Re-gluing Bridge

[Asquared]

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"Originally Posted on: Fri Aug 20, 2010 2:50 am"

The bridge on my Trameluc nylon string acoustic popped off last summer and it is time to glue it back on. When it came off it pulled some spruce from the top with it and I would like some advice on how to approach re-gluing it. Here is a pic:



Do I clean off the old surrounding glue but leave the pulled spruce on the bridge so it acts to fill the cavity or do I scrape it all off nice and clean and fill the cavity with something (what?) then re-glue the bridge? I am concerned that if I leave the pulled wood on the bridge it may not sit back down completely flush when I re-glue it.

I bought some hide glue thinking that would be best however I've not used it before so I'm unsure of approach. If I fill the cavity will it stick effectively to the filler - again what would be the best thing to fill with? Could I fill with some hide glue first, perhaps with some added wood dust (?) then level that off and glue to that surface? Or will hide glue act as a filler if I put enought in there? I'm guessing the tensile strength of the cured glue filling the cavity may not be very strong and will just pull apart again.

And if I get squeeze out, could the hot glue affect the finish before I get to wipe it off? Not sure what the finish is but I'm guessing a lacquer. This guitar was made under licence by Saga in Japan. A small piece of the finish has also been pulled away so I'll have to patch that up too. In fact I thnik it is going to be difficult to get a nice celan finish after re-gluing because the bridge looks like it may have been installed before the top was finished so it is sitting IN the finish.

Should I consider another glue?

Appreciate and advice.

Andrew

[jeffhigh]

Hi Andrew,
I am sure you will get more experienced advice than mine soon, but I will offer a few opinions.
-Dont rely on either hide glue or titebond filling gaps.
the only adhesives I would use in a gap filling situation are a good epoxy or Selleys 304
-don't use a filler
-If you are going to use HHG then practice first on other things before you do a bridge install, and you need to have a good quick clamping arrangement. I use vacuum and HHG and vacuum clamping for a bridge is a match made in heaven.
-HHg will not damage the finish and is easy to cleanup
-Cant tell for sure from the photo but it looks like there is a margin of finish under the back of the bridge, this is not good to leave there as it increases the glue line thickness.
-I would either leave the spruce on the front of the bridge and just remove any wayward fibres preventing it from seating and old glue, or remove it and inlay a spruce patch into the top before regluing the bridge.

[graham mcdonald]

I reckon the best way would be to very carefully remove those bits of spruce attached to the bottom of the bridge and reglue them to the soundboard. I would suggest a heat lamp to soften the glue and a very thin spatula (a ground down old butterknife from Vinnies is good) Hot glue would be best, as you can clean it up afterwards easily. Once the bits of spruce are back remove all the glue from the bottom of the bridge and from the soundboard where the bridge was. The broken off bits of lacquer are going to be tricky. You might (repeat, might) be able to glue them back with superglue, but it could get messy and will be noticeable unless it is a nitro finish. One the gluing surfaces are clean you can reglue the bridge, with the glue of your choice.

It is such a structurally bad design for a bridge with those narrow curved wings giving little strength to the torque of the strings

cheers

graham

[jeffhigh]

I'd agree with all that Graham has said, if you can get the spruce off the bridge and glued to the top that would be great.
Try to work out why this failed in the first place so you dont just repeat what was done before.
In the absence of abuse in the past such as use of steel strings or being left in a hot car, then you are left with poor assembly or poor design.
It may be worth making a replacement bridge with a larger footprint.

[Taffy Evans]

hi Andrew, I'd second Grahams advice. This guitar lived to play another day after some carefully thought out work.

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[Allen]

Taffy, you can't just leave us hanging like that.....come on mate. Show us the fix details.

[Taffy Evans]

On this one I removed half of the depth of the top and replaced it with new spruce. Both guitars needed removal and refitting of modified bridge plates.
Another guitar lives on...

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Top damage done by unknown repairer, filled with glue and dust.

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The bridge, top and epoxy laminate.

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Plays another day..

[Puff]

Did I miss something here?

[Mark McLean]

Andrew
I don't know if you have discovered the delights of Frank Ford's paes at frets.com?

If not you will probably get something from this:
http://www.frets.com/fretspages/Luthier ... ridge.html

and also from this one:
http://www.frets.com/FRETSPages/Luthier ... uebr1.html

Mark

[Asquared]

Thanks everyone for all that advice. Very helpful. I had a first go with hide glue today - definately need more practice Rolling Eyes

Frank Fords tutorials a big help, thanks for that lead. I'll let you know how I go.
_________________
My most creative ideas come from covering up my mistakes.

[Lillian]

Puff wrote:
Did I miss something here?


Well, there is always that possibility. Where do you think you got lost?

[Allen]

Great stuff Taffy. Thanks for posting these.

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