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8 string bass, first build

Discussion in 'Luthier's Corner' started by fenderfour, Jan 8, 2018.

  1. fenderfour


    Sep 3, 2015
    Seattle, WA
    I fell in love with the scroll on a f-shape mandolin a while ago, however, mandolin just isn't my instrument. So I started designing a bass with a scroll reminiscent of classic f-shape. It started with a sketch more than a year ago. It's a bit scratchy, but established some lines.

    it moved to some CAD design


    Then to some neck blanks. One is for this project, the other, who knows. It's not much more work to make an extra if you are already making one. The dark wood is cambia maple, which smells like maple syrup when you cut it. cambia maple is also called roasted maple. The wood is heated in an de-oxygenated environment. Not sure if it's more stable than regular maple, but I got it cheap, so now it's some neck blanks.

    The light stripe is regular hard maple and there are two purpleheart stringers.

    image6.jpeg image7.jpeg
    Laying out the neck:
    The paddle hasn't been glued on just yet. I'm noodling on the best time to do that given the need to taper and profile the neck. This is the current state of the neck as I consider the order of operations. If you have any advice I'd like to hear it. The neck will have a volute to support the peghead.

    I cut the 10 degree scarf using a chop saw and some jigs to hold it perpendicular to the fence. The cut was within 1/64 and needed just a little cleanup. I didn't get a picture of that setup.

    I got a huge piece of swamp ash for a good price. 9" x 5" x 5'. I think it weighed around 60lbs. Luckily, I have a 10" planer in my shop. Unluckily, the bandsaw blade wasn't up for resawing and I was being impatient, so the table saw and a wedge split the board.
    A bit more milling yielded the body wings. I laid out the pieces.

    Fretboard from LMI. This is where I realized my original plan to make a 34" scale 8 string wasn't the best. I happened to also have a 32" scale fretboard and everything flowed better with the 32". So my 34" scale bass became a 32". No worries. I just need to get another fretboard for that other neck.

    I've practiced carving some scrolls. It's not an easy task. This is the very first scroll I carved in soft maple. This is about 1/2 scale. Bigger scolls are easier to carve.
    I knew what I was in for. there was a lot of difficult sanding on the inside of the scroll to remove the saw marks.

    it's looking pretty good in raw form:

    and this is as far as I got this weekend, roughing in the bevels before I glue the wings on.

    I'm planning to get the scroll carved to 90% before I glue the wings on. The rest of the bevels will get cut, staying away from the neck interface area. The scroll will get cross-drilled and i will epoxy in a reinforcing member to prevent it from getting broken off. I'm toying with the idea of having the strap button machined into the reinforcing member. I have a metal lathe, i just need to sort out the geometry and get it coated.

    Bass details:
    fretted 32" scale
    8 string (Dual course)
    Schaller 8 string bridge
    import hipshot hardware
    Lace 7 string guitar "single coil"
    Passive output with treble bleed circuit.

    Yeah, the pickup choice is a little odd. I have a heavily modded Traveller MkII bass that I added a lace strat pickup to with passive p-bass wiring. It sounds pretty amazing. I wanted a clean aesthetic for this bass, so I'm taking a small risk with the pickup. I'm guessing it will be pretty great, especially with the octave strings.

    I'm a weekend builder, so this will probably take a while. Thanks for looking.

    Attached Files:

  2. ctmullins

    ctmullins fueled by beer and coconut Gold Supporting Member

    Apr 18, 2008
    MS Gulf Coast
    I'm highly opinionated and extremely self-assured
    Looks awesome! Subbed. :)

    A 34” scale fingerboard becomes a 32” scale fingerboard when you chop off the first fret.
    Dadagoboi, Leiria and fenderfour like this.
  3. Looks good. I used a “guitar” EMG select single coil on a short scale bass with a Teisco neck years ago and I sounded pretty good.
    fenderfour likes this.
  4. Leiria


    May 21, 2015
    Today I learned
    ctmullins likes this.
  5. fenderfour


    Sep 3, 2015
    Seattle, WA
    an update:
    The first necks turned into "not necks", mostly due to under planning, over cutting, and a failure to verify that the jointer was, in fact, set at 90 degrees, not 87.5 degrees. oh well. My shop mate pointed out that I make the prettiest scrap he's ever seen.


    Those will become Jacob's Ladder toys once I'm done hand sanding all of the bevels.

    The new neck is hard maple and with padouk stringers.


    I cut the scarf at the headstock on the chop saw again. Still sketchy, still only needed a little clean up with a block plane to get that satisfying vacuum fit.


    The wings were glued on. I used a piece of laminate covered particle board to work as a splint to keep the wings lined up to the neck blank.

    I worked the bevels around with a shinto saw rasp and a few other abrasive tools. I thought about getting out the angle grinder to accelerate this work. Seemed like a bad idea.


    The neck taper was cut on the table saw using a simple sled. The headstock is a lot longer right now. I stopped the taper cut way short so I can form the headstock. Also missing is the block to be glued on above the scarf. I'm sandwiching a block between the fret board and the neck instead of gluing it to the back of the neck. This doubles the glue surface and should be quite a bit stronger. I'm a little worried about tension from 8 strings pulling things wonky. The Headstock block will need to be drilled and routed for truss rod access, that is still on the to-do list.

    Happy with the progress overall. The more I do, the more I'm sure a mistake at the end will hose the whole project. Maybe it will. The second attempt will go better than the first.
    Scoops, Slidlow and Matt Liebenau like this.
  6. Looks great. I have to do bevels like that on a build, I've never tried it.

    There is a lot of tension on an eight string neck. I recently took the strings off my eight string and was amazed at the amount of backbow in the neck without strings on it. That truss rod is doing its job! I have a pretty shallow scarf on that build and it's holding up fine.
  7. ctmullins

    ctmullins fueled by beer and coconut Gold Supporting Member

    Apr 18, 2008
    MS Gulf Coast
    I'm highly opinionated and extremely self-assured
    Don’t forget that, with the same strings, a 32” scale neck will experience less tension than a 34”.

    Body looks awesome! Love that look, but it must be fairly labor intensive, yes?
    Dadagoboi likes this.
  8. fenderfour


    Sep 3, 2015
    Seattle, WA
    I used stringtensionpro (String Tension Pro) to calculate the tension for 34" (the original design) it was almost twice what a standard 4 string would have. To counter this, I'm adding two reinforcement rods to the neck. I'd like to use Bruce's carbon TOW method, but I think I'm too far along on this build to change directions there.

    I read that thread on short scale 8's as I was designing this bass. So much good info there.
  9. fenderfour


    Sep 3, 2015
    Seattle, WA

    Yes, lots of work on that scroll. I estimate 16 hours so far getting it cut, beveled and sanded to100 grit. The inside surface is the most difficult. I had to make a bunch of sanding sticks of different sizes and shapes to get in there.

    I hesitate to call it a scroll bass since that name carries a few different legacies in the bass world.

    I will have to sort out a way to reinforce the scroll. That's good ash, but I still worry about dropping the instrument and splitting the scroll off.
    ctmullins likes this.
  10. fenderfour


    Sep 3, 2015
    Seattle, WA
    More work this weekend. I glued on the headstock plate, but I didn't get any pics of that step. The plate is glued on top of the main body of the neck, on a 10 degree scarff. Once the fretboard is attached, the plate will be sandwiched between t it and the neck. I'm thinking about dropping a couple of splines on it too. Maybe I'm over-concerned about the string tension. /shrug/


    Pre-headstock plate glue up: The big block at the near end of the neck is the glue surface for the plate. I cut the neck taper on the table saw and wanted to stop well short of the headstock so I can shape it correctly.

    Also above is bonding the carbon support rods in.


    After the headstock plate is glued and shaped. Side note: the Festool Carvex is an amazing tool. I didn't think using a jigsaw would ever be a "good experience". That machine was able to get through 2"+ of hard maple and held a straight and relatively clean line. I'm not sure I would spend $400 on a jigsaw, but I'm glad my shop mate did. It made shaping the headstock end of the neck easy.

    I wasn't happy with the headstock shape as originally designed. It had a little scroll in the corner, similar to an F-shape mandolin. It was delicate and added length to the instrument. A quick adjustment got to what I'm calling the "cowlick"

    I learned a lot with the neck build. I will not be using the same steps next time.

    Spent some time shaping the fretboard and dropped in MOP dots. I set everything on the body to get a look at it.


    I made a small mistake on the fretboard. You can see the carbon rod and truss rod slot peeking out on the bass side of the fretboard end. I wanted some more interest/color on the body, so I'm already working on a decorative cover for it.

    And then it was lunch time. Had to cut the baguette on the bandsaw.


    Until next time...
    Dadagoboi likes this.
  11. ctmullins

    ctmullins fueled by beer and coconut Gold Supporting Member

    Apr 18, 2008
    MS Gulf Coast
    I'm highly opinionated and extremely self-assured

    Looks great! I do think you’re too worried about string tension; on the other hand it never hurts to over-engineer things.
    fenderfour and Dadagoboi like this.
  12. Beej


    Feb 10, 2007
    Vancouver Island
    Dude, seriously, safety first! Where is your eye protection? :rollno: :rage:

    What about children who see that? Think of the children - won't someone think of the children?!
    fenderfour and Dadagoboi like this.
  13. fenderfour


    Sep 3, 2015
    Seattle, WA
    I didn't get much done this weekend. I spent most of saturday helping a blacksmith friend move some heavier parts of his shop. I now have an arbor press to do my fretting on. Two actually, a gigantic 5 ton beast and the more bench-top friendly 1 ton.


    I glued the fret board on and started getting the neck thickness where I want it before profiling. It was all about the big draw knife and a couple of planes. Lots of pretty shavings on the floor.

    lesson learned this week: Rough in all of the shapes before assembly. Reducing the thickness of the neck on the band saw would have been much easier. I could have made a jig to hold the entire bass on edge, but that seemed a little too sketchy for me.
    Matt Liebenau likes this.
  14. 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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