Re: Air Use Calculations

[Chris Nugent <dirkpitt77@yahoo.com>]

      I have to agree with you, Gary.  I don't think
it's worth the trouble or the money to build in a
scrubber when I'm only down for about an hour at a
time.  If I were to get stuck on the bottom for longer
than that, I'm probably not coming back up again
anyways unless I flood the cabin n swim out.  As far
as the "surface and replenish" thing goes, it seemed
pretty easy to just design in a couple of fans and
some ducts to circulate some fresh air in while on the
surface.  

--- protek@shreve.net wrote:
>     I find it unusual that so many people who plan
> to build small subs want
> to design the air rebreather system first.  It seems
> like this is their
> first priority.  The thought of diving without O2 is
> unthinkable to so
> many.  But, depending on the volume of the air
> inside the hull, there is a
> time interval where one can breath the inside air
> only with no problems.
> Many subbers do this continuously with no use of 02.
>  The SAR (surface and
> replenish) method has worked for me in my sub, but I
> don't go for long
> duration dives where more is needed.  The cost of
> the materials for
> scrubbing for me would not warrant their use on
> short dives.  In other
> words, for me personally, I would not even turn it
> on till I had been down
> long enough to need it.
>     A no-scrubber time limit needs to be established
> though and adhered to.
>  Also, one must realize that emergency situations
> may extend down time to
> greater duration than the SAR method can handle.  In
> my case I have
> compressed air on board.  This does raise the inside
> pressure if used and
> that is another problem I will admit.
>     Scrubber systems do not take up much space in
> most cases.  The main
> weight is the O2 bottle itself.  If I were designing
> a sub again, I would
> leave space for the system and allow for the
> estimated weight but not
> concentrate on this systems fine details till I had
> a workable sub.  Then
> if you choose to use a scrubber it can be installed.
>     Once again, if you don't have a scrubber there
> is less safety built
> into your system.  So I am not saying to not use
> one.  I am saying that I
> don't in my sub.  And IF (and that can be a big IF),
> I never have to sit on
> the bottom without the ability to surface, I will
> probably never need one
> because of the duration of my dives.  Scrubber or no
> scrubber, if you do
> use the SAR method for a particular dive you should
> have an efficient
> method of purging the old air from the subs hull. 
> Opening the hatch for a
> couple of minutes is not enough as the air does not
> have time to exchange.
> 
> Gary Boucher
> 


=====
"Noisy outside, empty inside." - Confucius
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