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| bridge attachment question http://www-.luthiersforum.com/forum/viewtopic.php?f=10137&t=57000 |
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| Author: | phavriluk [ Thu Mar 06, 2025 10:23 pm ] |
| Post subject: | bridge attachment question |
I'll try to contain myself to a specific question: Today I retrieved a 12-string I made from the luthier/tech (he builds and repairs) I brought it to so that the failed center seam in the soundboard could be tended to. Nice job. He mentioned that my bridge needed to be reglued. Eh? That was a surprise. I got shown a gap at the rear of the bridge a bit smaller than a half-quarter that let the edge of a piece of paper slide in. The bridge shows no signs of coming undone, more like it was starved of its Titebond Extend in that area. So, what to do? I'm reluctant to remove and reglue the bridge when 90 percent of the glue area has good contact, and I'm also aware that the glue I used doesn't like to stick to itself. I have a local friend (organ builder, professionally) who uses HHG on his own woodworking projects. What's the downside of flooding the gap with HHG, and not removing and regluing the bridge? Thanks, folks. |
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| Author: | Jim Watts [ Thu Mar 06, 2025 11:51 pm ] |
| Post subject: | Re: bridge attachment question |
If this is a personal guitar and your confident it not coming undone, why do anything? You can always just monitor the situation and if the gap starts to grow then you can take action. I don't think I'd flood the gap with HHG. I don't believe it would do much. If you want to use HHG you'll need to remove the bridge and clean of all the old titebond unless someone can show that HHG works fine on top of old titebond. I've never tried it so I'm just going off of general wisdom on the HHG/titebond bond. |
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| Author: | Hesh [ Fri Mar 07, 2025 5:04 am ] |
| Post subject: | Re: bridge attachment question |
Hi Peter. The bridge needs to be removed, the surfaces (wood to wood) need to be cleaned up of all old glue, the gluing footprint needs to be expanded to just shy of the bridge foot print (just shy so the repair is invisible) and the bottom of the bridge fitted to the dome of the top so that full wood to wood contact occurs everywhere without a lot of clamping pressure. I use a single edge razor blade as a scraper to fit the bridge bottom to the top. I shoot for wood to wood contact everywhere in the fitment with just finger pressure. We will be using clamps but I shoot for great fit anyway prior to clamping. Before any of this occurs the instrument should be permitted to acclimate to 45% RH or in the range of 42 - 48% for several days so that you are not fitting something to a moving target. Any and all crack repairs should be completed so the bridge reglue is the last thing you do. Once it's a perfect fit I would reglue it in your case with Titebon Original or extend. Use sufficient clamps to have it well clamped everywhere. This may be four clamps. Peter it is a 12 string which has the most tension on the bridge of anything we do. Bridges should always be fully removed once they fail and reglued with all the care that we use on a new instrument. The back edge is the first to lift often in conjunction with a crack and both are indicators of drying out. So are the months of November, December, January and February. We see a lot of lifted bridges in these months. A lifting bridge should always be fully removed and redone properly it is one of the most important glue joints AND braces.... a bridge is a brace but an external one on the entire guitar. HHG is what we use but I would recommend Titebond Original or Extend for you since HHG has to be perfectly handled or it will fail. Titebond is much more forgiving and requires less associated stuff, water bath, etc. HHG also does not stick to other old glue unless it's reheated HHG and it requires near perfect wood to wood fit. HHG is not a gap filler either so no don't use HHG. |
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| Author: | phavriluk [ Fri Mar 07, 2025 12:16 pm ] |
| Post subject: | Re: bridge attachment question |
Thanks, everybody. I infer that HHG (1) won't stick to Titebond and (2) HHG doesn't like to gap fill, both conditions I put into play. Right now, I'll watch. I attached this bridge eighteen months ago and it hasn't shown any signs of lifting, and I am willing to wait for lifting to arrive before I try to reattach the bridge. I thought I followed all the rules Hesh listed for attaching a bridge, save for what may be a glue-starved area on the bridge. I'm aware of the higher force acting on a 12-string soundboard, but the bridge also is larger than a 6-string bridge, so I have a chance to get a headache figuring whether the higher tension is proportional to the larger footprint. And...the physics of string tension forces on the bridge...this bridge is slotted and the string ball ends are pulling on the bridge plate, not the bridge itself (no?). I can remove a bridge pin when tuned to pitch and the string stays put. Can I think the bridge ain't feeling the tension? Sorry, folks, these are the musings of a builder trying to feel my way through a problem without much education in the physics of bridges. Thanks for enlightening and explaining. I very much appreciate your giving me time and attention. |
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