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Hello everyone. I’m working on my first guitar and am trying to understand if the design lengthwise profile of the classical neck/fingerboard should be perfectly flat or if it’s supposed to have some built in relief. By ‘relief’ I don’t mean taper to set string action, but rather fret heights relative to one another.

In John Bogdanovich’s book he says “To compensate for the surface tension created by the frets, there should be a slight bow from about the fourth fret to the twelfth. At its center, it should only be approximately 1/64 inch. If necessary, plane the neck across the grain to add this bow.”

I’m not sure how to interpret this. Thanks for any clarification.

Joe

I think he is saying that you want 1/64 of relief, (ie bow) from the 4th fret to the 12th, and he planes it in .. sometimes ebony can be tough to plane with the grain if its highly interlocked, so you can do it across the grain, or in this case, across the fingerboard.

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Joe-
It's a mystery to me too!
It's not clear whether Bogdanovich is talking about pre-compensating for back-bow introduced into the neck by fret insertion, or whether he's recommending the final amount of relief after fretting...
What the heck is 'surface tension created by frets'?

Anyway, to answer your question- I generally don't put any relief into the fingerboards on my guitars and usually the neck either stays flat or 'pulls up' to add a bit of (uncontrolled) relief. If I'm going to err, I'd rather have a too-flat fingerboard, than one with too much relief.

Some classical builders (eg Kenny Hill) are putting 2-way truss rods into classical necks so that they can control relief. This is handy if the guitar is experiencing humidity changes (travel, change of season). But that's another discussion.

Cheers
John

The classical guys often seem to use "relief" with a different meaning to steel string makers.
What they generally mean is that they plane down the bass side of the fretboard a little to give increased vibrating clearance for the bass strings without needing to have the saddle higher on the bass side.
However I think in this case, Bogdanovich is saying that the process of fretting can tend to bow the neck backwards due to the fret tangs pushing on the sides of the slots and that you should have the surface slightly concave so it ends up flat after fretting.
I have never done this, and dont think it should be a problem with correctly sized slots.
But I now fret before installing the fretboard.

Ok, thanks guys. If a longitudinally flat fingerboard is the target, it sounds like I should be ok if I don't plane a ‘bow’ in the neck surface prior to installing the fingerboard.

Joe

I'm one of those Classical Guys.
Do you have a true straight edge long enough to go from the First to the 19th or 20th fret?

If you do.

You should have enough clearance at the ninth fret to put a business card underneath the 6th string and hardly deflect it.
It is not very crucial.
Kind of like doing spark plug gaps. If you are old enough, you know what I'm talking about.
If not - some one else in this forum will be able to enlighten you.
If not I'll come back an elucidate.

On the treble - first string - on the ninth fret - you can be flat or have a hair of relief. I like a minuscule of relief.
Again not crucial.

The important thing is that there is no back bow - anywhere!

These relief gaps are what you want after you have strung up the guitar -
SO -
You must prejudge the lift cause by string tension,
by preloading the neck and the body while truing the fingerboard.
Many ways of doing this - I'm sure you can imagine some.

The fret tang is of course something you need to consider.
If the gap you cut in the fretboard is too tight - you will get a back bow - this will mean extra work for leveling the frets - and even more work to add relief.

I will generally fudge, toward a loose fret channel, and rely on fish glue to fill any looseness in the gap.

This, I think helps to keep a fret tight, and if the glue gives a little, it just adds to an extra minuscule bit of relief.

Elman

I agree, totally, with that. A little relief goes a long way in giving a classical guitar that little bit of reserve some players want, without having ridiculous action at the 12th.

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