Well OK, here's my two cents. I've been welding for 40 plus years, and am
still learning but for my sub, tig roots and stick cover passes.
This gives X-ray quality welds, minimum porosity, and takes a hell of a
lot longer to do.
Shielding gas on BOTH sides for the root.
For compressive welds like internal stiffeners, a stitch method works
best. You don't need continuous welds (and a continuous heat stress zone)
around the circumference of the hull when a simple ring is being welded
inside. As the pressure increases, the hull will shrink around the ring and a
little "give" here is a good thing.
Ideally, putting the completed hull in an oven would be good, but
expensive.
Minimize welds to the pressure hull by welding on
tabs, then bolting whatever in place rather than welding some big
"thing" on there. This also makes it easier to change or up-grade when you get
new ideas or need something extra for a specific task.
Don't build anything you can't get to later. Gotta be able to grind and
paint on a regular basis.
OK......that was more like 5 cents. Keep up the enthusiasm, and remember,
this is supposed to be FUN!!!
Frank D.