Sharing air to maximize bottom time.

[Jim Kerr]

"at LEAST"..........***!!!!
Hey kid maybe you can do this now but,.........wait until you are 45 and see if you can still do an HOUR and 40 minutes on a AL80 :mooner:



Oh please tell us the most time you can do at 30feet on a AL80, ...will you be doing any swimming, or just laying on the bottom gazing at the surface in a comatos state?

I just did my longest dive in Yap on an AL80 in Feb 07.

BT =101 minutes
Max Depth= 51 fsw
Avg Depth= 27 fsw
Age= 54
Remaining Air= 500 lbs +/-

I am a big guy and not in the best shape either I'm sorry to say, but the more I dive the more comfortable I get in the water. It can be done!

 

[Jim Lapenta]

I see the reasoning for air sharing in the begining of the dive for buddies who know each other and using it as a skills drill. I would never share air to extend bottom time with an unknown. How do I know if she/he is all of a sudden going to panic and drag me with them? I dive long hose in ow even when solo.

On instabuddy dives if he runs low I'll watch him ascend but I'm not cutting my dive short. I make it a practice when I've paid big bucks for a trip to only dive with experienced divers I've checked out on a relatively easy dive first. If I'm paired up with someone and they are at 500 psi on a shallow reef and I'm at 1500-1800 plus then guess what? I'm not doing the second with them unless I'm getting paid to.

I usually get around 1 1/2 to 2 hours out of an al80 depending on the dive. I've done the benwood for 56 minutes and came back on with 1800 in the tank out of 3000. I've also had to herd cats(assist w/ow students) in 30 ft of water and used close to 2000 for an hour. That's chasing them down, keeping everybody together, practicing skills, etc. I'll be 48 on thursday the 21st.

The amount of exertion has a large effect on SAC. So as DA said 100 minutes on an al80 in one set of conditions may be nothing compared to much less in more strenuous ones. I hate doing air share with some newbies as they seem to be able to suck 500 psi down out of my tank in one trip around the pool. I don't use that much in 2 hours some nights. Last pool session involved doff and don, bailout, no mask swim with two students, free flow reg and a few other skills. Started the session with 1500. 3 hours later I was at 400 or maybe a little less and the night before doing air share I had 2400 and went to that 1500 in less than an hour.

Anyway no way I'd extend a divers BT by air sharing. a better solution is to try and pair up people who use air at similar rates or just end the dive. Especially with newer divers who could run into issues later on.

 

[Papa_Bear]

I have done two hours on an AL80 in Belize I went to 105ft and worked up Painted Wall to the top at 35ft to 25ft of water! I was back on board with 300psi! I don't use too much more than most of my female buddies so it isn't really necessary, but if we were 1000psi different I would if she was willing and there was something I wanted to see!

 

[dumpsterDiver]

One of the very few times where I failed to adequately monitor my buddy's air supply ended with the lady COMPLETELY draining her tank to zero at 100 feet and then giving me the slash across the throat. I was very upset (at BOTH of us for being stupid) and handed her the octopus, we immediately began the ascent. She later told me that she would have been in total panic if she and I had not practiced sharing my air (to extend our dive time) on the previous weekend.

It was funny because during the emergency she took the octopus and then positioned herself over my head and held onto my tank valve/first stage with a death grip. From this position, I could not see her, nor manage her bouyancy nor control the situation. If I spun around I was worried I would pull the octopus from her mouth, so i just left her there hanging above and behind me in my blind spot for the entire ascent. I was worried she might loose control of her bouyancy, but I could hear her breathing.

Afterwards on the boat, I asked her why she assumd this position behind me and in my blind spot (rather than face to face) and she said that is what she thought was the correct way, because that is where she positioned herself, when we extended our bottom time (while swimming) during the previous weeks dives.

I don't see it as a big deal if you don't let either diver get their own tank too low. I remember in cozumel I used to let this huge, fat cop take air from my wife. He would bum air off two people, just to get a decent bottom time.

 

[Jim Kerr]

There is a similar thread on this subject and on that one I objected to using a buddy's air for the sole purpose of extending bottom time. But after listening to the CAVE and DIR divers explain how they use it to maximise their BT while practicing vital skills and keeping with rock bottom presures I have to admit it makes perfect sense to me now. I also agree 100% with JimLap about not doing it with just anybody.


meltedtime,

As a new diver I would still suggest you not try this just yet. Get yourself a bigger tank and just dive as much as you can. The more you dive the more comfortable you get. You'll start seeing your SAC rate improve with time.

 

[Peter Guy]

Just to reiterate what was re-printed from a prior post -- SHARING GAS (AIR) IS OK TO DO, REGARDLESS OF THE REASON!

I really can't believe the people who write that "you shouldn't do it." Why not for pete's sake? (Always with the caveat that both divers maintain their "safety reserve gas" (aka minimum gas, aka rock bottom) which is needed to get BOTH divers to the surface.)

When the PADI instructor (who was to be my DM instructor but this was one of the reasons I decided to change) very indignantly informed me that it was UNSAFE to continue diving while sharing air I just had to shake my head. (And I'm also quite sure he had NEVER done an air share on someone's 7 foot hose!) What stupidity! (Note, he did say that it had been ages since he and his buddy (wife) had done an airshare -- but they didn't need to because they were always demonstrating such to students so they didn't need to practice together. Go figure.)

Anyway, my wife's SAC rate tends to be about 2/3's of mine (whether in warm or cold water) so why shouldn't we balance out our gas supplies while playing around in clear, warm tropical water?

 

[grazie42]

My regular buddy uses more gas than me so when he starts getting close to our turnpressure for the dive, he´ll hang on my longhose until I get close to mine...

I´ve had DMs and other people object to this practice using some of the, IMO, silly objections seen in this thread...

It won´t stop me/us from continuing this practice and it shouldn´t stop anyone else either...
It´s good practice and extends your dive without violating whatever level of safety you´ve decided is appropriate for the dive...

I´m not sure that I´d trust an unknown DM in this capacity though, I think you´d be far better off sharing with your wife...

ymmv...

 

[Ice Mike]

My regular buddy uses more gas than me so when he starts getting close to our turnpressure for the dive, he´ll hang on my longhose until I get close to mine...

Just for my information.

What do you consider to be turn pressure?

 

[grazie42]

Just for my information.

What do you consider to be turn pressure?

I was being deliberately vague...turn pressure depends on the dive...but it basically means the pressure at which you start your ascent (either directly, by heading towards the up-line or exiting a wreck etc)...a point that may need clarifying would be to not move further away from the point at which my buddy reaches turn-pressure unless a direct ascent is planned...

 

[8thElementDiver]

Is it more ok if you share air at the beginning of the dive?

That's an excellent, interesting, question.

It gives both divers the chance to become comfortable with sharing air while avoiding any potential problems from having only one air source.

My take is that, yes, it is more OK if you share air at the beginning of the dive. Plan a separation point of no less than 1500 psi, and plan to surface with both divers having at least a 500 psi reserve. And do a safety stop.