Is it worth paying extra for carbon rods in a bolt on neck?

Discussion in 'Luthier's Corner' started by DuluthDank, Jul 12, 2020.

  1. I'm thinking about a custom build, and wonder if the carbon rods are worth it. To me the big benefit would be reducing the chance of a ski jump forming, with increased seasonal stability as an added bonus. Any evidence to support that rods have any real benefit?
  2. Beej


    Feb 10, 2007
    Vancouver Island
    I like to use carbon fibre rods or aluminum spars to help with stability, but also like to use multilaminate wood construction where the the pieces are grain aligned before glue-up to help with stability too. (So viewed from the end, like this: \\\\||||//// ) The one-piece necks that I've built in the past have remained stable over time with CF rods. That said, there are thousands of one-piece Fender-style necks out there with no stiffening to speak of, that also remain stable for decades. I like to think of it as extra insurance. :thumbsup: I have never had a neck I've built twist, curve or backbow (knock on some CF stiffened wood :D ).
    Rôckhewer, wraub, rwkeating and 2 others like this.
  3. 5tring


    Sep 16, 2018
    The actual rods are not expensive - I think I paid £9 for the pair I’m using in the neck I’m building at the moment, and the labour is just cutting some slots and mixing some glue.

    So I think if you are going to the expense of a custom commission, the additional cost for CF rods will be a drop in the ocean.

    edit: I read your post as ‘I’m going to pay someone else to build me a custom’ and then read it again and perhaps you are going to build it yourself?
  4. 5tring


    Sep 16, 2018
    Regarding whether the rods actually do anything useful, I have 5 or 6 necks with no reinforcement and 1 with. When I’m adjusting a truss rod I can flex the neck on the non-reinforced necks with brute strength. With the reinforced one - no chance. So they definitely have a big impact on neck stiffness.
    DuluthDank likes this.
  5. GMC


    Jan 1, 2006
    Wiltshire, UK
    I've built a fine 6 string with no carbon rods and it's really stable. The 5 piece laminated neck helps a lot, as does a lot of Wenge and Purpleheart. In fact with a lot of purple heart neck really don't need carbon rods at all. I built a 5 string recently with a 5 piece wenge, purpleheart and paduak laminates and a pair of carbon rods and then neck is way stiffer than it needs to's actually quite hard to bend in a front bow!
  6. Yes, I'm looking to pay someone else to make it. Looks like the charge passed on to me would be about 60 dollars for adding the rods, so probably worth it in the scheme of things. People here are suggesting that they actually work, and it's not all marketing.
    Beej likes this.
  7. dwizum


    Dec 21, 2018
    I've put carbon bars in only two necks (a 4 string and a 6 string) and that's it. I have had zero issues on any necks - except, ironically, the 6 string with the bars. The truss rod needs a LOT of torque to get the neck to move at all, it's just way too stiff (wide profile, two big carbon bars, and made from stiff wood species). Luckily it's fairly true so it doesn't need much movement.

    Generally I use the typical dual action truss rods. They're reliable and give plenty of adjustment. Good wood selection and design will get you stability over time and lack of twists or ski jumps with no stiffeners needed. Hence I don't use rods any more. I can see how reinforcements make sense when they're incorporated in a holistic design, like @Bruce Johnson's custom rods which are designed to work in concert with carbon tow laid in the neck.

    Which, I think, speaks to the main point. I don't really see carbon bars or other reinforcements as an a la carte option you choose to include or not. You need to consider the whole design of the neck as a system, not as a set of independent options. Add CF rods to a neck that wasn't designed with them in mind and you're either just wasting effort or ending up with a neck that's too stiff (like my 6 string neck). Take carbon reinforcements out of a neck design that really needs them and you'll have the opposite problems.

    On that note, I would speak to your builder about how his necks are designed and how the choice of CF rods or not influences the rest of the choices you're making. It's important to consider two different things that are sometimes jumbled together - stability vs stiffness. More stability is essentially always a good thing, to a point of diminishing returns But more stiffness isn't always a good thing after a point, and you need to consider how stiffness impacts tone and adjustability.
  8. Arie X

    Arie X

    Oct 19, 2015
    i think some clarity is needed. "carbon rods" as in pressed graphite rods? or actual "carbon fiber" beams.

    ime, they can add some weight (material + glue) and can make truss rod adjustment a bit harder. actually CF beams are a better choice then rods because of the beam dynamics involved.

    frankly though, imo having a incredibly stiff neck is hard on the fretting hand. kinda like playing a piece of granite.

    as stated an in-depth discussion with the builder is in order.
    dwizum likes this.
  9. dwizum


    Dec 21, 2018
    I agree. The typical rectangular cross section pulltruded carbon rods stuck right under the fretboard are convenient but not really an optimal design. Of course we can argue whether it's important to optimize the design or not (since it's easy to over-stiffen a neck already) but putting rods on the compression side of the beam - which is already the widest, stiffest part of the neck, and is already capped by a typically very stiff fretboard, isn't really the most effective spot. That's why I like Bruce's design - put just a few tows way down as deep as possible where they will make more of a difference! The fact that such a small amount of carbon placed in the right spot working together with the custom truss rod allows his necks to be so thin and yet stable and stiff enough (but not too stiff) is a good example of a cohesive design where everything works together.
    wraub likes this.
  10. I've gone from being a fan to being against them. Many carbon rods don't cover the area ski jumps form in. When a rod ends there is an abrupt change in the stiffness of a neck making a spot weaker than the rest of the neck at the butt joints at the ends of the rod. Having a neck with inconsistent stiffness with abrupt changes sounds like a flaw to me. While it's becoming more common to have carbon run completely through the weak spots the classic carbon bar stops short of the nut and creates the weakest spot in the neck as wood was removed. Similar to a Les Paul truss rod cavity.

    I don't see many necks that need to be stiffer, I have seen necks that could be more stable and carbon can help with that.

    As already pointed out a few purpleheart laminates can make a neck very stiff. I understand the arguments for stability as humidity changes but my most stable neck doesn't have carbon. It does have an unlined purpleheart fretless fingerboard and neck lams which I suspect is the reason it's so stable.

    It's interesting to note early graphite necks were so stiff truss rods could not adjust the necks curve. Eventually necks were made less stiff so they could be adjustable.
    GMC, DuluthDank and dwizum like this.
  11. This is precisely why I chose to go without CF rods in my 5-string build. 5 laminates of Wenge/Purpleheart seemed like it just didn't need it.
    GMC and dwizum like this.
  12. Big B.

    Big B.

    Dec 31, 2007
    Austin, TX
    I use them on every build. The necks I've made without rods are noticeably more flexible than the ones without and I feel a stiffer neck equals better clarity in the low end. I dont have an issue with Bruce's method in practice, I just find carbon fiber to be such nasty stuff that working it by hand is not happening in my shop. Even the little bit of dust left over from working with the rods I use will make your skin break out and gets caught in your clothes.

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