max depth with an 80 cuft. tank

[MXGratefulDiver]

If you have been trained right, you know what your rock bottom reserve is based on real SAC rates and you don't need to rely on a rule-of-thumb like the 80/80 rule that is really just a line in the sand.

The 80/80 rule is similar to the end-your-dive with 500PSI rule often quoted. Both are simplistic rules for people too lazy or ignorant to take the effort to calculate their reserves properly.

The 80/80 rule ... like most rules of thumb ... is designed to be an easy-to-remember guideline for beginners, with the assumption being that as they progress in their education and experience they will develop an understanding of why those "rules" exist and when they are appropriate.

The best answer to the OP's question would be to learn something about gas management and then make your own ... informed ... decisions about what tank is appropriate for what depth.

... Bob (Grateful Diver)

 

[GrumpyOldGuy]

The 80/80 rule ... like most rules of thumb ... is designed to be an easy-to-remember guideline for beginners, with the assumption being that as they progress in their education and experience they will develop an understanding of why those "rules" exist and when they are appropriate.

The best answer to the OP's question would be to learn something about gas management and then make your own ... informed ... decisions about what tank is appropriate for what depth.

... Bob (Grateful Diver)

I am much less diplomatic than you.

IMO, if someone does not understand gas management, they should not be diving deep regardless of tank size. If they understand gas management, then they make your informed decision. In either case, I think this rule of thumb is moot.

 

[MXGratefulDiver]

I am much less diplomatic than you.

IMO, if someone does not understand gas management, they should not be diving deep regardless of tank size. If they understand gas management, then they make your informed decision. In either case, I think this rule of thumb is moot.

It is not moot ... it is intended to prevent divers who went straight from OW to AOW with little training, no practical experience, and only the most rudimentary idea of gas management practices from going deeper than the gas in their tanks would reasonably allow ... because the reality is that people DO go deep without understanding gas management. I can name several who died because of it. That's the reason the article I linked in my previous reply exists.

One of the exercises in my AOW curriculum is to have my students use a dive plan for a 100-foot dive to calculate how much gas they would need. The profile is one that is popular among divers of all levels at our local training site. Almost without exception, those using AL80's will come back and tell me they can't do the dive because they won't have enough reserves to accommodate a proper rock bottom.

For every diver who learns this, there's at least a dozen more who are out there doing that dive on AL80's and either coming back with barely any gas in their cylinder or having to make midwater ascents without a safety stop when they finally figure out they don't have enough left to complete the dive properly. Of that latter group, if they're lucky, they will be with a dive buddy who has enough gas left to share when it happens.

I agree with your premise, but there is a huge discrepency between what people should learn and what they actually do learn ... and one of my reasons for not encouraging people to go straight from OW to AOW is because it gives them a "license" to dive deep long before they actually acquire the skills or knowledge to make informed decisions about the risks involved.

... Bob (Grateful Diver)

 

[GrumpyOldGuy]

It is not moot ... it is intended to prevent divers who went straight from OW to AOW with little training, no practical experience, and only the most rudimentary idea of gas management practices from going deeper than the gas in their tanks would reasonably allow ... because the reality is that people DO go deep without understanding gas management. I can name several who died because of it. That's the reason the article I linked in my previous reply exists.

One of the exercises in my AOW curriculum is to have my students use a dive plan for a 100-foot dive to calculate how much gas they would need. The profile is one that is popular among divers of all levels at our local training site. Almost without exception, those using AL80's will come back and tell me they can't do the dive because they won't have enough reserves to accommodate a proper rock bottom.

For every diver who learns this, there's at least a dozen more who are out there doing that dive on AL80's and either coming back with barely any gas in their cylinder or having to make midwater ascents without a safety stop when they finally figure out they don't have enough left to complete the dive properly. Of that latter group, if they're lucky, they will be with a dive buddy who has enough gas left to share when it happens.

I agree with your premise, but there is a huge discrepency between what people should learn and what they actually do learn ... and one of my reasons for not encouraging people to go straight from OW to AOW is because it gives them a "license" to dive deep long before they actually acquire the skills or knowledge to make informed decisions about the risks involved.

... Bob (Grateful Diver)

I like your described AOW program, it is head and shoulders above the typical!

So back to the poorly trained divers (who cannot or will not practice gas management) we are discussing. if they decide to follow the 80/80 rule and get a bigger tank, do you think they will come back with more air or do you think because the have the larger bottle they will stay down longer and still comeback with barely enough?

 

[Rhone Man]

In the immortal words of John Chatterton: "If you don't have redundant gas supplies, you don't have any business diving deeper than you can swim to surface from on one breath of air."

 

[MXGratefulDiver]

I like your described AOW program, it is head and shoulders above the typical!

So back to the poorly trained divers (who cannot or will not practice gas management) we are discussing. if they decide to follow the 80/80 rule and get a bigger tank, do you think they will come back with more air or do you think because the have the larger bottle they will stay down longer and still comeback with barely enough?

Around here, they will generally come back because they get cold ... especially new divers in wetsuits. The deeper they go the colder they'll get ... which will tend to limit the amount of time they'll want to stay there. With a bigger bottle, cold will often determine the turning point before gas consumption or NDL becomes an issue ...

... Bob (Grateful Diver)

 

[dktexas54]

Simply put, where are the statistics to back up your claim?

Statistics! Man,what you talking about! I barely passed that course in college. This diving thing. I do for fun. Don't need statistics too tell me that diving at 100-130' with 80's is dangerous for the majority of divers out there. You tell me what the average sac rate is at 120 after you screw the pooch! Man, I don't know. Some people might suck that air like it was no tomorrow. Do all kinds of weird things. I am all about promoting dive safety and remembering that most if us are all RECREATIONAL DIVERS!! Many people on this board are professional divers and Tec divers and to those this thread is not addressed. I appreciate all the feedback and hopefully some new diver and someone who thinks they know it all may learn from all the good feedback coming from this thread
Cheers!!

 

[Blackwood]

The deepest I've had an Al80 is ~170 feet. Granted I emptied it at that depth and then switched over to the doubles on my back.

Easy (drift, for example) warm diving with a competent buddy, I'll take an 80 to 80 or deeper. Around here, nah.

 

[Mike Boswell]

Is an 80 cuft tank enough air to safely go beyond 80'? My answer is yes but not safely. Please share your opinion.

It depends.

 

[AfterDark]

This discussion sounds familiar...oh yeah! the old debate during the 70's can a diver get bent on a 72 cu ft tank? Boring..