Fingerboard camber questions

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


  1. Michael Glynn

    Michael Glynn

    Feb 25, 2004
    Seattle
    I recently noticed that scoop on the fingerboards of two basses I use have an interesting difference. On the first the scoop seems to extend from the nut to the end of the fingerboard, while on the second, the scoop seems to stop a little before the end. When checking with a 24" straightedge, this makes the second fingerboard appear to have a high point. It varies from about 1 to 2.5 inches from the end. If I press a string down at the end of the fingerboard with my right hand and pluck above there with my left, I get a buzzing/rattling sound on the second bass, but a clear tone on the first, as might be expected.

    I have noticed that I have difficulty playing hard pizzicato on the A string of the second bass without getting a rattle or clacking sound (This string has the furthest back "high point" at around 2.5 inches), whereas on the first bass I can lower the strings way down and pull as hard as I want with no buzz. I pluck near the end of the board.

    So, questions:
    1. Are both of these camber shapes normal?
    2. Could the shape be causing the rattling problem on the A string?

    Here's a crude illustration of the relative shapes of the fingerboards. Both boards are the same length, going to the D harmonic on the G string.
    fingerboard.jpg
     
  2. On a bass that's been set up for primarily arco playing, you want a flatter fingerboard to account for the different string excursion and a higher bridge.
     
  3. Michael Glynn

    Michael Glynn

    Feb 25, 2004
    Seattle
    Well, they're both ostensibly setup mostly for pizz, but with the ability to play arco fine as well. The max depth of the camber is not so different, but my question is more about whether the camber should extend the length of the fingerboard, or end before reaching the tip of the fingerboard.
     
  4. Don Kasper

    Don Kasper Supporting Member

    Just checked my board - the camber goes "end-to-end" like the top illustration.
    The lower illustration above looks incorrect to me (and my understanding of "scoop/relief".) Maybe the A string is oscillating and hitting/rattling against the portion of the board that is not adequately or correctly scooped?
    Maybe a Qualified Luthier will comment and clarify.
    Thanks.
     
  5. Michael Glynn

    Michael Glynn

    Feb 25, 2004
    Seattle
    Yes, the hitting sound mostly happens when I play the A string more than once in a row, and only pizzicato. My guess is that when the A string is already oscillating from a previous pluck, and I then bring my finger down into the string to pluck again, the string is bouncing off my finger directly into that high spot.

    I can see how if one were to scoop based on the entire vibrating string length, and measured from the string, which is of course at somewhat of an angle to the fingerboard and not parallel to it, one could end up with a cross section like I have on bass 2. Here's another crude picture showing the fingerboard, string (grey), and oscillating path (yellow). You can see that the tip of the fingerboard is not in the path of the string in this recreation. Of course, the vibrating section and string angle changes as you play up the fingerboard, and I imagine the shape of the camber is as much art as science in the end. Hoping some of the resident luthiers here will give their two cents.
    fingerboard2.jpg
     
    Don Kasper likes this.
  6. Greg Clinkingbeard

    Greg Clinkingbeard Commercial User

    Apr 4, 2005
    Kansas City area
    Black Dog Bass Works
    Dressing a fingerboard is as much art as science. It is possibly the most important aspect of setup.
    Personally, I wouldn't want to play a bass with that much camber that close to the nut. It isn't necessary and causes wasted effort.
    If you play an open string, it will have the greatest oscillation in the middle of the string and very little in the first few inches, which gets the most use.
    But, if the maximum scoop (relief, camber, dip, whatever) is in the middle of the string length, it will be hard to play in thumb position, and it's unnecessary.
    Why? The string will oscillate much less as the vibrating length is shortened. Try it and see.
    I put the maximum scoop at the end of the neck. Normally, it will be near the F on the G string. I use a consistent curve from one end of the board to the other. As a guide, I use the string diameter for the amount of scoop to have: 1-1.5mm under the G and 2.5-3.5mm under the E.

    Ideal string height at the nut is no more than a business card.

    This is what I do and it seems to work for a variety of players. YMMV.

    Disclaimer: More scoop generally gives the tone more fundamental. The string angle is higher, similar to raising the height at the bridge.
     
    Povl Carstensen likes this.
  7. Michael Glynn

    Michael Glynn

    Feb 25, 2004
    Seattle
    Thanks for your reply. Yes, my pictures are not meant to really show the actual shape or depth of scoop across the board. In general, the amount of camber feels fine on both basses.

    Do you have an opinion on whether the scoop should continue all the way to the end of the board, as opposed to stopping an inch or two before the end? And whether that could have an effect on clacking noise when pizzing hard?
     
  8. Greg Clinkingbeard

    Greg Clinkingbeard Commercial User

    Apr 4, 2005
    Kansas City area
    Black Dog Bass Works
    It might have that effect but there's theory and then there's reality. Does it?

    I use both a 6" steel ruler and a handy little thing called a fret rocker to find high spots. If either of those tools high centered, I'd get rid of the bump.
    It may cause a buzz.
     
  9. If the scoop does not go to the end of the board you wil get a high spot where it ends. So at the end of the scoop wherever it is on the board you must avoid a hard break of direction, so gradually go out of the scoop.

    In higher positions the fingerboard to string angle is much larger than on lower positions, so I feel there is no need to put the scoop up to the end of the fingerboard (I end a bit higher than the octave), but I'm still experimenting with that on a cheap Stagg EUB rosewood fingerboard that initially had a negative scoop (one big bump, the trussrod is useless on a Stagg as far as I have tried). It is just important to avoid any hard breaks of direction. The deepest point On the Stagg is now a bit higher the fifth (around the neck heel). But I'm no expert. Had a look at my double bass first before shaping the EUB fingerboard and did it only half way (in deepness) yet.
     
  10. james condino

    james condino Spruce dork Supporting Member Commercial User

    Sep 30, 2007
    asheville, nc
    Michael- thank you 1000 times for making a visual diagram. 99% of the time this question winds up being a bunch of hypothetical paragraphs that most likely leaves much of the crowd perplexed and unable to understand the conversation.

    Another important aspect is that there are two separate variables at work:

    1- the "scoop" / relief / camber

    2- the junction of the terminus of the neck (maple) and the continuation of the ebony fingerboard. The expansion / contraction of the two woods almost always is at different rates at that area and the flexing or bowing of the neck itself will stop there and take on a different curve for the rest of the ebony. One of the biggest challenges is that you'll profile the fingerboard perfect by the numbers with the strings off. Then when you add string tension, everything sometimes winds up being completely different in the tensioned neck. It gets even stranger if there is an irregularity in the wood of the neck or fingerboard.
     
    Last edited: Aug 19, 2017
    Greg Clinkingbeard likes this.
  11. The scoop not going all the way just seems like unfinished work to me.
     
    Matthew Tucker likes this.
  12. Heifetzbass

    Heifetzbass Commercial User

    Feb 6, 2004
    Upstate, SC
    Owner, Gencarelli Bass Works and Fine String Instruments, LLC.
    A lot of times when a player comes in complaining of a buzz on their FB, I find it has as much or more to do with the radius of the board as it does the scoop. Yes, there can be a high spot or bump on the board, but most times it is the string rotating back to the FB after attack. While it seems to be happening in the left hand near the fingers, it is actually buzzing towards the end of the board. I first check the radius and then make sure I have a good scoop from end to end.
    Not much scoop for me until around 2nd position, with the lowest spot being just below the octave. Everything else is just like Greg said. Checking for bumps, high spots, and pivot points along the string path. Plane first, scrapers if necessary, and if the grain is really wild sandpaper with an ebony backing block.

    I would think all things being equal, your diagram of the 1st FB is the correct one.

    BG
     
    james condino likes this.
  13. There is some really nerdy stuff on the web about Helmholtz motion of a plucked or bowed string that I don't pretend to understand. Knut Guettler did a lot of work in this area. The wave motions set up appear not to create simple arched sine wave shapes. The shape is distorted by energy applied sideways and downwards at the plucking or bow contact point. My own understanding is that plucking/bowing oscillates the string sideways in an elliptical motion that might decay towards a more circular motion if allowed to ring on freely.

    I can see that by carefully planning not only the amount of scooping but also its profile (how and where it is scooped) you might arrive at a constant angle between the string leaving your finger and the fingerboard as you move up and down it. I can also see that the E string requires more scoop than the G. What is not clear is the ideal profile that accounts for the height of the action and whether you are plucking or bowing (different places on the string). Instinct says that the curve made by scooping is slightly more pronounced in the lower positions and could gradually flatten as you move towards the bridge.

    I have never seen a fingerboard scooped like the second example above.

    Perhaps Arnold Schnitzer could help us here?
     
  14. Michael Glynn

    Michael Glynn

    Feb 25, 2004
    Seattle
    Thanks for all the replies. It sounds like in general luthiers would tend to extend the camber to the end of the board. As DoubleMIDI mentioned, if one does not, there will by definition be a high spot at the inflection point where the scoop ends, although it can be minimized. I should add that I'm not a luthier myself and have no intention on making any repairs to my fingerboard personally. Just looking for ideas why the second bass tends to rattle on the A string sometimes.
     
  15. Michael Glynn

    Michael Glynn

    Feb 25, 2004
    Seattle
    Interesting idea about the radius being a part of the issue. What are some of the problems with the radius that you find, how do you fix them, and what differences do you notice for pizz vs arco is this regard?

    Thanks!
     
  16. Blaine

    Blaine

    Aug 4, 2001
    new york area
    I would love to hear the step by step details of the process of planing a board. I dont seem to be able to find too much info on it. Are templates used? It always seemed to me the easiest thing to do would force a small backbow in the fingerboard and then sand it flat so when relaxed it would have a small scoop in the board, but the thumb position end of the fingerboard would bend much easier than the neck portion so I'm sure it's not a good idea.
     
  17. Matthew Tucker

    Matthew Tucker Commercial User

    Aug 21, 2002
    Sydney, Australia
    Owner: Bresque Basses, Sydney Basses and Cellos
    FWIW I'm of the firm opinion that the second fingerboard was only "finished" as far as the luthier who did it thought the player would reach! It cannot work for notes stopped near the hump. The fingerboard needs to be one smooth surface from end to end, no humps are allowed.

    I suppose it is possible the fingerboard was planed by a DIY whose plane dived at the end of the board, then the luthier tried to save a bad situation. But it is as Povl says, unfinished.
     
  18. Matthew Tucker

    Matthew Tucker Commercial User

    Aug 21, 2002
    Sydney, Australia
    Owner: Bresque Basses, Sydney Basses and Cellos
    simply put you start planing where you want the deepest point to be for each string, and then gradually work your way to the ends so you have a gradual and smooth sweep all the way to the desired depth with no bumps.

    And then you have to smooth all them out across the board so there are no ridges. and all the time you have to make sure that you respect the desired arch of the fingerboard.

    And you have to make sure that you choose the correct plane for that particular piece of Ebony, and plane in the correct direction for that piece, and know how to deal with splits cracks, tear out and divots, and then sand the surface with increasingly fine abrasives until you get a beautiful sheen. And then check it all again for minute bumps and maybe scrape a bit more and sand a bit more.

    and then string it up and play it, and hope there are no buzzes anywhere on the board, and if there are, take the strings off go back to scrape sand and polish and so on ..,

    quite simple really!
     
    Last edited: Aug 22, 2017
  19. Heifetzbass

    Heifetzbass Commercial User

    Feb 6, 2004
    Upstate, SC
    Owner, Gencarelli Bass Works and Fine String Instruments, LLC.
    I have a template that I like to use for FB radius. Can't remember off the top of my head what the radius of that circle is, but I chalk it up and rub it on the board. Most of the time, it's high on the outer edges. I plane/scrape/sand until that chalk covers most everywhere on the board.

    You can buy some jigs from International Violin, or Metropolitan Music that gives a pretty standard radius.

    I should say that in my experience, arco playing is the one that has the most issues with the radius. Some players have a very steep angle of attack with the bow, and are pretty aggressive players. They can "bottom out" the string especially on a down bow. A rounder radius gives the string more room to move.

    I am a pretty stout player with the bow. Sometimes I play a customers instrument and can't make it buzz, then they pick it up and it buzzes all over the place. Differences in technique.

    Best,
    BG
     
    Matthew Tucker likes this.
  20. robobass

    robobass

    Aug 1, 2005
    Cologne, Germany
    Private Inventor - Bass Capos
    I thought that a constant radius was not desirable, and the board should have a larger radius at the bridge end.
     
  21. Primary

    Primary TB Assistant

    Here are some related products that TB members are talking about. Clicking on a product will take you to TB’s partner, Primary, where you can find links to TB discussions about these products.

     
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