Necks without truss rods

[rudy4444]

I PM’d Steven and this was his reply: “As far as I've seen none of the three 160-group basses (K160, 162, 5965) ever got the adjustable truss rod, or even steel reinforcement. Kay didn't fully embrace the standard truss rod till '62.“

Thanks for that information. Kay must have treated their basses differently than their guitars. It would be interesting to know why they handled the two classes of instruments differently.

 

[JParsons]

You can build an electric bass neck without a truss rod. But there's some significant engineering and risk involved. You have to build the neck so that it bends under the load of the strings, to a set amount of relief. And then hope that it always stays within a workable range of relief through temperature and humidity changes. And a range of string load, from different tunings or different gauge strings.

It can be done. But the risk is that, if it doesn't come out right, it takes some serious rework to correct it. Do you want to have to level or replace the frets if you change string types, or have some seasonal weather? The purpose of a truss rod is to give you a small range of adjustment to handle those small changes in the bending of the neck.

And it's not as simple as just making the neck much stiffer, adding carbon fiber or other reinforcements. Stiffness and stability are two different things. Making a neck stiffer does not guarantee that it will be more stable. Or that it will bend to a predictable amount of relief.

I understand that completely. That's why I haven't take the leap yet!
Ken Parker's video series on YouTube has been an interesting resource. He goes through the engineering behind his necks, including material choices and a full demo of how he installs his carbon fibre shell. He also goes over the evolution of his designs over the past 30 years.
Very interesting stuff.