From: mayne@ds1.scri.fsu.edu (Bill Mayne)
Newsgroups: rec.scuba
Subject: Re: computer recomendations?
Date: 20 Aug 92 17:25:53 GMT
Reply-To: mayne@ds1.scri.fsu.edu (Bill Mayne)
Organization: SCRI, Florida State University

In article <1992Aug20.121548.12485@cattnts.canada.ncr.com> craig@cattnts.canada.ncr.com (Craig Campbell) writes:
>In article <10369@sun13.scri.fsu.edu> mayne@ds1.scri.fsu.edu (Bill Mayne) writes:
>>On the negative side Aladins (and Monitor IIs, if indead they are the same)
>>are so conservative I wouldn't be very happy with them for no-decompression
>>diving. The NDL at 100 feet is 16 minutes versus 25 minutes for the USN
>
>Am I reading this right?  To me, the purpose of a computer is to give me
>a seriosly multi leveled dive, automatically, and safely.  I have no problem
>with shorter no-deco limits...

I believe that you are reading me right, but that we are thinking of
different situations. The purpose of these comments, as well as other
unquoted parts, was to point out the importance of considering the
kind of diving that you want to do when selecting computers - or whether
to use a computer at all. I am not advocating the choices I make for my
diving, but exposing the trade offs.

The NDL may be very important if you are committed to avoiding decompression,
you place a high value on bottom time, and and your dive is not seriously
multi-level. Consider diving where the bottom is fairly level. I wouldn't
care that once I leave my maximum depth for a dive the computer gives me
more time, since there would be little to see or do in that extra time. And
dives don't have to have strictly square profiles for computers to be more
conservative than tables. If the whole dive is the 80-100 foot range a
conservative computer such as the Aladin or Monitor II will probably give
you less bottom time than the table gives you for a 100 foot dive. You may
have no problem with accepting shorter bottom times. But anyone considering
a computer should know what they are getting into. Anyone who expects longer
bottom times may be seriously disappointed. (Incidentally there are computers
which are even more conservative than Aladins, at least for some realistic
profiles.)

Computers are certainly convenient even for profiles which are not seriously
multi-level. But if they are very conservative there is a price to pay, in
terms of bottom time (not just the monetary cost of the computer) for that
convenience. A less conservative computer or even a table might then be
preferable.

> since the computer handles the deco in a 
>friendly fashion as well.  (I have a Monitor II and love it.)  Wether I'm a
>sport or technical diver, I still don't want to get bent.
>I must be misreading your intent, Bill.  (no flames intended)

I agree that the computer handles the deco in friendly fashion and I like
it, too, even when it keeps me hanging at 10 or 20 feet when the table
would let me surface - a not infrequent occurrence, even using air. I can
think of some exceptions to my general policy of sticking with the
conservative computer, but these would involve extreme exposures and
technical factors (e.g. nitrox and/or O_2 decompression). I'm all
for conservative decompression. But my conservatism costs me little or
nothing in the precious currency of bottom time because I'm willing to
decompress. I'm not as tempted to push the limits of my table or computer
as a no-decompression diver would be and this encourages me to use a
conservative table or computer and to use it conservatively.

If I wasn't willing to go into decompression mode I might not be so
conservative as to accept 36% less bottom time at 100 feet. Rather than
surface after 16 minutes as the computer would require I'd probably prefer
to get closer to the 25 minute USN limit, or at least the 20 minute Buhlmann
(and I believe PADI RDP) limit and get some of my margin of safety from a
safety stop, or from using nitrox or some other technical means.

Bill Mayne
Newsgroups: rec.scuba