

- Erik