Making wings for YSFlight models can be a challenge. And making wings with accurate, or near-accurate airfoils, makes the flaps and ailerons more realistic and easier to model.
Things You Will Need
- Blender 2.68
- Airfoil Importer Addon
- Blender 2.48 or Blender 2.49
You can find the Airfoil importer addon here: http://jak-o-shadows.users.sourceforge.net/blender/scripts/airfoilPlotter/blairfoil.html
Step 1: Install Airfoil Importer 
You will need to install the addon so that blender can import an airfoil. Depending on your operating system, the steps are a little different.
Windows & Linux Instructions: http://wiki.blender.org/index.php/Doc:2.6/Manual/Extensions/Python/Add-Ons#Installation_of_an_Add-On
Simply extract the airfoil importer from the zip file and install it.
Step 2: Find an Airfoil
Finding which airfoil used on a particular airplane can be a bit hard to find if you don't know where to look. One of the best databases for this information is found at UIUC here: http://aerospace.illinois.edu/m-selig/ads/aircraft.html
Find your airplane. The airfoil will be listed next to the airplane name.
Copy paste the airfoil name into google. This should bring you several websites. Look for either one from UIUC, or airfoiltools.com. This website will give you something called a .dat file which lists the coordinates of the airfoil shape.
Bring the airfoil into Blender
Move the .dat file into a known location on your computer. Open Blender 2.68 and import the airfoil using the addon. Refer to this website for any questions: http://jak-o-shadows.users.sourceforge.net/blender/scripts/airfoilPlotter/blairfoil.html
Once you have the airfoil imported. Export the airfoil as an .obj file. This can then be imported into Blender 2.49 or 2.48. Then you can use this to create your wing. Personally I'd recomend reducing the number of verticies to make your life easier. I suggest reducing the verticies by a factor of 4.
Why the trouble?
Going through the effort to bring a real airfoil into a YSFlight model helps you capture more realism, with relatively little work. The realistic shape also helps you mimic the control surfaces and other features in your wing better.