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would this be safe for a 6+ string neck?

Discussion in 'Luthier's Corner' started by jordan_frerichs, Apr 8, 2009.


  1. jordan_frerichs

    jordan_frerichs

    Jan 20, 2008
    Nebraska
    I am planing out a build, and was wondering if this was a stable neck plan for a bass with 6 or more strings.
    The neck blank will have quarter-sawn quilted cherry sides, a 3/4" or more purpleheart center, and 1/16" walnut accents between the cherry and purpleheart. The neck blank thickness will be 3/4" with a scarfed headstock, and i plan to go with 1 LMII truss rod, so i will only have to route a 3/8" channel. the fingerboard will be 34" scale quarter-sawn bloodwood, 10" radius.

    will this be acceptable for a 6 or 7 string, or should i add carbon fiber rods or 2 truss rods (i don't like the idea of 2 truss rods at all)? do you have any suggestions? also what are some common nut widths and string spacings, and some common bridge spacings and string spans for a 6-7 string bass?
     
  2. I would go with 2 truss rods - the bass side will want more relief than the treble side, especially if the player is heavy-handed. But you could probably get away with milling it into the fret tops.

    If you don't go with 2 rods, definitely go with CF.

    A 10" radius on a 6- or 7-string fretboard demands a fretboard thickness of at least 0.3" if you don't want the edges to be very thin.

    Check Hipshot for 6/7 string bridge spacings - nut spacing is a personal choice. When you have both, you have the neck taper.
     
  3. dblbass

    dblbass Commercial User

    Mar 24, 2007
    Beacon, NY
    Owner of MBJ guitars, Maker of fine sawdust for Carl Thompson Guitars
    I'd say one rod...but then again i always say one rod. no CF rods...but then again i always so no CF rods.

    My take is that if you are going to put an adjustable rod in a neck why make it harder to adjust by putting carbon fiber rods in? the neck is already gunna be stiff with a peice Purpleheart that big.
     
  4. jordan_frerichs

    jordan_frerichs

    Jan 20, 2008
    Nebraska
    2 truss rods are staring to make since. what if i did 2 truss rods, following the taper, and one cf rod along the centerline?
     
  5. [mother]If I've told you once, I've told you a thousand times....[/mother]

    CF rods add stability - they don't move with temp & humidity like wood does. They also smooth out any potential dead spots.

    Jordan that plan sounds fine, the only hitch is that you don't want the rods too far away from center. When you follow the neck taper, you'll want to make sure you don't come close to exposing the rod when you carve the back of the neck. Especially if you're shooting for a neck thickness under 1". I'd go with a thin rod like LMI's and plan out your neck's back contour, so that you still have plenty of meat underneath.

    I would also go with rods that adjust at the end of the fretboard - if you're going with a narrow nut spacing, you will remove (IMO) too much wood around the nut, making the headstock-neck transition weak. There are folks who do this, but mostly they add a volute to beef up that area.

    For a 6 there may not be enough room between the rods for a CF bar - on a 7 you can probably do it.
     
  6. jordan_frerichs

    jordan_frerichs

    Jan 20, 2008
    Nebraska
    Thanx for the reassurance. So, 6 string vs 7 string, strength wise, do you think the 7 would be more stable because the 2 rods and cf will have adequate room, or would a 7 be less stable, or would the extra string decrease stability/strength at all?
    I want a wider string spacing, like 19mm (standard 4 spacing), maybe slightly less. I just hope the LMII board will be wide enough for a wide 7. Having trouble deciding a good nut thickness. What range is a non-narrow 7string nut thickness in?
     
  7. Stone Age

    Stone Age

    Apr 13, 2008
    Connecticut
    Just "use good wood", right? ;)
     
  8. IMO 6 vs 7 depends entirely on whether the player will need 6 or 7....

    I think the 2 rods on their own already are good - yeah the CF will improve things, but its not like the neck will be all that unstable without the CF.

    I would NOT opt for regular 0.75" bridge string spacing, on either a 6 or a 7 - but maybe that's just me. I have 0.75" on a 5er and already it feels like a lot.

    Nut spacing - I personally lean toward pretty tight spacing at the nut. But then again I started on guitar before I began to play bass, so....
     
  9. dblbass

    dblbass Commercial User

    Mar 24, 2007
    Beacon, NY
    Owner of MBJ guitars, Maker of fine sawdust for Carl Thompson Guitars
    yep :)
     
  10. jordan_frerichs

    jordan_frerichs

    Jan 20, 2008
    Nebraska
    I mainly like to play punk music, or anything with adrenalin, that can start a mosh pit pretty easily, but for some reason, i keep designing and wanting to make specialty basses. slap is always fun, though, and i really want to learn to tap even half as good as jean baudin. This will mainly be fore stuff like that. I think I will bump it up to a 7 though.
     
  11. thirtypoint87

    thirtypoint87

    Feb 9, 2004
    Manager/Repairman: Music-Go-Round
    Hmmm.... I'm not sure about this. I just finished a bass that used cherry in the body, and it looks and sounds great. I'm not so much a fan of it as a neck wood though.

    Jordan, I'd strongly suggest swapping out quarter-sawn maple for the cherry in your neck design. It *will* be stronger and stiffer this way. If you must use purple heart in the neck, I encourage you to wipe it down with some acetone (or similar) to remove the oil in it and make it easier to get a good glue joint. To be honest, after a dozen years as a professional repairman and amateur (or part time, anyway) builder I can't see anything better than a 3 piece maple neck, in terms of performance. (i.e. maple for the stiffness, 3-piece for the stability)

    With a 6 or 7 string neck I'd go with two truss rods (with, y'know.... a maple neck) and no carbon fiber rods. The maple should be adequately stiff, and the two rods will allow you to set the neck relief "ideally", with a little more relief on the bass side than the treble side. Hope this helps......
     
  12. jordan_frerichs

    jordan_frerichs

    Jan 20, 2008
    Nebraska
    I have 2 cherry blanks that are amazing looking. one is under 2.5" so i want to split it and use as the sides of this, but the other one will be a fretless 4 string one piece with a granadillo fingerboard.
     

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