Repairing an already tight crack? What to do?

[Craig C.]

So, I have a problem. Or maybe don't. 

A Yamaha with a Gibson style neck has come in, and it looks like it picked up a knock in shipping, and the lacquer is cracked right by the headstock. But my main concern is what caused the lacquer to crack in the first place. It's in the right place, so sand down, and of course it's a crack in the neck. But the crack is so tight at this point, that I am having concerns/second thoughts about what glue to use or how to approach this?

The crack does not visibly open up when pressure is applied to the headstock, and there's still a little more than a centimeters worth of wood between the end of the crack and the other side of the neck/headstock. Under string tension the guitar is fine - but if I repair the lacquer, it's just going to flex enough there to crack it again. So, how do I get enough glue in there to stop it?

CA would seem to have enough capillary action that it could do the job, but CA isn't really ideal for neck repairs as it becomes a little brittle, no? Also would conceivably darken the wood. And I'm thinking if the CA fails and if there is a future repair the CA saturated wood would not respond well to hide or tite bond.

I don't think Titebond will go. 

Hide Glue has a low viscosity, but would I be able to get it in there? 

I have to sell this guitar on at some point, and I'd rather have it stable so that I don't have to worry about any potential customer coming back with a busted headstock down the road. 

I've even contemplated splines, but that just seems excessive at this point.

Any thoughts, suggestions? 

[Frank Ford]

It may seem counterintuitive, but the glue that will wick into the tightest crack is actually epoxy.

West System epoxy, for example, is relatively low viscosity, about like maple syrup.  Regular slow set epoxy will flow ever so slowly, like oil, and go into some really tight cracks to a surprising depth.  So, you could set things up with the peg head stressed forward as much as you dare, and start to drip a little epoxy onto the joint.  Maybe making a small dam with masking tape will give you a small reservoir for the glue.  Let it drain into the joint for an hour, and then wipe off the excess.

[Craig C.]

Thank you Frank.

That is fascinating...and it does seem counter-intuitive. I wouldn't expect Epoxy to penetrate the crack as well. But I am willing to give it a shot. I'll probably arrange a clamp and board so that the crack is slightly downward from the rest of the neck, and then make a reservoir as you suggested. 

[Lee Gendvilas]

I did as Frank suggested on a guitarron with a similar crack/break, but I could open it way more than yours. I had the opportunity to watch it flow. I used West Systems 206 hardener and 105 resin. It does take a while but it worked. Thanks Frank!

[Mark McLean]

Craig
Is that actually an open crack, or could it be the scarf joint, poorly executed and concealed? It seems in the right place and absolutely at right angles to the neck. But maybe I am mis-assessing it in the photo. If it is the scarf joint and it is solid then you really only have a cosmetic problem with the finish rather than a structural weakness

[Craig C.]

Hi Mark,

It's absolutely a crack. It's not even, and it also doesn't go all the way through (as I mentioned). It does look clean and at right angles, but unfortunately it's not a scarf joint. 

West Systems resin is probably not available where I am (Japan) but I will find an equivalent, do some testing, see how it works, and then get it fixed.