Headstock repair advice, please

Kalimna

Greetings folks,
My mother in law has a 20yr old Simon n Patrick 12 string that has suffered a headstock break. It is a guitar that gets a wee bit of abuse - played at church regularly and left in car boots frequently. The break is possibly due to a knock, but it is a mostly clean break along the scarf glue line with just a small piece of wood split along grain near the volute.
The faceplate is, i think, fibreboard as it is acting as a hinge right now without obvious fracturing.
I think the wood is mahogany/mahogany type for the neck, cedar for the top and unknown b&s.
It is also has a great emotional attatchment, having been bought by my wife and her brother as a gift. I do not know the monetary value, but that doesnt matter.

Given the glue line break, and no knowledge of the glue used, would the best thing be to separate the headstock completely, re-surface the pieces and re-glue? 
Would you recommend adding in splines to strengthen?
Whilst ive built a few guitars, and am constantly fixing my own mistakes, ive never attempted a repair of someone elses guitar. How straightforward is it likely to be? The finishing will not be an issue.

As always, i'd appreciate any help offered.
Adam

bencowling81

Same thing happened to my nylon string that was a gift from my parents after I passed my Grade 5. I fixed it using this. Now works perfectly. Probably wouldn't ever sell it on as highly devalued but that's not my concern with this one due to sentimental value. I didn't add any splices or anything but there is probably a lot more tension on the headstock of a 12 string acoustic than a 6 string classical. Either way, this glue is the business...
 https://www.amazon.co.uk/Titebond-5063-Original-Wood-Glue/dp/B0002YWZPW/ref=sr_1_6?adgrpid=53586413416&dchild=1&gclid=CjwKCAiA_9r_BRBZEiwAHZ_v19GNVU3HftR_CQyWhHtJCW5ZTOkjAUqh7l65-6__jjxLPYDn_o93lhoC6YgQAvD_BwE&hvadid=259055529540&hvdev=c&hvlocphy=1007171&hvnetw=g&hvqmt=e&hvrand=6797505337751349189&hvtargid=kwd-299904202490&hydadcr=14875_1829131&keywords=titebond+wood+glue&qid=1610038953&sr=8-6&tag=googhydr-21

RickLucas

Titebond!

ICBM

Kalimna said:

My mother in law has a 20yr old Simon n Patrick 12 string that has suffered a headstock break. It is a guitar that gets a wee bit of abuse - played at church regularly and left in car boots frequently. The break is possibly due to a knock, but it is a mostly clean break along the scarf glue line with just a small piece of wood split along grain near the volute.

Not too surprising - my experience is that these and other Godin-family guitars have the second highest rate of head breaks after Gibsons, and almost always at or just before the joint. This type of scarf joint unfortunately does nothing for the strength of the neck. (Unlike the type which runs the other way to under the fingerboard.)

Kalimna said:

Given the glue line break, and no knowledge of the glue used, would the best thing be to separate the headstock completely, re-surface the pieces and re-glue?

Yes. Although you could try using high-strength epoxy, that will generally stick pretty well even to most types of old glue (although not PVA). I've used it successfully on jobs like this, always heated as well which thins it and makes it flow better, and increases the bonding strength.

Kalimna said:

Would you recommend adding in splines to strengthen?

Yes, definitely - that makes the strength of the glue joint much less critical. Especially if you haven't resurfaced the pieces, I wouldn't risk it without.

Kalimna

Thanks for the advice - it confirms what i was thinking. Time to make a jig for cutting some spline slots! And to work out a way of maintaining alignment for re-glueing. Im thinking some kind of thin doweling (say a toothpick) that can register on both pieces to prevent slippage. 

I would certainly use Titebond for a fresh joint, but it is notorious for not adhering well to non-wood surfaces, which includes old glue. Epoxy should work, as ICBM states, and hot hide glue is perfect when gluing to itself, but PVA and derivatives not so much.

Cheers,
Adam

ICBM

Kalimna said:

Thanks for the advice - it confirms what i was thinking. Time to make a jig for cutting some spline slots! And to work out a way of maintaining alignment for re-glueing. Im thinking some kind of thin doweling (say a toothpick) that can register on both pieces to prevent slippage.

If the facing is still well-attached to both pieces, that's the main advantage of *not* separating and re-surfacing the pieces - the facing should hold the alignment perfectly. Difficult to say which has the greater pitfalls...

I think if it was me I would try epoxy without separating, with the assumption that I would be using splines anyway.

Kalimna

Yes, i had considered that too. I think i'll post up a couple of photos for perusal.
Is there anything you could suggest to clean up the surfaces without separating?