Double Neck U-Bass/Nylon String Design

Discussion in 'Luthier's Corner' started by nonoknapp, Aug 15, 2019.


  1. nonoknapp

    nonoknapp

    Jul 18, 2019
    STL
    Hey all, I spent a lot of time here as a teenager learning as much as I could about luthiery. It was an invaluable resource then as I'm sure it is today. I am studying 3D modeling and drafting, and have access to a CNC and ample woodshop through school. I do live looping performance using a Boss RC-300 and have been kicking around the idea for a U-Bass/Acoustic guitar double neck based on a modified Godin MultiAc design. I think it might be ideal for that context but I could use some input on the design before I start more detailed modeling.
    Doubleneck Looper Front.jpg
    First off, I'm considering moving the guitar scale toward the body end of the guitar so the nuts of the two necks are lined up. I figure this will help with balance, ease of strumming the guitar half, and overall size.
    Doubleneck Looper.jpg
    Next, the chambering. This will be used amplified only, so the chambering is just there for weight reduction. Does the current lattice look structurally sound under a .25 in. Spruce/Cedar top? Do you think a support under the bridges is necessary?
    Doubleneck Looper Rear.jpg
    Finally, I am kicking around the electronics. Definitely a piezo in each, two seperate preamps, a toggle switch between the two, and a killswitch. I am considering making the guitar portion a steel string instead of nylon, and throwing a lipstick pickup in for flexibility/leads. Also mounting a piezo under the top somewhere in the lower bout to use as a percussive instrument.

    I would appreciate input on any/all of the questions here, and any other ideas you may have. This is a pretty niche instrument, so I'm really just designing out of thin air and whatever specs I could scrounge up from the relevant instruments.
     
  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
    You had me at “doubleneck”. :cool:

    Personally, I wouldn’t line up the nuts, but my opinion is just from an aesthetic point of view. If you want to test ergonomics you could mock something crude up with plywood or foam or something disposable like that.

    Your chambering looks fine to me. You didn’t say what wood you planned on using for the back, but as long as it’s structurally sound (no obvious voids or cracks) it’ll be fine. Ubass strings are very low tension, right?
     
  3. Since it's electric only, I would make the bodies a bit smaller just for ergonomics sake. What is the width of the instrument at the widest spot? It looks wider than it needs to be, but it's probably not as big as it looks considering the short scales involved.

    This is a cool project - looking forward to seeing it go forward!
     
  4. nonoknapp

    nonoknapp

    Jul 18, 2019
    STL
    That's a good point, I figured it might look a little awkward. And there's plenty of empty space to adjust the balance point if need be.
    The ubass portion should be pretty low stress, from what I understand it uses chubby nylon type strings. Im going to use a 1/4 in top so I think the guitar portion should be pretty sound as well.
     
    ctmullins likes this.
  5. nonoknapp

    nonoknapp

    Jul 18, 2019
    STL
    Thanks for the feedback. I think its pushing 22 in right now, I'm going to try to adjust where the bouts join the neck and see if I can shave off 4-6 in of width.
     
  6. nonoknapp

    nonoknapp

    Jul 18, 2019
    STL
    Put in a little more work, body is down to 18" wide, fretslots are added and the neck the neck bases/cavities were added/cut. Thinking about dual soundholes, what do you think?

    Before
    Doubleneck Looper Front.jpg

    After
    Doubleneck Looper 1.1 NARROW.jpg
     
    steelin4u and ctmullins like this.
  7. Slidlow

    Slidlow Supporting Member

    Apr 15, 2009
    Oshawa, Canada
    Angle your necks in a little at the bridge and use a single piece bridge ala harp guitars.
     
    nonoknapp likes this.
  8. ctmullins

    ctmullins fueled by beer and coconut Gold Supporting Member

    Apr 18, 2008
    MS Gulf Coast
    I'm highly opinionated and extremely self-assured
    Nice, I like those "phases of the moon" sound holes. :thumbsup: One set or two, they both look good to me. Of course, it will depend on your plan for knobs...
     
  9. 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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