Gluing Top and Bottom Using Go-Bar

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scamp
Posts: 223
Joined: Sat Mar 26, 2022 8:19 pm

Gluing Top and Bottom Using Go-Bar

Post by scamp »

Beginner question of the day.
Thinking a bit ahead to gluing the top and bottom of the guitar.
Would like to use my Go-Bar setup.

Two problems I could use help with.

1) I would probably like to glue the bottom first so I can remove squeezed out glue from the inside (see problem 2 below). If I do, my question is what to use to support the top sides of the guitar. I could put it on a flat surface or I could put it on a 28 degree radius disk but neither seems right. I have been following John Hall's recommendation on shaping the sides and as a result the top is flat over the middle third (from about the max of the top bout to the max of the bottom bout) and then 28 degree radius from about the max bottom bout to the tail block and the same radius from the max top bout to the neck block. As a result, both a flat surface or radius disk as a support surface won't contact the top rim everywhere. A flat surface will have gaps at both the neck and tail end of the guitar and a radiused surface will have gaps at the waist. So.... what to do? My idea at this point is to start with a flat surface, then 1/2 inch foam pad over that and then a 2 inch wide masonite strip which follows the contour of the sides over that . Seems like this would provide a more or less conformal caul base that would more evenly distribute the pressure and contact the top side everywhere. Does this make sense? Any suggestions/comments welcome.

2) If I do glue on the bottom first, how do I gain access to remove the excess glue that seeps out, and messes up the look of the inside of the guitar? I plan on using Titebond glue. It seems like I might be able to glue on the bottom, using the method I proposed above with go-bars, wait about 10 to 15 minutes for the glue to set up, remove the bars and the body from the go-bar set up, scrape out the excess glue, and then put it back in the go-bar set up. Once again, does this seem to make sense? Suggestions/comments welcome.

Thanks in advance for your help
tippie53
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Location: Hegins, Pa
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Re: Gluing Top and Bottom Using Go-Bar

Post by tippie53 »

you didn't look at the videos
https://www.youtube.com/watch?v=M8qAvQ5ExSE
you keep them in the mold DO NOT TRY AND GLUE THE TOP OR BACK ON OUTSIDE THE MOLD
this video should clear up your questions I use the dish do the back first for as you said you can clean up nice
this way
John Hall
Blues Creek Guitars Inc
Authorized CF Martin Repair Center
president of Association of Stringed Instrument Artisans
http://www.bluescreekguitars.com
MaineGeezer
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Joined: Wed Aug 13, 2014 12:14 pm

Re: Gluing Top and Bottom Using Go-Bar

Post by MaineGeezer »

As John says, keep it in the mold while gluing on the back and top. It shouldn't come out of the mold until both are glued and the glue is dry. If you can leave it in the mold until the binding is on, so much the better.

For my last couple of guitars, I've been putting the back in my 15' radius sanding dish with a piece of paper in between to keep the back from getting scratched by the sanding disk, applying glue to the sides, setting the sides (in the mold) onto the back, putting my 25' sanding dish on top of the sides, then piling a lot of Really Heavy Things on the sanding dish.

Before gluing, make sure you have full contact all around. Putting a light inside the box will show up any gaps.

There are undoubtedly other, maybe better, ways of doing it.
Don't believe everything you know.
Anything is possible if you don't know what you are talking about.
When things are bad, try not to make them any worse, because it is quite likely they are bad enough already. - French Foreign Legion
scamp
Posts: 223
Joined: Sat Mar 26, 2022 8:19 pm

Re: Gluing Top and Bottom Using Go-Bar

Post by scamp »

John

Thanks for the video on how to put the top on using a go-bar.
Very helpful as usual.

Unfortunately, I still have a question on how best to put the back on.

If you do the same basic thing you did for putting on the top, you would put the sides with the top side down into the 28 ft dish and use the go-bars to push the back onto the sides. Unfortunately, in this case and unlike the case when you put the top on, the sides won't be in contact with the dish at the waist of the guitar. My concern is that putting pressure on the unsupported sides at the waist might cause the sides to twist or deform.

The good suggestion ( by MaineGeezer) to glue the back by putting the back into the 15 ft dish and driving the sides down into the back is interesting. Seems like I could use the go-bars to force the sides down into the back by putting a false top ( masonite ) on the guitar top. Maybe this is the way to go.

Comments???
tippie53
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Joined: Fri Mar 03, 2006 7:09 pm
Location: Hegins, Pa
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Re: Gluing Top and Bottom Using Go-Bar

Post by tippie53 »

look at the technique thats the point put the top down and then glue the top using the go bars after about 20 min you can take them off and clean up then do the top you seem to be overthinking things, keep it simple and do a dry fit and feel the process then add the glue. you will do well
John Hall
Blues Creek Guitars Inc
Authorized CF Martin Repair Center
president of Association of Stringed Instrument Artisans
http://www.bluescreekguitars.com
scamp
Posts: 223
Joined: Sat Mar 26, 2022 8:19 pm

Re: Gluing Top and Bottom Using Go-Bar

Post by scamp »

Yep. Probably am over thinking this. I guess it's because there are so many ways to mess up. It develops a sense of paranoia.

I do want to make sure I understand what your saying... You said

"put the top down and then glue the top ( did you mean to say bottom here??) using the go bars after about 20 min you can take them off and clean up then do the top"

My interpretation of what you said is ...

You put the guitar rims with the guitar top side down ( onto a flat surface or 28 ft radius etc. ) and you glue the back on using go-bars ( back of the guitar rims is now facing up ). After 20 minutes you can take off the go-bars, clean up the glue, flip the guitar onto a 15 ft radius disk, so now the back side of the guitar is down and the front side is up, and then glue the top on using go-bars.

Correct?
tippie53
Posts: 7011
Joined: Fri Mar 03, 2006 7:09 pm
Location: Hegins, Pa
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Re: Gluing Top and Bottom Using Go-Bar

Post by tippie53 »

that is correct
John Hall
Blues Creek Guitars Inc
Authorized CF Martin Repair Center
president of Association of Stringed Instrument Artisans
http://www.bluescreekguitars.com
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