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I have a Adi spruce top I'm attempting to use on number 2 (Black walnut/Adi J-45ish thing, Curly Koa bindings) that has been giving me some troubles.

First, after joining, the top falls just shy of completely covering the widest part of the lower bout. The gap is relatively small (~0.172 on each side). The curly koa (0.085) and b/w/b purfling (0.060) I was planning on using won't quite fill the gap. I am probably just going to go with a bit wider purling to cover the gap. Now the question. If if do this, there will still be a slight gap between the top and the binding, which is capped by the purfling. Is this alright? Should the gap be filled with something? I could glue on little wings to fill the gap if need be.

Second, this morning in noticed a hairline crack at the top, right side of the top. The top hasn't been brought to thickness yet (still about .140). The top can be positioned so that what appears to be the bottom or end of the crack would maybe fall 1/4 in. to 1/2 in. inside the body (after the lining). What's the best course? I am 99.9% sure the crack is the result of handling the piece and is not due to humidity related instability (the very top of the top in this area is super thin and I'm pretty sure the tear came from me picking the top up by the right corner )

Thanks!

Aaron

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Aaron Craig

Have you cut out the body shape or is the top panel still square? As long as the binding/purfling will cover the gaps completely and there's glue contact between the kerfed linings and the top at these points, you should be fine. As for the crack, I'd force some glue into it and clamp it closed before final thicknessing. Make sure the glue gets all the way into the crack - top to bottom. A picture of the crack would be helpful, though.

Good luck!
Chuck

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"To live a creative life, we must lose our fear of being wrong"
- Joseph Chilton Pearce

I sure wouldn't let there be any gaps between binding and purfling, or binding and top. Not only will it look lousy, but I think you're looking for trouble structurally ( or maybe buzzing,) too, as you glue the top to the sides. At any rate, the cosmetic reasons are enough for me.

If you're committed to using this top - and no reason why you shouldn't be, I'd take offcuts from the waist and join them to the widest part of the bottom bout - join a couple of wings on the top to ensure you've got sufficient width before gluing to the sides. If you're careful, you can probably join in such a way that the joins are invisible, and blend into the grain lines.

Agree with the other comment on the crack, but I'd use Titebond or Hide Glue - no CA. It'll wick into and stain your top.

The top has not been cut to rough shape and is still a squarish (I like words that end in "ish") shape. As for the crack towards the top, I doubt it would show up well in a photo, at least not without me prying the crack open and risking further damage. It currently is a hairline, tight fitting crack that is almost impossible to see from the top and just a smidgen more distinguishable on viewed from the back.

How would I go about insuring glue has adequately gotten in the crack? I hate to pry the crack open and risk increasing its size. Can I just try to press glue into the crack? Currently, the only glue I use is Titebond or Gorilla white glue (and CA where appropriate, but I don't think that would be a good idea here since CA stains spruce).

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Aaron Craig

I would add wings to the top to get the width, get them from the upper bout, slide the pieces down to keep the grain/runout the same - sounds like almost nothing would be left of these once bound, but you need the support under the purfling. Glue the crack as well, thinned TB of fish, or hide if you use that.

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Tony Karol
www.karol-guitars.com
"let my passion .. fulfill yours"

Thanks for the reply Chuck, Corky, and Tony. For the record, I would never consider leaving a visible crack between the purflings and the top. The gap I was alluding to would be hidden under the wider purfling, which would be wide enough to overlap the top. Will add some wings and see how closely they match. I would really like to keep the same width purflings throughout. Plus, if I don't like the look and need the wider purflings, the gap problem would already be solved.

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Aaron Craig

I use compressed (low pressure) air to blow glue into a crack. If the crack is all the way through, you can also suck it into the crack from the bottom with a shop vacuum, but just gently prying it apart and using your finger should get enough in to work.

Chuck

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"To live a creative life, we must lose our fear of being wrong"
- Joseph Chilton Pearce

Great tips Chuck. Thanks.

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Aaron Craig

I'd glue the little wings on the lower bout, just cause it's not that much trouble and it can't hurt. Don't need super perfect joints, just something to fill the gap.

For the crack, a couple weeks ago I split a top big time. Not quite all the way through, but almost, and about 3 inches long. First thing I did was hold the crack closed and swipe away all the sanding dust from the area to make sure it stayed pristine for gluing. Then I took some hide glue and thinned it down until it was good and runny, warmed up the top where the crack was, very gently flexed the crack open and slopped glue all along it and an inch or two past the end of it just to be sure I got the whole thing. Then flexed the crack open and closed a bit to work the glue in (probably not really necessary), squished at the glue with my fingers, added more glue, flexed open and closed some more. Then put blocks along the sides of the crack and a weight on top of them to hold it flat (without gluing the weight to the top ). If it's split all the way through, you'll want some pressure from the side as well. After the glue gelled up, I scraped most of it off the surface and then left to dry. Took quite a bit of sanding to get back to fully bare wood, but the crack itself is entirely invisible now. I can't even find it knowing where to look.

Titebond ought to work just fine too. I'd flex the crack open a bit, run some glue along it, and then mash it around with my fingers to get it worked in. But I'm more comfortable with hide glue for that sort of thing, because it can be thinned until it wicks into cracks almost like CA.

Now for a view from a contrarian,
why risk wasting a hundred or more hours of labor on a guitar that may end up having a top that comprimises the instrument. having cracks and buzzes in the future. I would rather spend some $$ and buy a new top rather than investing time in a troublesome piece of wood. Many people more knowledgable than myself may disagree with me, but I don't have the spare time to waste. My 2 cents...

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John Nowicki

I think John is indeed being a contrarian. The process of fixing up the top is a good learning experience and entirely doable. Add the wings, fix up the crack.

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Jim Kirby
kirby@udel.edu

Gluing narrow wings on the edge of the top will not compromise the instrument. Even if the joint is not completely covered by the purfling, it still will be supported by the kerfing. And if you follow the excellent advice on how to match the grain, the repair should be invisible.
An extra glue joint in the top is nothing to get excited about. The whole instrument is assembled with glue. I have built guitars with 10-piece tops, and they sound and survive just fine.

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John