|
Hi Dan.
You asked..."wouldn't you need to spend quite a bit
more time in the sub after you did your thing to depressurize which would make a
scrubber and oxygen system a necessity?"
You would just follow the normal dive tables for
offgassing the nitrogen from your body just like a diver does. The amount of
time it takes for you to offgas depends on how long you are down,
what mix you are breathing and at what depth you were at. So lets say you saw something from
your sub you wanted to inspect or retrieve. If you were only outside the sub a
very few minutes the nitrogen would not have time
to saturate your tissues and you would almost need
no time to offgas nitrogen from your body when you returned to the sub and
reconverted the sub to 1 atmosphere. The nitrogen saturation
would be lessened if you were breathing a nitrox
mix which has a higher percentage of oxygen than
normal air. Depending on the depth however, if
you stayed longer outside the sub, when you
returned you would
have to offgas the required time stipulated by your dive tables. As long as you reconverted your sub back to 1 atmosphere from
ambient, you wouldn't need a pure oxygen system
since your sub's atmosphere is now the same as the
atmosphere topside. Having a small pure oxygen bottle on board is a good idea
though since by breathing a small amount of pure oxygen when
offgassing nitrogen you speed up your decompression
time. But you have to be careful with pure oxygen and not breath it too long
since it can be toxic if you do.
If you converted your sub from 1 atmosphere to
ambient for the purpose of escaping from the sub and going topside, as long as
you did not stay in the ambient atmosphere but a few minutes before
you
bailed out you would not have any nitrogen buildup
in your tissues and could go right up without any decompression time. Remember
that when in the ambient atmosphere of your sub you are subject to the
same
pressures and nitrogen buildup as a diver outside
at that same depth. When bailing out never rise faster than your bubbles or more
than 1 foot per second for safety.
If you find yourself in a situation where you have
no control over your accent and are rising faster than that, yell as hard as you
can to expell the expanding air from your lungs to avoid them
bursting.
This could save your life.
I would recommend anyone operating a sub to become
a certified diver. I would say it is a must do. Diving teaches
you procedures that could save your life if you had to bail out of a
sub.
It isn't that hard or expensive and takes anywhere
from 1 to 2 weeks depending on how often your classes meet. It will run you a
couple of hundred dollars and is a good investment in safety and
knowledge
for anyone operating a sub.
Kindest Regards,
Bill Akins.
----- Original Message -----
Sent: Tuesday, April 26, 2005 8:12
AM
Subject: Re: [PSUBS-MAILIST] Converting
from 1 atmosphere to ambient for escape?
Interesting Bill! Very
interesting!
I must admit, designing a bottom hatch for divers
exit never came to my mind when building my sub. As far as doing this on
a Kittredge design sub, it would require quite a bit of
modification. There is only about 12 inches between the battery pods and
in that space already there is a variable ballast tank and two long slender
drop weights. I'm sure it can be done my moving things around some
though. You can add a few extra pounds of weight, maybe a 200, to the
design as still have enough buoyancy. Right now I carry, me at 160
pounds and an additional 395 pounds of removable lead.
I think the biggest draw back to this idea is the
amount of air you would need to carry on board to pressurize the whole hull to
reach ambient. In shallower water not a problem. Also, and I'm not
a diver so I'm not familiar with the details but, wouldn't you need to spend
quite a bit more time in the sub after you did your thing to depressurize
which would make a scrubber and oxygen system a necessity. I guess if
some small subs have diver lockouts they must have scrubbers and do the time
required inside the hull afterward.
BTW, Sorry Bill, if I got you in the position of
being perceived as anti Scuttle valve. That thread has floated around
here before with some opposition to it's value in a sub.
Keep thinking, your an asset,
Dan H.
----- Original Message -----
Sent: Tuesday, April 26, 2005 5:49
AM
Subject: Re: [PSUBS-MAILIST] Converting
from 1 atmosphere to ambient for escape?
I forgot to mention. If you have the room
for a diver lockout CHAMBER, you also have a built in
flood/scuttle valve. If you left the diver lockout chamber door open to the
hull and flooded the chamber, you flood the hull.
The above is assuming you DON'T have a
chamber door safety switch which made sure the chamber door was
fully closed and latched before the flood
valve could work, or you disable said switch.
You can also make a small 1 atmosphere sub have
a diver lockout (without a chamber) by pressurizing the interior to
equal the outside pressure and opening a lower hatch to escape as in an ambient sub.
Therebye changing your small 1 atmosphere sub
into an ambient sub for either diveing purposes or escape.
If you used this for diving purposes you could
reenter the sub, close the lower hatch, then let off interior air pressure
and change it back to a 1 atmosphere sub.
Small size interior space does not
necessarily preclude a diver lockout. Just become
ambient.
I wonder if anyone has built a 1 atmosphere sub
that converted to ambient and back again? The neat thing for diving
with it would be you could start offgassing the nitrogen from your body as
soon as you converted the sub to 1 atmosphere again
so you could stay underwater in the 1
atmosphere sub and offgas, then convert the sub to ambient and go out again.
I wonder how hard it would be to install an internal bottom hatch on
the Kitteridge 350 and pressurize it to ambient and back to 1 atmosphere
again?
Just more alternatives. I
like this forum as a sounding board for raw sub ideas that we can tweak
into workable ones. Some sub ideas might need refinement, more
discussion, or wise deletion, but none are stupid.
Kindest Regards,
Bill Akins.
|