Fretless neck setup

[Matt Hayden]

Is there a trick to getting a fretless neck set up just right? Should the board be sanded dead flat, and if so, what's the best way to do it? I've got one that notes out at about the 10th-12th fret, and it checks out as dead flat without strings.

[danove]

Please excuse my bad english. I'm not certain if you refer to fingerboard radius.
But if you are thinking about the lengthwise setup, please consider this:

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Following the form of the singing string there should be a sloop down to half the string length,
where the amplitude is large. Almost not noticeable at the Hi side, but more so at the Lo.

Some luthiers have the sloop ending earlier than the 12th fret.
A Swedish master luthier explained to me that this is made to adopt to
the soundbox own tone properties, reinforcing a certain tone amplitude.
This then should differ between type of guitar construction.

All this makes a huge difference to the action setup and how you are going to
like playing your instrument. With no frets you could easily try things out.
A bit time consuming, but it pays.
Frank of corse have a trick that could give you some ideas:

Also the fretboard should not dive after the neck joint, as often is the case,
but rather be lifted a bit towards its end.

[Nick Anthony]

if it has a truss rod adjust it so that the neck is as straigh as possible and plane untill flat...stew mac makes pre radiused cauls for just such a job...then set the neck with about 4 thous. of relief set the action to specs and you should be good

[FRANK]

NICK IS RIGHT ADJUST THE TRUSS ROD YOU DON'T NEED A STEW MAC RADIUS BLOCK FRANK USES A OLD PLANE WITH OUT THE BLADE AND RAPS SAND PAPER AROUND IT KEEPING THE RADIUS IS NOT THAT HARD THEN STRING IT UP ADD .04 TO .12 THOUSANDTHS OF RELIEF WATCH OUT FOR THE WOLFING SOUND THIS IS BUZZ ON THE FRET BOARD IF YOU END UP WITH THIS ADD MORE RELIEF MAX .15 TH BY NOTING OUT ARE YOU BENDING THE STRING?

[danove]

As you are doing a fretless, you could have som ideas from looking into the violin family.

Check this MovieClip
from 2:05, there is a deskription of the concavity - for as short as the violin strings.
- just an example to see how important it is.

The trussrod is of little help, if this concavity is not prepared for in advance.
Useless, I would say, to do anything but getting the neck back to original shape
after it beeing pulled up too mutch by string tension.
- because it affects the neck around a quarter of the length,
and not halfways where the string amplitude is at maximum.