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Hi Dean. I can see where a MBT malfunction can be frustrating at best, and
even scary.
I know that Superior is much like the ocean in many ways. In rough weather,
which can happen very quickly in Superior, an open ballast tank system could be
quite dangerous. Because most of my operations will be in the ocean, I've made
my ballast tanks mostly closed up with just holes in the bottom and all welded
stainless 12 gage for strength. I can imagine a scenario where the sub may get
flipped upside down or tossed around making an open ballast tank very risky.
Model testing showed the sub will flip back over and "right" itself quickly due
to the low center of gravity, but I lowered the center of buoyancy so I could
roll the sub on it's side ( slightly ) when submerged. The down side to this is
it will be less stable when surfaced and the ballast tanks are empty of water.
Even with the lower center of buoyancy, it won't flip on the surface but may
lean and wobble some if the swells are high or the surface is choppy. I don't
have a conning tower/hatch so the most freeboard I can get is about 24 inches,
and because the hatch ring sits in the center of the top steel hull dome, waves
could easily wash into the sub if It's open and the ocean is rough.
I'm planning on putting some type of inflated splash
guard up there but haven't finalized exactly what that will look like. Getting
pretty close on the design. So far it's looking like an innertube type
affair located under some stainless flaps to deflect wave wash around the hatch,
and rubber straps to keep it flat when submerged. ( might go with springs
instead.) This inflated ring will add top buoyancy when shallow in the
water column and in theory will be inflated just before I break the surface
after a dive.
The saddle tank set-up is the most stable side to side
for surface ops but it detracts from the submerged speed. You've got a nice "
deck space " on your boat and looking at the pictures it should be possible
to add a bottom "baffle" to your tanks. That will leave your windows clear of
obstructions but still give you the positive buoyancy so the ballast bubble
can't burp out if the dive angle gets to be too much. The baffle could be placed
half way up in the open tanks with holes open on the bottom so half the tank
would be closed off giving you enough bubble to bring the nose or tail up. An
internal sliding weight like the one I'm putting in could help too. Because it's
inside under the floor it won't get beat up or exposed directly to salt water or
pressure and will be fairly simple to do maintenance on, or
operate manually if the electric actuator fails.
There's been some discussion of inflated MBT's and there
are some good advantages to that. You'd be carrying less weight so
starting/stopping would be improved, and impact force would be decreased if you
hit something or had to stop quickly.
Like you said, your open water testing will show what works well and what
needs a little re-work this winter.
Looking forward to hearing about your test runs. Sounds like a lot of fun.
Frank D.
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