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Hi Hugh. I can't remember the hatch cover radius, but it's a 20 inch dome
with a 3 inch rise in the middle. I used a 1 inch thick by 2 inch wide flange as
the hatch base, with a 3/16 groove cut in for the O ring. That 1 inch flange
mates to the 1-1/2 inch hatch-ring flange and has three locking dogs. It weighs
about 85 pounds including the three bars on top. Two for the hinge and one for
the leaf spring not yet installed. The dome is made from the same steel as the
hull-AS 516-70. The thick rings are regular mild steel. I couldn't find any
heavy sheet in the 70 series steel.
I've almost given up using stick for welding, and TIG most everything. It's
a lot slower but the time saved chipping, grinding and cleaning makes up for it.
Plus the welds are easier to see ( Ya, getting old! )
I've got an old sketch of the stiffener ribs around some where and when I
get a chance, I'll post it. At one point I was going to use both inside and out
side ribs, but decided I prefer the inside better. The room taken up by the ribs
isn't really noticeable inside, and compression is a little stronger than
tension. Outside ribs are another thing to create drag as well.
I can relate to the "janitor" story. Often over the years, problems with
design have popped up, and the engineers will spend weeks trying to figure out
what the hell's wrong. At some point, they always ask the welder or carpenter on
the job what he thinks, and more often than not, a solution is found. Not by
lofty designs, but by common sense, and experience. I think some times people
get too wrapped up in the complexities and can't see the obvious.
Getting the FEA on your windows is a good idea. Mine are pretty simple and
follow the basic design, but with a slight addition. I'm adding gussets to the
inside where the base flange meets the window ring. Again, a little more steel
can't hurt. I did a job for NASA a few years back, on a pressurized wind tunnel.
At the time it was very hi tech and the windows on the test chamber were
like something from a Star Trek movie. The plexi was 6 inches thick and some
special kind of NASA plastic. Our little windows are very similar, except they
had gussets on their's. I liked the way they looked, so will use that option.
I'm sure those NASA engineers spent several million designing those little
windows. Must be awfully nice to work with tax dollars, rather than your own
check book. Frank D. Get trade secrets for amazing burgers. Watch "Cooking with Tyler Florence" on AOL Food. |