Repair And Restoration
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1950 Martin D28 with localized scary thinning.
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1950 Martin D28 with localized scary thinning.
Hey all. I’ve got the above-mentioned guitar on my bench. It had a neck reset and what appears to be a new bridge pad put in 14 years ago. It’s a crack-free guitar except for a couple of little hairlines running from the back of the bridge to the upper tone bar. I thought that was a bit weird. Inside, everything looks okay until I turn off the inspection light, at which point I can see the rosy glow of daylight through the top – this is just ambient shop light, not a focused desk lamp! I don’t have a Hacklinger gauge, but experience tells me this is super thin. I recall T.J. Thompson and Mark Stutman discussing a phenomenon they’d seen in 1970’s Martins with rosewood plates that was similar to this. – Dick Boak surmised it was an inadvertent thinning caused by the big stroke sander Martin used for finish sanding – a kind of rebound effect. It could just be aggressive cleanup after a particularly violent bridge pad removal. I don’t know. I’m tempted to put a 1mm overlay on the area with the grain running parallel to the top, just to make sure. Thoughts? Feelings?
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8 Replies
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Did you have plans to pull the bridge plate beyond the thinned top ?
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I’m going to keep that plate in place. Budget’s an issue.
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If the top looks like it has been over sprayed there was a really bad technique going around (long ago) to sand the belly off behind the bridge. Amazing luthier Jeff Malia in AUS was showing me around his shop on a video call, had one on the bench that had it done at one point. He had the back off though and was going to lay in several thin veneers of spruce to build it up. Much like a violin patch, but that doesn’t help your situation. Yes, definitely need some more mass there some how.
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Thanks Dave. I’ve seen the effects of the ol’ hump-sanding. This one is un-retouched and in pretty good shape overall. In discussion with the client, we’ve decided it definitely needs a little extra thickness for long term stability.
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I like the idea of gluing a cross grain veneer onto the soundboard 😊 .020” thick maple
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I don’t know. If you went cross grain, aren’t you risking splitting the top because the woods will expand/contract at different rates because of the different grain orientation?
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In classical woodworking theory, yes – crossgrain glue-ups are a real no-no, but we get away with it in guitarmaking all the time. We’re the rebellious bad boys of woodcraft! In this case I went with grain running in the same direction of the soundboard because I wasn’t really interested in adding additional stiffness beyond what would have been there at the beginning.
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Ted, when your video drops on this procedure let me know. It would be nice to add to this thread.
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