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Backbow Before Fretting?


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I'm a little curious...

I leveled my fretboard before attaching to the neck, and loosened the truss rod so that the truss rod and neck were flat. Then glued the fretboard down. I now have a bit of backbow from about the 4th fret to the nut, measuring with a straight edge, the gap is about 1.5 mm at the nut. from the 5th fret to the 24th, it seems level. Is this normal? (Note: the neck is NOT attached to the body yet.)

Will the string tension once set-up straighten out the neck or do I need to level (sand) the fretboard (again) before fretting? Would tightening the truss rod help? I'm not sure if I should proceed with fretting if my fingerboard/neck wasn't level.

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Did you make sure your neck was completely flat before you glued the fingerboard? It's also possible that the fingerboard radius is not equal in its entire length?

Did you make a scarf joint? If it bows at the 4th fret, near the scarf joint, it is possible that you didn't planed the joint flat.

String tension will apply pressure on the entire neck. A neck usually bows at the middle, around the 12th fret. I really think your neck surface wasn't planed flat... I would sand the fingerboard until it's leveled. For a better structural integrity, it's better to have a completely flat neck surface.

Check the neck from the side with a straigth-edge. You'll know if it's the neck, or the fingerboard.

Edited by MescaBug
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I suspect you intruduced the bowing during glue up - waterbased glues often do this, and/or not clamping the neck and fretboard to a deadstraight caul during the gluing.

You need to heatset the neck to straighten it, or remove the fretboard and reglue with a flat caul. To heat set, heat the fretboard with an iron, until the surface of the fretboard is too hot to touch for more than a few seconds. This should allow the glue joint to creep a bit, and allow the neck to be clamped up straight.

Leave the neck to cool (still clamped to a dead straight caul), and re-check for level once it's cooled fully. If it's still back bowed, try repeating the procedure, but use a shim in the 5-7 area to introduce forward bow whilst clamping - sometime you have to go past straight to allow for a bit of spring back.

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I would stop, and allow it a few weeks to settle. When you carve and shape a neck, it adjusts dimensionally after you are finished. When you apply a waterbased glue wood will expand, then contract as the moisture levels drop back down again. Surfacing a fretboard before attaching is good, but I always leave it a tad thick, because I do my final leveling attached(after the neck has settled).

If for some reason the neck is way out of whack after it has had several weeks to settle. Then you have to evaluate your options. First can the fretboard be leveled without losing too much thickness in your fretboard, if not... Then as Setch mentioned a re-set may be an option. If the neck is moving so much a re-set is not viable, you have something going on that is not going to be good down the road. I would pull the fretboard and do over.

Working in precautions can help to avoid issues with necks moving. Things like; Make sure your neck blank is well dried, during the carving process allow the neck to settle for a week or so in a semi close ruff carved state, use non waterbased glues (such as epoxy) to minimise introduced swelling during glue up, allow a bit(usually very small) of extra material for final adjustment and leveling, be sure your clamping is even(cauls and jigs are a good idea). Most importantly, give the neck time to stabalize before attempting to level it.


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I'm inclined to think that Setch may be right about introducing the bowing during the gluing/clamping. This is an Ibanez neck that I took off the orig. fretboard and put on a newly inlayed ebony one. When gluing, I didn't clamp with a caul, I followed the tutorial and "sandwiched" the neck and fingerboard between wood shims for clamping.

As for heatsetting the neck, Setch, can you discribe the process a little more for me? I really don't want to sand the fingerboard any more because of the inlays.

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