I have a question about fabric covering, for those of you who have experience in such matters. This isn't about model airplanes, but I can't think of anybody who would know more about this topic than model airplane builders.
I am starting a harmonica amplifier company, and I'm considering different ways to finish the speaker cabinets. I want something durable, good looking and reasonably easy to apply. I have an amplifier that I built for myself which I covered with an old bedsheet and clear butyrate dope. You can see photos of it here:This project turned out very nicely. It is exactly what I had envisioned when I started, a finished surface where you can see the pattern in the fabric through a clear glaze, just like an airplane. The only problem I experienced was that I had a lot of trouble getting the edges to stick to the wood where they went around corners. I ended up cutting most of them off rather than rolling them over the edges. In fact, you can see the uncovered wood edge next to the metal chassis in the top view. This problem was especially annoying whenever I got an edge to stay down and the next coat made it lift back up. That's one of the biggest hassle factors with butyrate dope, as far as I can tell. But all in all, it turned out well because I painted the dope through moistened cotton, and it tightened up and made a nice finish. The large surfaces came through with no bubbles at all. However, I am looking for something better for my intended application. (By the way, I plan to offer plain black to the general public, unless a customer orders something more flashy. The blue amp was fun, and I get a lot of comments.)
So far I've tried a few other methods. I tried polyurethane varnish, which was bad because it isn't thick enough to keep things held in place before it dries. I put the fabric in place with a tack coat of spray contact cement, but the polyurethane loosened it. I also tried polyester resin, which was not good at all. The finish is rough and ugly, it doesn't hold the edges down well, and it cures too fast. Then I decided to try plain old thinned white glue, topped off with a few coats of something waterproof. I thought I was on to something good because the fabric stretched out nicely and looked like it had been put on by a pro...until it dried. I was amazed to find the next morning that it had bubbled extensively. That took me by surprise.
Anyway, now that you're caught up with what I've tried so far, what would an old fashioned model airplane builder use to stick bedsheet-type cotton fabric onto an amplifier cabinet with no wrinkles and a nice glazed finish? I don't necessarily want to fill the weave. I just want it to stand up to abuse. I want a musician to feel comfortable about dragging it in and out of car trunks and nightclubs, and I want it to handle the occasional spilled beer or cigarette burn. On a scale of one to ten (or should it be one to eleven?) I'd give the butyrate dope a 9 for finish and a 7 for ease of application. It would have scored a bit higher if the edges hadn't lifted. Can you recommend something better? Water based acrylic? Water based polyurethane? Epoxy glaze?
I know that this type of finish used to be quite common, because my old saxophone cases are wood with a doped fabric finish, and they did a nice job. These cases date back to the 1920s and 1930s. Do you suppose they used nitrate dope? Would a base coat of nitrate make the butyrate method work any better?