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Can I make classical guitar neck thinner?

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Can I make classical guitar neck thinner?

Postby Marco Giovanni » Mon Nov 14, 2016 6:43 am

Hello to everyone.
I'm new to this forum and this is my first post, thank you for giving me opportunity to be the part of this community.

I'm not instrument builder (nowhere near that), but sometimes I do small repairs to my guitars and basses.
So, I have some experience, but definitely don't have enough knowledge about many craft details.

Right now I have Alhambra 3F guitar (flamenco guitar), and I would like to do one modification to it's neck.
It has mahogany neck (rosewood fretboard), which is 22mm thick at the first fret, and 25mm at the ninth fret.
I would like to make neck thinner, to be approximately 20mm on almost all frets.
If I do that, will the neck be strong enough to keep its dimensional stability? Or simpler said, will it bend under the string tension if I do this modification?
Guitar doesn't have truss rod.

Thank you very much!
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Re: Can I make classical guitar neck thinner?

Postby Barry Daniels » Mon Nov 14, 2016 10:38 am

Yeah, it will likely bend some. Maybe a little or maybe a lot. There is no way to predict this without more knowledge. Does the neck feel stiff?
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Re: Can I make classical guitar neck thinner?

Postby Brian Evans » Mon Nov 14, 2016 11:32 am

Without a truss rod you can only make the change and see what happens. 20mm is on the thin side of normal for a first fret measurement, but necks almost always taper towards the heel, 23mm might be a thin/normal at the 9th fret. It's possible the neck has some reinforcement inside that you can't see and would take well to the change, and .2mm is not really a lot of material to remove, just around .08".
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Re: Can I make classical guitar neck thinner?

Postby Marco Giovanni » Mon Nov 14, 2016 11:33 am

Thank you for your answer Barry.

I don't know what do you mean by:"does the neck feel stiff"?
I guess every neck must feel stiff, there is no other option? It can't be soft? :-)
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Re: Can I make classical guitar neck thinner?

Postby Marco Giovanni » Mon Nov 14, 2016 12:07 pm

Brian Evans wrote:Without a truss rod you can only make the change and see what happens. 20mm is on the thin side of normal for a first fret measurement, but necks almost always taper towards the heel, 23mm might be a thin/normal at the 9th fret. It's possible the neck has some reinforcement inside that you can't see and would take well to the change, and .2mm is not really a lot of material to remove, just around .08".


Thank you for your answer Brian!

Manufacturers info says that there is no truss rod.
You say it's possible that there is some reinforcement inside the neck. If there is, how can I check for it?
My idea is not to remove just 0.2mm but almost 5mm (the thicker part of the neck - around 9th fret). To me it sounds alot and therefore I'm afraid that neck will bend under the string tension. But, I've played some classical guitars which definitely had very thin neck (I'm sure it was thinner than 20mm) which felt great, and I'm also sure that there was no truss rod inside them.
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Re: Can I make classical guitar neck thinner?

Postby Alan Carruth » Mon Nov 14, 2016 1:07 pm

Why do you want to make it thinner? What is the profile like? Some production Classicals have a fairly clumsy neck profile; sort of flat in the middle and rounded off too fast at the edges. A more elliptical, or even egg-shaped profile a little thinner on the treble side, can be a lot more comfortable at the same depth.

When the neck is shallow you don't have as much leverage for the thumb in fretting, particularly for barre chords. Although Classical guitars carry less tension than steel strings, they also have higher action, and that can actually make more work for the left hand. Some years ago a local Classical player came around because he was having carpal tunnel issues. He'd gotten an 11-string guitar from a local maker, who had made the neck very shallow with the idea that it would make up for the added width to facilitate playing. The player got the idea that perhaps a bit of extra depth would help, so he started to build it up with duct tape. When he got it to the point where it was comfortable he brought it around to have me build it up. It's pretty easy to carve a neck down; building one up is something else....

22 mm deep at the first fret is perhaps a shade deep, but not out of line. I would not take more than 1 mm off, and don't get rid of the taper. With no truss rod that's needed to keep the neck stiffness up. Don't be surprised if the sound changes.
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Re: Can I make classical guitar neck thinner?

Postby Marco Giovanni » Mon Nov 14, 2016 1:30 pm

Alan Carruth wrote:Why do you want to make it thinner? What is the profile like? Some production Classicals have a fairly clumsy neck profile; sort of flat in the middle and rounded off too fast at the edges. A more elliptical, or even egg-shaped profile a little thinner on the treble side, can be a lot more comfortable at the same depth.

When the neck is shallow you don't have as much leverage for the thumb in fretting, particularly for barre chords. Although Classical guitars carry less tension than steel strings, they also have higher action, and that can actually make more work for the left hand. Some years ago a local Classical player came around because he was having carpal tunnel issues. He'd gotten an 11-string guitar from a local maker, who had made the neck very shallow with the idea that it would make up for the added width to facilitate playing. The player got the idea that perhaps a bit of extra depth would help, so he started to build it up with duct tape. When he got it to the point where it was comfortable he brought it around to have me build it up. It's pretty easy to carve a neck down; building one up is something else....

22 mm deep at the first fret is perhaps a shade deep, but not out of line. I would not take more than 1 mm off, and don't get rid of the taper. With no truss rod that's needed to keep the neck stiffness up. Don't be surprised if the sound changes.


Hi Alan! Thank you for your reply!

I want to make it thinner because I have two other (also nylon string) guitars which have thinner neck and which are therefore much easier for me to play, and I fell much more comfortable playing them. I guess also one important reason is that I don't have very big hand.
For instance, I have one Godin guitar (multiac nylon) which is very thin (18mm 1st fret, 20mm 9th fret), and Yamaha SLG200N (20mm 1st fret, 22mm 9th fret). They are both easier to play, but it's important to say that they both have truss rod.

Neck profile is I guess D shape. I'm looking on the internet the pictures of different neck profiles and D-shape seems to be the one my Alhambra has :-) As I said before, I'm not builder, so I'm not quite into the terminology.

Yes, I'm aware that neck has to have some depth, and that too shallow neck will also make playing problems. That's why I want the neck to be more like the other guitars I already have. If they are not too shallow to play, then I guess that Alhambra would also be fine with that thickness. So, I'm not really worried about playability but only if the neck will bend under the string tension.

When you say that you wouldn't take more than 1mm, you are talking about 1st fret or about whole neck?
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Re: Can I make classical guitar neck thinner?

Postby David King » Mon Nov 14, 2016 3:37 pm

Marco,
I thin necks necks from time to time but only when they have truss rods. As the others have mentioned the taper is very important as the stress on the middle of the neck is much higher than it is at the nut end. I would say remove a mm or 2 over the whole neck and see what happens. If you find that the action goes too high you'll need to pull the fingerboard off and add some stiffeners or a truss rod or both. At that point you can make the neck as thin as you would like but it's a lot more work and maybe this guitar isn't worthy of all the trouble?
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Re: Can I make classical guitar neck thinner?

Postby Bob Gramann » Mon Nov 14, 2016 4:35 pm

I sometimes counsel a player to sell the guitar he doesn't want and go buy the guitar he does want. Changing a completed guitar into something it wasn't intended to be can make it into a guitar that nobody wants. (People have brought me rescue projects where the modification didn't bring the desired results. Most of the time, those projects have been beyond my help within the given budget.) Saving some bucks is pretty insignificant compared to playing the instrument that's right for you for the rest of your life.
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Re: Can I make classical guitar neck thinner?

Postby Alan Carruth » Tue Nov 15, 2016 1:51 pm

Words of wisdom, Bob.

If you're determined to try, as David said, try removing a millimeter or so all along the neck, and see how it goes. Keep in mind that the stiffness is proportional to the cube of the depth: reducing the depth by 10% reduces the stiffness by something like 25%, and so on. If you reduce the stiffness too much you're pretty well stuck, since it probably won't be worthwhile to fix it. Better, as Bob says, to sell that one and get something that fits your hand right out of the box.
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Re: Can I make classical guitar neck thinner?

Postby Marco Giovanni » Tue Nov 15, 2016 2:00 pm

Thank you all for your answers!

Yes, I guess you are right, I want this guitar to be something that it is not.
It is smarter to just sell it and buy something else that fits my needs.

Still, just for my fun, I'll try to remove 2mm, I guess that won't make such a big difference.
I really enjoy sanding guitars and then applying french polish :-)

Thank you all, you're very helpfull!
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Re: Can I make classical guitar neck thinner?

Postby David King » Tue Nov 15, 2016 3:08 pm

Marco,
I would make some paper templates of the other necks that you like and use those to check your progress as you work on this neck. Keep all your lines straight by frequently checking with a straight edge. The quickest way to make the templates is with a contour gauge like this one:
https://www.amazon.com/General-Tools-Co ... 00004T7RA/
Put a layer of masking tape over the neck before using the tool as the ends of the wires are quite sharp.
I do all my fine neck shaping with a Nicholson #49 cabinet maker's rasp which I get pre-sharpened from Boggs Tool.
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Re: Can I make classical guitar neck thinner?

Postby Marco Giovanni » Tue Nov 15, 2016 3:53 pm

Wow, amazing!
I've never heard of tools like this one... contour gage duplicator.
That's exactly reason I subscribed to this forum, because on my own I would have never found out that tools like this exist :-)

Thank you very much!
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Re: Can I make classical guitar neck thinner?

Postby Rodger Knox » Wed Nov 16, 2016 1:07 pm

David King wrote:Marco,
I thin necks necks from time to time but only when they have truss rods. As the others have mentioned the taper is very important as the stress on the middle of the neck is much higher than it is at the nut end. I would say remove a mm or 2 over the whole neck and see what happens. If you find that the action goes too high you'll need to pull the fingerboard off and add some stiffeners or a truss rod or both. At that point you can make the neck as thin as you would like but it's a lot more work and maybe this guitar isn't worthy of all the trouble?


Compression fretting could be done instead of removing the fingerboard and adding stiffeners/truss rod. I would not recommend that approach because it is not easy and you need frets with varying tang thicknesses to do the job. If removing the material causes too much relief, I'd pull the fingerboard and install an adjustable truss rod.
A man hears what he wants to hear, and disreguards the rest. Paul Simon
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Re: Can I make classical guitar neck thinner?

Postby Ryan Mazzocco » Fri Nov 18, 2016 8:06 pm

Marco Giovanni wrote:It is smarter to just sell it and buy something else that fits my needs.

Still, just for my fun, I'll try to remove 2mm, I guess that won't make such a big difference.
I really enjoy sanding guitars and then applying french polish :-)


This seems a bit counterproductive if you ask me. (I know, you didn't) But if you plan to sell this guitar to finance buying the guitar you will feel more comfortable with I'm not so sure it's such a good idea to go meddling with it when it could cause irreversible damage making it unsalable. On the other hand, if you have the disposable cash and can afford to purchase a new one after ruining this guitar then go for it. You just may achieve the results you were wanting and can keep it as the perfect player. Then you don't have to sell it or buy a new one. Just understand that once you start carving on it you may not be able to sell it and the your whole plan is shot.
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Re: Can I make classical guitar neck thinner?

Postby Marco Giovanni » Fri Nov 18, 2016 8:30 pm

Ryan Mazzocco wrote:
Marco Giovanni wrote:It is smarter to just sell it and buy something else that fits my needs.

Still, just for my fun, I'll try to remove 2mm, I guess that won't make such a big difference.
I really enjoy sanding guitars and then applying french polish :-)


This seems a bit counterproductive if you ask me. (I know, you didn't) But if you plan to sell this guitar to finance buying the guitar you will feel more comfortable with I'm not so sure it's such a good idea to go meddling with it when it could cause irreversible damage making it unsalable. On the other hand, if you have the disposable cash and can afford to purchase a new one after ruining this guitar then go for it. You just may achieve the results you were wanting and can keep it as the perfect player. Then you don't have to sell it or buy a new one. Just understand that once you start carving on it you may not be able to sell it and the your whole plan is shot.


Hi Ryan!

I visited your website, you are professional guitar builder I guess?
Thank you for sharing your professional advice to someone like me (total amateur) :D
Yes, I'm very aware of all the risks you mentioned. But, about two years ago I had bass guitar that had a lot of things I didn't like. That love-hate relationship with that bass has been going on for quite some time already :mrgreen: Until, one day I "snapped" took sand paper, saw, and started cutting and sanding poor instrument. I also must say that until then I didn't have any kind of experience with that kind of work.
At the end, bass turned out to be better than before. Also, I learned a lot of things in that process, and I also must say that I really enjoyed all that work.

So, maybe I'm wrong, but I really belive that 2mm shouldn't destroy the instrument.
Maybe it even turns out to be so good that I wouldn't want to sell it.
Also, there is additional joy when you play the instrument which has some part of your effort in it.
Unfortunately, at the moment I'm not in the situation to try to completely build instrument on my own, but at least I can do some minor modifications :D

Anyway, thank you again for your advice! :mrgreen:
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Re: Can I make classical guitar neck thinner?

Postby Ryan Mazzocco » Fri Nov 18, 2016 9:37 pm

Marco Giovanni wrote:...you are professional guitar builder I guess?


I've been accused of worse. :lol: Let's just say I'm working on it.
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