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Hi, Bill,
Myles - first, Myles, I'm not sure whether you are a certified diver or
not. I'll operate on the assumption you aren't (for the
moment).
[snip]
"You do not need to have a
jettisonable keel in an ambient by its very design. The ambient will have an
opening in the floor [not necessarily] or a trapdoor that you can
simply jump right out into the water" - depends on the
egress design. A crisis situation rarely offers the opportunity to "simply
jump right out".
I will have to take the opposing view here.
First, Bill, you are used to a wet sub where bailing is simply a matter of
getting out of your seat. In a dry ambient, there are other issues at
hand. It takes TIME to egress and it is a luxury to be able to do
so.
On a non-saturation, no-decompression dive, I
would NEVER, under ANY exception, consider not having ditchable weights.
My life was saved because of a free ascent from over 25 metres - the only one
I've ever had to make since 1974. I've been under ice, on wrecks, night
diving, current, kelp, yadda yadda. I used to work commercially
u/w.
That having been said, there are only
two exceptions I can think of. As I mentioned above, saturation
diving and the other is decompression diving. Dropping weight from 400
metres deep on a sat dive is a death sentence. So is dropping weights
after a "shallow" dive at 100 metres for half an hour with no bottles on an
anchor line for stops. Same principle, different application.
Other than that, there is NO diving system on this
blue earth that should ever neglect having droppable ballast
[non-military].
[snip[
Your body can safely absorb a certain amount of nitrogen and be ok,
but too much nitrogen (saturation) can make you feel high and is
disorenting and can cause you to
make mistakes like you were drunk and even make you pass out and drown if
diving. That comes from staying down too long and not watching
your diving
tables.
Sorry, Bill - will have
to differ again. Apples and oranges.
The too much
nitrogen you are referring to is called "rapture of the deep" or nitrogen
narcosis and it hits different people at different depths. This
does NOT come from staying down too long - it is a function of depth. It
is a neurological condition. Saturation in and of itself is not
necessarily harmful.
Tissue saturation, different from nitrogen
narcosis, IS a function of time as you pointed out. Myles can make
a bounce dive to 60 metres, have no tissue saturation and yet be
absolutely stupid from narcosis. Ask me how I know.
[snip]
With dive tables you know how long you can stay down pressurized
at a given depth.
As a general rule this
is mostly accurate. The tables have large fudge factors built
in. It is also dependent on the amount of fat tissue in the diver,
whether the diver is at sea level or in a mountain lake, whether the diver has
pre-breathed pure oxygen, taken medication, drunk alcohol, the diver is
male, female or a child, etc.
[snip] There are some who might say a jettisonable keel
would be good in a 1 atm sub, but I don't think you will need it in an
ambient
[snip]
in a situation where you
need to slowly offgas the nitrogen and the best thing to do is have oxygen
bottles on board to help decrease more nitrogen getting into your
system.
Three things:
- Ascent should always, again without exception,
be controlled. Dropping PARTIAL hard ballast will increase the
chances of surviving the dive by having an ambient submarine that
surfaces slowly. Think SCUBA and an ascent rate of 20 metres per
minute.
- Pure oxygen deeper than about one-atm (10
metres) will kill Myles and all his buddies. That would be
embarassing.
- Unless you have a surface recompression
chamber on the deck of your surface support vessel with licensed operators
on board, it's probably a good idea NOT to make decompression dives from
your dry ambient.
This presumes that your bottom time is well
within no-decom limits. Should you allow slippage into a decom dive,
then run into trouble, you are indeed in rather deep doo-doo, especially if
you are on the heavy [meaty] side. If you get into a fix prior to
slipping beyond the no-decom window, you can bail. Slip a weight belt
around your waist first.
[snip] So
rocketing an ambient sub that's hull along with your body is under pressure to
the surface with the sudden decrease in
pressure and resultant bends and decompression sickness can kill you or give
you health problems for the rest of your life.
Exactly - hence the CONTROLLED ASCENT with
partially droppable ballast made prior to slipping beyond the no-deompression
window.
Rick
Lucertini
Vancouver, Canada
----- Original Message -----
Sent: Friday, October 28, 2005 2:18
AM
Subject: Re: [PSUBS-MAILIST] Another
nutcase here.
Bill,
Thanks for that. So
basically, you get the weight you need via the keel. That makes
sense. Also safer too by having the keel jettisonable, up she pops
like a cork, as long as you're not too deep and "bend" yourself I
guess.
I have been following the hull
test threads very carefully.
I don't like the idea of being
exposed to the depth pressures, even if it's not very deep. I seem to
be particularly sensitive towards that. I can't dive / swim very deep
without my head wanting to explode (implode I suppose).
Still
thinking.....pondering....planning.
Myles.
----- Original Message -----
Sent: Thursday, October 27, 2005 4:50
PM
Subject: Re: [PSUBS-MAILIST] Another
nutcase here.
Hi Myles.
In overcoming the buoyancy of the hull
you might make an ambient heavy by filling its keel with lead,
bricks, concrete, maybe even sand, anything heavy for
ballast.
I've seen pictures where fellows who were
taking their sub out for its first test took a bunch of bricks along
and if they weren't heavy enough, just started loading bricks
into the sub's
bottom until they were heavy enough.
To use the same weight as you said to make a
pressure hull, you have to build interior hull reinforcement rings, have a
thicker pressure hull and also worry about the
roundness of the pressure hull and how much
pressure it will take. You have to worry about leaks and hull penetration
fittings leaking. You have to do an unmanned
pressure test like we have been recently and
presently been discussing in the group's postings.
The ambient design does away with all that by
simply keeping the water out with air pressure. Theoretically the
ambient hull outer walls could be as
thin as a beer can since the pressure inside
will be the same as the pressure outside. Of course you wouldn't want to
make one that thin because it wouldn't be practical,
but it would be possible to do so. There are
fellows here who build pressure hulls all the time, but it is much
harder to build a pressure hull than an
ambient one. Although
there have been wooden, fiberglass and
epoxy pressure hulls made for 1 atm subs that didn't go very
deep, they still are much harder to
build than a ambient hull.
The main advantage of the ambient hull for
scuba depths diving is that you can make it out of practicall any material
and you can make it in almost any shape you want
and do not have to make it spherical as most
pressure hulls are to maximize resistance against extreme external water
pressure. The main detraction of an ambient design is that
your body will be under the same
pressures as a scuba diver at whatever depth you dive to and have to
adhere to dive tables just like a diver does so you don't get the bends.
Also
as you submerge and increase the air pressure
inside your sub to equalize the outside water pressure and keep it out,
you have to pinch you nose and blow to equalize your sinus
cavities just like a diver does as he
decends. Also you cannot exceed safe scuba diving depths so you cannot go
nearly as deep as a 1 atm sub can go. But for shallow sub
diving
not to exceed a maximun of 130 ft, an ambient
design would be much cheaper and easier to build than a 1 atm
sub.
Bill.
----- Original Message -----
Sent: Thursday, October 27, 2005
4:18 PM
Subject: Re: [PSUBS-MAILIST]
Another nutcase here.
Rick,
Love it !!
I was giving thought to an
ambient, since my dive depths aren't going to be very deep, but, I don't
really understand how you can make them heavy enough to sink. If
you can, why not just use that weight to make a pressure hull instead
? It's not totally clear to me. I can get access to good
quality pipe and weld so, I just thought it would be best to go 1
ATM. (By the way, plywood here isn't cheap.). Your concept
of keeping the costs down has a ton of merrit though.
Myles.
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