Min Gas?

[mainedvr]

Do you plan you're min gas and do a direct ascent or more of a multi level dive. So when planning your min gas you figure out what it is for different levels and when you reach that level you go to the next and so on.

So start off at 100' get to min gas start accent and go to around 80' and now you have a few hundred psi till your at min gas again and so on. And I am just referring to moderate OW dives that you do not need to worry about much more than getting yourself or your buddy up to the surface but your at the limits of Rec depths.

Just to be clear I am not asking permission I just was wondering how others approach this.

Thanks

 

[CptTightPants21]

Something like a quarry or a shore dive, you can plan a dive that gradually gets you to your exit. If you are diving in the open ocean up an anchor line you are basically ascending when you hit your calculated turn pressure as their usually isn't much to see once you begin the ascent unless the wreck has a lot of relief.

 

[gobuyastick]

Pretty much what CptTightPants21 said

 

[mainedvr]

I guess what I am asking is do you take the time say on a wreck that the sand is 100 feet and the deck is say 65-70 or something like that, do you plan you dive min gas based on different levels? Like actually take the time to write it down or whatever. And is that DIR so to speak or do you just make your ascent as easy as possible and not over complicate it so to speak with that much detail on a Rec dive. Again just curious my wife and I dive as much using the DIR philosophy as we are completely comfortable with (have taken some training) but don't get to dive much with other DIR minded divers. (Not judging other divers either just want to be clear)

 

[RainPilot]

I've committed to memory the rock bottom for a pair of divers for the depths I commonly dive in increments so 35m, 30m, 25m and so on up to 15m where it is 50 BAR from there up.

If its a proper multi level, the dive captain will point at depth gauge, then at SPG and give the switch sign. Not sure how standard that is but works for us. Doesn't really happen often but the bonus is we don't do a lot of rock bottom calculations any more, got the numbers down.

 

[mainedvr]

I've committed to memory the rock bottom for a pair of divers for the depths I commonly dive in increments so 35m, 30m, 25m and so on up to 15m where it is 50 BAR from there up.

If its a proper multi level, the dive captain will point at depth gauge, then at SPG and give the switch sign. Not sure how standard that is but works for us. Doesn't really happen often but the bonus is we don't do a lot of rock bottom calculations any more, got the numbers down.

Thanks that is what I was thinking, and once you do it enough like you said the numbers are in the head. While I was thinking about it I was looking for any major issues that may arise and don't see anything that stands out if you have enough gas to get to safely to the surface what else is there. Again not thinking of more "technical dives".

I was also trying to see if this was "standard" practice in some form.

 

[_Ralph]

For us, min gas isn't too much different between depths when diving doubles.

If we hit min gas as a first dive from full tanks means we are in some serious deco so that is our least 'worry' about squeaking another few minutes of bottom time.

Usually the trip home (scootering), deco and cold (water temperature) is our main factors.

Now in a purely recreational single tank sense.....

You can plan for a few min gas scenarios.

Square profile? Pretty much only 1 min gas.

Multilevel? 2-3 isn't uncommon. Min gas at your deepest, and an average depth (if you know the profile and stick within it).

If you hit either, you must ascend. No sticking around. You are breathing your buddy's gas, not yours!

_R

 

[PfcAJ]

Do you plan you're min gas and do a direct ascent or more of a multi level dive. So when planning your min gas you figure out what it is for different levels and when you reach that level you go to the next and so on.

So start off at 100' get to min gas start accent and go to around 80' and now you have a few hundred psi till your at min gas again and so on. And I am just referring to moderate OW dives that you do not need to worry about much more than getting yourself or your buddy up to the surface but your at the limits of Rec depths.

Just to be clear I am not asking permission I just was wondering how others approach this.

Thanks

If I have enough gas to get 2 divers to the surface then it's all good.

Nothing wrong with hitting min gas at one depth and shifting shallower and continuing to dive.

 

[mikeny9]

I've changed min gas/rock bottom on the fly from relief on a wreck before but looking back on it it's sort of questionable. Since the calculation is to deal with an emergency, what if that emergency occurs at a lower depth than you're hanging out at (wing failure, etc.) that would cause you to have to descend? I know it's one of those "what-if" scenarios, but it's something to think about. Maybe the conditions/situation will dictate it more.

 

[elgoog]

I calculated min gas for 10ft increments down to 100ft and use an easy approximation to remember the values. For me, that comes out to depth (in ft) x 10 + 200 (or 400 depending on the tank). Of course this formula is not exact and the approximation means I "waste" 100-200psi of gas in a single tank but it works for me.

I do the multilevel thing at sites I'm familiar with and err on the side of being conservative if conditions are not the greatest.