How deep can you theoretically go on single tank?

[Randy43068]

all the limits aside, how deep can you go on a single cylinder? was just wondering cause i keep hearing about recreational limits etc. etc. but see divers all the time go well beyond em and still have enough air to do their deco stops. just wondering if you guys really follow the 60ft max limit for OW, and 130ft limit for recreational diving?. i wasnt trying to be reckless, careless or stupid or anything but i may have been a bit naughty in my last couple of dives

Hum... to the bottom. Coming back is the problem.

 

[miketsp]

Since we're started, the optimal support team needed for one buddy pair to make a safe dive to 100' using AL80's would be this:
..snip..
So, according to my calcualtions, a team of 13 support divers will be sufficient to allow our buddy pair to make the 100' dive safely.

Within the NDL's of course. If our buddy pair wants to put their computers 2 minutes into deco then we have a whole other rat's nest of problems that have to be solved.

R..

:rofl:

 

[ClevelandDiver]

Since we're started, the optimal support team needed for one buddy pair to make a safe dive to 100' using AL80's would be this:

1 buddy pair (2 divers) both equipped with AL 80's

2 support divers equipped with dual AL 80's and 2 AL 80 stage bottles per diver, one of which will be carried as a redundant air supply for buddies #1 and #2 and one of which serves as a Murphy bottle to account for the possibility that one of the other stage bottles packs it in or that one of the support divers needs help. these two support divers will initially be stationed at 100' but will be relieved by 2 other similarly equipped support divers after 10 minutes, after which the first two support divers will take up station at the stop depth and wait for our risk taking buddy pair.

You need 1....no make that 2 DIR divers to offer bitter criticism and 2....no make that 4 other divers (call them redundant support divers -- After all redundancy is good) to follow around the DIR divers screaming "we don't care" through their regs during the entire dive. The DIR divers are, of course, not wearing computers, but their 4 support divers can keep them safe anyway.

Oh, and we need Leigh Cunningham. We just can't make a dive like this without Leigh Cunningham. (if you don't know who this is, see the attachment)

Finally, we need at least 2 divers on rebreathers to make the video.

So, according to my calcualtions, a team of 13 support divers will be sufficient to allow our buddy pair to make the 100' dive safely.

Within the NDL's of course. If our buddy pair wants to put their computers 2 minutes into deco then we have a whole other rat's nest of problems that have to be solved.

R..

And when you can't have 13 support divers, 12 tanks on one huge freakin' manifold will sufice..... Awesome picture. He must have been diving to 130 !

 

[mer]

Interesting that we never heard the PSI that the group "that knew how much air they needed to get from 130' OOA".

Uncle Ricky I don't agree with your math.

Let's go by some PADI tables here... they recommend 30 fpm ascents and if you are within 5 mins of the NDL (which you will always be at 130') the 3-5 min saftey stop is mandatory.

Also, 1CF/min is not an unreasonable rate for an emergency situation. I know people who are very muscular who can suck down 3CF/min when working.

Safety stop ( 1.5 ata, 2 divers, 1cf/min per diver, 3 minutes) = 9 CF or 350 psi
Ascent (average 3 ata, 2 divers, 1cf/min per diver, 4.5 minutes) = 27 CF or 1100 psi
And you will needed at least a minute to get things organized on the bottom... (2-3mins is a possibility)
Bottom (5 ata, 2 divers, 1cf/min per diver, 1 minute) = 10 CF or 400 psi

Well over 1800 psi needed.

Dive however you like, but please think ahead with what you need to get to the surface rather than just how to get back to the boat with 500psi.

 

[lamont]

Also, 1CF/min is not an unreasonable rate for an emergency situation. I know people who are very muscular who can suck down 3CF/min when working.

first time i took my SAC rate it averaged 1.1 over the whole dive, and that was just a newbie diver stressed out from the low-viz, and not someone afraid they were gonna die.

the people who make dive plans to 130 fsw on AL80s are assuming that the good SAC rate that they and their buddies have will hold when the **** hits the fan, and i don't really buy that...

 

[emelotto]

Well I remember once when we had to recover an object weighing about 5 tons in 85m and the only available tanks on board contained air. We knew exactly where the object was because we had located it by underrunning a communications cable that ran into it but this cable could not sustain 5 tons. There was supposed to have been a heavy cable with a bouy, but for some reason it was missing. So the diver (professional) reluctantly had to make a bounce to that depth with one objective - to tie on a 5inch polypropylene rope so we could lift it onto the ship.
He told me later that he had a really hard job remembering why he was there even though he was holding the free end of the rope in his hand, and as for remembering how to tie a knot he only managed it on the 3rd try.

Maybe it's not just a deep problem, but water conditions like cold or visibility... narcosis depends on a lot of factors!
Last mont I went a 52m dive, 16' bottom time, and came back with 80 bars after 51', but the visibility was about 50m. Everething is circunstancial.

 

[wedivebc]

Since we're started, the optimal support team needed for one buddy pair to make a safe dive to 100' using AL80's would be this:

1 buddy pair (2 divers) both equipped with AL 80's

2 support divers equipped with dual AL 80's and 2 AL 80 stage bottles per diver, one of which will be carried as a redundant air supply for buddies #1 and #2 and one of which serves as a Murphy bottle to account for the possibility that one of the other stage bottles packs it in or that one of the support divers needs help. these two support divers will initially be stationed at 100' but will be relieved by 2 other similarly equipped support divers after 10 minutes, after which the first two support divers will take up station at the stop depth and wait for our risk taking buddy pair.

You need 1....no make that 2 DIR divers to offer bitter criticism and 2....no make that 4 other divers (call them redundant support divers -- After all redundancy is good) to follow around the DIR divers screaming "we don't care" through their regs during the entire dive. The DIR divers are, of course, not wearing computers, but their 4 support divers can keep them safe anyway.

Oh, and we need Leigh Cunningham. We just can't make a dive like this without Leigh Cunningham. (if you don't know who this is, see the attachment)

Finally, we need at least 2 divers on rebreathers to make the video.

So, according to my calcualtions, a team of 13 support divers will be sufficient to allow our buddy pair to make the 100' dive safely.

Within the NDL's of course. If our buddy pair wants to put their computers 2 minutes into deco then we have a whole other rat's nest of problems that have to be solved.

R..

OK not fair, keyboards aren't cheap and they are really hard to clean when the coke sticks to the keys.

 

[drbill]

Haven't read all the posts in response to this, but I did have one important question: Is this a one-way, or a round-trip, to the maximum depth?

Although I do deep dives on occasion, I prefer to test the "limits" of how LONG I can stay underwater on a single tank. The more bottom time, the more potential video footage on a single dive.

 

[scubak]

I believe that to go "deep" to see cloud sponges, wrecks and what not....that you can do plain air...however, this is not the depth for an AL80 nor even a steel HP102. Once you hit 100ft you just add deco time and the safety margin is not enough. yeah, you might have a pony bottle but why not just band up your 102 or 104 or 80 and carry a sling and be safe?
I am really getting tired of "new" divers doing "bounce dives" to just get a bottom limit.
If you can't do the math...don't dive it. There is a reason for going deep and the equipment necessary to do it safely. Plus add in the factors of narcosis and deco times and you better know what youre doing so you don't become a statistic...
Safe diving to all.
Kirsten

 

[Hank49]

For the benefit of all n00bs reading this thread who've never dived beyond 60 feet I feel this should be said. IF YOU DO for whatever reason, find yourself at 200 feet (maybe you didn't pay attention dropping down the quarry or reef wall. I've seen it happen) trust me, you're not going to die. The ppO2 is 1.4 on air so you're not likely to black out. You will be narced but it isn't all bad. You COULD have an equipment failure but that's about as likely as having a front tire blow out going 70 mph down the freeway. Just keep a cool head and start your accent. You can go faster than normal (2 ft/sec) up to 140 feet too because the % pressure change is like going from 30 to 20 feet. From there go 1 ft per second to 30 feet and stop for 3-5 minutes (if you have computer, follow directions) proceed to 20 feet and stop for another 5, go to 10 feet and stop until your air is low. I've read a lot of posts here that make it seem like it can't be done and you'll die trying. It can be done and many people do it for fun. Dangerous? yes. But if it happens to you, don't panic. You'll be fine. Hank