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Why are the wood laminates in necks arranged perpendicular to the finger board?

Discussion in 'Luthier's Corner' started by Bassmanbob, Dec 3, 2003.

  1. Bassmanbob

    Bassmanbob Supporting Member

    I'm still in the planning stage of building a bass, and want to know why almost all multilaminate neck pieces are arranged perpendicular to the fret board instead of parallel.

    Does the perpendicular orientation of the laminates provide more stability to prevent bowing of the neck or does it just look cool to see the different colors of wood running down the neck?

    Thank you in advance.
  2. Nick Gann

    Nick Gann Talkbass' Tubist in Residence

    Mar 24, 2002
    Silver Spring, MD
    I am no luthier, but it makes sense to me. The neck bows in the axis that is perpenducilar to the fingerboard. The laminates provide more strength if they are perpendicular to the bow.

    Imagine this: Take a ruler, bend short end to short end. Now, turn the ruler on its side and try to bend it. It doesn't bend nearly as easily. Same principle.
  3. Skorzen


    Mar 15, 2002
    Springfield MA
    Because that is how it is done. actually not all are done this way, checkout JP's thread on how he makes a bass for more info. Some feel that it is more stabile to orient the laminates parrallel to the fretboard.
  4. Bassmanbob

    Bassmanbob Supporting Member

    Nick, thanks for your input, but I had figured that one out years ago in physics class in high school. That sounds nasty, but it wasn't meant to be.

    I really want to hear from the guys who are really making basses. Thanks.
  5. Bassmanbob

    Bassmanbob Supporting Member

    Yes, I'm looking forward to JP's responce.
  6. JP Basses

    JP Basses

    Mar 22, 2002
    Paris FRANCE
    In fact yes a single piece of wood higher than thicker would ba stiffer in this direction. However what's important here is the whole neck which is submitted to the bow. What I mean is that a three piece maple neck is no way stiffer than a one piece maple neck, it is just more stable in theory.

    You could however use laminate to inclue stiffer material in your neck, that is replacing the center piece by a composite material or by stiffer wood.

    Peace, JP
  7. FBB Custom

    FBB Custom TalkBass Pro Commercial User

    Jan 26, 2002
    Owner: FBB Bass Works
    The ruler is stiffer in the example here for reasons other than orientation. You have more thickness fighting deflection in one case than the other.

    It's probably part tradition, but the tradition might come down to the fact that I think you'll find it easier to get woods quartersawn in the direction that matters if you use vertical laminates rather than horizontal.
  8. JP Basses

    JP Basses

    Mar 22, 2002
    Paris FRANCE
    I've stopped to build laminated neck now and I'm back to one piece because it works just well if the wood is correcty selected.

    Now to answer your question, if I were to laminate, I would OF COURSE use horizontal lamination rather than vertical, it make more sense physically speaking.

    front and back of the neck are the areas that are exposed to more stress (they are the enveloppe of the neck submitted to the bow). You need stiffer material here...ideally one that would work well in compression for the board and in traction for the back of the neck (see how parker adds fiber to the back of their neck, same point. Also many baroque instruments maker were putting ebony on the back of they're neck, they had figured this out).

    Somewhere on the net (I think on the MIMF) someone demonstrates the role of the fingerboard in the neck stiffness...amazing results. If I come across the article again, I'll post a link.

    Last thing is that a glue joint is stronger when stressed in traction than in torsion.

    be sure to read Suburban article on basic physics (check his profile).

    Peace, JP
  9. JP Basses

    JP Basses

    Mar 22, 2002
    Paris FRANCE
    Sure Matt. this is just a simple physics calculation that uses the stressed "section" of the material and its elasticity module E (called Young modulus)

    this doesn't take grain orienation in account of course.

    Peace, JP
  10. pilotjones

    pilotjones Supporting Member

    Nov 8, 2001
    Joe Zon posted in a recent thread that he uses wood, graphite, and other materials in his necks. My guess (only a guess) is that he's encasing a slightly undersized wooden neck in a carbon fiber blanket. Whether that's what he does or not, I think it's a cool idea.
  11. Bassmanbob

    Bassmanbob Supporting Member

    Thanks guys. These are thought provoking and inteligent resonces.

    The reason why I ask the question was that I liked the idea that Modulus had with their Genesis necks. They place a thin laminate of composite material under the finger board parallel to the finger board. I like this idea and was thinking of adding it to my necks when I begin to build. Adding my own modification of course, otherwise why bother. I don't remember the way the rest of the Genesis necks were built, but it gave me an idea to continue with the wood laminations parallel to the finger board. Maybe two more layers, three tops.

    I also thought about orienting the grain of the three layers perpendicular to each other. The grain of the top layer (just under the graphite lamination) and the bottom layer (on the very back of the neck) both running the length of the neck. But have the grain of the middle layer of wood laminations running across the neck. The only problem with this that I see is that I would have to joint the middle layer against itself many times. I think that would reduce the stability of the neck and add a lot of extra difficult work.

    The other alternative would be to use two types of wood with three layers with the grain running the length of the neck. Like a maple/ bubinga/ maple or maple/ purple heart/ maple. The more I think about it, the more this makes sense.

    Please keep your responces coming. Bob
  12. pilotjones

    pilotjones Supporting Member

    Nov 8, 2001
  13. mslatter


    Apr 8, 2003
    I'm having a little trouble envisioning what you're describing, Bob, but it sounded like you were designing a neck with cross-grain glue joints. That is, glueing a piece of wood with grain running horizontally to one with grained oriented vertically. That's generally considered a weaker glue joint than grain-to-grain, since the two pieces of wood would move in different directions as moisture content changes. So if you're looking for the type of joinery to contribute to the stiffness and reliability of the neck, I'd be a little wary. I think plastic resin glue or epoxy would lessen the issue, but could introduce cracking problems. Again, I didn't follow what you were saying, so this could all be bluster.

    Really, I think you're overthinking neck stiffness. I'd stick with the tried-and-true single laminated neck to start with, using a straight grained piece of quartersawn lumber. Get fancy later.
  14. Woodboy


    Jun 9, 2003
    St. Louis, MO
    This from the Forest Products Laboratory of the USDA's Wood Handbook:
    "Aside from the beneficial effect of dispersing imperfections, available test data do not indicate that laminating improves strength properties over those of a comparable solid piece. That is, gluing together pieces of wood does not, of itself, improve strength properties unless the laminations are so thin that the glue bonds significantly affect the strength of the member."
    The latter instance brings to mind the necks on the old Framus instruments, which were made up of 100's of veneers glued together. Parker's bass has a similar veneer format, only the laminations are horizontal. If you glue two pieces of maple together, it won't be stiffer than a single piece of the same dimension. If you put a piece of purpleheart, for instance, inbetween the pieces of maple, it may be marginally stiffer, but I would rather have wood doing the resonating rather than all that glue.
  15. Suburban


    Jan 15, 2001
    lower mid Sweden
    Sorry for being so late on this;)

    Imagine this: take a set of rulers and glue them together to make a square block. NOW, see which way is the stiffer!
    THEN, make another block with the same dimensions. The top and bottom layer still being a ruler, but replace the rest with one piece of styrofoam. Compare stiffness with the previous, in both directions.

    You will find that using the same material, the horisontal (or Parallel To Fingerboard) laminations will be sligtly stiffer, due to rather specific physics (like 5 pages...).
    You will find, that when using a foam core, the PTF position will be quite stiff still! While the OTF (O for Orthogonal) will be softer.

    Anybody get my drift?
  16. pilotjones

    pilotjones Supporting Member

    Nov 8, 2001
  17. Suburban


    Jan 15, 2001
    lower mid Sweden
    You are quite correct, Peter Pilot!
    The thing is, that you can't neglect the Glue!
    It creates a blockage for the shear deformation of the laminates. I know you can do this better, Peter, but just to get you going, here is some "explanation".

    Consider, for simplicity (so I can get this done in english...), water in a tube. Due to friction, the water closesat to the tube walls will flow very slowly. It will actually stand still, if the water right next to it, inward, doesn't move, and, by shear forces, drag the outer lamell with it. Thus, by entering more walls in the tube, the flow is slower even if the total area is the same. Can you agree on that?
    Now, all materials work similarily. Internal lamells of atoms slide/shear to eachother when the material is bent. The more atom layers that are only limited by the next layer of the same material, the more flexible it is. But, if you put in another material, with different module and harder binding to the surface of the first material than the internal of that first material...it stops the atoms from sliding! The laminate is consequently stiffer.

    Sorry, guys, I do need to study some english... :meh: Perhaps Peter will be able to see where I'm pointing, and publish a good translation;)
  18. JP Basses

    JP Basses

    Mar 22, 2002
    Paris FRANCE
    No problem at all with your english Sub!

    Great explanation.

    Peace, JP
  19. pilotjones

    pilotjones Supporting Member

    Nov 8, 2001
    Suburban (anyone not interested in engineering - pagedown now!)

    Thanks for your explanation - your English is much better than you give yourself credit for. (And infinitely better than my Swedish - which is zero!)

    I think your are mixing explanations a little bit. Fluids and solids both do act in shear, but I think may be mis-applying the one case to the other.

    When a fluid has a shear force applied to it, such as when flowing near a wall, it acts much as you have said- at the walls, velocity approaches zero, and velocity increases with increasing distance from the wall. In a fluid however, there is what's known as infinite shear - it does not behave elastically; rather, given an applied shear force (such as pressure), the deformation will continue without limit as long as the force is applied, and to any distance. This is true for water in a tube, a river and its banks, air in a ventilation systems, etc. And as you have said, if you keep the water sectional area the same, but you increase the walls, you decrease the average distance from any layer or lamina (what I think you meant by "lamell") to a wall, and so you increase the drag (friction), and the flow is slowed down.

    In a solid, however, shear is finite, and is governed (ideally) by the relation: modulus equals stress over strain, or for shear, G (shear modulus) = shear stress / angular strain. So, as you have said, bending of a beam does result in shear stress longitudinally along the beam; and the amount of strain (shear displacement) is affected by the shear modulus of the material. Higher shear modulus will result in less strain, and therefore less bending of the beam. But, even if the glue does have a higher shear modulus (higher resistance to shear) than the wood (which I was not certain of - do you know this to be true?), the glue layer does not act to "block" all shear up to or beyond that layer. It simply acts as a layer with better (or worse) properties. The properties of the composite beam will be the sum of the properties of the component parts, with the parts farthest from the central "neutral axis" having the most effect.

    Put another way, in a fluid, layers do slide, and this sliding is, as you have said, resisted by friction; but in a solid, layers of atoms shear in an elastic manner, maintaining fixed relations with neighboring atoms, both within the layer and with neighboring layers.

    So, in a way, putting the extra layers of glass into a fluid flow cases it to act in some way "more like a solid;" but the solid, whether composite or not, already acts "completely like a solid."
  20. I'm pretty sure Jones might be right there. A big part of it depends on the shear strength of the wood and the wood-glue interface, and which one is stronger.

    On a side note, I just finished my first year of engineering, so I gotta decide what type of engineering I wanna do. Tossing up between Chemical (process sorta stuff, energy conservation) and Materials (a lot more of this sorta stuff). So, of those with experience, any reccomendations wouldn't hurt.

    Josh D