This is the technique I used in the Fokker D.VII:
Ernst Udet's Fokker D.VII (design by Fitter)
First glue thins stripes of cardstock from behind where ribs are supposed to go. Do not glue them to the very trailing edge, just a few millimeters inside.
Notice I didn't glue ribs on the leading edge either, as it would make it difficult top bend the wing afterwards.
Once they are very dry, turn around and press firmly from the front to mark the ribs.
Use precaution in this step to avoid damaging the paper or the print.
And there you have it. Nice effect.
Hope it helps
