Another method
Take photo copies of all your ribs from the plans, go to one of the large copying
stores they use the "good" ink, once you have the copied rib shapes , place
copies "upside" down on your balsa blanks and "rub" along the outlines with
MEK solvent, you then get a perfect print outline on each of your balsa blanks.
*ps while we are on the "ribs" topic I'm still searching for that "ultimate"
rib "sandwich" method, in which the final result is a perfect stack of tapered
ribs