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SBO 23 - The Long Black
- Thread starter Alex Xander
- Start date
I use shrink wrapped truss rods, so there's not not much of a need to break them free, but the intention isn't to have a truss rod that is glued into the neck, but to have one that sits in a channel where it is a perfect fit. From the perspective of an engineer (somewhere I do have some credentials) rather than that of a luthier (where I am very much work in progress,) bedding provides a more uniformly distributed load, rather than a point load, especially when routing a square bottomed channel. A uniformly distributed load with be more conducive to providing a consistent neck relief profile than a rod in not so snug channel. It should also be stiffer, with all else being equal.
@Bruce Johnson will weigh in with his wealth of lutherie experience, I'm sure. He is the oracle on this stuff
Alex Xander's got it. When you embed the truss rod in epoxy, the epoxy is completely surrounding the truss rod, in full contact with it everywhere. When it "breaks loose", all it's doing is sliding within that tight sleeve of epoxy. It's not opening up any gap between them. And the truss rod only moves a tiny amount as it goes from loose to tight. Maybe 0.060" at the threaded end, tapering to nothing at the anchor end.
The epoxy shell keeps the truss rod in solid contact with the wood. This allows the truss rod to do its job bending the neck better, because there's even load distribution and there isn't any freeplay to take up a gap or begin crushing the wood. It applies load as soon as it is tightened, and the adjustment is more predictable and accurate.
But the main reason why I embed my truss rods is to improve the sound of the bass. It gets complicated, and I'm not going to get into all the details here, but fully surrounding the truss rod with epoxy forces the wood and metal to vibrate together as one, combining their stiffness and strength and damping properties. In ways that I can control and predict. If there are gaps between the wood and the steel, then they won't necessarily vibrate together, and it can get messy.
I won't get into the full explanation here, but embedding the truss rod can bring out the clarity of the deep bottom end of a bass, while still allowing the neck to flex enough to bring warmth in the mid-range. It allows a happy compromise between a stiff neck and a soft neck.
12 months ago, I started gluing this beefwood together, but ended up going another direction for the build off. The body wings and solid ebony neck sat on a shelf for a good while until I pulled them out recently.
The bass (a piezo only 37” scale bass with flatwounds) is almost complete.
Here’s a sneak peak after a few coats of oil. Please ignore the butchering in the bridge cavity for the piezo wires. It will be covered for good once the bridge goes on.
I just have to finish this before the SBO starts. More to come soon 
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Sleek and super clean. Bookmatched lacewood on ebony. *chef's kiss*
Beautiful!
Beautiful!
Finished just in time for the next build off to start.
It’s a little bright, so I’m going to try and wire the preamp with cut only treble and boost only bass knobs.
Aside from that, I’m pretty damn happy. It was worth waiting a year to finish this one.
It’s a little bright, so I’m going to try and wire the preamp with cut only treble and boost only bass knobs.
Aside from that, I’m pretty damn happy. It was worth waiting a year to finish this one.
