Thom wroteColonIf we go back to the floating aircraft island concept, a ship that large need never come to port if it is tended by a support fleet and/or an airship! It can hide out in the North Sea acting as a mobile base for several raiding flights. If it does have to port for some reason, then it could do so under cover of night, slipping into it's secret fjord, then hidden with camouflage netting.
This is the reason I could never see pirate organization using such a thing, only a national government... and then only one that can dredge up >$12,500,000 dollars
* in period currency (the rough purchase price of a Fletcher
class destroyer) to fund the hull alone, and which possesses a location suitable to build it, the technology to maintain it, and the manpower to crew it. Only Great Britain manages to fit this requirement, or perhaps a 'Scandinavian Alliance' arising as a new power in the face of the calamity surrounding them.
I've never actually seen an actual concrete vessel (that I am aware of, anyway) though I have seen several canoes made of it. They are a popular engineering project for colleges, and I have lived near one college campus or another most of my life. I just knew that there were efforts during both World Wars to build merchants with alternative materials, and concrete was one of the more successful ideas. It seemed just realistic enough to manage, while just far enough to one side of reality to make things feel alien.
*This was an estimated cost for the vessel's hull- it would certainly be much higher once you figured in the ships fitting out, the labor costs, the project overruns, etc.