guitar back is coming up at the neck joint, wood glue or something else to rebind it?

[hangwire]

I bought a $20 4-string guitar from the 60s [a Weiss?] that I am planning to put nylon strings on and tune as a cello for a friend.

 

The back of the guitar is coming up at teh neck joint... on both sides going down to about the "horns"

 

I was going to get some wood glue and clamps to fix this... would anyone recommend a different binding agent, like JB weld instead?

 

Thanks for any info!

[hangwire]

funny pic, but kind of shows the back coming up on the side

[Terry Allan Hall]

So, essentially, you're going to take a tenor guitar and string it as a single course mandocello, but w/ heavier nylon strings? Cool!

 

I'd use yellow wood glue and, once clamped, let it dry for at least 4 days.

 

Hope it works!

[guitarcapo]

epoxy.

[hangwire]

wood glue [isn't all wood glue yellow???] vs. epoxy vs. JB weld

 

pro/cons

[Ohioarrow]

vs. epoxy vs. JB weld pro/cons

I think I'd hang loose on the JB Weld in favor of a smooth 2 part epoxy. I don't know how well wood glue would do you unless you intend to detach it the rest of the way so you have some surface area to get at.

 

Downside of epoxy, once it sets the sucker ain't coming back off without taking some wood with it. So I'd be darn sure that you got the joint right the first time and to wipe any excess off the finish areas otherwise you're gonna be sanding on finish.

[Samilyn]

I prefer wood glue for several reasons:

 

(1) I've done a lot of carpentry/cabinet work, so I already know how well it works;

(2) It is amazingly strong;

(3) Slow set-up time allows for readjustment if joints don't align perfectly the first time;

(4) Water clean-up while it's wet.

 

Procedure:

(1) Scrape off any old glue and/or dirt, etc. Get your exposed surfaces as clean as possible.

(2) Apply a thin bead of wood glue to as much of the surface you can get to. Sometimes I use a tiny paint brush to work glue into hard-to-reach places.

(3) Clamp.

(4) Wipe excess glue off with a moist (not wringing wet) cloth, then dry.

(5) Allow it to remain undisturbed for a few days. High humidity slows cure time. (TAH recommended 4 days)

 

Downside to wood glue:

(1) Requires clamping;

(2) Requires patience (long cure time).

 

My second choice would be smooth epoxy, as OhioArrow recommended.

 

Upside:

(1) Very strong

(2) Thicker bodied glue fills gaps if joints aren't very clean and/or smooth

(3) Cures fast - minimal clamp time.

 

Downside:

(1) Sets-up fast - get the joint right the first time. Once a composite material "kicks" that's it - you're out of time.

(2) Often requires chemical clean-up which is very bad for git finish. Don't be messy or use too much.

[dhoenisch]

I'll second wood glue, though for instruments, I only use the "Original Tite-Bond", which comes in a bottle with a red label, which you can get at any hardware store, or online luthiery supply store.

 

Dan

[Freeman Keller]

Samilyn is right. There are about three commonly used wood glues used for guitar building - hide (thats right, horse hide) which was used on all the vintage instruments but is a stinky hassle for the home builder (the premixed stuff in a tube is not as good as the hot pot kind), yellow (aliphatic resin or "AR") glue (most common is Titebond name) and white (forget the formula) glue (most common is Elmers). CA (superglue) is also used a lot for repairs and comes in several different thicknesses.

 

My first choice here would be AR if you can separate the two pieces, clean the old glue off and clamp it for 8 hours after putting the new glue on. If you can't get them appart CA could be wicked into the crack and it could be held together (by hand) while the glue dries (only a minute or two). Either of these will form a very thin bond between the two wood interfaces.

 

Epoxy would work but would form a sloppy mess around the fracture and as others have said, it is totally permanent. JB Weld is an epoxy like stuff with some metallic filler - it is commonly used to repair metal, porclean and other materials that can't be glued any other way. It tends to be rather unsightly.

[Ohioarrow]

Horse Hide, really?

 

I love this place I learn something new every day.

 

Question on CA. I would not have thought that superglue would be recommended because it has a tendancy to crystalize after a period of time, eventually leaving you back to step one. At least that's been my experience with superglues I have tried. (not on guitars - other household quick fixes) Or is there a special blend of superglue that does not have that side effect?

[Freeman Keller]

 

Horse Hide, really? I love this place I learn something new every day. Question on CA. I would not have thought that superglue would be recommended because it has a tendancy to crystalize after a period of time, eventually leaving you back to step one. At least that's been my experience with superglues I have tried. (not on guitars - other household quick fixes) Or is there a special blend of superglue that does not have that side effect?

 

 

Actually, I think it is cow hide

 

http://www.frets.com/FRETSPages/Luthier/Data/Materials/hideglue.html

 

Here is some other info from Ford. The main thing I have used CA for was repairing cracks that you can only slightly get open and have to wick the glue in

 

http://www.frets.com/FRETSPages/Luthier/Data/Materials/gluechart.html

 

Don't know if there is anything special about these but they are sold for instrument building and repair

 

http://www.stewmac.com/shop/Glues,_adhesives/Stewart-MacDonald_Super_Glues/Stewart-MacDonald_Super_Glues.html

[dhoenisch]

Yup, crystalized hide that you have to mix with water, and after it is absorbed, heat it up to 145 degrees, and you have glue, though you have to clamp your work quickly as you have maybe a minute to work with it before it starts to gel. Not the easiest glue to work with, but it's what I like to use for most instrument repair applications.

 

As for the CA glue, you can buy a special CA glue from Luthier supply stores which cost more, but are used on instruments all the time. I just use Krazy Glue for a lot of things like frets (if they don't fit in quite right) inlays, nuts, etc. I don't like to use it for much else. I stick with either hot hide glue, Titebond, or Epoxy, if I absolutely have to.

 

Dan

 

Edit: Dang, Freeman beat me to it.

[bjorn-fjord]

From the looks of that guitar, the separation of the back is symptomatic of much bigger problems.

 

It's hard to tell from the photo but it looks to me like the guitar is in the advanced stages of complete collapse. The reason the back has separated is because the neck has pulled forward over the years and tipped the entire headblock (major structural component inside the guitar where the neck attaches to the body) forward breaking the glue joint between the block and the back.

 

If this is the case, the action should be very high and there will likely be a pronounced sinking of the soundboard around the fretboard and soundhole. As well, the sides have likely twisted under the tension.

 

Now obviously you probably don't expect much from this instrument having paid only 20 bucks for it. If it were an expensive guitar I would suggest some pretty serious reconstruction. But because it is more of a project than an heirloom I'll make some simpler suggestions.

 

If the back has not completely separated from the headblock, steam the joint apart. Then, apply two-part epoxy to the headblock and force the entire neck back to the point that the strings are a reasonable distance from the fretboard. Now, with your third hand, clamp the back to the headblock so that the neck is held in this "forced back" position. This may be a two person job.

Wait 24 hours, remove the clamps and then repair any of the cosmetic issues, binding, etc. Then string it up to tension and see if your pizzicato cello friend can get any nice sounds out of it. If not, hang it on wall.

[Samilyn]

......If the back has not completely separated from the headblock, steam the joint apart. Then, apply two-part epoxy to the headblock and force the entire neck back to the point that the strings are a reasonable distance from the fretboard. Now, with your third hand, clamp the back to the headblock so that the neck is held in this "forced back" position. This may be a two person job.......

 

I sure wish I had one of those. Mine's never around when I need him.

[hangwire]

 

From the looks of that guitar, the separation of the back is symptomatic of much bigger problems. It's hard to tell from the photo but it looks to me like the guitar is in the advanced stages of complete collapse. The reason the back has separated is because the neck has pulled forward over the years and tipped the entire headblock (major structural component inside the guitar where the neck attaches to the body) forward breaking the glue joint between the block and the back. If this is the case, the action should be very high and there will likely be a pronounced sinking of the soundboard around the fretboard and soundhole. As well, the sides have likely twisted under the tension. Now obviously you probably don't expect much from this instrument having paid only 20 bucks for it. If it were an expensive guitar I would suggest some pretty serious reconstruction. But because it is more of a project than an heirloom I'll make some simpler suggestions. If the back has not completely separated from the headblock, steam the joint apart. Then, apply two-part epoxy to the headblock and force the entire neck back to the point that the strings are a reasonable distance from the fretboard. Now, with your third hand, clamp the back to the headblock so that the neck is held in this "forced back" position. This may be a two person job. Wait 24 hours, remove the clamps and then repair any of the cosmetic issues, binding, etc. Then string it up to tension and see if your pizzicato cello friend can get any nice sounds out of it. If not, hang it on wall.

 

 

you are correct, but

when I clamp the back, the action goes down to a normal level which is why I assumed that glueing it would fix this issue...

 

am I wrong to think this?

[bjorn-fjord]

 

you are correct, but when I clamp the back, the action goes down to a normal level which is why I assumed that glueing it would fix this issue... am I wrong to think this?

 

 

No, you're not wrong. As long as the glue has held on the top of the block things should more or less line up when the back is returned to it's regular position. However, a guitar that has reacted to the pull of the strings as dramatically as this one has will likely show some other signs of distortion that will not be corrected by simply regluing the back to the block.

 

In truth, the separation of the back from the headblock usually occurs after other nasty things have already occured. Usually the first sign of trouble is the bowing of the soundboard around the bridge and the dipping of the soundboard around the soundhole. Together, these problems can make a guitar unplayable. If you think about the physics of guitar collapse it makes sense that the degree and speed of collapse increases exponentially over time. As the neck pulls up, the reduced back-set (of the neck) causes the guitar to be increasingly less resistant to the forces trying to fold it in half. It may take many years before a guitar starts to show signs of fatigue but once these indications appear, it's not long before the guitar needs major surgery. Anyway, I digress.

 

There is a good side to this. The separation of the back from the headblock may afford you an opportunity to perform a kind of neck reset that counters all the other problems the guitar likely has. You can do this by pulling the neck past the point where the back lines up with the sides and gluing it in this position. This will require some router and binding work, but if you're up for it you could give the instrument another 20 years of life.

 

By the way, tenor guitars, such as this one are under a lot of stress in spite of having only four strings. The strings are tuned lower but are of a heavier gauge and the instrument has a much longer scale length than a six string which greatly increases the overall pull of the strings.

 

I'm guessing that this is more than you wanted to know about this issue. You could just go ahead and glue it up and hope for the best. The action is likely to be pretty high but a cellist may not care.

[Samilyn]

Not knowing much beyond the basics about guitar construction and physics, I always appreciate these insights from our resident experts.

[hangwire]

No, you're not wrong. As long as the glue has held on the top of the block things should more or less line up when the back is returned to it's regular position. However, a guitar that has reacted to the pull of the strings as dramatically as this one has will likely show some other signs of distortion that will not be corrected by simply regluing the back to the block. In truth, the separation of the back from the headblock usually occurs after other nasty things have already occured. Usually the first sign of trouble is the bowing of the soundboard around the bridge and the dipping of the soundboard around the soundhole. Together, these problems can make a guitar unplayable. If you think about the physics of guitar collapse it makes sense that the degree and speed of collapse increases exponentially over time. As the neck pulls up, the reduced back-set (of the neck) causes the guitar to be increasingly less resistant to the forces trying to fold it in half. It may take many years before a guitar starts to show signs of fatigue but once these indications appear, it's not long before the guitar needs major surgery. Anyway, I digress. There is a good side to this. The separation of the back from the headblock may afford you an opportunity to perform a kind of neck reset that counters all the other problems the guitar likely has. You can do this by pulling the neck past the point where the back lines up with the sides and gluing it in this position. This will require some router and binding work, but if you're up for it you could give the instrument another 20 years of life. By the way, tenor guitars, such as this one are under a lot of stress in spite of having only four strings. The strings are tuned lower but are of a heavier gauge and the instrument has a much longer scale length than a six string which greatly increases the overall pull of the strings. I'm guessing that this is more than you wanted to know about this issue. You could just go ahead and glue it up and hope for the best. The action is likely to be pretty high but a cellist may not care.

 

Thanks very much... I'll have some time Staurday to really look at the guitar inside and I will review your posts and most likely post back

[hangwire]

Ok, so I am looking at it... there is no bowing on the front and teh neck appeares to be right in teh block without any seperation or cracks.

 

So, from what I read, I should put wood glue on that neck block and the 'seam' and clap it down for a few days... right?