We don’t manufacture the tether cable ourselves (it comes from a supplier), so I’m not certain.
For reference, here’s a photo of our tether. I’ve cut it at different points to show the different materials and sections, and tried to group together the fibers and wires to make it clearer what is what:
From an efficiency standpoint it would make the most sense to me if the foam jacket is applied continuously as the cable gets assembled, so I would naively assume that’s what happens, but can’t guarantee that it’s actually the case. It’s also possible the sheath gets wound around the bundle, followed by a separate stage where it gets wound onto a reel as the foam is deposited onto it.
If it was done in sections I imagine there would be some form of irregularity at the joining points of subsequent sections, which is not the case from what I can tell, so that’s at least some evidence that the jacket is likely applied continuously.
Again, I’m not sure, but I imagine the centering is done by maintaining a constant tension on the wires and fibers as they get pulled through where the foam jacket is being applied.
The foam is the jacket.
I’m not sure, and it’s very possible our supplier wouldn’t share that information with us even if we asked. They make and sell a product to a specification, and how they achieve that is up to them. While I agree it’s intellectually interesting to learn about these things, I suspect that the exact formulations and processes they use are likely “trade secrets” to avoid others underselling them by replicating their work without needing to put in (and pay for) any development effort.
As above, the foam is the yellow jacket.
Given we don’t provide any strict buoyancy values (and buoyancy varies by water temperature and density anyway), it wouldn’t surprise me if some water absorption is expected at depth. It has been mentioned previously by some users as a phenomenon they’ve noticed occurring.
I’m not really sure what you mean by this. A tether is a passive component, so if it’s precisely neutrally buoyant at the start of a dive, and has absorbed some water by the end of it, then it must be slightly negatively buoyant at that point (assuming that the water temperature and composition remain unchanged throughout the dive).
Given the fluid density is not guaranteed to be maintained, the buoyancy of an object in that fluid is already not a fixed property. Presumably that’s partly why minor density changes of a tether are treated as an expected part of operation rather than a design/manufacturing flaw 