Official Luthiers Forum!

So how does one determine neck angle when setting the neck for a nylon string?
What differences are there to steel string?

My usual go-to is a straightedge with a matchstick taped on the end to allow for a 1/16" clearance above the top when straightedge it laid on the neck (no fingerboard, no bridge) and extended to the saddle position. Voila. Neck angle determined.

With a classical, I'm doubting my technique.

Someone please throw a pointer my way.

Thanks,

dave

Generally (at least how I do it) you decide if you want to build an arch into the top, and how much of an arch. You can build with a dead flat top, then the angle is Zero. Most of the classicals built in the 20th century have some arch. The neck angle is equal to the amount of arch. If your top arch is three mm.s, then you move the neck three mm.s back. If you were to build in the Spanish style, face down, a three mm. arch in the top would require a three mm. shim under the neck.

Brent

So set it dead flat with the top with no back angle.

I’ll turn my straight edge over, with no shim under the end, and use the angle between the top and side to get the neck angle. The top has a dome to it. Rather than radiusing the braces, the fans were all pressed into a 25’ dish. I think the transverse braces had a little radius on them too.

The body is done. Neck is far along, I’ve just dragged my feet on the angle.

Thanks for the help.

You CAN build flat, but most luthiers are using and arch of some kind. Three mm. seems to be the most common, after that the guitar sounds very banjo-ish. The arch is actually built into the solera (workboard). Working 'face down' changes the whole concept compared to steel strings. I have a formula written down somewhere, I'll post it if I can find it.

I recently converted a classical to a bolt-on neck due to high action. I set the straight edge that was sitting on top of the frets, extending to exactly the top of the bridge. It worked out Ok. The saddle had about 3/16” showing with an action of .070" on the high e and .080" on the low E, which, I think, is considered low for classical guitars, but it seemed buzz free to me.

Nylon strings need a higher action due to the larger vibrational envelope of the strings. Strong player might need 4mm on the bass string and 3 - 3.5 mm's on the treble side. This is considered standard action I'm fine with 3.5 and 2.5 mm's myself. Most prefer this, but a concert player may need higher action. Also, the neck set is usually negative on a classical due to the high action numbers. you might want to investigate this.

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Jim Watts
http://jameswattsguitars.com

What James said. I've had classical players want 4.5 mm (12/64!) on the low e. Nylon strings have much less tension than steel, thus the larger envelope and higher action.Takes getting used to, but it sure is easier on the fingertips!

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formerly known around here as burbank
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http://www.patfosterguitars.com

It's player dependent you can go for concert classical which can be at the 12th 9/64th high e and 12/64th low e and that is that expanded vibrational envelope that Jim speaks of. Classicals require higher action but it does not need to be sky high and most of the time should not be if you consider the specific player and their needs.

Rarely does anyone bring us a classical for this kind of action except for one classical guitar teacher who is teaching concert classical. The vast majority of classical guitars that I service are asking for the action to be lowered greatly! I would guess that it's over 50 annually that want the action much lower to maybe 2 who ask for concert classical action.

So I go 7/64th and 9/64th high e and low e Dave when in question how low and for people who tell me as low as possible I go 5/64th" high e and 7/64th" high e. All of these are measured at the 12th.

Regarding neck angle dome, no dome is irrelevant if you are registering or trying to register the straight edge in respect to the bridge. The bridge is where it is and we are not going to change that. What I typically see is a neck angle where a straight edge just skims the top or is just below the top of the bridge.

So drop the match stick and set for the straight edge to skim the top or be just below the top of the bridge and you will be good.

Remember too as I shared here in my set-up toot for steel strings there is a sequence to a set-up that also will have impact for setting the neck angle. Since you adjust the rod first which is out of play in most classicals with no rod nut slots are next. Classical strings need slightly higher nut slots or they will sitar out and this slightly higher nuts slots also raises the action at the bridge.

So set the angle as I suggest, cut the nut slots and then set action with the saddle at the 12th but set the action for the player. It's not going to work well for someone who does not care about concert classical technique and want wants to strum 4 Non Blonds or Leonard Cohen and doesn't want high action. String selection is key here too again non-classical classical guitar players will want less tension, go "normal" and D'Addairo standard classical strings have filled the bill here for hundreds of ones that I've done.

If this is for a hard core classical player go 9/12 on the action (9/64th" and 12/64th" at the 12th) and higher tension strings may be desired too. Just always, always consider the player especially for a nylon string guitar because the vast majority of them in my US market are not shooting for concert classical and instead will be asking for that kind of action to be dramatically lowered.

The equation I've always used is this one I've borrowed from another forum. Numbers in the key are just for example.

N=(FB+FR+(A*2))-(D+SH)

SH = String Height at Saddle (12)
FB = Fingerboard thickness (6)
FR = Fret Height (1)
A = Action at F12 (3.5 @ E6)
D = Doming at bridge (2)
N = Neck Angle (?)

Not sure if its been mentioned but classicals typically have a positive neck angle instead of the negative neck angle of a steel string. If you're using a negative angle I don't think this equation will apply.

I agree with Jim and Pat. A negative neck angle is usually required. Easy to make a drawing with your fingerboard thickness, first and twelfth fret height, desired action height. This will give you a straight line you can extend to bridge location. Measure 10-11mm down from the line and this is the distance from the bottom of the string to the soundboard. Juggle all your other variables like dome and you're there. A properly built nylon string guitar will not experience a big rise of the soundboard as it ages.

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Stay with the happy people.
--Reynolds Large

P.S. Start your layout drawing with a straight line representing a zero neck angle. Input the measurements stated above. You'll probably arrive at a saddle height of 12-13mm, which is too high. You can then slice the drawing at the 12th fret to essentially make a hinge. Slide the neck half up until you get to 11mm. This will give you some room to lower the action a wee bit if necessary.

_________________
Stay with the happy people.
--Reynolds Large