Graph documentation [was: Re: Meaning of GF settings]

[Linus Torvalds]

On Tue, Jan 8, 2013 at 12:14 PM, Jan Schubert <Jan.Schubert at gmx.li> wrote:
>
> Just a note: Suunto is not using Bühlmann and GF settings at all but
> RGBM which has a little different approach and might (!) allow divers
> surface earlier than Bühlmann in case it thinks there are no
> (mentionable) bubbles in your tissues

Yeah. In theory. In practice, I have had to turn my Vyper Air to 50%
RGBM because otherwise it gives me *much* less time under water than
other dive computers.

Of course, it might well be that it's much more conservative at depth,
and much less so in the shallow areas. But judging from my trimix
dives, the HelO2 (which doesn't have that 50% RGBM mode, but seems to
then act similar to the Vyper Air *with* that mode enabled) wanted
longer deco stops than any of the dive computers Dirk was diving.

So at least from personal experience, Suunto computers tend to be more
conservative than most. And that's what the general rumor mill says
too.

I do wonder if the issue is that you didn't do the 3-minute safety
stop *after* the deco stop, and the Suunto really wants you to.

My Suunto's often give an additional 3-minute safety stop after the
deco is over (*), and we laugh at it when it does that ("It gave us a
ten-foot ceiling for ten minutes, and now it wants a safety stop"),
but I do wonder if maybe the logic for the Suunto safety stop is "the
ceiling is less than 3 meters, so we do a 3-minute safety stop". And
the deco classes will have taught everybody to ignore it.

Anyway, so what I suspect is going on is that Suunto considers a small
amount of tissue saturation (probably that "less than 3m ceiling") to
be "no deco", even though that obviously isn't the same as not having
any tissue saturation at all. Otherwise you couldn't do no-deco
diving, after all.

            Linus

(*) To make it worse, it doesn't seem to give it immediately. You can
have waited for your 10" ceiling to clear, and the computer doesn't
say anything, and then ten seconds later it says "Oh, do a 3-minute
safety stop too".