This post could serve as a test how long it takes for good ideas to hit ground.
SpaceX now is using single stainless steel sheets welded into narrow cylinders then welded together to make long fuel tank.My proposal is to use single tape like steel sheet welded spirally. One continuous weld , one sheet to create long cylinder.
Edges could overlap few cm ( iches) and double weld increase strength, prevent leaks.
Now we could wait and count how long it takes for good ideas to been implemented ( after being rediscovered independently)
In our case whole fuel cylinder can be welded quickly and cheaply in horizontal position on gigantic machine.

www.space.com/spacex-starship-prototype-first-2020-flight-soon.html

The same method could be used to stack reinforcing blocks in drilled by Boring company tunnels.Instead of consecutive cylinders, lets do spiral.


www.teslarati.com/elon-musk-spacex-starship-production-well-underway/

" Spiral way" could be also used to create huge structured in space for future space station. Rolls of steel could be welded spirally to create large airtights cylinders. Roll is easy to fit inside rocket compartment for transportation into Earth orbit.