chrpai
Contributor
I like the term Simplified Rock Bottom.
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...//... Rock bottom also changes with conditions, ...//...
IIRC, those that developed the concept and coined the phrase "rock bottom" say it does include calculations for elevated SAC rate, time to focus, all normal stops, etc. Rock bottom also changes with conditions, can't be calculated without knowing your buddy's SAC rate, is the same for the buddy team, and dictates the absolute turn time.
That's why I said it might be better to call your version "minimum gas" or "chrpai's/uncfnp's/lowviz's minimum gas" (or whatever) if you're inclined to come up with your own alternate definitions. Obviously you're free to calculate that in whatever way you'd like.
...//... Hope those guys weren't too offended.
So when I solo dive I have an AL40 with me. It's overkill for my max depths but it rides nice and easy and can be turned into a deco bottle one day. ...//...
...//... When I buddy dive, I'm fine with leaving 100psi per 10' of depth. So at 80' that's 800 psi or 28.78CF of gas. If you spend 1 minute at depth, ascend at 30fpm to 50 then 20, hang out there for three minutes and then ascent that is an average depth of 36'. If each diver has a SAC of .75 ( total 1.5 ) that's 22CF of gas that's needed.
As GUE teaches "minimum gas" (which used to be called "rock bottom", until they discovered it doesn't translate well into a lot of languages), it includes a fudge factor for a stress increase in gas consumption, and also assumes you will complete all planned stops. This is important because the NDLs you use in the system assume you will do "minimum deco", which is one minute stops from half maximal depth.
If you have reserved enough gas for the ascent, and both of you are in control, and your skills are good enough to do it, why not do the stops? On the other hand, if you are sharing gas with an unknown diver, and both of you have been diving in a system that assumes a direct ascent at 60 fpm is acceptable at any point, then I probably wouldn't try to prolong the air-sharing ascent.
By the time you have gotten a tech pass from GUE Fundamentals, there is no doubt in anyone's mind, including yours, that you can execute a precision ascent while sharing gas. You will have done it a great many times.
Perfect OW deco bottle. Caves require more.
Which is why I like my 19cuft pony bottle for everyday dives.
The rock bottom calculation changes as the dive progresses
Anyway it's still a Maybe - if you're at a constant depth, it's not going to change either way