In the last part of what’s fast turning into a warped neck saga, we talked about up-bow (that is, relief or, more to the point, too much relief). Now let’s look at its opposing bedfellow, back-bow. That done, we'll examine some similar neck deformations that can fall under the umbrella of 'warped' neck.

Back-Bow

Yep. As you’d expect, back-bow looks like up-bow just going the other way. Back-bow, however, is probably more genuinely a member of the neck warp family. While up-bow is most likely caused by string tension pulling the neck into that shape, back bow is (probably) a result of actual warping of the neck wood.

There are some instances, where an instrument has been stored unstrung for a long period, that the truss rod can pull the neck into back-bow (remember that a tightened truss rod will pull against string tension — no tension and it’ll pull the neck back). A neck that pulls into back bow all on its own, though, that’s proper warp. 😉

Given that it’s a same-but-opposite situation, working to remedy a back bow follows a similar pattern to up-bow. I’ll mostly skim there so check last week’s post on up-bow for more detail.

Heat-treatment

I’d guess that back-bow is one of the more common complaints that see repairers reaching for their various heating devices. As before, with the caveats mentioned, it’s definitely on the menu of possible solutions.

Levelling

Levelling the frets or (more likely) the fingerboard during a refret might be worth considering. This is mainly useful for minor bows only.

Corrective refret

Not so useful a method when dealing with a back-bow. In theory, it’s possible to install frets with tangs narrower than the slots and this may be enough to let string-tension pull the neck straight. However, the problem with narrow fret tangs in a wider slot should be obvious. They won’t hold. Glueing frets might help but, with regular tension changes during restringing, there's a good chance those frets won’t be in the neck for long.

The ‘extreme’ option

Again, removing the fingerboard and levelling the exposed face of the neck itself is an option. Of course it’s a big job but it has the advantage of being likely to give good results and providing the possibility of adding some stiffening support to the neck. Definitely worth considering if the guitar warrants and your wallet allows.

Ski jumps

If you’ve been hanging out here for a while, you might remember we’ve talked about ski-jumps before. In fact, we went so far as to try define the different types of guitar neck ski-jump you might see.

End-of-neck ski-jump

The end-of-neck ski-jump, is a rise in the last few frets of the neck. A hump develops and causes nastiness like fret buzz. While the jury’s still out, I suspect strongly that shimming under bolt-on necks is a strong contender for causing a lot of this issue.

Regarding potential fixes (after you sort out the neck shim issue), we’re talking about levelling. If you’re lucky, there will be enough height in the frets to get away with levelling the hump out of them. Otherwise, you’re looking at a refret and a fingerboard level.

Heat treatment isn’t suitable here and the more involved methods mentioned above aren’t needed.

12th-fret ski-jump

12th fret or octave ski-jump (more common on basses).

This can be better thought of as a kink in the neck that occurs somewhere in the 12–17 fret area. It’s more common on basses than guitars and probably indicates a neck that’s weak in this area. Like up-bow, this one is string-tension related.

Regarding a fix, that’s more complicated. Heat treatment, in my opinion, isn’t an option here. The levelling methods might work for minor kinking but, if the neck is weak here, there’s most definitely a fear it will happen again.

Removing the fingerboard, levelling, and installing reinforcement is an option but, as noted, this is a big job.

Worth throwing into the pot at this point is the elephant in the room carrying a bolt-on neck. With a ‘modular’ guitar like a Fender bolt-on or similar, the option of scrapping a neck and replacing it with a brand new one should be considered. In many cases, this can be a lot cheaper (and easier) than some of the fixes. These ski-jump issues are more prevalent on bolt-on instruments. The end-of-fret ski-jump is typically a straightforward fix but a 12th fret kink can be problematic. Some players are reluctant to change a neck but it should be kept in mind.

S-Shaped neck

We’ve talked about these before. We can treat them similar to an end-of-neck ski-jump. Levelling the fingerboard tends to be the remedy for this most of the time. Heat-treatment isn’t really on the cards.

Again, it might be appropriate to remove the fingerboard and sort out the neck with levelling and/or reinforcement on the right guitar.

More warping next time.

This article written by Gerry Hayes and first published at hazeguitars.com

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