Official Luthiers Forum!

Hello forum. I'm not a luthier but a classical guitar student although I do plan to get involved in refretting, nut/saddle making and minor repairs.

The cedar top of my Spanish made guitar has developed a three inch long crack in the grain adjacent to the neck joint an eighth of an inch away from it - (treble side.) A .008" (.203mm) feeler guage now fits snug - it was a .002 last week. There is soft wooden brace plate beneath the crack area and I can feel the crack partially through this material.

I think this is common with classical guitars and I'm guessing that this neck joint area must be a high-stress point. I would like to repair this myself and I'm hoping there's a standard and reliable repair technique that's commonly used. I can widen the crack slightly by gently pressing under it.

Thanks in advance for any help.

That is a very common area for a crack to occur on a Classical. It's not exactly a minor repair either. You will have to cleat it on the underside of the Soundboard. It gets even more difficult if the crack remains open after humidifying.
If the instrument has any decent value it might be worth reconsidering your plans, especially considering that you have no experience. If it's junk, well that's a different matter.

I have read about this and they say that it happens when the ebony shrinks crossgrain wise and literaly drags the top towards the fretboard causing it to crack.
ebony takes long time to become stable.
some luthiers choose to leave a no glue gap near the edges of the fretboard on that area.
one in particular makes a very thin channel on both bottom edges of the FB on the area where it contacts the sounboard, then he fills the gap with ebony dust and wax or something.
that leaves room for the FB to shrink in the future (if its ever going to) whithout "draggin" the top to it.

I glued a fingerboard on my classical this week, and my teacher told me this type of cracks can happen when the fingerboard is glued on in a relative humidity that is too high.
Can't be of much help on the repair though, sorry about that.
good luck.

Use fresh hot hide glue, and even if you bodge the repair a bit it can be redone at some point in the future without too much trouble. If you can pull the crack together then you can work the HHG into the crack by flexing the top slightly and working the glue into it with your finger. Pull the crack tight before the glue gells (I often use masking tape to pull it tight) , and leave it for a day to dry.

These cracks are common & should NEVER happen on a properly
built guitar with aged woods.
Could you feel the fret ends sticking out of the F.B ?

Oil the f.b
If need be, do it twice.
Let the oil soak in till it disappears.
Get the guitar in at least a 50% humid room.
The board will swell back up & be less prone to shrinkage (in the future)if oiled.
When the cracks swell closed, glue them.

Then finish touch is a matter of what kind of finish has been used.

Mike

_________________
Mike Collins

The other thing is.... Don't ever push anything into a crack to see how big it is... You need the wood to completely conform with itself on the other side of the crack - and it won't when you shove stuff in there....

As a few here have mentioned - humidify this instrument and get it into the hands of a luthier.... It's not an easy repair for an amateur because of where it is relative to the neck blocks/foot in there... Frequently, you can't get proper clamps and such in there to push cleats into place...

Don't even consider anything like Gorilla glue, epoxy, or any of it's ilk.... It only creates huge, globby messes that don't hold together any better than cracked wood... and they are nearly impossible to remove without a hammer and chisel...

Thanks

I greatly appreciate the advice. It does make sense that FB shrinkage would place tension on the top and cause the crack. I'm not a luthier but I do agree with the post above, that this should not happen had properly aged woods been used in construction. I was thinking of oiling the FB again and was about to ask about this. I thought this might help to alleviate the stress to the top and maybe close up the crack a little. I use Planet Waves 'Hydrate' on the FB every two or three string changes so I'll give it another good dousing. Any other oil suggestions would be welcome by the way. I'm keeping the RH up as well and the bout curvature looks good. The fret ends protrude only barely - enough to just catch the thumbnail as it passes over the FB edge.

When to glue? Should I oil the FB and wait a few days to see if the crack closes? If the crack does close, per the foregoing advice, how am I going to get the glue in there? The gap is still only .008 at its widest so would it not be best to fill this with glue to stabilize it and reduce any further stress? After oiling, wouldn't a slight pushing together of the grain be preferable to a pulling apart force on the grain?

I had thought of gently sanding the clearcoat along the fault line and using plumber's tape to mask along each side of the crack. Good or bad?

Is it possible to stain the glue to approximate the grain color, either before or after application?

After gluing, can I spray nitro-cellulose over the crack repair?

This is Lucida 777 with about a $500 used market price. I don't mean to usurp the advice of taking it to a luthier and I know a professional luthier is the best option but it's very much a matter of cost and distance. I feel that with the right guidance, I can affect a good repair.

Remove the strings, obvious I know but it has to be said.
Forget about oiling the fretboard. It won't do anything for the crack. Oil (if you must) after the crack is repaired.
It's pointless staining the glue. That only suggests that you want the glue to fill a gap. 0.008 is still wide to do an effective repair. Keep the humidity up and see if it closes a little further. Once it closes sufficiently the best glue for this is HHG, rubbed in with the finger whilst flexing the crack a little. You will also have to make sure that there are no steps in the joint.
If the crack opens up try gluing once or twice again. That's the beauty of HHG, the new will dissolve the old and you will have a well sized joint.
I once had a Guitar in with the same type of crack but the customer wanted a cheap repair. It took 3 attempts with the HHG, as far as I know it's still holding out 2 years later. Ideally you want to reinforce from the inside.
If the gap refuses to close the only sensible option is to put a very thin splint in there.
My advice is to leave the finish alone, no sanding or spraying. It's very easy to make a real mess of this.
Although very well seasoned wood will lessen these type of cracks it won't entirely eliminate them. Ebony, Spruce and big swings in humidity is all that it takes.

[quote="Michael.N."]
Forget about oiling the fretboard. It won't do anything for the crack. Oil (if you must) after the crack is repaired.
Oiling will help swell the f.b. back up.
Thus hopefully preventing another crack in the futere.
It may also help to close the crack some as the f.b. swells up.

Mike

_________________
Mike Collins

This thread reminded me I have to fix the same type of crack.
I think mine is due to string tension,
because the top at the end of the fretboard is sunk in a little bit.
I am going to put a full length cleat of 1/8" x1/2' crossgrain spruce, and glue with tb1.
I'll do the other side of the fretboard as well.
I'm not a pro though,
and this guitar isn't a very expensive one

You might be right. I just find it hard to understand how it's going to swell something like Ebony when it can hardly penetrate the surface by 0.2mm!!

Given what Todd Stock has said about ebony, I wonder if any one has tried to bake fingerboards similar to what some folks do with soundboards....?
Tom

_________________
A person who has never made a mistake has never made anything!!!

Toasted fretboards!
Might be a nice new gimmick!
Actually might be good, too.
High heat kiln dried.

I must say thanks again for all the replies. I appreciate the help. With HH glue in hand, repair day is approaching. The guitar has been well humidified over the past few weeks and the crack shows no signs of further widening. Hopefully it's reached its maximum.

I would like to stain the HH glue to match the grain. Stewmac.com says you can do this but must I buy a whole pot of expensive stain? Is it that special or can I use the hardware store variety? I'll experiment first and see how it bonds and how it looks. The glue is already golden so maybe no stain is even needed.

The comments about FB oil make sense. I can't see how oil can make any appreciable difference to such a dense wood as ebony except with a FB that is extremely dry, but on the other hand, I have read that too much oil can swell the FB and raise frets. Maybe it's the case with rosewood - me no expert here.

I'll post photos when done, for better or worse.