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Composite headless neck?

Discussion in 'Luthier's Corner' started by MPU, Oct 23, 2010.


  1. MPU

    MPU

    Sep 21, 2004
    Valkeala Finland
    I'm toying with an idea of making an alder/carbon/rosewood composite headless 5-string neck. I'm planning to make the neck core from lightweight alder, them laminate a 2mm carbon skin over it (200g carbon fiber cloth with epoxy, 7 layers). After baking this to harden I'll mount a dual action trussrod and rosewood fretboard.
    I've worked quite a lot with glass/carbon fibers so the work itself will be no problem. I'm not sure if 2mm skin is stiff enough to make the neck strong enough to resist the string pull. Maybe adding carbon rods/tubes to make the neck even stiffer?
    Does this plan sound ok or should I change something?
    I know I could always make the neck out of wood, but this time I really want to make a composite neck.
    Marko
     
  2. Hi.

    I'm no expert on CF products (or making them), but with a solid core, 2mm shell sounds way too much to an engineer like me ;).

    A somewhat comparable item like a 40mm fishing rod with 1mm wall thickness, bends less than an eqvivalent wooden stake. A half round cross section behaves differently than a round one of course, but the principle is roughly the same.

    You are going to make the CF to fully enclose the alder I guess?

    Regards
    Sam
     
  3. MPU

    MPU

    Sep 21, 2004
    Valkeala Finland
    Hi Sam,
    thanks for your reply. I'm planning to make the CF skin for the back of the neck (C-profile CF "half tube") No CF under the fretboard.
    Marko
     
  4. Keith Guitars

    Keith Guitars Supporting Member Commercial User

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

    I think 2mm of 200g carbon will be much more than enough.
    The Parker Fly basses had a single layer of CF cloth over a core of laminated mahogany. Those necks were very strong.
    Since the CF is at the very back surface of the neck, it is all in tension and not so much is needed to gain strength.

    If you do use multi-layers, consider putting alternate layers on a +/- 45 degree bias ('diagonal' direction). This will add a great deal to the torsional strength of the neck.

    If you use the full 2mm skin, I expect that your truss rod will have a very difficult time moving this neck.

    Best wishes, and please put pictures if you continue this project!

    -Martin
     
  5. MPU

    MPU

    Sep 21, 2004
    Valkeala Finland
    Thanks for your reply Martin. It sounds like I'm making the skin thinner, maybe two or three layers only. That will make the skin 0,6mm to 1,0mm thick.
    Marko
     
  6. MPU

    MPU

    Sep 21, 2004
    Valkeala Finland
    Here's a few pics so far. I made an alder core and laminated 4 layers of cf cloth on it in a vacuum bag. At the moment the neck is in the boiler room curing, after 24 hours curing there's going to be 4 hours post-cure in the sauna (65deg C) to get the final strength. The surface is not smooth yet, but I'm hoping to get it smooth by light sandind and 2 coats of epoxy before final sanding.
    Marko
     
  7. markkoelsch

    markkoelsch

    Sep 6, 2008
    First of all, I would laminate the core in a unidirectional cf with the fibers oriented in the long axis of the neck. It depends on the weight of the cloth and how tightly you can get them packed as too how much you need. Then you can get other fabrics over that.

    Are you going to vacuum bag this layup to try and get the best compression of the laminate, and to get optimal resin to cloth ratios?

    Also, what epoxy are you going to use, and does it require an above room temperature cure? I have done some composites too, but in really large, high performance "model" rocketry.
     
  8. You won't make a good vibration transfer path. The wooden core is glued across neck length and the carbon filaments are put diagonally.
     
  9. MPU

    MPU

    Sep 21, 2004
    Valkeala Finland
    I's already vacuum bagged, curing at the moment. It's going to get post-cure in 65deg C, it's not needed but it adds a lot to the strength of the epoxy. I use SP115 resin. The skin is 1mm thick, four layers of cf cloth, 200g/m2 if I remember right.
    Marko
     
  10. MPU

    MPU

    Sep 21, 2004
    Valkeala Finland
    In the twill cloth there's fibers running on two directions and they are oriented along and across the neck. Besides, when the laminate is cured I highly doubt there's any difference in sound transfer with fiber orientation. Some cf necks don't even have continuous fibers but are made of cf mass. I've made a guitar neck this way before and it sounded just great.
    Marko
     
  11. pilotjones

    pilotjones Supporting Member

    Nov 8, 2001
    US-NY-NYC
    This would make sense if all you were concerned with was the bending stiffness of the neck. But since torsional rigidity is also very important, what Marko has done is good.

    And that should be more than sufficient.

    Firstly, vibration path is not simply along the axis of a plain wooden neck, it is also crosswise at the same time, although at a different speed. Secondly, the speed of sound in carbon fiber composite is faster than the longitudinal speed in wood due to its higher stiffness/density ratio, so slowing it down a bit (by some factor 0<x<29%) by using the 45 degree fiber bias may even make it sound more "woody."
    True. Also, Modulus necks are made from built-up fiber sheets, and then the air space in the mold is filled with epoxy/carbon powder liquid.
    And here is proof. All else does not matter.
     
  12. MPU

    MPU

    Sep 21, 2004
    Valkeala Finland
    Here it is. Alder core, cf skin, maple fretboard, alder body, brass hardware, custom-made 5-coil pickup. Feels nice and plays nice as well. You can hear a short sound clip at http://maihinnousu.net/s/10077
    I think the vibration transfer path is fine as it sounds just like a 5-string bass to me. The neck reacts to the truss rod fine, but it's a lot stiffer than my Moses Steinberger neck where I have to use light strings to get proper relief.
    Marko
     
  13. That looks awesome, more pictures of the whole bass please.

    lowsound
     
  14. MPU

    MPU

    Sep 21, 2004
    Valkeala Finland
    I'll try to take pics tomorrow morning.
    Marko
     
  15. pilotjones

    pilotjones Supporting Member

    Nov 8, 2001
    US-NY-NYC
    That looks great, Marko. I'd also like to see the pics if the whole thing.

    Between the headlessness, the alder neck, and the smallish body, I bet it's pretty light. What does it weigh?
     
  16. miziomix

    miziomix Über on my mind Commercial User

    Sep 28, 2009
    Milan, Kuala Lumpur, Paris.
    Bass builder @ MüB.
    I like it!! and it sounds good to me. more pix please! :)
     
  17. MPU

    MPU

    Sep 21, 2004
    Valkeala Finland
    Thanks for the replies. Unfortunately I didn't have time to take and post pics this morning. I'll be back home on Monday so full pics will have to wait for Tuesday.
    Marko
     
  18. joenoone

    joenoone

    Mar 21, 2009
    Clermont, FL
    Any pictures yet?
     

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