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PostPosted: Mon May 10, 2010 8:52 am 
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Contributing Member
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Joined: Wed Aug 31, 2005 7:30 am
Posts: 1792
Location: United States
Brad Goodman wrote:
Babicz guitars use bolted bridges, They are adjustable for intonation.

Brad, his design is completely different: strings bear down on the bridge like an archtop, and are attached on the lower bout.

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Laurent Brondel
West Paris, Maine - USA
http://www.laurentbrondel.com/


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PostPosted: Mon May 10, 2010 1:48 pm 
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Brazilian Rosewood
Brazilian Rosewood

Joined: Sat Jan 15, 2005 12:50 pm
Posts: 3933
Location: United States
Bolts work well enough in holding things together when the load is shear: so long as the two pieces are thick enough to distribute the forces properly, and the compression of the two faces is sufficient to keep them from sliding, you're golden. The load on a guitar bridge is _mostly_ shear, but it's that pesky torque lifting up the rear edge that causes most of the problems. In that case, once the glue (if any) lets go, the rear edge of the bridge curls up, and the top, in effect, curls down, so it just keeps peeling along. When the break reaches the bolts they are huge stress risers; much more rigid than the wood of the top or the bridge, so the load gets concentrated there. The amount of distortion you can see on a bolt-on bridge that has started to lift and not been properly cared for is really astonishing. Ultimately, if not repaired in time, the bolts simply rip through the top. Yes I've seen that.

The EKO 12 I got in Naples in, iirc, '69, had the solution for that: the bridge bolted through to a thick aluminum plate that spread the load. Oh; you want tone? oops_sign


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PostPosted: Mon May 10, 2010 2:27 pm 
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Walnut
Walnut

Joined: Mon Feb 01, 2010 4:59 pm
Posts: 25
Focus: Repair
Status: Professional
FWIW, I did a bridge repair a few months ago where the bridge was glued just as you are planning with epoxy and with the typical top finish extending under the bridge. The bridge had pulled up and brought with it half of the wood underneath it. I had to route the top and inlay new top material. As for removing the epoxy from the bridge bottom, that was a real bugger to get off and smoothed out. I had to charge the guy 2.5x's the normal bridge repair fee.

On the other hand, scoring a trace outline and scraping away to the edge is very simple - nothing beats a good wood-on-wood joint and Titebond, etc, especially compared to the above repair! 8-)

Related to this, and I saw some comments about CA. I had a Martin DX1 (composite top) with a pulled bridge a few weeks ago. Titebond will not work in this case, so I experimented with CA and epoxy, gluing tiny blocks to the top and seeing which adhered the best. The wood block glued with epoxy was the easiest to knock free . . .


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PostPosted: Tue May 11, 2010 11:45 am 
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Brazilian Rosewood
Brazilian Rosewood

Joined: Fri Nov 03, 2006 6:50 pm
Posts: 2711
Location: Victoria, BC
First name: John
Last Name: Abercrombie
Status: Amateur
Since this discussion has changed focus from "how to keep the bridge on for good", to "how to make it easy to remove".....

I was just wondering if anybody has considered putting a label (far) inside the guitar with a list of the glues/joinery used.
It could be helpful to a future repair person.
For instance, removing a bridge glued with titebond/PVA (or epoxy) glue is quite easy with heat only; not so with fish or hide glue.
Is that neck dovetailed or dowelled on, etc....


John


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