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Hi Frank, What flow rate into the back shield box do you recommend. Also I
recall some tape that you used to be able to put on the back of a weld. Is
that still around and was it any good? From memory it used to help support the
occaisional exuberant puddle. As you say TIG is best for the root run. Weld
gap, Wire size and approx current setting for various thicknesses would be a
great help. We may as well bleed you for as much info as possible. Chs, Hugh From:
owner-personal_submersibles@psubs.org
[mailto:owner-personal_submersibles@psubs.org] On Behalf Of ShellyDalg@aol.com Hi Glen. The wire James recommended is good stuff and will work
fine. The process of welding a pressure vessel is a little complicated and
there are a few things to keep in mind. Make sure the groove is very clean and uniform in profile. I would
recommend TIG welding the "root" as this makes a clean beginning for
subsequent weld beads. Pre-heating the base metal before welding is a good practice. It
helps make strong welds, and minimizes stress build-up. Use spacers/struts inside the hull to help maintain
"round" while you weld. Using gas coverage on the back side of the weld also helps to keep
the weld clean. A simple box made of sheet metal attached to the back side with
tape or magnets, and filled with shielding gas works well. Just big enough to
cover the section you are welding. Then after laying down the weld bead in that
area and letting it cool down slowly, move the shielding box to the next weld
area. Continue the gas flow to the box until the weld has cooled some what to
prevent oxygen from contaminating the weld bead. Grind/clean the beginning of each weld where it meets the previous
weld. Most "inclusions" occur at the start/stop zone. Take your time doing "fit-up" and keep the base clean. Welder "position" is important too. It's much easier to
make a good weld if you are in a comfortable position. Welding in the
"flat" position is best, as gravity works in your favor. Practice a little before each welding session, and try to stay
comfortable. It's easier to make uniform welds when the position and machine
settings are the same. Don't get in a hurry. Take your time. Be comfortable. It will be a very rewarding experience and you'll feel good
knowing your welds are strong. Remember, your life depends on that. Good luck
with your project, and send us some pictures. We love to see the process of a
sub being built. Ask lots of questions, and have FUN! Frank D. Great
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