[_yb2s]

Yes, this doesn't make sense to me either. I suppose it could help prevent bucking and crack propagation, because as the walls of the sub started to bend, one side would have to suddenly be in tension? Still, I wonder if a pure plastic/epoxy hull would have actually been stronger than composite in this situation.

[marcosdumay]

From the design they published of it, I do really think they intended to have the carbon fiber tensioned between a pair of titanium rings.

I understand epoxy doesn't deal well with that, but with the right plastic, I believe it could work very well.

[_yb2s]

It is a carbon fiber tube with a hemispherical titanium cap on each end. The caps push inward under pressure putting the carbon fiber hull under compression, not tension.

[johnwalkr]

That would only be possible if the rings were fixed relative to each other, which they are not.

[marcosdumay]

Yeah, you are right. It's not tensioned between the rings then.