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 Post subject: Gluing Braces
PostPosted: Thu May 09, 2019 10:35 am 
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Mahogany
Mahogany

Joined: Thu Oct 20, 2016 7:22 pm
Posts: 72
First name: Nathan
Last Name: Peirson
Country: USA
Focus: Build
Status: Amateur
Hi folks, I have a 1978 Washburn 12 string acoustic that belongs to a friend. It was her recently deceased Father's and she asked if I would repair it for her. She is a casual player and not looking for a "new condition repair", which is a good thing. When I opened the case I found the bridge separating from the top. It was still strung up and probably just stored that way for a while. There was considerable "Belly Bulge" and once I removed the strings and was able to look and feel inside, discovered both X braces as well as a lower tone bar brace have separated from the top below the bridge. My question is, which order should I go in in terms of gluing the braces back on? My natural inclination is bottom to top...tone brace then X braces and, should I try and "Flatten" the top a bit with a long straight caul across the top to help with the bulge. I am not sure the bulge will just gradually recede as I glue the bracing. It is a laminate top, that was quite apparent once I removed the bridge (some of the veneer came up with the bridge. I could see the second veneer level in small areas, thus my next question; should I "fill" the smaller voids in the top with smaller pieces of spruce veneer before I glue the bridge back on? Thank you in advance for any advice. I must say that I would rather not remove the back to get at the braces and hope do do this through the soundhole. Thanks! I very much appreciate this community and the service and camaraderie it provides.


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 Post subject: Re: Gluing Braces
PostPosted: Thu May 09, 2019 6:37 pm 
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Koa
Koa

Joined: Thu Nov 04, 2010 1:46 pm
Posts: 1695
First name: Freeman
Last Name: Keller
Focus: Build
Status: Amateur
Just curious - are the braces split or has the glue seam with the top parted? What happened at the ends of the X (they are frequently tucked into the kerfing, often the tone bars are also)? What condition is the bridge plate it (is it all chewed up from string balls? And do you have enough long clamps and can you make cauls that will fit the braces? Maybe one of those StewMac turnbuckle thingies? Last but far from least, before you took the bridge all the way off, what was the neck angle like?

As far as order, when I build a guitar I glue both X braces in a go bar against a radius dish, then add the tone bars and finally the finger braces - you may not have that luxury. Frankly, without seeing the guitar, I would be inclined to take the back off and do it right. I'd also guess the neck needs resetting which would make it easier to do the inside work first, then you know what your final geometry needs to be.


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 Post subject: Re: Gluing Braces
PostPosted: Sat May 11, 2019 1:36 am 
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Cocobolo
Cocobolo

Joined: Sun Apr 25, 2010 4:46 pm
Posts: 309
First name: Mark
Last Name: McLean
City: Sydney
State: New South Wales
Zip/Postal Code: 2145
Country: Australia
Focus: Build
Status: Amateur
Hi Nathan
You are describing all of the typical ills of a worn out cheap plywood 12-string. Visit any decent sized pawn shop and you will find a few with identical symptoms. I bet you it is in need of a neck reset too. The pressure of twelve steel strings over a few decades just wrecks these plywood boxes, which were not that well constructed in the first place. So the first question to ask - before “how do I fix it?” - would be “is it worth the effort?”. Sorry, but it has to be said.

If you do want to try to resurrect this carcass you have a lot of work ahead of you. If the top belly is severe you could try flattening it with heat and some cauls (I recall a good tute by Frank Ford at frets.com). You would want to do this before trying to reattach braces. A minor belly is something you could leave alone. Regluing braces through the soundhole is a tough choice and you will need to think carefully about clamping options. The StewMac scissor clamps or expanding clamps came to my mind also, but they are fiddly. You could also do something with magnets. But it would be a whole lot more straightforward with the back off.

Even after all of this is done you might then find that the neck angle is aweful. Let me guess, has this thing already had all of the saddle sanded down and some of the bridge height removed to try to get better action? If so, you are going to need to reset the neck, and who knows what the anatomy of the joint is, or what glue was used. If the bridge has been shaved you will want to make a new one rather than glue the old one back on.

So - is this lady a very good friend? Or am I talking you out of it?


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 Post subject: Re: Gluing Braces
PostPosted: Sat May 11, 2019 3:24 pm 
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Mahogany
Mahogany

Joined: Thu Oct 20, 2016 7:22 pm
Posts: 72
First name: Nathan
Last Name: Peirson
Country: USA
Focus: Build
Status: Amateur
Here are a few pictures. Bridge removed and bridge plate: Plate looks OK but looks like water damage of some kind, at least staining.
The client/friend recently lost her Father to a heart attack and this is sentimental to her. As I said, she is not a serious player, just a strummer. I am doing this as a favor and kindness. It is also helping my own repair knowledge. It is the best way to learn.


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 Post subject: Re: Gluing Braces
PostPosted: Sun May 12, 2019 12:12 pm 
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Koa
Koa

Joined: Thu Nov 04, 2010 1:46 pm
Posts: 1695
First name: Freeman
Last Name: Keller
Focus: Build
Status: Amateur
Nathan, you are not getting a lot of responses (maybe because people don't quite know what to say) but I'll tell you what I see. I have repaired a few broken braces - both split and loose - but never anything like that.

I have a whole bunch of these in different lengths -

https://www.stewmac.com/Luthier_Tools/T ... lamps.html

I would say that you probably should have at least one of each size, two would be better. The are kind of hard to orient on a brace - get some of these

https://www.stewmac.com/Luthier_Tools/T ... Cauls.html

File grooves slightly wider than your braces so they will sit on top of the brace and not twist sideways. Glue doesn't stick to the UHMW which makes them a better choice than wood cauls and the hole is designed to snap onto the end of the clamp.

Make a curved clamping caul for the outside. I would make the radius a little bit flatter than what you measure with the belly, but I doubt if you can go all the way to 24 or 26 foot. Your goal will be to take as much belly out as you can but you'll still end up with some I'm afraid.

It would be much easier to pull the neck now - its just going to be in the way and you need to reset it anyway (depending on how much you can reduce the belly)

Practice getting the clamps in the sound hole and onto the braces - make sure you can apply enough pressure to bring the brace tight against the top. You are going to be severely limited by the number of clamps you can get into the soundhole. Ideally you would glue all the braces at the same time - I just don't see that happening. One problem is that once you've glued one side of the X you'll have less flexibility on the rest of the braces.

Personally, I'd remove the back and do them all at once. Either way work the glue under the braces with a pallet knife - it will be messy. AR would be my choice for working time.

Once the braces are glued you'll know what you are dealing with at the bridge. Its a pretty usual looking failure - your goal is to get the top as flat as possible and repair any deep damaged areas, fit the bridge to the curve of the top, and glue the whole mess back together. The bridge to top seam is the most stressed joint on the guitar, the fact that its a 12 string (with about 50% more tension) means its going to be even worse. Take your time and do this right (and tell your friend to use light gauge strings and down tune a couple of steps). Again, I've got some special UHMW cauls that I've made for regluing bridges - and again, glue doesn't stick to the caul

Attachment:
IMG_4767.JPG


Attachment:
IMG_4769.JPG


Now you have some idea of the actual geometry, set the neck accordingly and string it back up. Deal with frets, make a saddle (and nut if it needs it), do the setup and bingo.

Last thought, it doesn't make any difference what kind of player your friend is, your goal is to make the geometry playable. There are way too many old inexpensive 12 strings that simple aren't playable because the neck angle is wrong and the action is impossible. As long as you are going thru all this effort, make it right.


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Last edited by Freeman on Sun May 12, 2019 3:41 pm, edited 1 time in total.


These users thanked the author Freeman for the post: nathanpeirson (Sun May 12, 2019 8:48 pm)
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 Post subject: Re: Gluing Braces
PostPosted: Sun May 12, 2019 3:06 pm 
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Cocobolo
Cocobolo

Joined: Sun Apr 25, 2010 4:46 pm
Posts: 309
First name: Mark
Last Name: McLean
City: Sydney
State: New South Wales
Zip/Postal Code: 2145
Country: Australia
Focus: Build
Status: Amateur
Freeman knows what he is talking about - some good advice there.
The pictures show a pretty severe deformity of the top. The rotation of the bridge area is quite marked. To flatten this you will need to clamp something across the whole width, like Freeman said. Heat may also help. Take a look at this epic repair blog by Frank Ford and scroll down to Day 9 where he uses a heated sandbag to remould the soundboard. His is different from yours because he is pushing it out from the inside - but the same principle might be useful to you.
http://www.frets.com/FretsPages/Blogs/K ... lapse.html

If you are going to glue the braces through the soundhole this tool might be useful. It is a bit expensive, but maybe the owner of the guitar would agree to buy you some new tools that you need for the job - in lieu of payment. Then everyone is a winner.
https://www.stewmac.com/Materials_and_S ... Wedge.html
Add the clamps you need to the shopping list, and maybe a few of these:
https://www.stewmac.com/Luthier_Tools/T ... _Jack.html

Alternatively - magnets. Do you have any rare-earth magnets? I made a brace clamping system that worked pretty well using really strong magnets and something like those white UHMW cauls that Freeman showed. You can make your own cauls from kitchen chopping boards that are the same UHMW plastic. I cut out some discs from UHMW boards, routed triangular grooves on one side to fit over the brace, and used a forstner bit to cut a shallow hole on the other side that was just the right size for a strong magnetic disc to sit in. Position it and place another strong magnet on the outside of the guitar, and you have an effective clamp (if they magnets are really strong ones).



These users thanked the author Mark Mc for the post: nathanpeirson (Sun May 12, 2019 8:48 pm)
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 Post subject: Re: Gluing Braces
PostPosted: Sun May 12, 2019 3:40 pm 
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Koa
Koa

Joined: Thu Nov 04, 2010 1:46 pm
Posts: 1695
First name: Freeman
Last Name: Keller
Focus: Build
Status: Amateur
In my humble opinion rare earth magnets won't do the job. I use them all the time for installing cleats and closing minor cracks, but to pull those braces and that top together you need some real mechanical advantage. When you think about how much pressure a go bar creates you get the idea.



These users thanked the author Freeman for the post: nathanpeirson (Sun May 12, 2019 8:48 pm)
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 Post subject: Re: Gluing Braces
PostPosted: Mon May 13, 2019 8:33 pm 
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Cocobolo
Cocobolo

Joined: Mon Oct 17, 2011 4:10 pm
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First name: Bob
Last Name: Gramann
City: Fredericksburg
State: VA
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I’ve made some of those turnbuckle brace jacks like StewMac sells, but often, I just make a stick the right length to go between the back, or a back brace, and the top brace I need to reglue, and then clamp the top or back down to the brace with a cam clamp on the outside fo the guitar across the stick. The advantage of using notched sticks on the inside is that it is a lot easier to place multiple sticks to support a brace than to mess with those turnbuckle jacks. I protect the finish from the cam clamps with appropriate cauls.

I worry that the bridge shown may not be able to get enough purchase on the top to stay there after you glue it. The top gluing surface needs to be restored to nearly perfect before you replace the bridge. Is there any downside to making a new bridge with a larger footprint on the tail side?


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 Post subject: Re: Gluing Braces
PostPosted: Mon May 13, 2019 9:11 pm 
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Cocobolo
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I would also remove the bridge plate and put a new maple one with the grain oriented at 45 to the top grain. This should help flatten the top. Then reglue the braces.


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 Post subject: Re: Gluing Braces
PostPosted: Sat Jun 01, 2019 5:05 pm 
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Mahogany
Mahogany

Joined: Thu Oct 20, 2016 7:22 pm
Posts: 72
First name: Nathan
Last Name: Peirson
Country: USA
Focus: Build
Status: Amateur
Well, I went for it with re-gluing braces. Just finished gluing up the bridge. That I’m not as certain of as the laminate under it was in rough shape. I added small replacement veneer in spots. Guess I’ll find out when it all dries.ImageImageImage
These are just a few photos. I appreciate all the advice.



Sent from my iPhone using Tapatalk


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 Post subject: Re: Gluing Braces
PostPosted: Sat Jun 01, 2019 8:28 pm 
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Cocobolo
Cocobolo

Joined: Sun Apr 25, 2010 4:46 pm
Posts: 309
First name: Mark
Last Name: McLean
City: Sydney
State: New South Wales
Zip/Postal Code: 2145
Country: Australia
Focus: Build
Status: Amateur
Looks like you got the job done. Nice effort!
How did you end up clamping the braces?


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 Post subject: Re: Gluing Braces
PostPosted: Sun Jun 02, 2019 9:30 am 
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Mahogany
Mahogany

Joined: Thu Oct 20, 2016 7:22 pm
Posts: 72
First name: Nathan
Last Name: Peirson
Country: USA
Focus: Build
Status: Amateur
I cleaned under the braces as best I could, vacuumed it out and compressed air. Then laid down masking tape on either side to reduce glue squeeze out issues. I used Titebond original in pipettes to get the glue up under the braces and then used the clamps in the picture. They have leather glued to the clamping surfaces. In one of the photos there is a long clamping caul across the upper face of the guitar to bring the body down to a reasonable arch. I left it on until I had the main cross braces glued (both had pulled below the bridge). After the cross braces were done I did the same to the lower braces. I had to make cauls to fit over the cross braces to glue the bridge wings. The braces were right where the clams needed to go. I tried using mirrors and even my endoscope while gluing, but as expected, my arms just got in the way. I wish the endoscopes had a wide angle lens. They seem to be great for just looking around inside smaller instruments but that's about it.


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