Hello and good morning nation!
I have been building solid CBG style guitars for the last 3 to 4 years now and in all my builds, I always install a non-adjustable truss rod into the neck. Usually 1/4 inch thick metal rods.
The reason I do this was from watching too many manufacturing videos on how they build guitars and how they install truss rods. I figured I must be doing the right thing. My ignorance tells it reinforces the neck.
However, I saw a video from a Fender authorized shop, and the builder was installing a truss rod. And to my surprise, the truss rod was a flimsy wiggling thing, like a string of spaghetti.
I understand the truss rod is to settle any bowing that the neck may accumulate over time. But what about reinforcing, does it reinforce? Am I wasting metal rods?
I saw acoustic guitars built too and they get a nonadjustable permanent truss rod shaped like a T.
Hi again IG, thanks for coming back, It's always good to hear how members' suggestions benefit others.
One thing that is also important in designing a stable neck is grain orientation. I always use neck material that is sawn on the quarter from the log, for full size and CBg style guitars. This is a way to add resistance to string pull when not using a rod.
In the photo, you can see what I mean if it ain't like that I'll come back another
day and pick the eyes out of the stack.
The other photo shows how I would oppose the grain to get stability from timber cut just off the full quarter...
And of course, a nice stiff fingerboard also helps.
I should mention that not all Maple necks are quarter sawn. But that is a hard and pretty stable species.
A simple metal rod does not offer much reinforcement. As mentioned, an adjustable metal rod laid into an arched channel can be tightened to introduce some back bow. Watch a YouTube vidoe of someone cutting a channel into a Fender style neck.
If you install a two way truss rod that can bend both ways, you can just cut a simple straight channel that need not be arched.
If using a fixed truss rod or beam, there are lots of choices in aluminum or carbon fiber. As mentioned, a bar on edge has a wider profile and more rigidity than a square or round rod. It's also easier to route a square edged channel and fit it in tightly than a chaneel to house a round rod.
Another way to stiffen the neck is just add a 1/4" fretboard. That makes the whole neck thicker and stiffer. If you shape the back, you don't have to worry so much about removing too much material.
If you put in any kind of rod, it should fit in snugly for the best function.
Another option is a laminated neck. Instead of one piece of wood, glue 3 or more together and cut to size. The varying grain directions make it stronger and stiffer than a single piece of wood. This is sometimes used on full sized bass guitars without truss rods. It can also be really pretty!