soundboard has gone berserk (cupping) - not assembled yet

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wombosi
Amateur luthier
Posts: 144
Joined: Wed Jan 31, 2018 10:00 pm
Location: Great Barrington, MA

soundboard has gone berserk (cupping) - not assembled yet

Post by wombosi » Thu Feb 21, 2019 10:11 pm

James Lister wrote:
Thu Feb 21, 2019 9:37 pm
How long did you leave the top after removing the first donut and gluing the second? This might have caused the problem.

I know some makers are switching to epoxy, but there's really no reason to. Luthiers have been using water based glues for centuries without problem. It's just a question of learning how to do it properly.

James

I had used a piece of wood as a caul couldn't really see the donut too well. So when I removed the clamps about 30 minutes after installing the first donut, I noticed the piece had slipped and immediately removed it, very easily with the mason tool (cigarette lighter to intermittently heat up the tool).

I just removed it again but it was a lot more work and I caused some minor damage. It looks like my rosette "diamond" tiles, installed with epoxy, maybe shrank and now I see much more visible black epoxy lines between each tile. Not the end of the world, but worse than it was.
Also a tiny separation where the two soundboard halves were glued together (titebond) at the upper part of the soundhole. Probably too much heat. I'm not too worried about this.

I now have the top clamped down onto a piece of MDF with a piece of plexiglass as the caulk (the hauser template).

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