On Thu, 11 Mar 2004 22:56:21 -0500
Gregg Iverson <golftooter@xxxxxxxxxxxx> wrote:
>
> Doesn't surprise me that the French would be among the leaders here.
> They started the whole aqua lung apparatus. My dad's scuba teacher (LA
> county instructor) certified in France. They made him use their
> equipment. Double hose, had to swallow the seawater to purge! This was
> back before 1960.
Ahh, the double-hosed aqualung....glad we've developed beyond that.
>
> What do you go that deep to see?
Wrecks, mostly. Big boats sail over deep waters. Big boats which sink tend
to do so over deep waters too.
> You will need some really good lights at that depth.
Yup, in particular for photography. A battery of HID lights are almost
necessary ;)
> BTW, what is your down time? When I was a volunteer fireman,
> we used fiberglass tanks that weighed much less. Because of all the gear
>
> and stress, most could only get about 15 minutes from a 1500 cubic inch
> tank. You wouldn't get many photographs at that rate!
>
Well, it all depends on the dive. The longer bottom time, the longer
decompression required. So the more gas is needed -- which goes back to the
whole logistics-issue. If there's a boat and support divers who can bring
down fresh cylinders on deco stops, then the bottom time can be pretty
long.....Largely long enough to get time to take cool photographs.
Typically we'll drag along two cylinders of backgas (2x15l at 230 bar), as
well as a couple of slung 10l stage/deco cylinders with "oxygene enriched
gas" for deco. That's what one person can carry on his body, and allows for
relatively long dives at moderate depths (60-80m). As I said, 100m+, and
the logistics starts to become excesive ;(
(The alternative is using rebreathers, which allow you to reuse your
expired gas (after removing the CO2, obviously). You can have hours of
bottom time with those, on a relatively small cylinder, and you can
optimize your deco since you'll always be breathing as O2 rich a gas as
possible at a given depth. I've never done that, but it's next on the list
of "things to try")
Enuff about the non-photo related diving, or else the list mum will send me
a nasty mail that I'm OT ;)
--thomas
> gregg
>
> >Comex (french comercial diving operation) have gone to 701m (in a
> >chamber, breathing a hydrogen-oxygen mix) and regularly do working dives
> >at 300+ m-- as do the US navy.
> >
> >Me, I only occationally go below 60m since the expenses of Helium as
> >well as the logistics (you need lots of gas at depth) are quite
> >extensive and air just is nasty below 60m. Below 100m, and you need
> >excessive amounts of logistics in place, and it's hardly worth it for
> >just recreational diving-- 60-100m is possible, but only worth it if
> >there really is something to see. Still, in those cases where there is
> >something worth going down for, it's probably also worth
> >photographing.....hence.....
>
>
>
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--
------------------------------------------------
Thomas Heide Clausen
Civilingeniør i Datateknik (cand.polyt)
M.Sc in Computer Engineering
E-Mail: T.Clausen@xxxxxxxxxxxx
WWW: http://voop.free.fr/
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