She clearly indicated it was the computer that set the 31 hour surface
interval.

This is what began my discussions with them on the validity of computers
- and led to his inane (to me) notion that because the computer
integrates depth-time so well, that its computation of nitrogen load in
the body is correct v. the slop in the system and the slop in tables and
the many unknow-ables...

It does sound a bit odd, but perhaps we are reading a bit too much
into language translation - for a Swiss, French, German & Italian are
their official languages, so English is probably in 3rd or 4th, with
the country's 4th language of Romanish being less common overall.

Being that it was a midweek break, I recall that there are "take a day
off" recommendations from DAN, etc, so I think that this could be that
they were simply electing to take a mid-trip break day, but what got
lost in translation was the explanation of "who" (man vs. computer)
was calling for it.

The Swiss may come off as conservative & reserved in some things, but
there's some real surprises when you really start to look.   For
example, if they were so paranoid about personal safety, they wouldn't
have had explosives in place wired to blow tunnel in the country up
through the 1990s (& later).  Similarly, lets not forget that it was
the Swiss who did some of the earliest diver-test trials with trying
to figure out DCS ... and I believed that I mentioned here awhile back
that I had the pleasure of meeting one of those original military
divers a few years ago...one of the ones who got pretzeled, IIRC, due
to a post-dive increase in altitude.

-hh

On Feb 1, 4:14 pm, Alan Browne <alan.bro...@FreelunchVideotron.ca>
wrote:

See, that's just plain weird.  However, Swiss are known to be
extremely conservative.  Since most computers can be programmed for
extra-conservatism, even Suuntos, it's possible she had hers
programmed to ensure she had extremely low residual nitrogen.
Nitrophobic!

====================
The reason for her conservatism is obvious.
She's Swiss.
There are airliners that don't fly as high as her house.
hoges in WA

On Feb 1, 4:14 pm, Alan Browne <alan.bro...@FreelunchVideotron.ca>
wrote:

See, that's just plain weird.  However, Swiss are known to be
extremely conservative.  Since most computers can be programmed for
extra-conservatism, even Suuntos, it's possible she had hers
programmed to ensure she had extremely low residual nitrogen.
Nitrophobic!

No, it was mid stride.  They programmed a 2 day out before flying to dry
out their wetsuits...

I've put my Suunto Vyper into Deco .. I've never had it insist on any
sort of huge surface intervals, which does make this sound like the
Swiss Lady likely had some sort of violation, so the computer locked
her topside.

Of course, a magnitude of 31 hours also kind of sounds like it could
have alternatively been a "Time to Fly" time requirement; if this was
the cause of her skipping her last day of holiday, this could be
another possibility.

Given how conservative the Suunto is even at its most liberal
settings, I'd generally be more concerned about losing a day of diving
for it locking up, than the DCS risk from not fully completing its
deco schedule.

BTW, if you do put a Suunto into Deco, do be aware that it is
surprisingly fussy about your hang depth:  you really need to get up
to the top of the glass ceiling in order to clear the stop in anything
even remotely close to the time that it says it will take.   IIRC, my
first experience was something like an 8-10 minute obligation, which I
did at my usual 15-17fsw safety stop depth, but which after ~15
minutes, hadn't budged more than a few minutes...so I came up to
~11fsw and it took around another 10 minutes to clear the remaining 7
minutes or so.   All told, I had nearly a half hour hang at <20fsw
before it was finally satisfied, and that was from a profile that
probably was within the ancient USN Table's no-stop limit of "25 min @
100fsw" square profile...so how much DCS risk was there, really?

They were what...all of 3ft long?  :-)

-hh

On Jan 29, 3:03 pm, Ecnerwal
<MyNameForw...@ReplaceWithMyVices.Com.invalid> wrote:

If you've never run a Suunto into deco, you must dive conservative!
But deco or not, I never argue with my Suunto.  Perhaps that's what
Alan's Swiss lady friend did; maybe her 31-hour imposed surface
interval was because she screwed up.  I hadn't considered that.  I
even try to obey the optional deep-stop recommendations on my D9, and
would rather profane God than disobey a mandatory imposed deco stop.
Normally it's NDL all the way to the surface, but I've had it
occasionally impose a 1-minute mandatory "safety" stop on dives when
I'm ascending directly rather than taking my time exploring shallower
realms on the way up.  I usually dive nitrox, so it's only made it
into unplanned deco a few times, but when I dove the Spiegel Grove
using optimal nitrox mixes (29% for a bounce to 140 on the first dive,
followed by 35% for a max of around 90'), the bastard stuck me with a
minute at 20' and 8 minutes at 10', right when there were 6 man-eating
huge barracudi at 15' on the mooring line.  I turned my back to the
sinister fishies and did my time.

There are conservative computers, and there are aggressive computers.
Buy one to suit your personal style. One reason to use a conservative
model is that people do get bent diving within the bounds of tables and
computers - this should have been mentioned in class.

But if you are an aggressive diver and buy a conservative computer, you
will probably just ignore it and go diving when it's locked you out for
a deco violation - I've certainly see people do that. As such, an
aggressive diver should choose an aggressive computer, so it's at least
of some use to them. But an aggressive diver is inherently more likely
to get bent, period.

The recreational tables are not really formulated with an eye to diving
every day for nearly a month. Many people choose to take a day off (or
limit it to a half-day of diving) in the middle of a mere week of diving.

Computers can also penalize you for the things you *actually* do, as
opposed to the nice clean plan you didn't actually follow - for
instance, if you ascend faster than you should on tables, the table
doesn't know that. If you ascend faster than you should with a computer,
it can slap a fudge factor on your surface interval to allow for that.
My conservative (Suunto) computer will penalize for ascent rate, lack of
safety stop, insufficient surface interval and several other things as
well as actual missed decompression stops. The latter would be per the
manual, as I've never run it into decompression - it and I are well
matched.

Screwing up threading to save a post:

That's "independent tests by other people" - the aforementioned Rodale's
for one. The methodology seemed pretty decent. They were specifically
trying to get past the vague claims of of manufacturers.

They've done it for several years: here's 2005
http://www.scubadiving.com/gear/2007/03/2005-fin-test
http://www.scubadiving.com/gear/2006/11/2005-fin-test-protocols

I don't actually own a pair, though my wife does. I have used hers when
I was surface snorkeling and she was sitting on the boat, and my
impression is that they are better than the paddle fins I use. Since I
can outswim her with the ones I use, and we almost invariably are each
other's buddies, there's no point in me getting any, at least until
these ones break.

First, thanks for all your replies, gents.  Very educational.

The Swiss couple I met (and usually had a drink or three with almost
daily) insisted on the merits of their computers.  The lady, one day,
took a full day out of diving (they were there for diving only over a
3.5 week period) as her computer told her to take a 31 hour surface
interval.

She had been making daily deep dives (first dive) to 100 - 130 feet
almost daily followed invariably by a shallower dive 30 - 60.

As I learned to use the tables and 'chain' successive dives together, I
could see no trend indicating that one would accumulate a large required
surface interval.  At least not on the basis of two dives per day, the
first being to 130'.

So the question goes, are the computers too conservative?  (Tables too
loose?).  I know the computers also "give" as they integrate finely and
give "credit" for the fact that a 45 minute dive to 130 feet is not all
spent that deep, but it seems in integrating overall tissue N2 they are
too conservative.

The second question goes, the Swiss told me there are places in the
world that will not take you out diving unless you have a computer.  Is
this so?

Thx.