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Carbon strip and truss rod placement questions

Discussion in 'Luthier's Corner' started by bajerovaquero, Dec 8, 2011.

  1. Hello everybody
    Im building this maple-wenge neck for a sixer
    The thing is now scarfed and glued. The 7mm rosewood fingerboard is also ready
    Im planing to use two truss and carbon fiber reinforcement, for any reason I want to build a stiff neck, I want this bass to be my main axe so he will be traveling a lot in a soft bag.
    So the next step will be routing truss rod and carbon slots.
    The 2 carbon strips has a 2,5x5mm section. Maple center measures 10mm wenge on each side 20mm, truss rods 6mm, nut 54mm
    I was wondering about how to place them all...
    The original plan was put carbon in the center and truss on the sides to maximice the action of truss rods.
    Now I´m considering about place the truss rods in the center and rods on the sides.

    Does anybody has an advice about this?
    How do you deal with six string necks?
    Double truss rods?
    Which truss distance is advisable to get a separated action from each truss?
    Which configuration will have the greatest torsional strengh?:ninja:

  2. spiraloutnj


    Dec 8, 2011
    all of that time and effort and not going to put it in a hard shell? :eek:

    I would definitely do the one center, 2 side strips for the utmost strength but I made a 7 string with dual truss rods, dual carbon rods on the outsides of the fretboard and a 1/4" wide slot down the middle of the neck for LED wiring and it worked out well. Very stiff and strong (pics available if the finished product ;) ). As far as the placement, i'd probably stick the rods in the center of the strips of wenge. that keeps them in a safe spot so you don't cut into the channels if you're doing a thin profile and i'm a stickler for symmetry :)

    that's just my $.02, i'm sure there are other's with a different opinion but that's what works for me. I don't think you'll be as worried about torsional twist as you will be with the amount of counter force the truss rods will have to endure with the string tension, which will be halved with the dual rod setup. I think when I did the 7, the rods were spaced about 1" apart? I don't remember offhand. I know the nut width was 2 1/8", though, so probably 1" give or take...
  3. Keith Guitars

    Keith Guitars Supporting Member Commercial User

    Aug 25, 2004
    Woodstock, NY
    Builder: Martin Keith Guitars

    Neck blank is looking good!

    Why do you plan to use two truss rods?
    Remember that truss rods allow adjustment, but they do not necessarily help with stiffness.

    Also, if you are using a two-way rod, you may have to make a very thick neck to have enough wood "behind" the rods, if they are off-center. The single rod on-center is at the thickest part of the neck, so the whole neck can be thinner and more comfortable.

    When you level the fingerboard surface, sand a little more relief into the bass side than into the treble side.
    This should allow you to use only one truss rod and still have a correct setup.

    If you are trying to make the stiffest neck, I would suggest the single truss rod, and the largest pieces of graphite you can fit. Put them in "on edge" so the 5mm dimension is vertical, as this is the strongest way to install them.

    Attaching your fingerboard with epoxy will also help with stiffness and stability.

    Best wishes,
  4. Thanks for responding
    When you play in more than five bands, seriously consider using a soft bag, thats it. Instruments should be made to be used and abused:ninja: Just kidding, but I live with my bass on my back taking a bus to go another rehersal with another band, so a soft bag is mandatory.

    I´m currently working with a Tune TWB-63, this bass needs a setup twice a year and I found pretty useful having two truss rods, it really helps to get a different relief in both sides, anyway I really appreciate your suggestion of sanding more on the bass side.
    Also not sure about "thinner=more confortable" for me the confortable thing is more in the balance of the instrument and how the neck falls in your left hand... who knows maybe Its a kind of masculine compensation:D
    I feel curious about gluing the fingerboard with epoxy, I use to work with Titebond.
    When talking about necks I feel stiffness and stability are basic and esential...
    Do you always use epoxy for fingerboards?
  5. spiraloutnj


    Dec 8, 2011
    but epoxy has a tendency to creep over time... i've also had times where it doesn't cure... mfr recommendation of 50/50, 2 different times, 2 different packs... (stupid loctite brand, i guess).

    when i used dual rods, I managed to get the neck thickness on the 7 I made down to .78" but I made the fretboard pretty thin to do it for extra meat on the back of the neck. the allparts dual action rods are much shorter than the stewmac ones, also.
  6. Keith Guitars

    Keith Guitars Supporting Member Commercial User

    Aug 25, 2004
    Woodstock, NY
    Builder: Martin Keith Guitars
    Epoxy is far, far less prone to creeping than Titebond or other aliphatic resin glues (white glues, yellow glues). Bad epoxy is no good - but that's true of anything.

    Actually, one of epoxy's best features is its creep resistance. Among practical glues for guitarmaking, only hide glue is better for creep resistance.

    Titebond is very poor in creep resistance, especially when there's any heat involved. It starts to fail quite dramatically around 140F, which is easily reached in a hot car during the summer. You can take Titebond-glued fingerboards off guitars with only a 100W lightbulb.

    Notwithstanding your experience, good quality epoxy, properly mixed, applied, and cured, is better than Titebond or other water-based glues for all kinds of reasons.

    Quick primer on epoxy basics:

    -Get good epoxy. For guitar work, the best room-temp epoxy system is the West Systems resin with #205 hardener.
    The "A" size kit is good for several dozen necks and costs less than $50 bucks online. A bargain.

    -WEIGH your epoxy when mixing, and mix by weight. Digital gram scales cost about $10-20. It will be way worth that to avoid a bad glue joint.

    -Mix thoroughly. Stir, scrape the sides of the cup, stir again, scrape again, etc. Really mix.

    -Apply to both sides of the joint. Use a small paintbrush if possible. This will improve penetration into the wood pores.

    -Work fairly quickly. Pre-adjust all your clamps so you only need to turn them once or twice until tight. Have everything you need nearby. Keep your shop a little cool if you can't work quickly, as it will slow the cure time.

    If the epoxy starts getting thick and jelly-like, you've waited too long. Get the clamps on ASAP.

    -Post-cure your parts by warming them up to about 150F for at least a couple of hours. Wait until the squeeze-out is brittle and glassy.

    -Clean up. Wear gloves. Don't eat the epoxy. You know...the basic safety info.

    It's not rocket science, and it definitely will give you a good strong joint with high resistance to creep.

    Titebond and similar glues also introduce water into one side of the neck blank, which can cause backbowing and instability during construction, especially in critical operations such as fingerboard leveling and fretting.

    It's just better, in my opinion.

  7. HaMMerHeD

    HaMMerHeD Supporting Member

    May 20, 2005
    Norman, OK, USA
    Thanks for that info, Martin. Though it's not my thread, that's great info to have. I've been thinking of switching to epoxy from titebond, but I have not had great experiences with the stuff. It's all my own doing of course, as I was clearly using it wrong. Anyway, that's good information, and thanks again.

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