It was actually the second try at a CF tube. The first had flaws and issues and was either "repaired" or replaced by other manufacturing companies.

Reference to the repair/replacement of the cf tube: https://techcrunch.com/2023/06/20/a-whistleblower-raised-saf...

"The Spencer-built composite cylindrical hull either was repaired or replaced by Electroimpact and Janicki Industries in 2020 or 2021, prior to the first trips to Titanic."

I'd really like more detail on that tube's layup schedule.

Solid 5inch thick carbon composite OR a sandwich design with thick outer facesheets of carbon fiber? I suppose under that pressure not much would take the hydrostatic loads other than carbon, but that seems thick compared to everything I've seen made out of composites.

There are videos of them building it. From what I remember, they rolled carbon fiber around a cylinder, making the flat part of the cylinder. Then they mated two titanium half spheres to the end of the carbon fibre cylinder. This was done using some kind of "glue". Meaning that the middle part had no titanium.

I think it was in Sub brief YouTube video. https://www.youtube.com/watch?v=4dka29FSZac&pp=ygUJc3ViIGJya...

Thanks, I see now. Wow, that's a thick layup.

I saw a bit of video where they showed the construction- it’s a few inch wide band of carbon fibre wrapped around an inner tube like a spool of thread until it reaches 5” thickness.

Here's a write-up on the composite part of one of Oceangate's vessels:

https://www.compositesworld.com/articles/composite-submersib...

...since that article is from 2017, it is not clear that this was the unit that actually failed.

Very interesting. Ties sub tech to Steve Fossett, who was working with Scaled Composites before his death.

Not saying they are related at all but I am reminded of this:

https://en.wikipedia.org/wiki/VSS_Enterprise_crash