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I'm finishing up my first classical build and am at the stage where I need to do the final fingerboard prep before I install the frets. I'm looking for some clarification on the fingerboard prep and hoping some of you classical guys can help me out.

Background on the build
My primary reference for this build has been Bogdanovich's book. While I've made a few slight tweaks to the design all the body and neck geometry was taken right out of his book. I've also been comparing his methods to other books and info I've gathered here on the forum.

Leading up to this stage I did like he said in step 12,14-15 and planed a slight bow into the neck blank (aprox 1/64 at the center between the 4th and 12th fret positions) to compensate for surface tension created by the frets. Now I'm looking at page 245 - Before Fretting. Midway through the paragraph he says "The fingerboard must be relieved slightly on the bass side from about the fifth fret to the sound hole, to provide additional clearance for the bass strings..... The total relief at the 12th fret should be approximately .020." So my understanding is that this is a straight taper on the bass side of the fretboard starting at the 5th fret. If I were to mark a line .020" down from the face of the fretboard at the 12fret and draw a line starting at the face of the fretboard at the 5th fret, through my mark at the 12 fret and extending it to the end of the fretboard than I would have the correct taper? Am I understanding this correctly? He uses the term "total relief" which is causing me some confusion.

If anyone can confirm that I am understanding this correctly, or have something to add, I would appreciate it.

Also, thanks to all those who helped me with the 18 hole bridge thread last week. I've made a few prototype bridges and really like how the 18 hole thing is working out.

Josh

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Josh House

Canadian Luthier Supply
http://www.canadianluthiersupply.com
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House Guitars - Custom Built Acoustic Instruments.
http://www.houseguitars.com

The fretboard taper on the bass side can be thought of as giving the string more room to move in the middle of it's arc, and thus the idea of tapering from the 5th or so to the 12th or so fret means just that - it doesn't mean continuing the taper to the end of the fretboard. It's more like dishing out the fretboard along it's length on the bass side.

Another consideration is whether you want the 1 mm+ higher action at the 12th fret on the bass strings to translate to a 2mm+ higher string height above the top at the saddle, or whether you want string height at the saddle to be uniform.
If the latter is the case, you do need to do a taper of the bass side along the entire board - if this is done, it will create a board that looks like it is twisted clockwise when you look down the board from the nut end. This is independent of the additional scooping of the board to give the extra room for the bass strings to move, which in and of itself does not change the fretboard thickness at the soundhole.

_________________
Jim Kirby
kirby@udel.edu

Depends on what you have for a neck angle. I taper my boards on the treble side from 7 mm to 5 mm at 19, and from 7 mm to 4 mm at 19 on the bass side.

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Waddy

Photobucket Build Album Library

Sound Clips of most of my guitars

Some classical guys like to taper down the bass side of the fretboard to get higher 12th fret string height without having the saddle higher on the bass side. They confusingly call this relief which most guys here would use to refer to bow in the neck.
I don't, I just leave it flat

Hmmm. . . it's neither bow or relief. That describes a taper across the width of the fretboard, so effectively the Bass side of the fretboard is thinner than that of the treble.
There are a few ways to approach this. I don't know how Bogdanovich does it but I taper across the width of the fretboard as described previously. I also plane in some small relief or scoop - a touch on the treble side ( 0.1 mm's) with more on the bass side (0.3 mm's). The tiny amount on the treble side is only done to stop any hint of back bow or buzz.
I don't taper along the length of the fretboard or give it any of this 'twist'. I've never found that to be necessary. The neck is given an angle and the underside of the fretboard is tapered towards the soundhole from when it crashes into the body at the 12 th fret.

If part of the fretboard is dished or scooped, what happens when fret levelling? Are they all taken down to the level of those in the lowest part of the scoop?

No that would just result in taking all the relief away. You have to level with a much shorter block, something that spans 3 or 4 of the lower frets. I seldom have to use a block anyway. I glue and clamp my frets in which means that I only have the odd fret that needs a touch taking off it's top. Sometimes they end up a bit worse than that and they require more work. Don't ask me why that is.

I have that same experience, Michael. I can never figure it out!

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Waddy

Photobucket Build Album Library

Sound Clips of most of my guitars

I leave mine flat with a slight taper on the bass side for string "amplitude", under the assumption that properly sized frets and slots should not cause backbow and string tension will induce relief...which it does...and over time often too much with no truss rod recourse.

Thanks for all the replies. Like I have been thinking, there are many ways to tackle this issue and they probably all work. This has given me some more to think about. I plan to string up the guitar and take some measurements before I put the frets in. That way I'll still be able to tweak the board if I need to.

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Josh House

Canadian Luthier Supply
http://www.canadianluthiersupply.com
https://www.facebook.com/canadianluthiersupply?ref=hl
House Guitars - Custom Built Acoustic Instruments.
http://www.houseguitars.com

Steve, Do you use any kind of neck reinforcement? If so how effective have you found it to be in resisting the tendency for the neck to develop too much relief? In my guitar I have a 1/4" of carbon fiber.

Josh

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Josh House

Canadian Luthier Supply
http://www.canadianluthiersupply.com
https://www.facebook.com/canadianluthiersupply?ref=hl
House Guitars - Custom Built Acoustic Instruments.
http://www.houseguitars.com

Out of curiosity what sort of neck angle do you use on your classicals?

Josh

_________________
Josh House

Canadian Luthier Supply
http://www.canadianluthiersupply.com
https://www.facebook.com/canadianluthiersupply?ref=hl
House Guitars - Custom Built Acoustic Instruments.
http://www.houseguitars.com

Close to 2 mm at the nut. That said, I also have a raised and dished lower bout similar to Bogdanovich and Romanillos.

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Waddy

Photobucket Build Album Library

Sound Clips of most of my guitars

Thanks Waddy, your method sounds similar to what I have done.

_________________
Josh House

Canadian Luthier Supply
http://www.canadianluthiersupply.com
https://www.facebook.com/canadianluthiersupply?ref=hl
House Guitars - Custom Built Acoustic Instruments.
http://www.houseguitars.com

Josh
I did indeed use CF/Hardwood/CF laminate in my last neck.
I could induce a slight bend in it by "leaning" on it so im hoping it will just deflect a little and not keep going over the years.