Re:

["Marsee Skidmore" <heyred@email.msn.com>]

As for malfunctioning O2 valves, redundancy is a good thing. If one shut off
valve is good, then two are better. The same applies to O2 tanks, regulators
and metering valves. A lotta guys might consider two complete systems with
crossover and isolation valves.

As for open vs. closed ballast tanks, see SFreihof's notes on Boyle's Law.
Bouyancy due to the air volume in an open ballast changes with depth, but
the rate of change decreases with depth. The trade-off issues vary depending
on your operating depth. Do you want to deal with another pressure
vessel(s)? Do you have enough compressed air on board to allow ballast
adjustments at depth? Have you got the power to dive with a bit of positive
bouyancy? Stuff like that.
-----Original Message-----
From: Jonathan Wallace <jon@whoweb.com>
To: personal_submersibles@psubs.org <personal_submersibles@psubs.org>
Date: Friday, March 13, 1998 6:58 PM


>From: "Sean Walinga" <swalinga@telusplanet.net>
>To: <personal_submersibles@psubs.org>
>Subject: Re: Acrylic viewing dome
>Date: Fri, 13 Mar 1998 18:35:45 -0700
>MIME-Version: 1.0
>Content-Type: text/plain;
> charset="iso-8859-1"
>Content-Transfer-Encoding: 7bit
>X-Priority: 3
>X-MSMail-Priority: Normal
>X-Mailer: Microsoft Outlook Express 4.72.2106.4
>X-Mimeole: Produced By Microsoft MimeOLE V4.72.2106.4
>
>Hello all,
>I have been wondering about this type of thing as well.
>
>>With respect to O2 regulation, I'm using a standard (ball type) O2 flow
>meter
>>to regulate the flow into the cabin at .2-.5 lpm.  I have a standard O2
>>analyzer to monitor FO2 percent and a barameter to monitor cabin pressure
>>to insure it neither increases or decreases.  The flow rate needs to be
>>adjusted based on an individual's rate of metabolizing O2.  Hope this
>>helps.
>
>    My question is "What happens if the O2 valve malfunctions while
>submerged at 50M?" If the O2 tank starts an uncontrolled release of O2 into
>the cabin while submerged...  well...  I think that's probably bad.
>Does anyone know of a device or valve that will "pump" excess cabin
pressure
>out into the surrounding atmosphere (water).
>
>    My second question is "Is it OK to have the hard ballast tanks (for
>nuetral bouyancy) open to the environment or must they be a pressure tank?"
>All the reading I've done indicates that they should be a pressure tank but
>I wonder about having them open to the atmosphere. Has anyone made their
>nuetral bouyancy tanks soft (or open to the atmosphere)?
>
>    My thrid question is "What is the best way to connect an acrylic (or
>polycarbonate) cylinder to an acrylic (or polycarbonate) hemisphere?" A
>steel collar with a special fitting on either side seems to make sense to
me
>but any ideas would be welcomed. Anyone have any idea about special
fittings
>as well?
>
>    Lastly, Daniel, if you manage to get viewports made in your plastics
>fabrication shop, maybe the group would be able to purchase their viewports
>from you?
>
>Thanks everyone!
>Sean
>
>
>