For Patrick and Joe.
Joe is right Patrick. That is ONE way to do
it. As Joe described, by having a constant flow of air going into the hull's
interior from the air tanks and exhausting any
extra internal air pressure outside (by using an
overpressure valve) if it is not needed to equalize against the outside water
pressure. I assume this is how Rick and Joe are keeping their hull interiors
almost completely dry.
I did not realize Rick and Joe were using constant
air flow in their ambient designs. Now I see why their hull interiors are almost
devoid of water vapour.
I say ALMOST, because there is still some
condensation that can form inside the hull interior from the moisture in
the air that was inside your hull before you closed the hatch. This
forms
water droplets inside the hull due to temperature
level drops, just as water forms on the outside of a cold glass of icewater.
This can happen in a 1 atm sub too.
As Rick pointed out earlier this can be handled by
dessicant absorbant which is a powder which absorbs water.and
basically wicks water out of the air. The air in their tanks is much
dryer than normal air also so this helps too.
However; this method uses a lot of air with it
flowing constantly. This would be fine if you have a diesel running an air
compressor to replenish your air tanks on the surface. Not so good if you are
just running
electric and using finite air tanks. Suspose you
are at the depth you want to be and are no longer descending. You just want to
run horizontal. Now there is no increase in external water pressure. But in the
system
Joe described your air is still constantly flowing
and any extra not needed to equalize the hull is exhausted outside. You can see
this wastes a lot of air that you are not using for breathing.
So there are a few different ways to equalize your
ambient hull against outside water pressure by using internal air pressure
Patrick. Some designs have the operator
completely dry and breathing from the air that was
in the hull when the hatch closed, and then when it becomes stale he can breath
from a scuba regulator.which exhausts his co2 outside the hull via
a tube and one way exhaust valve. Or he can just
start off breathing from the scuba regulator and keep the cabin air in reserve.
Some designs just have you breathing from the air in the hull without any
provision for breathing
thru a regulator and when the cabin air becomes
stale you have to surface. It's a good idea to take a spare air small bail out
bottle with you for emergencies though.
What all ambients have in common whether they have
an opening to the water (like in an upside down glass) and use the rising water
level to trip a float, valve or sensor
which then activates their air tanks to vent,
or whether they are closed to the water and use a
valve or sensor, is that they use internal air pressure to push back against the
external water pressure. Thus removing the need for a pressure hull at
shallow depths. The thing is Patrick, there is
more than one way to skin a cat with ambient designs.
Bill Akins.
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