BYO) Fingerboard bump at body joint

Craig Bumgarner

What is going on with the bump in the fingerboard where the neck joins the body on many gypsy guitars? Clearly the result of the transition of the fingerboard from the neck shaft to the body, but what exactly is going on? I have my own guesses, but some of my guesses seem to conflict, so I would be interested in the opinions of others.

The most significant fallout of the bump is the frets in the same area fret out sooner than others as the action is lowered and often seems to be a limiting factor how low the high E string action can be.

The advice I have seen on this is to taper the fingerboard from the 14th fret to the 21st fret by about a millimeter, but this does not always seem to work, even seems to make the problem worse sometimes.

I note not all Selmer style guitars have either of these problems even though the construction appears to be very similar. For instance of two Duponts I owned, one did, one did not have the problem.

Any thoughts appreciated.

CB

Jeff Moore

The wood shrinks differentially - across the grain lots, end grain (or lengthwise) not so much. It's most likely to happen from drying, but unless wood is seasoned (20 years is nice), it'll still shrink even though it has a stable humidity as the resins in the wood (resins don't just lose water but other volatile compounds) that dry and harden over time and simply as the fibers age and the cell structures slump a little.
Back to the question:
Shrinkage with the grain, as in the end block, at the 14th, 15th, 16th etc... fret is less that the shrinkage across the grain in the neck - fretboard. The result is that the end block structure retains the dimensions it had when the guitar was built more or less, while the neck (shrinking across the grain) in thickness and width shrinks more over time.
The only preventative is using well aged wood, not something our "just in time" economy can withstand much of. A old luthier is more likely to have some well aged wood, but only if she invested in wood young, and planned many years in advance or finds a source for such wood.
This phenomena is in no way truer of Sel-macs than any other guitar.

The only good solution is to take out the frets and level the fretboard. Oh boy!
I suppose you can just work on the fretboard under frets 14 - 21, but by the time this shrinkage has happened you perhaps need all new frets anyway.
If your frets aren't worn out, you can just level them. Some will of course look shorter because of the bump at the 14th fret, but who cares as long as they're all level?