Hi folks, About to start on a new build. It's going to be a mod of a mandolin body into a 3-string, 25.5" scale, fretted electro-acoustic. My last build went well but I get a buzz mid fretboard...unless I raise the action at the bridge...clear case of need for a "tetch" of bow in the middle. I am very VERY new to truss rods but I think that's the way I need to go. Single, double, aluminum, solid, carbon fiber, non-adjustable etc etc...which way to go? Are they easy to fit? Straight channel cut into neck? Bowed channel? How does one determine the length of the rod? Any hints in fitting one or designing the neck around one?

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  • Doublecheck while its strung up, lay a long straight edge along the frets between the strings that goes from the first to the last fret, there should be the tiniest bit of forward bow, an itty bit of sunshine between the straight edge and the middle frets.

    And use a much shorter straight edge covering 3 frets at a time.  It should sit flat and firm.  On a high fret that needs attention it will rock.

  • It sounds like the strings have bowed the neck after the strings have been attached. It sounds to me like the bow has happened too far up the neck.

    Think of it like this, you want a slight C shape bow in the neck running between the nut and the last fret (most times the string pressure will give this bow after the strings have been attached due to string pressure). To me it sounds like you have an S type bow or the bow only runs down to the 11th fret.

    You can correct it by leaving the guitar strung to tune for a couple of weeks to let he wood/guitar settle, then level the frets again. Now you wont have that slight bow we look for but it will/should get your string height down to a playable level that you can correct with bridge adjustment.

    Another consideration before doing this would b to switch to higher scale lighter thinner strings first before settling because they need less clearance from the fretboard as they 'wobble' less when you pluck them. They suit life better on a totally flat fretboard.

    Its just an idea, but i hate seeing an instrument sit there with a problem that hinders play.

    • I was wondering if the natural string tension would help give the bow needed. I'm going to let it sit for another week or two and see what happens. Still hard to know what to do for my upcoming one though.
  • You shouldn't need a truss rod on a 3-string hardwood neck. What wood did you use on your last build? Also, was your fretboard raised above the level of the box? Lotsa times, with a fretboard exactly level with the box, and no back angle 2-3 degrees) on the neck, you will get mid fret buzz.
    • The neck was Sapele and the fretboard was black walnut. Fretboard was about 6-8mm above the box. No back angle. Figured the back angle wouldn't make much of a difference because I can raise the bridge well above the height of the nut anyway.
      • Stable woods, normally. Hmmm. When you sight down the neck from the headstock (similar to Moritz' pic above), can you see the bow?
        • Don't have it in front of me at the moment, I'll have a look when I'm back home.

          To be honest I think the neck was VERY true...at least at first. I haven't checked the buzz specifically for a couple of days or so.

          I suspect it is bowing a bit but as to how much...not sure.

          Would a truss rod basically allow for adjusting these tweaks in and out as needed? I get so picky and these things bother me in an almost OCD way.

          Thanks for ALL your support everyone! It's very helpful!
          • Tom,

            Send pics: down the neck, side view strung up, showing nut and bridge height, as well as break angles at nut and bridge. We'll help you get it sorted.
  • There's a simplier alternative for stiff and solidly built necks, I learned Taffy Evans uses the same construction:

    306608682?profile=original

  • Sounds like you need to level the frets with a file on your last build to get rid of the fret buzz, most guitars do. Please see https://www.youtube.com/watch?v=mbShXHx6ejg and there is many more videos.

    I have been used this truss rod http://www.stewmac.com/Materials_and_Supplies/Truss_Rods/Adjustable... works great with a 25 1/2" scale the rod is 18 1/8" long 3/8" tall 1/4" wide. The truss rod goes from the nut to just past the 21st fret in length. The basic idea is to adjust the truss rod to return the neck back to flat as needed when the guitar is stringed and tuned. Most three string or four string guitars don't need a truss rod for the most part a good hardwood neck is all you need.

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