Hi,

I have been thinking about it:

The instructions i recieved were:
"Airfoil 1 (wing root): top 5%, bottom 8%, thus giving 13% of thickness. Many real planes have such an inverted airfoil which I often used without problems"

If I were to take a NACA 0005, this would be 5% of the chord thick at the maximum thickness; Since it is symmetrical, taking the top coords would leave me with 2.5% thickness.

Similarly, if i took a NACA 0008, and took the bottom profile, I would have something that is 4% thickness.

Additing these two coords sets together would give me 6.5% thickness and not the 13% thickness?

Am I on the wrong track here?

Thanks!