Tips and tricks for lining up cracks.

[Ian Pender]

I have a Larrivee on the bench right now that was dropped against a stool. There are a number of bad cracks in the back that I need to fix, and one of them, the inner most one, just won't line up. One edge of the split is raised and overlapping the other edge. I've reached inside the guitar and attempted to push outwards and separate the crack, but it just isn't budging. What would you guys suggest I do here? I'm thinking of using this as an excuse to buy some rare earth magnets for clamping backs, but I don't feel comfortable putting much more pressure on this split to get it to line up proper. Was thinking about using a teeter clamp as well, but I don't think that'll cut it. Any ideas?

[Mark McLean]

The edges of the crack match each other and they would like to rejoin.  It looks like you need an expanding force against the sides to push the edges of the crack outwards so they will get back into position.  I haven't done this sort of repair before but I think it could work if you use an expanding turnbuckle pushing against two cauls that match the interior shape of the sides.

I use things like this to expand the sides against an exterior mould.  You could do the same inside the guitar by introducing the parts through the soundhole and then assembling them inside and cranking the turnbuckle slowly to push the sides out.  Get them far enough open to overcome the overlap and get a bit of glue into the gap.  Then release the pressure and it will self-close.  Your magnet idea would be a good way to keep them aligned while the glue dries.  Then maybe some cleats on the inside, and you need to do some finish repair on the outside. 

[Paul Verticchio]

Is it properly humidified?

[Ian Pender]

Seems to be, but I've got a humidifier in the case anyways.

[Greg Mirken]

My approach to a crack that won't align because one edge is overlapping is to pare the overlap down with an exacto blade. It doesn't take much, and don't touch the finished surface. Just take off enough wood to let the proud edge slip back into place. You're going to put cleats inside anyway, so it's not a structural weakness.
First, however, try more force, either in on the edge that's sticking out or out on the edge that's proud on the inside.

[Robbie Collins]

I just did a crack like yours, Ian. I tried Mark's method and everything else I could think of but nothing worked. Finally, I did as Greg suggests. It was a ragged crack to begin with so it took a lot of CA to level. Not what you'd call an invisible repair, but a French polish on the back pulled it all together.

[Ian Pender]

Alrighty. I'll glue up the outer most crack first, and if that doesn't help the inner one go together, I'll shave it down a bit.

Now, on a related note, I haven't done much work on these UV cure finishes. Do you think French polish is the best way to do a touch up here, or would you recommend something else?

[Ian Pender]

I was thinking about just using CA for the touch up.