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Hi Stan.
You wrote...."The Hunley had a pressure hull"
Just because you build a sub with a strong hull able to withstand pressure,
does not mean that you cannot use that hull as an ambient hull. You could build
a thick hull out of steel
with reinforcement hoops and still use it as an ambient hull if you wanted
to. Having a pressure hull does not preclude using it as an ambient hull. Just
having a pressure hull does not
mean it has to or is necessarily being used as a pressure hull until
you CLOSE OFF any means for water to enter the sub's interior. This is
the key thing I overlooked with the Hunley. You wrote...."I don't see anything ambient about the Hunley's
design".
I may well be wrong in thinking that the Hunley is a COMPLETELY
ambient sub, but she does have attributes and qualities of being ambient in her
design.
Let's analyze them.
1. An ambient sub allows water to enter its INTERIOR to dive. The Hunley
did this with her open top and open to the hull interior ballast tanks.
2. The water pressure entering the sub's interior when an ambient sub
dives, compresses the atmosphere in the sub's interior just as it did with the
Hunley.
3. An ambient sub uses air to force water out of the sub's INTERIOR to
surface, just as they did with the Hunley.
So, to address your statement, it is clear that just having a pressure hull
does not necessarily preclude being ambient, and the Hunley had at least 3
design features of an ambient sub. This is what confused me and made me think
she was COMPLETELY ambient.
In looking at it very closely I see where I was incorrect
in thinking she was COMPLETELY ambient. I realize my mistake and now
believe she was a hybrid with features of both an ambient and a pressure hull
sub.
Here's where I was incorrect in thinking she was COMPLETELY
ambient.
1. I did not take into account that the Hunley could CLOSE OFF her
ballast tank's valves and thus prevent outside water from freely coming in
without just using air pressure to keep the water out. WHEN the ballast tank
valves were CLOSED OFF
the Hunley SWITCHED from being an ambient sub (letting water into
her hull INTERIOR and compressing her atmosphere), and
became a pressure hull sub.
Ambient subs do not prevent the water coming in by a closing a valve
like the Hunley did. They are ALWAYS open to the water coming in and keep
it out by pressurized air pressure only. They have to use a pressurized air tank
in order to do this.
Since the Hunley did not have pressurized air tanks she could not do
this and deviated from what we consider to be ambient by being able to close off
any water coming in by closing her ballast tank valves.
When she SWITCHED from ambient operation to pressure holding by closing her
ballast tank valves, she became a pressure hull even though her atmosphere
was compressed and no longer at 1 atm.
Discussing the Hunley has taught me a lot. I have never seen a sub with
ballast tanks quite like her's. Also these discussions have taught me that so
called 1 atm subs are frequently not 1 atm and I think we need a new term to
catagorize
submarines and submersibles that more accurately reflects their true
interior atmospheric pressure.
I invite anyone to disprove that the Hunley did not have the 3 attributes
of an ambient sub I listed above, or to disprove that just because a hull
CAN BE a pressure hull, that it also cannot be an ambient hull and switch
between being ambient to pressure holding.
Kindest regards,
Bill Akins.
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