I am rebuilding the wings on my Merlin. My intent was to use the old
foam rib cores as templates but they differ from rib to rib, clearly
some have been replaced, not to mention some really shoddy
workmanship, warped ribs, broken ribs etc. So I search the web for
the airfoil type and find that it is supposed to be a Clark Y. Simple
enough I print out a Clark Y from Profili, not even close. So I
measure the thickness and find that a Clark Y15 has the right
thickness but still not even close to my ribs on the aft part of the
upper camber.
The upper part of my ribs are nearly straight from about 10% behind
the spar back. My suspicion is either remarkably careless building or
errors carried forward on the factory template. It is much easier to
make the upper cap strips this way ie straight, no camber.
So the question is, do I go with the Profili Clark Y, or perhaps the
NACA 4412 or ?
My only hesitation on the Clark Y is the affect of the trailing
suspended ailerons on the Clark Y. Most of the Clark Y applications
had the ailerons built into the wing. I called the Merlin Factory they
said just use the old ribs.

Thanks, Zac