So I’m trying to make my own bass guitar which includes making a neck. Already I’m inexperienced and never had to actually think about truss rod length, type, and material but now I need one. The problem is my build is a little unconventional (hence I’m making it myself). The bass is planned to be 36 scale which means I have to move the bridge back and move the frets. The neck should stay the same size correct? would I need a stronger truss rod for the added string tension? What sizes are even normally used?
Enjoy the benefits of a premium membership!
Upgrade Account
-
TalkBass has been independent since 1998. Add your voice.
Create a free account to reply to discussions, view embedded media, and browse with fewer display ads.
Join free Log in
Want zero display ads or expanded classifieds tools? Compare plans.
How do I know what truss rod I need?
- Thread starter Harper Oliver
- Start date
Hello Harper;
I've recommended that your thread be moved over to the Luthier's Corner section. The Moderators will probably do that. We'll help you over there. We have many threads about the structural design of necks, truss rods, internal reinforcements, etc. And many project threads showing the construction of custom necks, including some extra long scale ones. We'll answer your questions and guide you along.
You can either make a longer body to be able to move the bridge back 2" or you can make a longer neck. Most 36" scale bases have longer necks than regular 34" bases.
The truss rod should be almost as long as your fretboard; the exact length will deppend on your paricular design. Any comercially available truss rod should be strong enough, you might have to adjust it a bit more but that's it, no need for something stronger than regular run off the mill truss rod.
The truss rod should be almost as long as your fretboard; the exact length will deppend on your paricular design. Any comercially available truss rod should be strong enough, you might have to adjust it a bit more but that's it, no need for something stronger than regular run off the mill truss rod.
Hello Harper;
First things first. You need to build the neck to be strong enough to handle the tension of the 36" scale strings. And you need to build it so it will be stable and won't warp or twist. Extra important on an extra long neck. This is all about careful selection and drying of the wood, and aligning the grain and rings as you cut it. If you do all that well, then a standard truss rod will be able to do its job easily. You cannot depend on the truss rod to correct a neck that's warping because it's built poorly.
Here's a thread that covers this subject:
About That Quartersawn Maple.....
My quick recommendations:
To build a 36" scale bolt-on neck, I would use maple in a 3-piece V-laminate form, as shown in that thread. Start with a flatsawn board, saw it into strips, and rotate and flip them to get the right ring shape. You can add two decorative ribbon strips if you like. You need to be careful on the thickness of the neck, not making it too thin. Don't go thinner than 0.800" at the 1st (fingerboard surface to back) and 0.950" at the 12th.
For the truss rod, I recommend one of the standard Double-Acting Double-Rod designs. There are different suppliers, but Luthier's Mercantile (LMII) will make them up in custom lengths for you. The length of the truss rod will depend on your design, but the working length should start between the nut and first fret, and end within a half inch of the back end of the heel. For a 36" scale 20 fret neck, adjusting at the headstock, that would be about 23 1/2".
Okay I see. So flat-sawn planks are going to have less chance of warping than quarter sawn. Also making sure the grain is parallel with the cut, using three pieces to dry evenly, and even a resin coat would help in this case.I’m assuming maple is going to be more predictable and stable in this case? Would Mahogany be too soft to be able to hold that tension reliably?
Mahogany is a lot weaker than maple. On an extra-long scale neck like this, from mahogany, I'd recommend adding some internal structural reinforcement. Some kind of vertical plates between the laminated strips, like aluminum or carbon fiber.
