Regluing tail block

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Regluing tail block

Postby Enrico Schiaffella » Thu May 16, 2019 7:55 am

Hello fellow luthiers.
I have a classical guitar that I need to reflue the tail block to the soundboard that came loose following an impact. Is there a precise technique for this? Do you think the only way would be to remove the binding?
Thanks Enrico
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Re: Regluing tail block

Postby Bob Gramann » Thu May 16, 2019 9:15 am

I had a steel string guitar where that happened. I worked out a stick system to align the block with the edge and set up the clamping cauls. I warmed the inside of the guitar with a hair dryer. I had my wife, with her skinny arms, pour hide glue in the top corner so it would flow into the gap. Then, she wiped clean inside with a lightly wetted rag. I put in the sticks and clamped it. No binding removal was necessary. It all depends on the precise situation. Every break seems to be different.

(As pleased as I was with that repair, I eventually retopped that guitar because of a different issue.)
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Re: Regluing tail block

Postby Paul Breen » Thu May 16, 2019 12:32 pm

The work can be done through the sound hole. However, if the binding is already off or loose and there is damage to the adjacent lining, there may be an advantage to pulling the binding back to address those issues.

I put strips off acrylic mirror cut to fit through the sound hole and a light, so I will have a good view in there. That also serves to protect the back of the guitar from glue drips. I have used thin spatulas taped to a dowel rod with a dollop of glue on the blade to deliver the glue (repeat as required) and also use a hypodermic rig to get glue in hard to access places. You would also want a reaching tool with some cloth bound to it that can be dampened and used for glue clean up once the glue is applied. Titebond does a good job with a previously glued, dirty joint. I would probably use that unless this is a high quality instrument.

Palette knife glue delivery works best with Titebond but you could also use hot hide glue if you work fast. I have also had very good success with thinning the Titebond with water a bit and injecting the glue with my hypo rig. Hot hide can be delivered this way as well but the trick is to keep the glue hot once it's loaded in the hypo rig. I do that by laying the rig on a piece of Black laminate and heat with an Infra Red lamp. Infra Red will not heat reflective surfaces but the Black laminate gets quite hot and is sufficient to keep the hide glue hot in the rig.

The glue injector came from Stew Mac. I use plastic and Brass tubing with a hypodermic needle taped to the Brass tubing with electrical tape. The Brass tubing shapes are somewhat job specific, so I make new shapes and lengths to suite the nature of the work as necessary.

Hopefully the pictures will help explain.
long reach gluing.JPG

hot glue injector.jpg

Glue injector rig.jpg
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Re: Regluing tail block

Postby Enrico Schiaffella » Fri May 17, 2019 6:09 am

Many thanks. Very useful. I will put it into practice
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