Official Luthiers Forum!

For those of you using carbon fiber in your necks. How far are you spacing that from your truss rod?

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Brock Poling
Columbus, Ohio
http://www.polingguitars.com

I run them parallel to the outside edges of the neck, so they splay out slightly. I use 1/8"x3/8" on end, with the outer edge of the CF rod about an even 10-12mm (1/2"-ish) from the edge of the neck, which ends up putting the outer edge of the CF rod on the imaginary 'midline' between the edge of my truss rod channel (HotRod) and the edge of the neck. I have varied this slightly, but that's where I tend to have them end up.

Couple of gratuitious shots:
http://www.xs4all.nl/~mvalente/guitarpics/Neck_GAB1_01.jpg



The last two are electric necks, but the same applies to my acoustics.

That is a good idea.... thanks.

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Brock Poling
Columbus, Ohio
http://www.polingguitars.com

Brock, I've been using 1/4" x 3/16" x 18" Carbon Fiber installed 1/8" from the edge of the Allied Lutherie truss rods I've been using. I place a 3/8" shim on my router table fence after cutting the truss rod slot and cut a slot about 1/4" to 5/16" deep right into the headstock. The carbon fiber is expoxied in with a 1/4" wide filler strip of wood over top. The filler strip is flushed with a hand block plane and sanded smooth. The filler strip increases the surface area of wood on fretboard if you use Titebond, if you epoxy your fretboards on you can skip this step. The carbon fiber extending into the headstock is flushed with a dremel cutoff blade. For what it's worth this was the method recommended to me by Tom Ribbecke and for lack of imagination have adopted it.

Mattia great picture. Your method has appeal to me as I suspect your goal is to stiffen and prevent neck twisting? Out of curiousity if I may, how well does your truss rods work using 1/8" x 3/8" installed on end?

Whatever method you go with you'll want to cut your fret slots a little deeper than you would with a non CF reinforced neck. It'll make a little easier for the truss rod to work. Anthony Z38681.808275463

[QUOTE=Anthony Z]Mattia great picture. Your method has appeal to me as I suspect your goal is to stiffen and prevent neck twisting? Out of curiousity if I may, how well does your truss rods work using 1/8" x 3/8" installed on end? [/QUOTE]

That's kind of the idea, yeah. The strings run in that plane, roughly, so distributing them like that just made sense to me. I've done them parallel as well, and that worked. Ultimately, I think if a piece of wood's going to twist, no amount of CF will stop it completely.

I do have to make sure they're close enough in that there's no risk of carving into them (neck cross section helps), but the 1/2" from the edge thing has worked so far.

As for adjustability, so far, no problems, but I've only used this particular setup on one laminated neck (and a baritone neck at that), and I've only built about 7-8 guitars with CF rods in the necks. Works fine on the mahogany (honduras and african) necks I've used, and I intuitively felt I needed them for the bolt-on flatsawn fender-type necks (which often feel a bit 'rubbery' to me). The necks are stiff, but so far, they've not been too stiff to adjust on either electrics or my acoustic, and it's not like I use crazy heavy strings on the electrics (10-52 sets, mediums on the acoustic, which pulled relief into theneck anyway, even a touch too much). I'm a little worried things might get a touch too stiff on laminated necks, or on the rosewood necks I'm going to be trying (on electrics) in the nearish future, and I've been considering either installing the rods less deep, or using CF tubes (intothewind has them, they're cheaper than bar stock, lighter, but also less stiff). I'll report back when the neck guitar neck goes together (walnut/maple/wenge laminated acoustic neck) if I do find it 'too stiff'. I do tend to move the neck manually (ie, bend it), then adjust the rod, so as to prevent undue strain on the adjustment nuts.

For now, HotRod+2 CF bars is a recipe for a successful, even, nicely stiff neck.

How can you have a neck that is "too stiff"? Whi would you depen the fret slots(in effect, 'kerfing the neck'), to make it weaker?

I build me necks to hold straight without the rod's help. The rod is there mostly to appease the folks who buy them.

Build it stiff, built it straight(through trial and error over the years, I've found a little back-bow in mine lets the string's pull bring the neck to the proper(.005-.008") relief 90% of the time. A few necks have proven stiffer and didn't pull enough, and some require a tiny bit of rod to bring them to spec, but most hit it on their own. I wouldn't dream of making an neck weaker so the rod can be more effective. The best truss rod system is the one where the rod isn't needed, IMHO.

Mario (and others...) .... how do you compensate for players who primarily play in open tunings?

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Brock Poling
Columbus, Ohio
http://www.polingguitars.com

I dunno. If the neck is stiff enough, it should be able to handle any reasonable tuning, no? Do you take out your truss rod wrench every time you change tunings?

I guess if a client told me he intended to keep the guitar in a particular tuning that has much more or less tension, I'd take that into account while building the neck(less induced backbow if it'll be a lower tension tuning, more if it will higher tension).

And if the player wants something too weird or that I don't completely understand, I just tell them to go find someone else to build the instrument <bg> Honest! It's better to specialize than to generalize, and if we aren't familiar with the intricacies of certain styles of playing, we shouldn't build the instruments. I don't play classical, or even steel string fingerstyle, and thus don't build them, for example.Mario38683.5729050926

Brock,
   I use 1/8"X1/4" on end to either side of the truss rod. I keep them paralel to the truss rod edges and about 1/8" away on each side and they run from the 17th fret all the out the front of the headstock before I cut the head angle into my neck billets. This provides a great deal more strength across the critical transition of the straight neck barrel into the head stock as the typical runout is created by the angle being cut. I prefer a one piece neck and have repaired enough broken necks that have suffered damage at this point due to the weaker portion being present and wanted to come to a conclusion that can minimize its possibility.

Kevin Gallagher/Omega Guitars

I just figured with all of the extra pull of open G tuning that some compensation should be built in for that.

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Brock Poling
Columbus, Ohio
http://www.polingguitars.com

Brock....

I use the same ones Kevin's using, and do essentially the same thing except that I space mine about 1/4" from the edge of the truss rod channel on each side, I don't flare them out like Mattia's doing because I let them float out to support the tongue of the fingerboard and it would be a major pain to cut the top channels that way. Also I go all the way to the Upper Transverse Brace, which is about the 20th I think, a little further than Kevin.

There might be some pictures of them on my website, I would space them out a little wider but the issue is if you get too far from the edge of the truss rod channel you can run into them while carving the neck. Haven't done that yet but it worried me enough that I stay close to the truss rod, they still do their job and keep the neck stable. Amazingly the neck still gets the proper amount of bend from the pull of the strings even with the rods in there...

Cheers

-Paul-

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-Paul-

Patriot Guitars

Mario, I agree an ideal neck is one that doesn't need a truss rod. But stuff happens and sooner or later some necks may need a tweak/change of relief to suit a player's preferred action, tuning or a change of string gauge, change in climatic conditions or all of the foregoing. Even with a carbon fiber reinforced neck and a truss rod I like the flexibility to make fine adjustments. I've got guitars of various vintages back to 1978 where the truss rod has never been touched and some that are tweaked every couple of years.

Mario what do you do if the strings don't pull the neck to the desired relief?

Before I started reinforcing with CF I spoke with a number of notable builders whose guidance ranged from - "you don't need CF reinforcement" to if you do "cut your fret slots a little deeper" the later was Tom Ribbecke's advice -- I am sure all of those builders were right for their own reasons.

Not to argue with you Mario -- you do it your way with success -- I do it my way and in the end neither of us is doing it wrong. IMHOAnthony Z38683.6938310185

[QUOTE=Brock Poling]
I just figured with all of the extra pull of open G tuning that some compensation should be built in for that.[/QUOTE]

Brock,

Do you mean open G - DGDGBD? This has the 6th, 5th and 1st strings tuned down a step so will be less tension.

I think the CF rods help a little if people use lots of open/modal tunings and tune between them a lot - especially those where the 5th string goes between G and A and the 2nd string between A and C.

I do mine like Kevin and Paul parallel to the truss rod and fairly close to avoid carving into them when shaping the neck. I used to stop them where the neck met the body but now build the neck up to around the 18th/19th fret, insetting it into the top and running the CF rods up to this point to.

You get neck stiffness/rigidity and the truss rod functions just fine - no need to cut deeper fret slots. I use them in all the necks I have done including laminated ones.

Mike Doolin has a theory you can find in his excellent Intonation articles on his website that the CF rods help give the neck a sort of tonal "neutrality" that helps eliminate dead spots. Note sure how true this is but Alan C may have some views.

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Dave White
De Faoite Stringed Instruments
". . . the one thing a machine just can't do is give you character and personalities and sometimes that comes with flaws, but it always comes with humanity" Monty Don talking about hand weaving, "Mastercrafts", Weaving, BBC March 2010

what do you do if the strings don't pull the neck

Force a little into it. Gently warm the fretboard, and use a clamp and jig that we use on older Martins that had the non-adjustable necks. Leave overnight, and she's ready to go. If we'd have a really stubborn one, we could pull a handful of frets, enlarge the slots a hair, and re-fret, but I've not had to go that far.

I understand what you're saying with regard to seasonal changes and the like. I'm just thinking that with the CF in there, if it's too stiff for the rod to do much, then the strings won't do much either(which is good), and conversely, if a neck does pull in a bit with time, then this one will also respond to the rod.

I just have a different way of looking at things, methinks...

As usual Mario is completely right. No such thing as too stiff a neck, particularly for transmission of vibrational waves. (They are not sound waves until perceived by the ears and interpreted as such by the brain, thus the tree that falls in the forest makes no sound unless the fall is 'heard' by something).

As for open tunings DADGad particularly, I keep dedicated guitars in that and open D with balanced string sets that maintain the proper tension on the top.

Colin

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

What are some good "less expensive" sources for CF?

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tim...
http://www.mcknightguitars.com

I've yet to find any source that's significatnly cheaper than the 'bulk' pricing on StewMac and/or LMI's website for 1/8"x3/8" stock. If anyone out there can prove me wrong, please do...

In Harry Fleishman's class we used graphite tubing from Into The Wind which is quite a bit less expensive. I haven't compared strengths of the tubes to the rectangular carbon fiber rods that Stew Mac sells.

Note that these are not the same as the fiber glass rods that Into the Wind also sells that people use for go-bars.

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Jonathan Kendall, Siloam Springs AR

Jon...

I attended one of Harry's setup classes and got to see the use of tubes first hand and to be honest I didn't like them at all, you have to use so much epoxy to really get them in there that I think you defeat the purpose of having them in the first place. I know Harry talks about how they vibrate better than the rectangle ones, that's all fine and good, but you simply don't get the same strength as you do by using the 1/8 x 1/4 ones.

Also to Mario's point, in a perfect world I would just use the CF rods and no truss, but guitars move with not only the seasons but with age as well. You can still get a good deal of bend out of a neck using the truss rod even with the CF rods installed, I put them in to stiffen the neck and to help keep it stable.

Mattia there are a number of places that sell CF in the same sizes as LMI, try CTI or http://www.acp-composites.com I have worked with both when building gliders and I have used .010 CF layment from ACP for my braces and was very happy with the results, you can also get all kinds of other cool things from them including nomex (double top heaven)...

Cheers

-Paul-

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-Paul-

Patriot Guitars

Paul: I've checked there, but unless they've got killer discounts on fairly small-ish orders, the price for bar stack is within about a dollar of what LMI and StewMac charge. Which kind of defeats the purpose, since any minimal savings is killed by shipping costs (fact remains that I do, invariably, order something from StewMac and/or LMI once in a while).

[QUOTE=Sprockett] Jon...

I attended one of Harry's setup classes and got to see the use of tubes first hand and to be honest I didn't like them at all, you have to use so much epoxy to really get them in there that I think you defeat the purpose of having them in the first place. I know Harry talks about how they vibrate better than the rectangle ones, that's all fine and good, but you simply don't get the same strength as you do by using the 1/8 x 1/4 ones. [/QUOTE]

Yeah, I was looking at those Stewmac ones and thinking that it looked a whole lot cleaner. Although, I don't remember using that much epoxy, they fit pretty snug in the bottom of the slot.

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Jonathan Kendall, Siloam Springs AR

http://www.acp-composites.com/

Seems like close to perfect timing for some shameless self promotion.
Having spend 15 years as a composite Engineer and a former supplier of the carbon fiber reinforcement to LMI (95-2000) I have recently decided to start producing reinforcement rods and sheets again, while giving my daughter some experience in starting a business. We currently have stock being cut at a waterjet cutter and expect to be able to start selling in the next few weeks. Pricing details are currently being worked out trying to be fair to all.
With that said if Lanceor or Brock would PM me about advertising here I would be very interested. Especially seeing how I just did! Jim_W38684.8739583333

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Jim Watts
http://jameswattsguitars.com

if prices are good jim I bet us olf'ers, myself included, would love to
support your business!

you can add my e-mail to your list of people looking for more info and
pricing!

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John Mayes
http://www.mayesluthier.com