Thanks for your help. If I read your chart correctly, I could put nitrate dope over the polyurethane 'U', and then put Butyrate over that. I don't want to go to 2 part mixes, the plane isn't that spectacular. If my idea is functional, it is a choice between Sig and Brodak dopes. Let me know if you think this will work. They plane is an old one and the covering over the wings (with open areas, not all wood) is tore in a couple of bays.