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I always wondered this. I assumed it was for stability but I had a conversation with Chris Forshage yesterday and what he said made sense. He tried carbon rods in some of his necks and concluded that it does nothing. The carbon rods flex easily in your hands so they are not providing stability and do not keep the neck from twisting or bowing. So he doesn't do it anymore.
That made complete sense to me...
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02-05-2016 10:17 AM
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Just taking a shot in the dark, but what if they work by reducing the amount of wood in the neck that could react to heat and humidity? That might lead to less frequent need for truss rod adjustment.
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Possibly in order to reduce the weight of the neck. Carbon fiber tuning pegs are used to reduce the headstock's weight.
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It's possible that the rods Carvin uses are stiffer than the ones Chris Forshage tried. CF can be engineered such that it's much stiffer than metal rods of the same dimensions. I've definitely come across thin cross-section carbon-fiber objects that you can't flex easily (e.g., tennis racquets, bicycle seat/chain stays). So his experiments might not really speak to your question.
Originally Posted by jzucker
Assuming Carvin has carbon-fiber rods that work, they probably use them just because everyone else uses steel. Just like they only sell directly via catalog/web because everyone else sells through retailers. They're different.
John
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More importantly, Jack. What did you order from Chris?
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From Warmoth:
"The stiffening bars installed on either side of the truss rod in Super Bass necks enhance stability and add mass, which helps to eliminate dead spots. Steel is standard. Graphite bars are also available for an additional $60. Our graphite bars are over-sized for steel-like rigidity with less weight, and exhibit a warmer tone."
Warmoth Custom Guitar Parts - Bass Truss Rods
Super-thin neck players also think in helps prevent twisting.
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The carbon fiber "rods" I get from LMI are MUCH stiffer than maple or mahogany.
I have never compared weight, but the difference would be very small in the total neck weight anyway. I suspect they are lighter per unit volume that maple.
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A fairly common size is 1/8" x 3/8". The 1/8" direction is surprising floppy, but the 3/8" direction is very very stiff. When installed flanking the truss rod as is common, I think they provide little to no protection from neck twisting since this is the 1/8" direction. The strength is in the direction that fights against string tension. When installed this way, much of the burden is taken off the truss rod. You still have to adjust the truss rod for the relief you desire, but it is small easy adjustments. You're not cranking hard on the rod. This alone might not be enough to bother using CF in a neck, but there are a few other possible benefits.
If we assume the addition of CF makes the neck a little stiffer, and I can't say exactly how much stiffer, maybe 10 or 15%, we might feel that there is better long term stability in the neck and less need for truss rod setting touch ups. What I like, at least conceptually is that, if the neck is stiffer, the amplitude of the resonances that will inevitably be there should be slightly less and this should even out hot and dead spots on the neck. The neck resonant frequencies are interacting with the note you're trying to generate less.
I can see how some might find all this too minimal or nonexistent to bother with. For me, if it's a big baseball bat maple neck, it certainly doesn't need CF. If it's a laminated neck I may or may not put it in depending on materials and design. I usually do put it in for a one piece Mahogany neck, and definitely for Walnut. If you let it extend under the nut into the headstock, it may also lessen the chances of a headstock snap. I find adding CF is fairly cheap and easy and I don't think it hurts in any way. So even if I'm wrong about the benefits, no harm done!
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Many luthiers (and myself) agree that it effects the tone adversely but I'm not going to say anything more on the subject.
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Just like wood, not all carbon fiber is equal.
Properly manufactured/formed carbon fiber is much stronger than steel for the weight.
There's a reason you don't see steel aero bits on race cars, but the de-facto is carbon fiber. Steel surpasses CF in heat circumstances. The downforce on aero bits is thousands of lbs.
Your OP says somebody said carbon 'does nothing' and that makes sense to you but then your last post says carbon affects the tone adversely. Not sure which you're going with.
A steel rod when tapped will definitely have more harmonic content than a carbon fiber rod (I have owned many dry carbon bits for my car) but transfer of energy is a different matter. Ken Parker uses carbon fiber on his archtops for the neck join.
How much a truss rod's resonance affects a guitar's tone is a whole other argument. Gibson used a rubber sheath on their Historic Les Paul's for years and people said it makes a difference. In my experience, other factors superseded such an observation by manyfold i.e. I could not attribute any common tonal characteristics to the dampening of a rubber sheath on the truss rod.
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Many also feel the exact opposite. Tone will always be a subjective matter. Originally Posted by jzucker
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Weight, on the other hand...
Last edited by Fidelcaster; 02-05-2016 at 07:18 PM.
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My two Carvin guitars have been the most stable out of anything I've ever owned. My 2003 has never needed a truss rod tweak, and my 2015 has thus far been as sturdy. Once they finally make a semi-hollow 7 I will never have to buy from another company again
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In cases where I knew the neck would need stiffening, I have always used strips of purple heart in a way similar to the photo in Grez's post (to hide them), or I laminate them into the neck blank (to show them). In my opinion, constructed with optimum woods and grain orientation, most necks don't need stiffening. Unusually thin necks, or unusually soft woods, or say a flat-sawn fretboard such as bird's eye maple--in those cases I would definitely add some stiffening element.
Last edited by kenbennett; 02-05-2016 at 09:43 PM.
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Carbon fiber is definitely more stable that steel. I would be skeptical if the dimensional stability difference would be noticeable. Also, the harmonics of carbon fiber is way different than steel, but again, I would be surprised to hear a difference.
One nice advantage, if they actually thread the carbon fiber rod, is that there is much less chance of corrosion. Ever try to adjust a rusted truss rod nut?
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one things for sure, they don't prevent the dreaded neck hump. I know from experience with a a particular boutique gypsy guitar builder
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I read somewhere that this is the reason, no need for truss rod tweaking anymore. Originally Posted by JSanta
My two Carvin guitars have been the most stable out of anything I've ever owned. My 2003 has never needed a truss rod tweak, and my 2015 has thus far been as sturdy. Once they finally make a semi-hollow 7 I will never have to buy from another company again
Which makes me wonder: I have been told that this dry central heating cold weather season affects somehow in the neck's wood so that the truss rod must be relieved and humidifiers must be used.
And then comes the CF and the need to tweak is gone. Wasn't it the wood in the first place after all? Does the winter air dry the metal of the truss rod, not the wood?! (Here should be a smiley if I used them.)
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Even with CF rods low humidity can shrink the fingerboard causing fret sprout or binding cracks on the edge of the frets. Also cracks in the top of spruce tops (flat or carved).
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Because there's more than one way to skin a cat? Originally Posted by jzucker
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The interesting thing is that the carvins with the carbon fiber rods were probably the least stable necks of any guitar I've ever owned.
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The only thing that *I* can establish from this conversation is that he was not able to make it work so he dismissed it. Originally Posted by jzucker
So, my interpretation of the meaning of your post is that by agreeing with him you assume that if he couldn't make it work, nobody can?
Working with Carbon Fiber Reinforcement Materials | stewmac.com
Carbon Fiber Reinforced Neck | Strandberg Guitarworks
This materials' been around for a relatively long time; but, as everything, it needs a particular skill set to correctly apply it to your product line to or the repair work you're doing to make it work as intended. An analogy would be that just by knowing of all scales will allow you play Jazz.
As I always say, "it's not the hammer, is how to use it"
HTH,Last edited by LtKojak; 02-06-2016 at 11:43 AM.
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