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After installing a back strip the back cracked along a grain line. Should I just scrap it from this point? The wood in question is oak
I’ll try to get a good pic w the crack open



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Bare wood, not yet on an instrument, just happened? No need to trash it. This is a perfect place for CA in lutherie. Flex the plate enough so that the crack closes, then hit with as much thin CA as will wick in. Then hit the book matched area for the crack on the other side you haven’t yet seen. It’ll be fine — at least it shouldn’t crack a second time in the same place.


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CA is not perfect especially on Oak it will show it shows up under finish
if you have another back start over

_________________
John Hall
blues creek guitars
Authorized CF Martin Repair
Co President of ASIA
You Don't know what you don't know until you know it

Worst case you could cut it out and install a 1-2" wide center wedge of different wood. Or convert to a smaller size guitar. But I'd just work some hot hide glue in there and continue on. Use a wider inside reinforcement to cover it so you don't get stress concentration on the glued grain line.

Oops — I stand corrected. Confess that I’ve never used it on oak. Certainly CA stains some woods, but I’m surprised oak is one of ‘em.


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If the crack closes neatly and invisibly, I wouldn’t necessarily trash it. Flex it open, saturate the inside of the crack with thinnish HHG. Clamp shut sideways as if joining the plates. It’s right near the center so on the inside use a little wider center reinforcement strip that covers the cracked area. Done properly its a well-glued crack with a very big, strong cleat.

This won’t cost much extra time and once done you can flex it, and even expose the back to a humidity fluctuation if you like to see if it’s suitably strong.

If it seems suspect or if the crack won’t close invisibly, I’d cut the middle of the back out and put the halves aside to be rejoined for a narrow body instrument in the future.

IMHO just glue it back together and carry on. Titebond is perfectly fine for this kind of thing. You can use masking tape to 'clamp' it shut. That's a lovely oak back and nice back strip too.

If you have hot hide glue that is what I would use. Red oak is an open pored wood and hide glue tends to be invisible under finish unlike some other glues which can be hard to get out of the pores (If it's white oak that might not be a problem).

I have to say something
Hot Hide is ok but it is questionable to some cracks . Not all cracks are the same. I suspect that this cracked along that joint because the wood may not have been cured enough and at this point you are going to keep being haunted by it. Oak especially as it has the trilose grain structure. That is what makes it water proof and why it is used for cooperage. The grain also has great medullary rays that help make it stable. So with this cracking and if you have another piece I would swap it out. I too like to fix things as things happen but there are times biting the bullet is the best thing to do.
If the wood is still shrinking this will not go away

_________________
John Hall
blues creek guitars
Authorized CF Martin Repair
Co President of ASIA
You Don't know what you don't know until you know it

What is wrong with reinforcing the inside with a strip of wood? I guess a lot depends on end use (client?)

I had a similar issue with walnut (owner gave me a chunk of a tree). I warned him this could be an issue, and it did crack. He agreed to the risk. But I got it reinforced. U cannot tell looking at it. But if wood is not fully cured/aged, then this could happen somewhere else.

oak is a lot split prone
I think the wood may have been a little green. White Oak is a beautiful wood and can be stained dark , it can be fumed and there are lots os ways to work with this in guitar making.
If your making a guitar why build a known problem into it?
In this case the building can start fresh and will be much happier in the end.

_________________
John Hall
blues creek guitars
Authorized CF Martin Repair
Co President of ASIA
You Don't know what you don't know until you know it

If it were a $5K set I'd do what I could to salvage it, but it is not and if it were me I'd replace it.

_________________
Bruce Sexauer, luthier
http://mojoluthier.com

Glue it up and set it aside. In a year or so you'll know if it's usable but don't use it now.

————
What I’m going to do is
1- practice repairing such a thing as this and do the best I can
2- not build with it
—————

As a new builder I have plenty of issues to contend with as the culminate down the road into a final instrument without having a know problem built in

Guys and gals thanks so much for your input it is always much appreciated

B Snow


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John Shelton probably offered the best advice - glue it up and set it aside for now. And I would also set aside the side set and any other oak you may have from that source if you don't think it is completely dry yet.
Cracks that happen through accidental handling can often be glued up and never cause a problem and if undetectable the piece can still be used. Checks and cracks that happen during the drying process can make the wood unusable.