Old Expy
 

Well, I got the wing on my 4*60 (built upside down) apart, and after ten minutes with a heat gun pulled the shards of the dihedral brace out.

Doesn't look too bad.

Anyway, there is old epoxy on the inside ribs. I tried scraping it off under heat and it worked ok, but how clean does it need to be?

I'm going to insert a new rib-shaped "shim" between the wing halves to correct the dihedral angle and add a new brace before applying the fiberglass tape.

Do I have to get down to bare wood or what?

GB

Old Expy
 

As long as it's relatively smooth, you should be ok.

Old Expy
 

You don't need bare wood. Covering (at least Ultracote) sticks pretty good on Epoxy and CyA.