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One if my bridges lifting
http://www-.luthiersforum.com/forum/viewtopic.php?f=10137&t=43946		 Page 1 of 1
Author:  Beth Mayer [ Fri Aug 08, 2014 12:37 pm ]
Post subject:  One if my bridges lifting
I gave a J45ish Dread to a pro musician less than a year ago. It has a square (non-belly) Zircote bridge, glued with Titebond, 24.75" scale length and the owner is using medium gauge strings.

I have a few questions before I tackle my first bridge removal and re-glue:

1) the square bridge obviously has less gluing surface area than a belly bridge. Should I make him a new bridge, or was this just a poor gluing job.
2) I did not rabbet the edges of the bridge to account for the finish thickness just under the bridge perimeter....how important is this to do?
3) with Titbond on Bearclaw Sitka, what temperature should I heat the bridge to to remove without tearing out top wood fibers
4) if there is any tear out of fibers, how do you get the glue residue cleaned off the wood of the top and bridge without losing those fibers you want to re-place?

Any other tips or observations would be appreciated. This was only my second scratch-built guitar and the first that I used a non-belly bridge on. I haven't gotten it back from the owner yet to inspect it, but he said it is lifting "a little" so I'm hoping having him immediately de-tune it and bring it right away will prevent harm to the top until I can get it off.

Thanks for the help! Beth
Author:  Glen H [ Fri Aug 08, 2014 3:41 pm ]
Post subject:  Re: One if my bridges lifting
Hi Beth, I would blame the glue job before the bridge. The contact between bridge and top must be close. If there is a finish ridge around the perimeter, I would either rabbit the bridge the same, or remove the ridge to get full contact. On mine, I just get all the finish off completely on the full bridge footprint.
For removing a partially attached bridge, I heat it up by contact with a small travel iron. I don't have the nice, small heating blankets (wish I did). I put my other hand on the inside of the guitar and feel the temp of the bridge patch. When I feel it warming, I try to work a flex blade up under the bridge (I made mine by sanding down thinner a flexible putty knife). Remember, you want it hot, but not any hotter than needed. You are not only heating the bridge to top join, but the glue in the center seam and the glue to the bridge patch. Don't be afraid, you'll get the feel. When it hits the right temp, most times, the blade will slide on in.
When you get the bridge off, you'll have a better picture of why it failed.
Author:  Haans [ Sat Aug 09, 2014 7:04 am ]
Post subject:  Re: One if my bridges lifting
I would also switch to HHG. It's easy enough to use, and works extremely well. Heat the bridge with a heat gun and mask around the bridge before gluing. Clean off the glue once it's clamped and then pull the tape. Leave clamped for 24 hrs.
I use pyramid bridges all the time and have no problems...
Author:  Beth Mayer [ Sat Aug 09, 2014 9:21 am ]
Post subject:  Re: One if my bridges lifting
Thanks, Glen....I just remembered, he had a Baggs piezo installed after I gave it to him. Can that be tethered somehow when I pull it into the body, then allow me to pull it back through the hole in the slot when the bridge is back on?

Thanks, Haans...I bought my HHG from LMI, and I think its 190gm or about there. I've seen mention of measures over 300 gm. Will this affect its strength and do I need stronger HHG?
Author:  Glen H [ Sat Aug 09, 2014 12:24 pm ]
Post subject:  Re: One if my bridges lifting
I'm not sure I understand your situation with the pickup, but your hhg gram strength is fine.
Author:  Tim Mullin [ Sat Aug 09, 2014 12:59 pm ]
Post subject:  Re: One if my bridges lifting
Beth: You'll probably want to disconnect and pull the under saddle piezo out before you remove and reglue the bridge. Find some installation instructions for the model installed -- that'll guide you as to where and how to disconnect. You'll likely need some soldering skills to disconnect and reconnect. If it's the one I'm thinking of, you'll find the connection on the little circuit board that is part of the end-pin jack. I've done a couple now that were like this.

As for HHG versus TB. There are countless bridges glued with TB that have survived many decades without failure. A thick glue line resulting from the bridge held up by a ridge of finish is a formula for failure for any glue (except maybe epoxy). Likewise, oxidized, oily or otherwise contaminated surfaces will also compromise adhesion. Your failure is more likely traced to technique, rather than your choice of glue. Both HHG and Titebond original are appropriate.
Author:  Beth Mayer [ Sat Aug 09, 2014 3:21 pm ]
Post subject:  Re: One if my bridges lifting
Tim Mullin wrote:
Beth: You'll probably want to disconnect and pull the under saddle piezo out before you remove and reglue the bridge. Find some installation instructions for the model installed -- that'll guide you as to where and how to disconnect. You'll likely need some soldering skills to disconnect and reconnect. If it's the one I'm thinking of, you'll find the connection on the little circuit board that is part of the end-pin jack. I've done a couple now that were like this.

As for HHG versus TB. There are countless bridges glued with TB that have survived many decades without failure. A thick glue line resulting from the bridge held up by a ridge of finish is a formula for failure for any glue (except maybe epoxy). Likewise, oxidized, oily or otherwise contaminated surfaces will also compromise adhesion. Your failure is more likely traced to technique, rather than your choice of glue. Both HHG and Titebond original are appropriate.


Thanks Tim. Unfortunately, I have no soldering skills and would not like to have my first effort be on an expensive pickup system (he had it professionally installed because I told him I wouldn't do it). I had assumed that all I would need to do to remove the bridge is to pull the under saddle transducer through it's hole and let it flop in the body while I did the work, then pull it back through the hole when the bridge is replaced. I don't understand why I would need to disconnect anything.
(My question was about how to get the transducer back through the hole after replacing the bridge. I know some K&K's come with a little loop that you can attach a thin wire to on the free end of the transducer, and you can thread the wire back up through and pull the transducer out that way. I didn't know if any of you repair guys had a trick for that. )
I sure appreciate the help! Beth
Author:  Cal Maier [ Sat Aug 09, 2014 4:10 pm ]
Post subject:  Re: One if my bridges lifting
If it's the Baggs pick up I'm thinking of that is 3/32" or 1/8" wide and maybe 1/16" or less thick, you should be able to pull that back into the guitar body, re glue the bridge, re drill the bridge slot hole and pull it back into the slot without too much trouble. The pick up is fairly flexible and should be easy to remove and replace in the bridge slot.

Cal
Author:  Tim Mullin [ Sun Aug 10, 2014 1:37 am ]
Post subject:  Re: One if my bridges lifting
The one I'm remembering I believe was an old Fishman and had a kink at the end of the piezo where the cable joined, and I couldn't bend it to poke down the hole without mangling it. Had the hole been bigger, or the connection at the end of the piezo more flexible, then feeding back into the body would have been easier. I just now looked at the instructions on the Baggs site where the Anthem is shown installed from the inside. So, if that's what you got it, makes sense just to reverse the process.
Author:  Haans [ Sun Aug 10, 2014 5:43 am ]
Post subject:  Re: One if my bridges lifting
Beth, the 190 gram strength works just fine. Make sure you have the spruce clean of the Titebond. A sharp chisel used as a scraper will take it down to the spruce again. The bridge can be sanded or wet and scraped clean again.
Author:  Beth Mayer [ Sun Aug 10, 2014 11:29 am ]
Post subject:  Re: One if my bridges lifting
Tim Mullin wrote:
The one I'm remembering I believe was an old Fishman and had a kink at the end of the piezo where the cable joined, and I couldn't bend it to poke down the hole without mangling it. Had the hole been bigger, or the connection at the end of the piezo more flexible, then feeding back into the body would have been easier. I just now looked at the instructions on the Baggs site where the Anthem is shown installed from the inside. So, if that's what you got it, makes sense just to reverse the process.


Thanks, Tim.....and I will have a look at Baggs's website.
Author:  Beth Mayer [ Sun Aug 10, 2014 11:37 am ]
Post subject:  Re: One if my bridges lifting
Haans wrote:
Beth, the 190 gram strength works just fine. Make sure you have the spruce clean of the Titebond. A sharp chisel used as a scraper will take it down to the spruce again. The bridge can be sanded or wet and scraped clean again.

That's great, Hans. I just made up a new batch of HHG, so I'll be able to use fresh stuff.

When I have the guitar in hand, I'll get pictures of the failure. I'm really sad that this happened, but as always when I make a mistake, I know I'll learn a lot from it.

I sure appreciate appreciate all the help form everyone [:Y:]
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