max depth with an 80 cuft. tank

[Tigerman]

Well, it could be a buddy team that has grown gills and use like -0.1cf/m?

 

[phil8diver]

Nothing wrong with going down to 40 meters (131ft) with AL80 given that you are fully aware of your air consumption and plan it accordingly. 99% of my dives are on AL80 and usually my first dive in my area (Anilao) is around 35 to 38 meters (115 to 124 ft). Proper dive planning is what matters.

 

[blueman9]

Nothing wrong with going down to 40 meters (131ft) with AL80 given that you are fully aware of your air consumption and plan it accordingly. 99% of my dives are on AL80 and usually my first dive in my area (Anilao) is around 35 to 38 meters (115 to 124 ft). Proper dive planning is what matters.

I agree and for those that were wondering on my post, it was deep water certification with a specified to the minute dive plan. (don't have it on me it was about a year and a half ago) with roughly 7 minutes dive time, and safe accent speed with two 2 minute stops every 30 feet and a full safety stop at 20ft. We there were 4 divers.

 

[UCFKnightDiver]

Nothing wrong with going down to 40 meters (131ft) with AL80 given that you are fully aware of your air consumption and plan it accordingly. 99% of my dives are on AL80 and usually my first dive in my area (Anilao) is around 35 to 38 meters (115 to 124 ft). Proper dive planning is what matters.

When do you turn your dive, at what pressure?

I agree and for those that were wondering on my post, it was deep water certification with a specified to the minute dive plan. (don't have it on me it was about a year and a half ago) with roughly 7 minutes dive time, and safe accent speed with two 2 minute stops every 30 feet and a full safety stop at 20ft. We there were 4 divers.

Do you remember your turn pressure? Also it is beyond me why someone would want to spend 7 minutes on the bottom, and the rest of the dive doing an ascent.

 

[David_57]

Beyond my understanding why anyone would want to dive to 140ft on 80 cuft of air other than a bounce dive so they can say they have been to 140ft.

As for making a accent in an OOA situation from anything over 50ft is ridiculous in my opinion, lets face it you could take a boat load divers and guaranteed all of them would be hard pressed to make it from 50ft let alone 100ft in an OOA situation. the only way to prepare for a OOA situation at 100ft and over is having a good buddy or a pony available to you. Having said that sure I have dove many times over a 100ft down South without a backup air source but that's the risk I was willing to take, is it safe no way, and would not recommend this to anyone, up to them to weigh up the risks and decide.

 

[miketsp]

..snip..
As for making a accent (SIC) in an OOA situation from anything over 50ft is ridiculous in my opinion, ..
..snip..

I was face to face with an OOA diver at 85ft and instead of taking my spare this diver preferred to do a CESA - and survived. The ascent must have started with empty lungs.

I followed at a fast but safe rate and got there in time to give a tow. Fortunately for me my dive was just starting.

 

[Tigerman]

Beyond my understanding why anyone would want to dive to 140ft on 80 cuft of air other than a bounce dive so they can say they have been to 140ft.
...

Well, I wouldnt go there on air with any size or ammount of tanks.. Its just not worth it to have (according to tables) about 8 minutes max bottomn time, not to mention youre getting to a point where getting seriously narced is quite likely..

 

[eelnoraa]

I think it all depends on how long you want your dive to be. Just this weekend, I used an LP72 tank, descended to 100ft, stay there for maybe 10 minutes before ascending. The entire dive including descent, asdent, safety stop was less than 25 minutes, came up with 800psi left. I wished I could stay down for longer, at least the time should be limited by NDL not air, but it was the only choice with rental.

 

[dktexas54]

Here is a hypothetical gas plan: Please be critical if i am wrong.
1.) lets dive to 130' to see a wreck. equipment: 80 cuft, computer, no pony, octo. assume buddy has same setup. assume sac rate of 35psi based on real measurement taken at 60' over time avg in current and non current. calm, no panic consumption rate.
2.) dive: a.) decent- assume 1 fps./60'min. start with 2950 psi
calulation: 130 seconds to reach target. avg depth while decending 65'. so, 65/33+1=2.97 ata
2.97 ata x 35psi=103.95 x 2.17 minutes=226 psi consumed on decent
b.) 9 min at depth- lets say we vary our depth by 20' and average 120' for the 9min swimming around the wreck.
Calulation: 120'/33+1= 4.64 ata
4.64 ata x 35pis=162.4 x 9 minutes=1462 psi consumed on bottom.

something goes boom in the night- your dive partner is signaling low on air or worse , ooa. you swim over and give him your octo.

lets assume this all took one minuite to realize and sort out.
so,
calulation sorting out:
120'/33+1= 4.64 ata
4.64 ata x 35pis=162.4 x 1 minutes=163 psi comsumed on bottom.
now, lets see what gas we have left.- decent 226+ bottom 1462+ sort out emergency 163. that equals 1851 psi used.
assumptions: are heart rate is up, our consumption is up. Worst case lets say our total consumption for both divers now is triple or 105 psi sac rate x 2= 210 psi sac rate. ok, we have to start our ascent to 15'. lets forget a deep stop, we have an emergency. so,
calulation to 15' from 120 with two divers.
average depth from 120-15=105/2=53'+15=68' avg depth.
68'/33+1=3.06 ata x 210 psi sac rate =643 psi min consumption rate. lets go at 60' per min , but we should be doing 30' or slower that means is will take 68 seconds to reach 15'.
consumption is 643 x 1.13 min or 729 psi. now, we are at 15' for a safety stop. what gas is left.
1851 +729=2580 psi.

3 min stop : 15/33+1=1.45 ata x lets say were calmer now and back to 50 psi rate per diver or 100 psi total. so 1.45x100=145psi x 3 min safety stop or 435 psi consumed on safety stop.
2580 + 435=3015 psi. We're OOA at 15'. obviously we would have had to cut our safety stop short.

Please forgive if my math is off. My point with this and with this thread is that yes, you can dive with an 80 to 130,150 whatever. but, what if as we used to say in the corp, a cluster f happens? I believe that all divers should prepare for the worst and hope for the best. Too all those who dive regularly deep with 80's, i say go for it, but don't convince new divers its safe and the proper thing to do. I say that if you want to dive below 80 on a regular basis, get advanced training, learn to dive doubles,etc. i am older now and limit my diving to 80-90' max. i sling a small pony everytime i dive regardless of depth. i use an air integrated computer which measures my actual consumption rate and gives me an accurate air time remaining at any moment in time. I suspect i could under best conditions make a cesa ascent from 50'. I would dump weights, ahh slowly and kick steady. I carry a spare air and my plan is if i cannot locate my buddy or someone else after a short period of time, then i can take a deep breath, ahhh and start up, before i run out of air, i would take two breaths on the spare air and start ahhing again. this way, i make it last until i reach the surface. This is my last ditch emergency plan. Hope you have yours.

 

[miketsp]

Here is a hypothetical gas plan: Please be critical if i am wrong.
1.) lets dive to 130' to see a wreck. equipment: 80 cuft, computer, no pony, octo. assume buddy has same setup. assume sac rate of 35psi based on real measurement taken at 60' over time avg in current and non current. calm, no panic consumption rate.
2.) dive: a.) decent- assume 1 fps./60'min. start with 2950 psi
calulation: 130 seconds to reach target. avg depth while decending 65'. so, 65/33+1=2.97 ata
2.97 ata x 35psi=103.95 x 2.17 minutes=226 psi consumed on decent
b.) 9 min at depth- lets say we vary our depth by 20' and average 120' for the 9min swimming around the wreck.
Calulation: 120'/33+1= 4.64 ata
4.64 ata x 35pis=162.4 x 9 minutes=1462 psi consumed on bottom.

something goes boom in the night- your dive partner is signaling low on air or worse , ooa. you swim over and give him your octo.

lets assume this all took one minuite to realize and sort out.
so,
calulation sorting out:
120'/33+1= 4.64 ata
4.64 ata x 35pis=162.4 x 1 minutes=163 psi comsumed on bottom.
now, lets see what gas we have left.- decent 226+ bottom 1462+ sort out emergency 163. that equals 1851 psi used.
assumptions: are heart rate is up, our consumption is up. Worst case lets say our total consumption for both divers now is triple or 105 psi sac rate x 2= 210 psi sac rate. ok, we have to start our ascent to 15'. lets forget a deep stop, we have an emergency. so,
calulation to 15' from 120 with two divers.
average depth from 120-15=105/2=53'+15=68' avg depth.
68'/33+1=3.06 ata x 210 psi sac rate =643 psi min consumption rate. lets go at 60' per min , but we should be doing 30' or slower that means is will take 68 seconds to reach 15'.
consumption is 643 x 1.13 min or 729 psi. now, we are at 15' for a safety stop. what gas is left.
1851 +729=2580 psi.

3 min stop : 15/33+1=1.45 ata x lets say were calmer now and back to 50 psi rate per diver or 100 psi total. so 1.45x100=145psi x 3 min safety stop or 435 psi consumed on safety stop.
2580 + 435=3015 psi. We're OOA at 15'. obviously we would have had to cut our safety stop short.

Please forgive if my math is off. My point with this and with this thread is that yes, you can dive with an 80 to 130,150 whatever. but, what if as we used to say in the corp, a cluster f happens? I believe that all divers should prepare for the worst and hope for the best. Too all those who dive regularly deep with 80's, i say go for it, but don't convince new divers its safe and the proper thing to do. I say that if you want to dive below 80 on a regular basis, get advanced training, learn to dive doubles,etc. i am older now and limit my diving to 80-90' max. i sling a small pony everytime i dive regardless of depth. i use an air integrated computer which measures my actual consumption rate and gives me an accurate air time remaining at any moment in time. I suspect i could under best conditions make a cesa ascent from 50'. I would dump weights, ahh slowly and kick steady. I carry a spare air and my plan is if i cannot locate my buddy or someone else after a short period of time, then i can take a deep breath, ahhh and start up, before i run out of air, i would take two breaths on the spare air and start ahhing again. this way, i make it last until i reach the surface. This is my last ditch emergency plan. Hope you have yours.

I already commented about SAC rates in an earlier post when I considered 1 cfm pessimistic, but based on the even more pessimistic scenario you just presented with not just one but 2 divers somehow managing to consume 35psi normally and 105psi under stress (!!!!), this buddy pair should not even be thinking about planning a dive to 130' on an AL80 until they get a lot fitter and a lot more comfortable in the water.
In fact they really need to find another more relaxing hobby.