Conn flat top bridge repair

[David Hutson]

I have done some bridge repair on this flat top acoustic, I have re secured the bridge to the body but the body/top is also pulled up causing the bridge to set to high, I need ideas on pulling it back down and how to secure/brace it. My thoughts have been to fabricate a light weight block of wood in the correct size and type? then connect the front to the back directly under the bridge. The guitar was stored while strung so the top has been pulled to it's present position and has been trained to stay in the distorted position I am estimating that it is pulled up approx 1/8 of a inch.
My repairs so far were done by neatly sanding the area under the bridge and the bridge it's self then clamp and bond with a quality epoxy. I will post some more info and pic's before I go any further on this, I'm fishing for food for thought right now.
Thanks for your help, Dave

I would appreciate any ideas on.
1. Method to use.
2. Type of wood for the support if used.
3. Type of adhesives to use.
4. Any and all trouble saving ideas you might have.

[JC Whitney]

You may want to look into a JLD Bridge Doctor - Stewmac sells them. If you search the MIMF you'll find them mentioned in a number of threads.

[David Hutson]

I think I may try to keep it damp from underneath and apply weight to it for a while and see what kind of results I can get with out any modification.
If you can offer any do's or dont's on this I would appreciate them also. Thanks

[Mark Swanson]

The solution is not to add moisture to the top, it will only harm the guitar and it will return back to where it is now. Adding extra wood blocks would just harm the tone. The right way to do this is to remove and replace the bridge plate inside. The right time to do it is when the bridge is off. Removing the plate can be quite tricky, but replacing it will flatten the top back out and then you can re-glue the bridge.

[David Hutson]

Thanks, Mark
By applying weight to it I meant that I would set weight on the bridge it's self to slowly train the wood to return to or close to it's original position, using temporary blocks/jacks inside the body to prevent it from going back down where I didn't want it to. I don't understand how this would harm the tone of the instrument if you could give a short explanation I would appreciate it. As for removing the bridge I don,t think that can be done any longer with out doing major damage, when I put the bridge back on originally I used thinned out epoxy and let it wick into the wood on the top and bridge then clamped it thoroughly Im sure the bridge has become one with the top, to remove it now would require machining / cutting the bridge away from the body

[David Hutson]

Mark, I reread your post, I got the part about the blocks and tone.

[Bill Raymond]

David, epoxy will release with heat.

[Mark Swanson]

Yes, it will. But too bad you used it, it will make a lot of extra work. Wood glue is all you need because the bridge and top should fit well together with no gaps.
Most everything has been tried to get tops to flatten back out when they are bellied, but the real cause is failure of the bridge plate most of the time. You can feel free to try a Bridge Doctor before you go any further, it may give you enough help.

[Michael Lewis]

There are very few applications for epoxy in guitar repair, and attaching the bridge to the top is not one of them. Oh, it CAN work, but like Mark said, it will make a lot of unnecessary work in the future. One of the main issues with epoxy is it can creep over time, and heat speeds this up.

The Bridge Doctor will help a great deal to flatten the hump of the top, but so will replacing the bridge plate and bridge which is the proper way to do it. You should check carefully for any loose braces in the bridge area, as loose braces can contribute to the hump, and if the guitar has been through big humidity changes it becomes more likely.

[Todd Stock]

Whoh...let's not throw the baby wookie out with the wig factory trash!

Epoxy formulations vary quite a bit, and some repairs that are simply not economically feasible with traditional methods are doable with a good structural epoxy. Yes - quick-cure grocery store epoxies like the 5 minute Devcon stuff never really gets hard - they are designed to absorb shock across the joint, so are formulated to flex. A good laminating epoxy like West, Maas, and other quality brands will do quite well at providing a stable, non-creeping joint...especially where there are gaps or thicker sections in the glue line where waterbased stuff like Titebond would perform poorly and lace in cavities.

As for creep, structural, laminating epoxies like West 105/20x will creep no worse than Titebond when hot, and unlike Titebond, can be post-cured to raise the glass transition temp above the point that you'll ever see in use. Cold creep with fully cured structural epoxies is going to be so minimal in realistic glue lines that it's essentially nil...pay attention to mix ratio.

I'm not recommending epoxy for joints that need to be opened for future repairs, but the world is filled with cheap instruments that will not support several hours of labor at $80-$100 per hour to keep them in service...smart use of a good epoxy for some of these repairs is the difference between sending the guitar to the landfill and a few more decades of service.

[Barry Daniels]

As a former repairman, I would have to admit to the use of more epoxy than I would like to admit. Also, now that I am using Trevor Gore's building techniques most of my new guitar builds are getting the epoxy treatment. West Systems makes a great range of epoxy products.

[David Hutson]

Re : Bridge plate replacement. What is the method or methods that are used to remove the old bridge plate from inside the body, and what type of adhesive was likely used to install it originally?

[Barry Daniels]

It takes special made tools to heat and pry the plate loose. Not for the faint of heart.

[David Hutson]

Whoh...let's not throw the baby wookie out with the wig factory trash!

Epoxy formulations vary quite a bit, and some repairs that are simply not economically feasible with traditional methods are doable with a good structural epoxy. Yes - quick-cure grocery store epoxies like the 5 minute Devcon stuff never really gets hard - they are designed to absorb shock across the joint, so are formulated to flex. A good laminating epoxy like West, Maas, and other quality brands will do quite well at providing a stable, non-creeping joint...especially where there are gaps or thicker sections in the glue line where waterbased stuff like Titebond would perform poorly and lace in cavities.

As for creep, structural, laminating epoxies like West 105/20x will creep no worse than Titebond when hot, and unlike Titebond, can be post-cured to raise the glass transition temp above the point that you'll ever see in use. Cold creep with fully cured structural epoxies is going to be so minimal in realistic glue lines that it's essentially nil...pay attention to mix ratio.

I'm not recommending epoxy for joints that need to be opened for future repairs, but the world is filled with cheap instruments that will not support several hours of labor at $80-$100 per hour to keep them in service...smart use of a good epoxy for some of these repairs is the difference between sending the guitar to the landfill and a few more decades of service.

[David Hutson]

I have done some bridge repair on this flat top acoustic, I have re secured the bridge to the body but the body/top is also pulled up causing the bridge to set to high, I need ideas on pulling it back down and how to secure/brace it. My thoughts have been to fabricate a light weight block of wood in the correct size and type? then connect the front to the back directly under the bridge. The guitar was stored while strung so the top has been pulled to it's present position and has been trained to stay in the distorted position I am estimating that it is pulled up approx 1/8 of a inch.
My repairs so far were done by neatly sanding the area under the bridge and the bridge it's self then clamp and bond with a quality epoxy. I will post some more info and pic's before I go any further on this, I'm fishing for food for thought right now.
Thanks for your help, Dave

I would appreciate any ideas on.
1. Method to use.
2. Type of wood for the support if used.
3. Type of adhesives to use.
4. Any and all trouble saving ideas you might have.

Upon further inspection, The area behind the bridge is relatively flat leading up to the bridge, the bridge it's self is slightly tilted forward after re gluing and clamping, then the top falls off like a roller coaster to the sound hole. (exaggeration) As to using the bridge doctor which I intend to do this will rock the bridge back to parallel to the top but I am still left with a high bridge/action that again upon further inspection is a combination of the neck and bridge being pulled into a slight ( U Shape ) over time.
Where I stand now, after some more work I have a acceptable Action, how ever I have worked the saddle down to the point that my E string doe's not make hard contact with the saddle any longer the bridge doctor will help slightly but not enough to make hard contact. I am thinking my only cheep easy solution is to cut slots from the peg hole to the saddle lowering the exit point of the string from the peg hole enough to cause hard contact with the saddle. Keep in mind this is a Conn F 6 model guitar that to the best of my knowledge is not a high dollar instrument and I would just like to achieve a nice playable setup with out going into the neck issues.
Thanks for any inputs...

[David Hutson]

Upon further inspection, The area behind the bridge is relatively flat leading up to the bridge, the bridge it's self is slightly tilted forward after re gluing and clamping, then the top falls off like a roller coaster to the sound hole. (exaggeration) As to using the bridge doctor which I intend to do this will rock the bridge back to parallel to the top but I am still left with a high bridge/action that again upon further inspection is a combination of the neck and bridge being pulled into a slight ( U Shape ) over time.
Where I stand now, after some more work I have a acceptable Action, how ever I have worked the saddle down to the point that my E and B strings do not make hard contact with the saddle any longer the bridge doctor will help slightly but not enough to make hard contact. I am thinking my only cheap easy solution is to cut slots from the peg hole to the saddle lowering the exit point of the string from the peg hole enough to cause hard contact with the saddle. Keep in mind this is a Conn F 6 model guitar that to the best of my knowledge is not a high dollar instrument and I would just like to achieve a nice playable setup with out going into the neck issues. Thanks for any inputs...

[Todd Stock]

Check the upper arms of the X brace and the upper transverse brace for separation with a .0025 feeler gauge...if there is excessive distortion in front of the bridge, there may be brace issues involved. You'll also see this on instruments where the upper arms of the x have been compromised by scalloping (hint: taper, but do not scallop).