Bob Branstetter said:
Now that we are (hopefully) finished with this ammonia business, I would like to hear some of the details involved for you to bend the bass back.
I realize these are a lot of questions, but I would really appreciate knowing how you did these things.
(1) Where did you get your wood and was it green or dry when you got it?
(2) What did you use for a container to prepare the wood for bending?
(3) What material did you use to make the clamp? and did it warp during the bending process?
(4) About how large were the wedges you used?
(5) What did you use to hold the water and how did you heat the water and keep it hot?
(6) How long did the actual bending process take?
(7) How long did you wait before you attempted joining the two pieces and exactly how did you go about doing the joining?
(8) Did you graduate the back or leave it even?
(9) Once you had it on the bass, have you noticed any springback or other problems?
(10) Any problems you encountered during the process?
1. Bought it from John Tepper, of Tepper Tonewoods. Thoroughly air-dried.
2. Didn't have a container that big, so I used large rags, and kept 'em wet for a few days...cold, mostly, though once in a while I poured hot water over the mess.
3. I used 1" plywood decking on both sides, clamped all around, as tightly as I could manage--which effectively sealed the two halves in the center, so that after I began wedging them apart, I could pour the water inside the widening curved opening. It didn't warp, and I can use it again. Incidentally, as the opening got wider, I jammed strips of cloth into the seam, to stop leaks--the clamps couldn't totally seal it.
4. The wedges started off small, until I got a big enough opening, and gradually worked up to about a 2" wedge in each "end" (closer to the center of upper and lower bouts, as I saw fit). In the center I made a wineglass shaped wedge, and clamped the flaring center back in, to flatten the center a little...otherwise it was developing a steep peak in the middle that I really did not want.
5. Already addressed this one, sort of, but, after I thought the bending was complete (mostly cold), I conferred with Bill Fulton, and he opined that without heat it might just go back to flat (he could be right). So I made a steamer of a small metal drum, and 1" high-temp plastic hose, and closed off the completed curved gap with thin plywood, to hold steam, and steamed it from the inside until it was hot to the touch on the outside. It was late, and I decided to call it good, and go off to bed. It has relaxed a little, but maintained the curve I had hoped for...mostly.
6. I kept pecking away at it for about a week before the steam-heating process. I couldn't afford to break it and start over.
7. I allowed it to dry for several weeks, including when I noticed the mildew, and sprayed it with bleach-water to kill it, then had to wait for that to dry.
8. I graduated the back a LOT, as it had been 13mm thick. the center is now about 9mm, and the thinnest parts around 5-6mm. I'm not done-- I had a bunch of things take higher priority for several months, and will not be able to get on it again for a few more weeks.
9. It is not on the bass, yet, but is sitting in the open air in my shop, unsupported, unclamped, and is maintaining its shape apparently. Incidentally, I also bent the upper break, using wet rags and a clothes-iron. I bent it full thickness (9mm, anyway), to allow carving afterward. It took about 2-1/2 hours as I recall--maybe more. This was another late-night fling.
10. Problems? They all looked like problems to me, as I had never done any of it before.
PS. Now that I think aboiut it, I did carve the bend area in the upper break down to about 5mm, as I was afraid 9mm would be tough to bend--and I arched it, thinking I could maintain the arch through the bend, thus making a compound curve. That didn't work-- the arching went away, and the bend area ended up actually a little concave. :-( (Ah, well...it was worth a try.)
