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Cliff,
I don't think bracing running lengthwise will do
much to prevent a sub from collapsing. You really do need rings to support
the hull. True, they can be either in the inside or the outside, but they
just don't look good on the outside, it's more resistance in the water and more
place for corrosion on the outside. I put mine on the inside and there
they make places to add things like brackets for equipment by clamping to the
ribs instead of welding after the hull has been painted.
I made T framing by rolling both parts of the T,
separately then welding them together. Of course the inner part is easiest to
role but rolling steel the hard way isn't impossible. I machined three
wheels with groves in them to fit the frame piece then mounted the
wheels on ball bearings and then on shafts. They were arranged
in sort of a triangle. The center wheel was adjustable to adjust the circle
diameter as I rolled it each pass and had a sprocket fixed to it that I
drove with a slow gearhead electric motor. It wasn't fancy but it
worked.
Once I had all the rolling done, I fabed up a jig
on a steel plate with a bunch of pins in a circle to weld the
T-frames together on. After that is was just push the
frames in the hull and rotate them into place them weld away! You may
have to jack a little and stager your welds to keep the heat from warping the
hull while your welding. It's good to stager weld the frames when your
welding them also.
If your just using A-36 steel, you can buy small
section I-beams and rip them down the center of the web and then role them as
they are. That way you already have T's to start. If you do this, be
careful to cut them EXACTLY in half and keep the height consistent down the
length of the piece or they won't role in a true circle.
Dan H.
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