3 or 5 minute Safety Stop?

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...//... Rock bottom also changes with conditions, ...//...

My definition is actually closer to yours, yes there is an absolute turn. Primarily due to this turn calculation, some divers think that rock bottom is just a single number. The rock bottom calculation changes as the dive progresses. I'm sticking with the way the originators intended it, no changes implied.
 
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.


That definition isn't mine but was taken from an Internet dive page.

Another definition from Rock Bottom. I believe this is a DIR forum:

"Plainly put, “Rock Bottom” is the minimum amount of breathing gas that a diver will need in an emergency to get both he/she and his/her buddy to safety."

Seems to me to be a definition that allows for a little bit of common sense. Remember, this is recreational limits. By definition that means that safety stops are optional, and in this context, it actually means extra stops or extra times on safety stops are even more optional.

So do I feel that it is required by the scuba powers that be to carry enough extra gas for extra safety stops and time for me and my buddy? No. Even if I had the gas (and with my SAC I probably would) would I hang out to share air for extra time beyond the recommended time in an OOA situation? No.

i admit that I don't know the official definition.

Sorry that I actually think about what I do and why I do or don't do it instead of just following the "rules."

BTW. Thank you for the compliment of grouping me with Chrpai and Lowviz. Hope those guys weren't too offended.
 
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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.
 
...//... Hope those guys weren't too offended.

That's funny. No, we think about what we do and why we do it too. Nothing more than that. -not always right either. (speaking strictly for myself) :wink:

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. ...//...

Perfect OW deco bottle. Caves require more.

...//... 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.

Which is why I like my 19cuft pony bottle for everyday dives.
 
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.
 
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.

Not sure you are addressing this to me but here is the answer specific to me and my prior posts only:

Dive plan A: ascend with added "deep stop" with 5 minute safety stop
Dive plan B.: typical ascent with 3 min safety stop

Scenario 1: Eric and I are diving as a buddy team. One of us has a catastrophic air loss. Since we are both anal about our gas supply I know it won't be a simple OOA. At this point, dive over, air share and revert to ascent plan B and on our free ascent safety stop I''ll even hang in horizontal trim if you like but I prefer vertical (in OW free ascent I just feel like I can keep a better eye on my surrounds in this position). In reality, we would just switch to our pony bottle.

Scenario 2: Eric went off the boat with the hunters so now I am "solo diving" with the reef group. A nonbuddy runs OOA. His buddy mia. I start sharing air and definitely revert to plan B which is almost certainly that divers planed ascent, anyway, assuming he had a plan. In reality, I'd probably just set him up with my pony to make the free ascent. If he panics, I'm not tied to him.

So no, in none of these unlike events would I feel the need to plan those extra stops into my rock bottom calculations. And remember, I did not say I would not do safety stops, I said I would not do the extra stops.
 
Perfect OW deco bottle. Caves require more.
Which is why I like my 19cuft pony bottle for everyday dives.

I can sling an AL80 if wanted. I'm too cheap to buy more then one pony so I just make the 40 work.

I doubt I'll ever do tech diving or cave diving though...
 
The rock bottom calculation changes as the dive progresses

Probably more accurate to say that the number changes, rather than the calculation. Anyway it's still a Maybe - if you're at a constant depth, it's not going to change either way
 
https://www.shearwater.com/products/swift/

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