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I have the FB  glued onto the neck of the '37 Hauser model I've been working on, my first classical guitar, and it's planed dead flat along its length.  The Courtnall book suggests that it will be fine to fret it this way, but I've also read that I should be leveling the neck with a little downwards force applied (a bar clamp attached to the headstock with a 2 1/2lb weight on it, so it's a little back-bowed) in order to give the neck .006" - .010" of relief at the 7th fret when the clamp is removed. This is supposed to bring the neck back to level after the frets are applied.

The fret tangs are nearly a perfect fit for the fret slots, perhaps two thousandths thinner.

I'm not sure which approach to follow at this point.

Did you test if that weight actually flexes the neck. 1Kg and a bit is almost nothing. So its .006, so better check in real. 

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Build log

Many builders will taper the finger board from the nut to the sound hole a couple of millimeters.  Often, they will taper more on the bass side, say an extra millimeter.  Hauser's '37 plan calls for the fret board to be 6mm at the nut and 5 mm on the treble side at the sound hole/19th fret, and 4mm on the bass side at the 19th fret.  The plan also calls for about.002 to .004" slack or relief in the finger board,  That's probably what the weight would do.

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Waddy

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listen to Waddy. 2mm on treble and 4mm on bass

Waddy,

Does that represent a Torres-stye neck, with no forward pitch?

I've been using a 2 or 3mm forward pitch to the neck, so that I have to trim the fretboard to get it to sit flat from the 12th fret to soundhole, and then I plane the extra bass side relief into the fretboard from the 3d to 12th fret.

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Jim Kirby
kirby@udel.edu

.002" sounds pretty close to me. The bead on the fret wire may compress the board a bit more than you anticipated. The fret board that I just did had a slot size of .023" and I used wire at .0185" fretting while the neck is still square to compress the board to the max and avoid any back bow. It came out nice and flat.............I usually rely on string tension to pull it into a little relief. 

As opposed to relief, tapering the board has to do with maintaining a high enough action without having a too high bridge. This can also be done by putting a lift in the neck or by doing both. Tapering away the bass side additionally obviates the need to have the saddle significantly higher on the bass side.

 

Some recommend not simply a taper, but a complex curve. This is based upon long observed shapes of the vibrating string, so that you can keep a minimum height and still keep a minimum of buzzing. I cannot locate the reference now, but I recall that Jose Ramirez III said something like -- put a little curve between the fifth and seventh fret. The most precise of the builders who put a relief in the fingerboard would probably not rely on bending the neck back during finishing, becasue that would not provide the exact control of the curve. I think they would use a plane or scraper and build the curve that they want directly.

By the way, even decades ago I had already heard that many people saw the strange shape in their Ramirez necks and mistook this for a post construction warp. They took the guitars to repairmen, who did not know better and accommodated the owners by planing the neck level. Both assumed that the guitar was thus improved, when, in reality, the action was worsened. This also happened during routine refretting.

On my latest Ive put 3mm up at the nut, and with 3mm+ of lower bout doming I managed to get a good action while having a normal bridge and saddle (not low which means you have to shave the bridge if the neck bows up and not too tall to create strong levering and top distortion).

I did taper the bass side starting at the 9th fret though to have an equal height saddle, same as David mentioned.

I guess that on my next i will go back to a flush 180 deg neck and heavy FB tapering. One of the advantages is that you shave away a good deal of ebony. It does count if you try to get an extremely light instrument.

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Build log

The Hauser plan calls for a 2mm tilt of neck at the nut end, not including the taper in the finger board.  All of this, however, depends on how you build the guitar...  How much dome do you have in the top?  Do you raise the lower bout in the Solera per Bogdanovich or Romanillos, or do you scoop it out for doming the top?  Or, do you build it flat.  Some do.  If you are building the Hauser plan, you should get a copy of American Lutherie #31, or whichever Big Red Book has that issue.  There is a lot of information in that article on the '37 guitar.

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Waddy

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I'm building the guitar using the solera outlined in the Courtnall book - 25' radius carved into the solera and a 2-3mm tilt at the neck end. The neck was glued onto the top in the solera. I've been following a method outlined by David Schramm, and so far when I check the action using his method, it's within spec. I'm also getting the measurements outlined in the Courtnall book, in the paragraph that outlines a method for the preliminary checking of the action.

My FB is a bit thicker than the Hauser plan at the soundhole. I could taper the entire lower end of the FB at this point, but this will effectively give the FB a downward slope toward the bridge, so I'll need to be careful not to go too low and check the action height often.  If I understand all the information here correctly, I should get the taper correct first, and then get the relief into the board.

Man, I thought I was confused before...

Alex,
If I understand you correctly, you tapered the bass side, but only starting at the 9th fret. If you mean the part from the 9th towards the bridge is tapered, then that would build a reverse relief on that side, which I think is the opposite of what you would want. If you taper the entire length of the bass, you will keep the saddle down, but have zero relief. If you want what I think is proper relief, you need to depress the area aroung the 7th fret, so you have a very slight bow in that side of the fingerboard. However, most people do not try to put in this relief.

The Romanillos method has the solera creating a 5mm drop at the end of the guitar starting from just beyond the waist. This combined with about a 25' radius at the bridge location and extending (to a gradually lessening degree...) forward through the soundhole area gives the top not only a side to side arch but a pronounced arch from front to back (i.e."domed"). The neck lift is 2mm.

This creates a seemingly complex geometry to the body/neck but because the top where it joins the sides is curved downward while the center is arched upward, the 2mm creates enough lift to keep a normal bridge height. The fretboard has a slight taper. 

What you'd see if you looked at my Ramirez 1a is that the face of the fingerboard actually twists as per comments above.   With steel string guitars, we normally make the bass strings higher off the face than the treble strings (discounting the arc of the fingerboard and saddle).   Some of the great classical builders prefer to keep the strings more or less the same distance off the face at the bridge and compensate for greater bass string excursion by adjusting the surface of the fingerboard.

Bill,

Ouch, I hope I didn't mess it up :( 

Here it is in different words:  the nut end of the neck is set forward 3mm. That allows a perfectly flat fingerboard. But before fretting I thought it might help to shave a bit off the bass side starting from somewhere between the 9th and 12th up to the 19th. As a result the bass side is almost 1mm lower at the 19th. Nothing extreme. Just that I use low or medium tension basses and these buzz easily compared to high tension or a 660 scale.  Seems to play ok for the moment.

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Build log

If it plays OK, that is the bottom line.

But everything can be improved.  The more I think about it the more i like the ideea of a dished center. The open and first few positions do not buzz, while having comfortable action at the higher frets.  Sounds ideal.
Only if would work on a 650 scale with low tension strings. Ramirez's 1a come in 660 by default?

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Build log

Two approaches to fingerboard shaping can be taken, both producing the same end result.

Looking at the 19th century instruments, including Torres. The neck was built straight but with a very slight relief bow so that when the fretboard was fretted the back bow caused was cancelled out leaving a flat fingerboard. The fretboard itself was tapered being say 6mm at the nut and 4mm at the soundhole. Saddle height was probably 0.5mm higher on the bass side to allow for the greater amplitude of the string vibration. Or, on some later instruments the bass side of the fingerboard was graduated down from the 5th fret or so to the soundhole and the saddle more or less straight. This is the approach I have taken on a recent Torres 'copy' as being more authentic than the second method.

Today however, most builders will build in a 2-2.5mm forward angle on the neck itself when gluing on the back. This means that the fingerboard does not need to be tapered in thickness. The same slight dip in the centre of the neck before gluing on the fingerboard will cancel out the backbow from fretting. Again the bass side is relieved from about the 5th fret. The Bogdanovich book has probably the best explanation of this system.

Both systems will work fine.

Interestingly (to me anyway) on lutes that employ more strings and have a greater string pull than a nylon strung guitar, the fingerboard veneer is dead flat and on the same plain as the flat top, all that we do is have the bridge (no saddle remember) is higher on the bass side. We do however use gut of graduated size tied on as as the frets to reduce any buzzing.

Colin

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I don't believe in anything, I simply make use of a set of reasonable working hypotheses.