Strange question about scale length and number of frets.

Discussion in 'Luthier's Corner' started by BusyFingers, Feb 9, 2018.

  1. BusyFingers

    BusyFingers

    Nov 26, 2016
    I am considering having a custom guitar (not bass) neck built for a body. I have a couple of options in terms of the body and the original scale neck that goes with it.

    Option 1: A guitar with a 25.5 scale length neck with 22 frets.

    Option 2: A guitar with a 25.5 scale length with 24 frets.

    Both guitar fretboards end right where a neck pickup is, so there is no way to extend the fretboard beyond where the neck pocket currently is.

    Am I correct in presuming that if I want to have a 24 inch scale neck built for one of these guitars, I would be able to squeeze out a couple more frets out of the one that currently has 24 frets?

    Or is this not enough information to say definitively? My presumption is that the bridge on the 24 fret one is positioned in such a way as to allow for more frets on the neck. Is this correct?
     
    Last edited: Feb 9, 2018
  2. Your 25.5" scale is the rough measurement from the nut to the bridge. The number of frets determines, in part, how long your fingerboard is.

    The point of the 24th fret is that it is 2 octaves higher than the open string (one octave higher than the 12th fret note). The location of that note will not move, regardless if you have a fret under it. (IF math serves me correctly, that point is ~6-3/8" from the bridge (or 19-1/8" from the nut). One of the luthiers will set you straight if I'm wrong.)

    If you wanted to, you could probably run frets all the way up to the bridge. You would just need a really, really long fingerboard.
     
    Groove Doctor likes this.
  3. Arie X

    Arie X

    Oct 19, 2015
    well, as scale length is set between the nut and the saddle it is a fixed value, 25.5" for example. adding or subtracting the number of frets is achieved buy adding or subtracting the length of the fingerboard.

    if i understand your current problem correctly, the bridge is going to be fixed to the body assuming a scale length of 25.5"? swapping in a shorter scale neck (24.0") will bring the neck closer into the body. to make this work, moving the neck pocket in closer or relocating the bridge will have to happen.

    keeping the 25.5" scale and adding a few reasonable amount of frets can be done by increasing the fretboard extension provided one doesn't interfere with any neck pickups. the same goes for shortening the instrument's scale length by moving the neck forward or moving the bridge forward. basically you have to be aware of where your hardware is to pull off these mods.

    hope this helped.
     
  4. BusyFingers

    BusyFingers

    Nov 26, 2016
    Sure, I understand that, but knowing that the guitar has a neck pickup and the current positioning stops it right at the last fret, does that have a bearing on my original question?
     
  5. BusyFingers

    BusyFingers

    Nov 26, 2016
    Yes, maybe I should have referenced that both guitar fretboards end right where a neck pickup is.

    I get that I would lose frets now matter how I slice it, but will I be able to eek out more from the body that originally had the 24 fret neck?
     
  6. Arie X

    Arie X

    Oct 19, 2015
    what kind of guitar is this?
     
  7. If you want a 24" scale neck, you will need to move the bridge 1.5" closer to the headstock. This may play havok with your bridge pickup, assuming there is one.

    I'm guessing you may be able to eek out a couple more frets with the shorter scale but I believe the bigger question is, "Why would you want to?"
     
  8. BusyFingers

    BusyFingers

    Nov 26, 2016
    The 24 fret one is an Ibanez RG1521.
    latest?cb=20101215135947.jpg
     
  9. BusyFingers

    BusyFingers

    Nov 26, 2016
    Sure, and without moving the bridge I would have to take 1.5 inches off the end of the fretboard... Hmmm... I think I understand now.

    What I want to manage is a 22 fret 24 inch scale neck on a body made for a 25.5 inch scale neck. And if I am currently undertstanding this right, the 24 fret version may be able to pull this off, though it may require a bit of a move of the bridge, too.
     
  10. Ok. Had to go in the basement and actually measure this. So, if you keep the bridge in the same spot, on a 25.5” neck if you measure from the bridge, 24” hits just on the bridge side of the first fret so you will loose about one to one and a half frets. If you are starting with 24 you should be able to get 22 frets out of the shorter scale neck.

    Fretboard Calculator

    If you have the guitar in hand, the fret calculator above gives you the distance from the bridge to the frets so you can plug in your numbers and measure from the bridge saddles to the end of the neck pocket and see where that comes out.
     
    TundraMan and IamGroot like this.
  11. BusyFingers

    BusyFingers

    Nov 26, 2016
    The 24 fret one is an Ibanez RG1521.
    latest?cb=20101215135947.jpg
    This was really helpful. Thanks everyone
     
  12. Arie X

    Arie X

    Oct 19, 2015
    what's you're going to basically do as seen here on this 22.5" scale Mikro:


    preview.jpg


    is shorten up the "playing compartment" although not as drastically. you'll have to do or have done for you: some routing, making some new holes and covering/plugging old ones, etc.. and if you care, some finish work. also, the required neck pocket work needs to be done right or you'll have problems.

    if you're willing to have one, a pick guard can help a lot in terms of appearances. if you have the skill set, all of this is do-able if not then money could be a barrier for you. pretty much anything can be done guitar wise it just depends upon how far you want to go :)
     
    Last edited: Feb 9, 2018
  13. My bad. I thought, for some reason, that the OP wanted 26 or 27 frets on a 24" scale.
     
  14. Arie X

    Arie X

    Oct 19, 2015
    can't happen and still be musical, although it would be weird to play.

    you need the "rule of 18" to position frets correctly. basically a geometric progression of 1.0594.

    -take desired scale and divide by 17.817. this is nut to first fret distance.
    -take desired scale length and subtract that first fret distance.
    -then divide by 17.817. you will have the distance from the nut to the second fret.

    then repeat this process for all of the remaining frets.
     
  15. T_Bone_TL

    T_Bone_TL

    Jan 10, 2013
    SW VT
    My simple thought experiment - if you are not going to (or are not able to) move the bridge, consider "shorter neck" as "put on a capo" - say at the first fret.

    Now, counting the capo'd first fret as the new nut, the former 24th fret (or 22nd fret) is the 23rd or 21st fret, and the new 24th or 22nd would be in/on the pickup.

    Clear?

    If you want more frets before that neck pickup, a LONGER scale will get you there.
     
  16. 40Hz

    40Hz Supporting Member

    May 24, 2006
    home
    I don’t know if I fully understand what you’re asking, but for a 25.5” scale length your 24th fret will be offset 19.125” from the nut.

    So you’ll only have 6.375” (or 6 and 6/16 inches) of space between the 24th fret and the bridge.

    That doesn't leave you a lot of space for mounting your pickups.
     
  17. IamGroot

    IamGroot

    Jan 18, 2018
    1.0594 is good approximation but if you multiply it 12 times you need more significant digits.

    2 raised to the 1/12 power will give you a better result on a spreadsheet.

    Where on the fret do you measure the distance.

    My father was a classical guitar builder.
     
  18. Bruce Johnson

    Bruce Johnson Gold Supporting Member Commercial User

    Feb 4, 2011
    Fillmore, CA
    Professional Luthier
    Here, I'll do the math for you:

    On your Option 1 guitar 25.5" scale, 22 fret, the end of the fingerboard is at the 23rd fret position. Therefore the distance from the bridge Zero line to the front side of the neck pickup is 25.5-18.746=6.754".

    On your Option 2 guitar 25.5" scale, 24 fret, the end of the fingerboard is at the 25th fret position. Therefore the distance from the bridge Zero line to the front side of the neck pickup is 25.5-19.483=6.017".

    So, those are the fixed functional lengths of those two bodies, assuming that you are keeping them unchanged. Yes, the 24 fret body is shorter in length, so on any custom neck you build for it, the fingerboard will be longer.

    Now, if you build custom 24" scale necks to fit those bodies, keeping the bridge and neck pocket positions the same, you'll get:

    On the Option 1 22 fret body, the fingerboard will be 24.0"-6.754"=17.246". On a 24" scale neck, the 22nd fret is at 17.265", so your heel end would be just shy of that. Therefore, that neck would have 21 frets.

    On the Option 2 24 fret body, the fingerboard will be 24.0"-6.017"=17.983". That's just shy of the 24th fret position (18.000"), so that would end up as a 23 fret neck.

    Do you see how that works?

    If you play around with scale lengths in the range of 23" to 25", you'll get approximately the same result on both instruments: You'll lose one fret as compared to the 25.5" scale neck.
     
    Last edited: Feb 10, 2018
    Engle and BusyFingers like this.
  19. RichSnyder

    RichSnyder Columbia, MD Supporting Member

    Jun 19, 2003
    Drop tune to D standard and put a cap on the second fret to see if you like how a shorter, 22 fret neck would feel and sound like.
     

  20. Thanks Bruce. I ran the numbers through that fret calculator and was about to post something similar but you beat me to it and probably more articulately to.:smug: