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Hi Kori,
Welcome to the group. I, also live in the "land of fruits and
nuts!"
I think you have it understood pretty well. I also want to have the
option of increasing buoyancy to neutral with a shot of air to purge the hard
trim ballast tank a little if I take on additional weight. Additional
weight could be from accidentally letting too much water in the trim ballast
or picking something up with the manipulator arm. If you don't have
an air purge capable hard trim tank, then the only option is to put some air in
the MBT. Once you do that, neutral buoyancy becomes a challenge if you
want to descend or ascend very much without surfacing.
Yes, to have larger hard trim ballast tanks is doable, just more structure
and plumbing required. They can be inside or outside the hull. If
they are inside, they have to handle internal pressure safely. If outside
the hull, they better be able to withstand the external crush pressure or have
automatic pressure compensating air available. If a large one
crushed at depth, the results could be scary and perhaps tragic.
It's interesting to note that those with actual pilot experience aren't
saying that large TB tanks are important. Leaving lead at home means you
have a smaller internal sub to start with and having large trim ballast tanks to
use when taking passengers just makes the sub larger (greater
displacement) to handle the extra load. The space in the tanks
is not functional for living or using for anything but buoyancy, weather you are
using them or not. In effect, what you have done is limit usable
internal space in single person mode in exchange for not carrying lead. If
you're pulling a 5000 lb submersible, another 180 lbs of lead isn't too big of a
deal. (Less than 1% of the total weight).
Gene
Central Ca.
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