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Gluing question

I'm building a CBG with a reinforced neck. I routed a channel down the neck and used epoxy to put a square steel tube inside, and I plan to glue a fingerboard over it. Because I'm a bit clumsy, epoxy got all over the neck, and after it cured, I used a Dremel with a sanding attachment to remove the excess epoxy. But now the sanded surface is a little uneven. This picture shows the worst spot, and the rest is less visibly uneven, but if I run my finger over it, I can feel a slight ripple. When I dry fit the fingerboard, the largest gaps are roughly 1/32" wide. My question is, should I try to smooth the surface out before gluing the fingerboard on, or is it close enough to go ahead and glue it? And if I should smooth it out, how should I go about doing that? Thanks!

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Permalink Reply by ChickenboneJohn on April 5, 2017 at 6:11pm

I could see for the way you'd glued on the "backstrap" that there wasn't enough overlap to do the job. It needed to extend up the neck about 2 inches inches past the pickup notch if it is to take any actual load. Putting bolts thru the weak spot will do nothing, and may actually make it worse - the while thing is effectively going to "hinge" on that really thin part at the edge of the pickup notch, where there is no backstrap reinforcement behind it. As a general principle, the thinnest part of the neckstick inside the box should be no thinner than the main part of the neck itself, and you need a decent backstrap/heel overlap of 1 1/2 - 2 inches from the edge of any deep notches to enable the glue joint to do its job. Tough job to learn from, but onwards and upwards.

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Permalink Reply by Mark Betzhold on April 5, 2017 at 6:32pm

Do you think it would help if I were to glue and/or mechanically fasten another piece of 1x2 onto the neck, so as to effectively extend the backstrap? Also, I should clarify that the spot where the cut was deepest, and where the upper 1x2 broke, was on the lower corner of the notch, i.e. in the third photo above, the left side of the notch is where the extra cut was. I don't know if that changes anything, but I figured it might be worth mentioning.

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Permalink Reply by darryl kernaghan on April 5, 2017 at 8:14pm

Even better would be to heat and soften the backstrap joint, remove the old back strap and replace it with a new one going a couple of inches beyond the notch, generally backstraps protude beyond the box and can be rounded or shaped like a heel on a conventional guitar if you like

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Permalink Reply by ChickenboneJohn on April 6, 2017 at 5:23am

Just glueing on a little block to extend the back strap will have no structural benefit at all, you need a continuous piece of wood to extend right across that weak spot. Bite the bullet, do it right and saw or plane off what you've got and glue a new piece that extends up the neck a couple of inches.

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Permalink Reply by ChickenboneJohn on April 6, 2017 at 6:06am

This little sketch might help show how to avoid the problem in future.

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Permalink Reply by Moritz Voegeli on April 5, 2017 at 7:44pm

For your future builds: to get a perfectly level neck or fretboard, check first that your work surface is really level before attaching a sanding belt; another solution is attaching the sanding belt with two wedges to a 2" to 0.75" or so aluminum or steel profile: here a short one which fits into the photo, long wedges for demonstration only:

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Permalink Reply by JL on April 12, 2017 at 4:00am

A related idea, glue some side rails to the neck like shane showed in one of his videos, he makes the neck 3x wide around the point where the pickup is cut in, so its like a pocket instead of a thin spot.