The actual process to make CF is first the design is made. The shapes of the fabric are pulled right from the model, and cut on a cnc gantry machine (or by hand in small shops), then laid up in a clean room with resin in molds made on the CNC.
From there it goes into an autoclave after being sealed in a plastic vacuum bag. The autoclaves typically run a top secret curing program. Every shop has their own "recipe".
During this process, the CNC machines are tasked to machine another mold, but this time with grooves cut around the inner profile of the part, and around any holes, where you insert foam vacuum seal.
After the part leaves the autoclave, it is sent to the CNC department to machine in the vacuum mold.
All of thes above processes are done to make flat sheet, shapes, and full blown parts. The flat sheet molds are of course just flat sheets of tooling board, but the entire process is the same.
But...
A c-channel made out of carbon fiber would have no bend in either direction because the layers would also wrap around the C, creating a weave in two directions. Unless you are talking about machining it into a C-channel? Then yeah, that would be a worthless endeavor.
We made carbon fiber I-beams for a few military projects in the carbon fiber shop I worked at that did exactly that. We alse made a LOT of C-channel rails used in helicopters and other aircraft, like wing spars for drones. Trust me, it does not bend in any direction. It will twist, but not bend. And crossmembers would solve that twisting. Which we did use in a lot of our assemblies. C-channels, tied together with c-channels. Much like an automotive chassis.
And the cost to manufacture would not be much more than flat sheet, but that is doing it in house. You only have the additional mold and cutting mold to make, which could be done in a couple hours each at most, even if the rail curved in 3 dimensions.
But you can make carbon fiber at home. It's not difficult. So no reason a small machine shop couldn't take that on. You just need a vacuum table to pull the air bubbles out of the resin and an oven to finish cure it. An autoclave would do the job all in one. Small ones big enough to make a hundred or so of these rails wouldn't be terribly expensive. You can buy small ones for use at home for less than a couple hundred.
I made the mold for this cockpit area (if you want to call it that) start to finish my first day on the job. It's actually the electronics cover. We built this entire drone in-house in about 2 months and there are carbon fiber c-channel spars running through the wings. You could have a guy standing on each wing tip.
The actual process of laying the weave as well as time in the autoclave to cure the resin would be almost identical for flat sheet or c-channel. So in the end, the only difference is making the molds. Which as I said, wouldn't take long at all.
And the actual machine time to machine the c-channel rails vs the flat rails would probably actually be a lot less time cutting the c-channel, because you're only driving one tool down one face, as opposed to driving around the entire profile.
