Fingerboard camber questions

Discussion in 'Setup & Repair [DB]' started by Michael Glynn, Aug 18, 2017.

  1. Don Kasper

    Don Kasper Supporting Member

    Is that called a "compound radius"? Smaller radius at the nut; larger radius, getting flatter, as you move toward the bridge.
  2. robobass


    Aug 1, 2005
    Cologne, Germany
    Private Inventor - Bass Capos
    I would just call it conical as opposed to cylindrical. Of course the scoop goes into it too, so maybe a nonlinear cone?
    stefaniw80401 and Don Kasper like this.
  3. Matthew Tucker

    Matthew Tucker Commercial User

    Aug 21, 2002
    Sydney, Australia
    Owner: Bresque Basses, Sydney Basses and Cellos
    you and your technobabble :)
    robobass likes this.
  4. Heifetzbass

    Heifetzbass Commercial User

    Feb 6, 2004
    Upstate, SC
    Owner, Gencarelli Bass Works and Fine String Instruments, LLC.
    Yeah Rob, it is flatter at the nut end. So, we could call it compound, parabolic, all kinds of stuff. It's the business end near the bridge I'm most concerned about.
  5. Don Kasper

    Don Kasper Supporting Member

    I thought it was flatter (larger radius) at the bridge end of the fingerboard?
    Am I compound confounded?
    Thanks for your time and expertise.
    stefaniw80401 likes this.
  6. I have also always thought (presumed) that as the fb gets narrower towards the nut, the radius got smaller, but I suppose I am corrected. And looking at my bass, ofcourse I can now see that the fb does not curve as many degrees at the nut as at the end of the board.
  7. robobass


    Aug 1, 2005
    Cologne, Germany
    Private Inventor - Bass Capos
    Well, the radius is smaller at the nut on my basses anyway.
    stefaniw80401 likes this.
  8. Correction to (hopefully) avoid confusion:
    The radius of the fingerboard is larger at the nut, but the curvature is smaller there than on the bridge end.
  9. I would say the curvature is smaller, ofcourse, but the radius bigger..? Not necessarily, imo.
  10. robobass


    Aug 1, 2005
    Cologne, Germany
    Private Inventor - Bass Capos
    I'm completely out of it here. curvature is smaller, but the radius bigger? What does that mean?
    Don Kasper likes this.
  11. If the curvature is small, the radius of the circle which contains the low curvature part is big.
    A highly curved part is contained in a much smaller circle.
    Sorry, mathematicians point of view (not that I am one of them).
  12. eh_train

    eh_train Supporting Member Commercial User

    Jan 12, 2004
    Owner, Stand Up Guy Basses (Repair/Sell/Buy upright basses)
    Joey Nager wrote a helpful article on this exact subject ('Fingerboard Geometry') that was in the second to last issue of the ISB magazine Bass World. I'd recommend it to anyone interested....


  13. zeytoun


    Dec 19, 2008
    Portland, Oregon
    Once, for an EUB project, I ordered a moderately priced ebony fingerboard from a vendor. It needed very little dressing, and played well right out of the box. Later, I did another project, and ordered another fingerboard from the same vendor. It's shape was very similar to your second picture. It rattled a lot, especially as I played closer to the big "bump" near the end.

    I held a 15" metal ruler on it's side along the length of the fingerboard, and shined a flashlight from the other side, so I could see exactly where the gaps and bumps were along each string's path. I wanted the gap to be about credit card thickness and ever so slight concave at most points in the board. Near the bottom of the fingerboard, it went convex, and the ruler teeter-tottered a millimeter or two.

    It took a lot of dressing to improve this (I won't say "fix" because it was never as good as the first board. I'm not a luthier.)

    It was not an expensive fingerboard, so I assume it was either poor quality control/finishing from the source or that the ebony warped or expanded a bit after it left the factory.
  14. Michael Glynn

    Michael Glynn

    Feb 25, 2004
    So with the second fingerboard, when you plucked near the end you got rattling, but after reshaping it to have the scoop go to the end, it was improved?
  15. zeytoun


    Dec 19, 2008
    Portland, Oregon
    More or less.

    Although, to clarify, the last section (around the octave, give or take) of the fingerboard is actually pretty flat. But if you're using a long ruler (or are drawing a line from end-to-end) there appears to be a gap the whole length.

    I aimed for a shape like the second example in the image below:

    Slight curve toward the nut, flatter toward the end of the board.
    Last edited: Aug 28, 2017
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