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Hi David,
I'm not an expert on domes. I read the relevant parts in
the Stachiw book & Brent has sent me a lot of diagrams wich I'll forward to
you.
I have a 500mm dome 10mm thick, a 500mm dome 3mm thick
& are getting a 500mm x 25mm thick blown dome made up. I may end
up with 2 x 25mm thick blown domes as the guy making it
was't 100% happy with his first attempt.
I am having the flange trimmed to 10mm & mounting it
in a block of acrylic & fiberglass. Then attaching my closure mechanism
& hinges
directly to this. I have done a bit of mold making,
casting & fiberglassing in the past, so thats why I'm going the way I
am.
With the 10mm area of flange keyed into the fiberglass the
dome won't lift off wich is a problem in shallow water. The block of acrylic /
fiberglass will also support the inner bend of the flange
wich is a weakness.
Anyway I'll be able to test this out a bit with all these
domes.
I've been going 1atm, ambient, 1atm, ambient, 1atm over
the last year. I don't think its a lot cheaper going ambient. My 25mm thick
blown
dome is costing $1000- NZ this should be good for
operating to 250ft. The 10mm thick dome cost $128- NZ.
Like you I'm building to a budget, fortunately I'm not
married anymore so can happily throw what little money I do have at the sub
without
being made to feel severely guilty.
Can relate to the need to do something practical on this
project. There is so much reading / research to do & its good to do
something
practical that makes you feel you're progressing. Will
send those diagrams off site.
Alan
----- Original Message -----
Sent: Tuesday, August 18, 2009 7:33
PM
Subject: RE: [PSUBS-MAILIST] Ambient
running on nitrox
Alan,
I see my ambient as a stepping
stone. I would much rather make an ambient than perhaps never make a sub at
all.
My compass would work in an ambient!
How
big is your acrylic dome and does it have a retaining lip built on? I am
having trouble seeing how to deploy the one I have at
resent.
David Bartsch
From: alanjames@xtra.co.nz
To: personal_submersibles@psubs.org
Subject:
Re: [PSUBS-MAILIST] Ambient running on nitrox
Date: Thu, 13 Aug 2009
15:24:57 +1200
Hi Jay, Thanks again,
The ambient sub is now dead & buried. I'm
considering using my acrylic dome as a gold fish bowl.
Had done research on oxygen toxicity & was
aware of my parameters to avoid central nervous system
toxicity & pulmonary & ocular toxicity. I
was intending to have O2 monitoring but as you advised,
they
can be suseptable to moisture & in an ambient
there is more of that.
As said, the main flaw in this plan was the fact
that When you got in, it would have a normal O2 concentration
& so if you cruised under the surface
you'd very quickly deplete your O2, with no nitrox comming in.
Also the fire danger.
It's great to be able to submit these ideas &
have them critiqued. I thought I was on to a winner there.
Regards Alan
----- Original Message -----
Sent: Thursday, August 13, 2009 11:38
AM
Subject: RE: [PSUBS-MAILIST] Ambient
running on nitrox
Alan,
Your
ambient sub will definitely be unique and have several complications that
are not encountered in a typical ambient PSUB. You are going against
convention in the technical diving community in that for all practical
purposes you will have a rebreather without a means to monitor your oxygen
levels. You have much more to worry about than just fire. While
I admire your computations, I do not believe that they are as straight
forward as you lay out. In reality, when you look at your proposed
life support system, it would be termed a feed-and-bleed case and these are
governed by a differential equation vice a linear decrease in the oxygen
level. As it has been many years since I have had to contemplate this
particular type of equation used in this manner, I will leave it to you to
conduct further mathematical research.
You
should do a literature search on Dr. Bill Hamilton and oxygen
tolerance. The onset of oxygen toxicity can be rapid, with little
forewarning, and have tragic results. There are two types of oxygen
toxicity, one due to high partial pressures at depth and the other due to
length of exposure. And since most ambient subs involve some parts of
the body being immersed in water, you need to take in to account thermal
exposure. Something many people do not consider is that an exposure to
72 degree Fahrenheit water for an hour will put most people mildly
hypothermic…with this comes a significant decrease in mental acuity and
muscle strength. Don’t remember where you plan on operating but
exposure can be a significant factor.
R/Jay
Resepectfully,
Jay K.
Jeffries
Andros Is.,
Bahamas
Save the
whales, collect the whole set.
From:
owner-personal_submersibles@psubs.org
[mailto:owner-personal_submersibles@psubs.org] On Behalf Of Alan
James
Sent: Tuesday, August 11, 2009 10:30 PM
To:
personal_submersibles@psubs.org
Subject: Re: [PSUBS-MAILIST]
Ambient running on nitrox
Thanks for your
reply Jay these emails can take some time.
Thought I had you
on the regulator issue.
As said on my
initial post, I'd have to think on restricting myself to the dive time
tables for air & the dive depth for nitrox as there would be a dilution
of the O2 content.
However at say
99ft the O2 in a hull with an air volume of 200 liters would be 312 liters
with a 39% nitrox mix. This would give me 144 liters of O2 before
I
got down to
the 21% O2 mark. This is 9.6 hrs at .25
liters per minute consumption. Not to mention the air at 39% O2 replacing it
to keep the sub ambient.
Quite a safety
margin seeing I'm restricted to decompression times. Also no need for a
dedicated O2 feed.
I'll be using
a scrubber & for the ambient system, a pipe open to the sea,
comming up through the hull with probes down it leading to a solenoid
valve.
As the water
level increases it hits the probes wich activate the solenoid valve letting
air in to equalize. Excess pressure bubbles out the pipe.
Like a dive, it
will need planning & building in margins of error.
My main concern
that I'll look into at depth is the fire risk.
Thanks for the
shared experience of the moisture vulnerable O2 monitors.
I won't be
trusting one with my life.
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