RE: ambient preference

["Stymer" <stymer@home.com>]

The company doing the ambient subs is International VentureCraft Corp. at
www.ivccorp.com . The system is passive for ascent control and active for
descent control. There are some technical details at
http://www.ivccorp.com/tech.html . There may be more details elsewhere on
their site, I don't remember.

My biggest concern is always uncontrolled descent. At least with an ascent I
know where I am going, how far it is and how long till I get there. I also
have a pretty good idea what's there when I get there. When you ascend, so
long as you only make yourself slightly positively buoyant, and have a way
to bleed off the expanding air as you ascend, the ascent will be slow and
painless. The key to a safe ascent is sufficient exhaust capacity for the
expanding air.

Good descents are the result of sufficient 'on-demand' air supply so that
you can keep the ballast tank air volume consistent and keep the sub at
about neutral buoyancy. If your sub has an internal volume of 30 cu ft, and
you plan to descend at a rate of 1 foot per second, you need to be able to
deliver 1 cu ft of air per second. With a safety margin, you will need to be
able to deliver at least 2 cu ft of air per second continuously for every 30
cu ft of airspace in your sub. This calculation does NOT work for the
exhausting of air on ascents because the air coming in for descent control
is under pressure (140psi?) where the cockpit air being exhausted is not
pressurized. The key to a safe descent is sufficient inlet volume.

Did I miss anything?

Stymer



>-----Original Message-----
>From: owner-personal_submersibles@psubs.org
>[mailto:owner-personal_submersibles@psubs.org]On Behalf Of Alex Wolfe
>Sent: Tuesday, April 13, 1999 10:20 AM
>To: personal_submersibles@psubs.org
>Subject: Re: ambient preference
>
>
>  I saw a neat idea a while ago to control the volume of the air pocket
>(ascent-wise only)... they had a pipe fitted through the hull with an
>elbow and second segment, to form an "L" shape:
>
>   |
>   |
>  =====
>   |  ||
>   |  ||
>   |  ||
>
>well, you get the idea...  Idea being that the air pocket will not grow
>beyond the bottom of the pipe during ascent, pipe being able to rotate
>so you can alter the size of the air pocket to compensate for load,
>etc.  What scares me the most is the descent portion... from what I
>understand (am I correct??)
>most dry ambient "subs"
>just use a free-flow air delivery system to vent the cabin (and keep
>your air pocket to the level of the pipe/hole/whatever).  If you begin
>to descend faster than you can compensate for decreasing air volume you
>can either sink uncontrolably or drop some weight and go "pop" to the
>surface (from depth and pressue no less).  I guess this is what scares
>me.  Does anyone have any insight on this?  Keep in mind I'm *not*
>speaking from experience, only trying to figure out how not to damage
>myself :-)
>
>Alex
>
>
>
>P.S. there's a link to an ambient sub maker from the "links" section on
>the psubs page.  i forget the name of them, but they advertise some
>kind of "electronic" control for bouancy issues.
>
>
>> My biggest concern with the design is uncontrolled
>> ascent.  I'm don't know
>> what preventive measures have been tried or
>> proven.....  I'm listening.
>
>
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