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Old 11-10-2017, 05:24 PM
Br1ck Br1ck is offline
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Default Archtop braces

I have the back off an old archtop of unknown origin. Probably out of the Harmony factory. Solid birch top back and sides. There are two top braces that go the entire length of the top much like mandolin tonebars. One had a small crack which I glued. They seem to be very solidly glued on so I'll leave them, but the braces are easily 3/4 inch tall. I was thinking of thinning them, but thought I'd ask here first. Part of the charm of the guitar is it's funky tone and next to no sustain. I just ordered some JJB pickups to put in while I have the back off.

I bought this guitar cheap to route binding grooves and glue binding on as practice for my mandolin build. I'm also going to refret the neck for practice too. I'm going to jack the neck into a decent angle. glue the back on, trim the excess at the heal end and bind the guitar. Currently it has painted binding.
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  #2  
Old 11-11-2017, 04:38 PM
Alan Carruth Alan Carruth is offline
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I'd be loath to trust a glued up top brace on an archtop. They're there to counter the down pressure of the bridge on the top, which can be considerable, depending on the break angle over the bridge. They don't usually crack under the load unless the grain direction is wrong or they were abused. A glued crack is not going to be as strong in the long run as a proper solid brace would be. I know it's a pain to fit a new brace, but sometimes you've gotta do what you've gotta do.

It's impossible to say whether you could get away with reducing the brace height. Again, the stress on them is higher than you might think, and they have to take that load for years without distorting noticeably. Also, we don't know how strong the top itself is, or how much load that might be able to carry. Some of those old ones had fairly thin tops, sometimes even plywood, that depend on the stiffness of the braces to hold up. Some folks use deflection testing of one sort or another to determine whether the top is stiff enough, and you could look some of that info up if you want something better than a seat-of-the-pants guess.
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Old 11-13-2017, 02:28 PM
Br1ck Br1ck is offline
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The crack was 1" on one side 1/4" on the other. When the neck was flexed back into place it was closing the crack, not opening it. I got squeeze out along the whole joint. so I'm going with that.

Since this is a $100 guitar and bought as a vehicle to practice my skills, no big deal. It is a very thin pressed solid top. It was cheap and probably overbuilt to begin with, so I took a minimal amount off the braces by tapering the ends. They are still very thick but not quality wood.

If it were even a Kalamazoo, I would take more care. JJBs going in before the back goes back on. IT's going to be a roots and old timey instrument. I really think I'll play it a lot.

I refretted it yesterday, and glued the separated spots on the top. For a first fret job, not bad. I left three thousandths relief when I leveled the frets figuring the strings would add more. Time will tell.
__________________
2007 Martin D 35 Custom
1970 Guild D 35
1965 Epiphone Texan
2011 Santa Cruz D P/W
Pono OP 30 D parlor
Pono OP12-30
Pono MT uke
Goldtone Paul Beard squareneck resophonic
Fluke tenor ukulele
Boatload of home rolled telecasters

"Shut up and play ur guitar" Frank Zappa
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