If "reasonable wood" for the neck, reinforcement needed?

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If "reasonable wood" for the neck, reinforcement needed?

Postby Michael Thames » Tue Nov 01, 2011 4:36 am

Trevor Gore wrote....."A stable neck can be manufactured from a wide range of woods. Further, if reasonable wood is chosen, the author’s experience has been that it is unnecessary to complicate the manufacture of the neck by using multiple laminates of either wood or composites to add stiffness and stability to the neck. Adding carbon fibre to the neck does not seem to produce any audible advantage whilst adding significantly to the build complexity".


What's a "reasonable neck? I guess at this point we need more data from Mr. Data himself....... are you talking about steel string guitars, classical guitars, maple necks, cedro necks, mahogany necks? What thickness of the necks? 19 mm at the nut, 22mm at the nut, 24mm what? Do you enter into your experience, the effects of humidity changes?

Personally, I won't make a guitar neck of Cedro without a carbon fibre reinforcement. I've experienced first hand a Cedro neck made with a thickness of 21.50 at the nut, tapering to 23.50 at the 9th fret have more bow than a neck with the same dimensions reinforced with carbon fibre, the carbon fibre neck had almost no forward bow,in comparison to the un reinforced neck. Sorry no Data because there are far to many variables in the Cedro, ebony etc. besides I'm not a numbers guy.

Apparently, I'm not alone in this way of thinking, as Martian, taylor, Ramieriz, Bernabe, and countless others use reinforced necks as well. However if we listen to Trevor Gore there is absolutely no need for this is "reasonable wood' is used, whatever the heck that means.

Can't see any charts or numbers, so probably not data! But it is "the author's experience". The ASA (Acoustical Society of America) and their review panel didn't have a problem with any of that, and they're pretty data driven. I've measured and listened to lots of guitars, some with CF in the neck, some without. I've built guitars with CF in the neck (incorporated in various positions and ways) and many more without. I can't hear any difference that I can attribute to the CF, neither can I measure any feature in their sound spectral responses attributable to CF in the neck (...may explain the absence of data...) not in my guitars or anyone else's that I've been able to measure/listen to. Are you saying you can pick a guitar with CF in the neck in a blind listening test? Love to see your data if you can. Happy to be convinced.


Here Trevor passes off his experience and the ASA peer review panel as verification of his hypothesis, yet amazingly in the same paragraph he asks me for "DATA". Making ridiculous assumptions that I can pick out a carbon fibre reinforced neck from one that isn't. Hell.....I can't even pick out a spruce, or cedar guitar in a blind test, as gifted as I think I am, but that doesn't mean spruce sounds the same as cedar, we all know it doesn't. I think I would have better luck if I could actually play the spruce or cedar guitars and sink my nails into them a bit.

Trevor also states he can't measure a spectral response attributed to CF. How Trevor can even claim to be able to measure, or not measure this on a completed guitar is mind boggling, considering the subtle differences in all materials and building techniques. Did Trevor make one guitar without CF, then take off the fingerboard and insert a CF reinforcement and perform his tests? I doubt it, and yet he claims to be able to do this, but, he demands data from the rest of us and expects us to just take his word for it.

Lets kick this around shall we? It will be great fun.
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Re: If "reasonable wood" for the neck, reinforcement needed?

Postby Alexandru Marian » Tue Nov 01, 2011 7:09 am

I don't like that the thread starts a bit too personal, but here we go anyway:

My oldest guitar is 5y old, cedro with no reinforcement, 22/24, hasn't changed the slightest bit. Same for the next 4 ones. On my 6th I added a rosewood insert as requested by the customer. Since then I split my necks based on density and requested thickness and profile. For a low density, or very thin neck, I will add rosewood or ebony. I am just closing the back on a guitar made from cedro weighting 575Kg/m3, pretty much same as mahogany. I didn't add any strip to this as it already felt very heavy and solid. I think about 520Kg/m3 is a good split point for me. Keep in mind cedro as with all other woods varies greatly in density, and so does the stiffness and likely the resistance to creeping under string tension. The cedro I measured ranges from 360 to 600Kg/m3 !
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Re: If "reasonable wood" for the neck, reinforcement needed?

Postby Trevor Gore » Tue Nov 01, 2011 7:35 am

I'll ignore all the personal slights.

My experience was related:

"the author’s experience has been that it is unnecessary to complicate the manufacture of the neck by using multiple laminates of either wood or composites to add stiffness and stability to the neck".

Not a hypothesis, or anything else, just my experience. I would point out that I use a different style of neck joint from most, with continuous neck wood the full length of the fretboard and nearly always with an adjustable truss rod, even for classical guitars. Historically, I would guess hundreds of thousands of guitars have been made without extra neck reinforcement (or adjustable truss rods) and have survived quite well.

and:

"Adding carbon fibre to the neck does not seem to produce any audible advantage whilst adding significantly to the build complexity."

I posed a question to Michael Thames:

"Are you saying that you can pick a guitar with CF in the neck in a blind listening test?

This was answered rather strangely, but we get the gist:
Michael Thames wrote: Making ridiculous assumptions that I can pick out a carbon fibre reinforced neck from one that isn't. Hell.....I can't even pick out a spruce, or cedar guitar in a blind test, as gifted as I think I am...


I'll take that as a "No".

I couldn't detect any systematic difference either, so I stopped using CF in my necks.

End of story.
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Re: If "reasonable wood" for the neck, reinforcement needed?

Postby James Lister » Tue Nov 01, 2011 11:11 am

Michael Thames wrote:Lets kick this around shall we? It will be great fun.


There would be more chance of it being fun without the personal edge...

My own experience is as follows. The oldest guitar of mine I still see from time to time is about 10 years old. No reinforcement, good quality cedar neck wood, no discernable movement. The oldest guitar of mine I have kept was built with similar quality and density neck wood, but had a slightly thinner fingerboard. Over the first few months, the neck moved significantly (slightly less than 1mm increase in action). It was otherwise a very nice guitar, so I kept it for myself, and since that first movement, it seems to have stabilised, but it was enough to persaude me to start using some reinforcement.

My experience with much older guitars tells me much the same thing. Most of them have no reiforcement, and most of them are still fine after many years, but from time to time you'll come across one with neck problems, and no obvious reason for it in terms of the quality of woods used. That's why I'll stick with using carbon fibre. It's really a question of insurance, I want to do as much as I can to improve the stability of the guitars I make, provided it doesn't adversely affect the tone, and for me it doesn't really significantly add to the complexity of the build - maybe one extra hour out of 120+.

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Re: If "reasonable wood" for the neck, reinforcement needed?

Postby Robert England » Tue Nov 01, 2011 3:14 pm

I agree with James, that a carbon fibre rod inlayed into the neck is worth the extra expense and effort, as insurance. I helps me sleep better at night not worrying about neck movement spoiling a guitar I have put 200 hours into. :)
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Re: If "reasonable wood" for the neck, reinforcement needed?

Postby jaujau » Tue Nov 01, 2011 4:43 pm

if so, what sort of measurement should the carbon rod be at?
and is it worth the trouble of installing it after the top is glued to it? to make it go all the way to the 14th fret?
or is it only necessary to put it in the weakest spot of the neck? from about the nut to the 9-10 fret?
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Re: If "reasonable wood" for the neck, reinforcement needed?

Postby Robert England » Tue Nov 01, 2011 6:38 pm

jaujau wrote:if so, what sort of measurement should the carbon rod be at?
and is it worth the trouble of installing it after the top is glued to it? to make it go all the way to the 14th fret?
or is it only necessary to put it in the weakest spot of the neck? from about the nut to the 9-10 fret?


The reinforcement I use is from LMII, part number "GR0", which is 3/16" by 1/4" by 18". I inlay it right under the fingerboard, flush with the top of the neck, using epoxy. The rod starts up in the head, under the headstock plate, and goes all the way back into the heel, at about the 14th fret. Obviously, this is the Spanish Slipper Foot method of construction. This method requires the rod to be inlaid prior to gluing the neck to the soundboard. Other people probably do it differently,
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Re: If "reasonable wood" for the neck, reinforcement needed?

Postby Alan Carruth » Tue Nov 01, 2011 6:45 pm

As Alexandru points out, cedro varies as much as any wood in density, and presumably, Young's modulus. I've also run into planks of cedro that had rather high built-in stress, so they could move when you carve the neck, for example.

Like James, I had one that moved after it was strung, and have been putting a CF rod in when the wood is light ever since for insurance.

I've used various sizes of rods over the years. In all cases, I try to get the CF as far down in the neck as I can, with a filler piece between it and the fingerboard. As David Hurd showed, a CF rod just under the fingerboard is right on the neutral axis of the neck, so it's loaded primarily in shear. CF is really best used in tension, so dropping it down a bit should help, so long as it's well secured.

I'm not sure if a CF rod actually adds much to the stiffness of the neck: that could probably be calculated, and a few experiments would help too. What it does, when properly loaded, is to limit the amount that the neck will 'cold creep' under load. Once the CF is taking a good share of the tension stress, and the fingerboard is in compression, the creep will stop or become negligable.

If the rod does contribute to the stiffness of the neck it could raise the pitch of the 'neck mode', possibly enough to get it to couple with the A-0 'Helmholtz-type' mode. That can have an effect on the timbre in the bass. So far as I can tell, neck taper, and keeping the headstock light are of more use in this regard, but, again, I haven't done controlled experiments, which would be time consuming in any case.
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Re: If "reasonable wood" for the neck, reinforcement needed?

Postby Chris.Conery » Tue Nov 01, 2011 7:09 pm

So what's a guy to do? As one who has barely broken into the double digits, I look to you folks who have built 100's for definitive advice.

I can't imagine that a graphite composite bar in the neck will have a noticeable effect on the sound of the guitar. But the construction of the neck certainly affects the playability. I personally like and my customers seem to approve of a thinish neck, 21 to 22 mm all the way down (a la Friederich). After an early guitar with a thin neck seemed to have too much bow in it I began to install graphite rods. There is still some relief - you have to play pretty hard to get any buzzing.

Chuck Morrison was at my shop last week showing me one of his wild (and interesting) experiments. When he saw a couple of my necks with graphite in them he poo-pooed the whole idea - never uses them he says. And now we have guys like Trevor and Micheal in disagreement.

So I guess my questions are:
Can it hurt?
Does it help? How do we know?
Am I just wasting my time?

Cheers,
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Re: If "reasonable wood" for the neck, reinforcement needed?

Postby Alexandru Marian » Tue Nov 01, 2011 7:22 pm

Al, good point about the stress. For a few guitars now, I cut a narrow slice off the neck. If it stays reasonably straight over the next couple of days, I use the neck, and use the strip (if wide enough as a back brace)
If not, discard the neck for glue blocks. I already encountered two where the sample twisted noticeably so I am very happy that I didn't use those blanks.

The FB is another factor. I have been wondering how much effect its stiffness has, at least on the relief if anything. Not all ebony is equal and I encountered a few boards that went rather floppy when thinned to 6.5mm. For the moment I put them away.
Also, one of these away FBs cupped noticeably (about 1mm of depth) for no reason. It was dry, reasonably old, well cut. Used others from that batch with no problem. I don't know how much it took but I noticed it after about 3 weeks; my shop humidity is quite stable. From now on I am bringing the boards to final thickness, wait 1 month and only then slot and glue them to the neck.
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Re: If "reasonable wood" for the neck, reinforcement needed?

Postby Marcus Dominelli » Tue Nov 01, 2011 7:53 pm

Hi Michael,
Maybe you take all this stuff more seriously than Al does! :wink: Or maybe yer' just itchen for another heated debate.

I've said it before. Graphite rods are a cheap form of insurance. They cost $20 each, and it does'nt add much time to the building process at all to rout a slot and epoxy one in.
Why take the chance that the neck may bend from string tension over the years? I know most don't have this problem, but it's our job as luthiers to make the best guitars we can, even if they cost a little more , and take more time to make.

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Re: If "reasonable wood" for the neck, reinforcement needed?

Postby Michael Thames » Tue Nov 01, 2011 10:31 pm

Not a hypothesis, or anything else, just my experience. I would point out that I use a different style of neck joint from most, with continuous neck wood the full length of the fretboard and nearly always with an adjustable truss rod, even for classical guitars. Historically, I would guess hundreds of thousands of guitars have been made without extra neck reinforcement (or adjustable truss rods) and have survived quite well.


Trevor, my apologies...... did I miss something, you don't use neck reinforcements, but you use a truss rod? Perhaps I didn't read far enough in your peer reviewed paper. Or perhaps you don't consider a truss rod, any form of reinforcement?

Yes, I've had a 1938 Santos in my shop the neck was a whooping 24 tapering to 26 no problems other than it was basically un playable by modern standards. I guess now I'm Mr. data now and need more information about what a reasonable neck is and the tolerances.

BTW, I've seen problems with necks on almost every 19th century guitar I've examined, they typical have thickness of 19mm with no taper. I defiantly reinforce with carbon fiber on 19th century guitars, however according to you this is not needed if "reasonable wood" is used.

I couldn't detect any systematic difference either, so I stopped using CF in my necks.


Yes, and my question would be "where's your data" I've admitted I can't hear a difference other than a bit more sustain ( sustain I guess wasn't part of your spectral response analysis) but that's highly subjective isn't it, that's in relationship to my guitars, because I'm much more aware of the subtle changes I've made in each one. If you are asking me if you could randomly play 10 guitars of various makers in a blind fold test and could pick out carbon fibre reinforced necks, then you are asking an absurd question. Yet you say..... "neither can I measure any feature in their sound spectral responses attributable to CF in the neck" so you have actually determined that CF does not effect the "spectral response" So the reasonable question would be how you determined this what method did you use? Was it the touchy feely method, or the Data method? If it was the touchy feely method why do you then insist others provide data?

Trevor, You can't have your cake and eat it too. You can't ask people for Data when observing relatively obvious things, like is a transverse bar stiffer than an fan brace, then on the other shoot from the hip concerning necks, and CF etc, then when questioned about your reversal of methodology claim it was peer reviewed.

If you are going to sell books and have your work in the public eye then you should also prepare yourself for a disagreement or two. You can't demand data from others, without holding yourself to your own high standards, then when the heat is turned up, cry personal attack, you left yourself wide open on that, for those of us who are lowly touchy feely peasants...... the meek shall inherit the world.
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Re: If "reasonable wood" for the neck, reinforcement needed?

Postby Michael Thames » Tue Nov 01, 2011 10:48 pm

Marcus Dominelli wrote:Hi Michael,
Maybe you take all this stuff more seriously than Al does! :wink: Or maybe yer' just itchen for another heated debate.

I've said it before. Graphite rods are a cheap form of insurance. They cost $20 each, and it does'nt add much time to the building process at all to rout a slot and epoxy one in.
Why take the chance that the neck may bend from string tension over the years? I know most don't have this problem, but it's our job as luthiers to make the best guitars we can, even if they cost a little more , and take more time to make.

Dominelli Guitars


Marcus, Al is dear to my heart, we kinda go way back on other blogs. So on occasion, I like to give him a hard time just to make sure he is still alive, and ticking.

I didn't know you said that about CF rods, but I couldn't agree with you more! Why take the risk...... exactly! I've had some flamenco players come back into the shop and have me carve their necks down to 19mm at the nut, on one occasion I actually carved into the CF rod, I noticed but he never did, I told him it was a knot in the wood.

Also, now I put two rods in the Dresden's after witnessing the first Dresden's neck bow alarmingly forward when tuned up from 415 to 440........ I defiantly learn a thing or two from that experience.

Yea what's the time setting up a router or table saw and running ten necks through there? Mixing a little epoxy and waiting overnight......... big deal! It makes us sleep better at night.

The last time I orders CF it worked out to about 10 bucks a guitar, but I only reinforce up to the heel, I see no reason to go more than than that.
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Re: If "reasonable wood" for the neck, reinforcement needed?

Postby Michael Thames » Tue Nov 01, 2011 10:50 pm

jaujau wrote:if so, what sort of measurement should the carbon rod be at?
and is it worth the trouble of installing it after the top is glued to it? to make it go all the way to the 14th fret?
or is it only necessary to put it in the weakest spot of the neck? from about the nut to the 9-10 fret?


I use a 3x10mm rod.
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Re: If "reasonable wood" for the neck, reinforcement needed?

Postby Michael Thames » Tue Nov 01, 2011 11:03 pm

I don't like that the thread starts a bit too personal, but here we go anyway:


Oh Alex, don't be such a flatliner....... I'm just testing Trevor's passive aggressive English manners.

My oldest guitar is 5y old, cedro with no reinforcement, 22/24, hasn't changed the slightest bit. Same for the next 4 ones. On my 6th I added a rosewood insert as requested by the customer. Since then I split my necks based on density and requested thickness and profile. For a low density, or very thin neck, I will add rosewood or ebony. I am just closing the back on a guitar made from cedro weighting 575Kg/m3, pretty much same as mahogany. I didn't add any strip to this as it already felt very heavy and solid. I think about 520Kg/m3 is a good split point for me. Keep in mind cedro as with all other woods varies greatly in density, and so does the stiffness and likely the resistance to creeping under string tension. The cedro I measured ranges from 360 to 600Kg/m3 !


Ya know Alex, from my experience string tension is not the problem when it comes to neck stability. The problem is humidity changes. Having a Cedro neck remain stable in your living room, is a bit different than, a concert guitarist traveling from Singapore one day, and playing in Phoenix, Arizona the next. That's why people like Trevor Gore put truss rods in all his guitars, but then oddly enough write a peer reviewed paper saying neck reinforcement is just a big freaking hassle, go figure.
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