DumpsterDiver emergency ascent from 180'

[Colliam7]

among them that an AL13 can make more of a difference than is widely acknowledged in the many pony cylinder discussions on SB, for dives within recreational limits.

I honestly don't think the issue in previous discussions has been whether an AL13 can make 'a difference'. ANY redundant air supply, including a 1.7 cf Spare Air, is better than nothing (EXCEPT where it instills a false sense of confidence in the diver that causes them to push limits in an unreasonable manner). Rather, the discussions have been more about what represents a reasonable redundant air supply for diving at recreational limits (130'). Clearly, that was one of DD's pet issues, and he made no secret of his disdain for larger bottles. And, he and I, among others, disagreed on that point.

If I go out of air at 180', or even 130', I would certainly prefer to have an AL13 to nothing. But, I also would prefer to plan for such a contingency, if I am going to be diving alone (as he was), and carry a redundant air supply of sufficient volume to avoid being in the position of DD in the video, 'inflating the BC, and Trying to get shallow ASAP'. But, he didn't go out of air at 180'. It is notable that he made much of his ascent on his (leaking) backgas, and only after he was shallower switched to his AL13, after which he made a slower, controlled ascent.

DD is a good diver, with considerable experience, and I am not surprised that he successfully reached the surface. But, my primary insight from this video is not so much that an AL13 'can make more of a difference'. Instead, it is I have no interest in diving to even 130', much less 180', on a single back-mounted cylinder (which I have periodically done in the past), without a reasonable redundant air supply. I can probably drive across Death Valley National Park in a car with a punctured flat in the trunk, and a donut on one of the wheels, put there 'emergently' after I had a flat in the middle of the desert. But, I wouldn't start the trip that way.

 

[CuzzA]

ok, so here's what happens here and why it is still stupid.

After watching the video that is a 4 minute ascent from 180ft, with no safety stop. Avg ascent rate of 45ft/min. Quite slow given the circumstances, though I think failure to perform a safety stop on a 180ft dive regardless of whether it is a bounce dive or not is just dumb.

13cf is more than enough to take you up from that depth, with that ascent rate, with no safety or deco stop, and no time at the bottom to resolve an issue. What it can't do is keep you with your buddy, bring you back to the anchor line, resolve a situation at depth before starting ascent, complete a deco stop, or deal with an escalated SAC rate.
With his ascent rate, that bottle contains enough gas to allow up to a 0.8cfm SAC rate with no time spent anywhere. Just a continuous ascent rate. If you want to plan that cavalier on your safety buffers then so be it, I've done stupider things in the water as has anyone who has been diving for any length of time, but anyone who advocates that that is safe and smart has never done the math.

I spoke to DD privately about the incident (not this thread) a couple days ago so I can offer a couple of points regarding the discussion. First, he would tell you he isn't advocating anyone ever dive the way he dives. I think he's always been pretty open about that even when he was allowed to participate here.

I questioned the size of the pony on that dive, but in retrospect, everyone is different. A 13 worked for him, I would have probably chose to carry a minimum 19 and more likely a 40 at that depth. But, that's because I don't know my limitations on how I would react during a complete SCUBA failure at that depth. The take away regarding pony size is we need to understand our abilities and personal needs.

Regarding the safety stop, I believe the intention was to do one, that's part of the reason he launched the bag, but then he spots the bag caught in mono filament which is horizontal and would appear someone is trolling for fish. So do you just hope you don't get hooked or since you were never in deco, abort the safety stop and make sure you're not about to be snagged from the ocean? Tough call. Getting snagged is likely to cause serious bodily injury. Becoming symptomatic due to the incident and aborting the SS is not as concerning because A) There's a chamber near by and B) He could always grab another tank and off gas.

Nevertheless, I think the video illustrates why redundancy is so important when solo diving.

Now, what I thought was troubling was the fact that since this incident I've now seen TWO videos within a week where the freaking diaphragm blew out of the first stage. The stated cause was the o-ring was older than one (1) year.

 

[uncfnp]

Why are you unable to do a valve shutdown? We require all of our students to perform this in the pool and use their ability to reach the tank valve as the height requirement for their rig. No exceptions. It is easier than reaching the isolator in doubles

Physical limitations. That's why I am fanatical about making sure my tank is on before splash, especially if I am not carrying a pony.

Don't get me wrong. I think its a great skill for a recreational diver to have. Not necessarily for the shutdown option but more so to open a closed valve. But I was not aware any agency required it as part of recreational training, except maybe GUE.

 

[tbone1004]

Physical limitations. That's why I am fanatical about making sure my tank is on before splash, especially if I am not carrying a pony.

Don't get me wrong. I think its a great skill for a recreational diver to have. Not necessarily for the shutdown option but more so to open a closed valve. But I was not aware any agency required it as part of open water training, except maybe GUE.

not an agency requirement, a program and individual instructor requirement

 

[tech3324]

Can anyone ascertain from the video what exactly failed on the 1st stage? Have a look at 10:04:

 

[tbone1004]

IP creep due to HP seat failure caused the diaphragm to unseat which resulted in pressurized air entering the ambient chamber. Once pressurized, the silicone environmental seal extruded *he'll have a donut inside the cap and somewhere in the ocean is the plug that extruded out* which resulted in HP air going directly through the first stage.
Not something caused by a 1+yr old o-ring, bad HP seat and likely had IP creep prior to the dive which proper pre-dive checks would have identified *use your IP gauge folks!*

Note, this is the exact situation that happened on my HOG D1's during my first ever cave dive in training. You will be able to use the LP side of the regulator because the whole thing is pressurized, but not for long as you have lots of air going straight out the end of the regulator

 

[elbig]

Out of curiosity, is this a diaphragm vs piston problem? Would a piston be just as likely to have this or equivalent kind of problem?

 

[CuzzA]

Not something caused by a 1+yr old o-ring

Thanks for the explanation. The o-ring comment was the response from the manufacturer.

 

[halocline]

First, he would tell you he isn't advocating anyone ever dive the way he dives.

No, he just frequently posts about his extremely aggressive dive practices, he's been doing it for years. If that's not 'advocating' I don't know what is.

If an unknown diver posted half the crap that he has, he would get skewered on this board. It's not much different than a kid posting a video of his speedometer at 120 on facebook.

 

[2airishuman]

I honestly don't think the issue in previous discussions has been whether an AL13 can make 'a difference'. ANY redundant air supply, including a 1.7 cf Spare Air, is better than nothing (EXCEPT where it instills a false sense of confidence in the diver that causes them to push limits in an unreasonable manner). Rather, the discussions have been more about what represents a reasonable redundant air supply for diving at recreational limits (130'). Clearly, that was one of DD's pet issues, and he made no secret of his disdain for larger bottles.

It is my sense that the ScubaBoard "received wisdom" errs on the side of being unnecessarily conservative in this area. The usual recommendation is to use an AL40 because anything less is too small. This recommendation is arrived at by using: an emergency at maximum recreational depth (130'), an elevated SAC throughout the ascent, an extended problem resolution time at depth, and a textbook ascent with safety stop, leading to the conclusion that an AL19 is slightly too small and the next larger size cylinder in widespread use is then an AL40.

I believe that the marginal safety benefit an AL40 provides over an AL19, on most real-world solo recreational dives, is vanishingly small. (I would agree that some dives warrant larger reserves. Among these are dives taken to the very edge of recreational depth limits, dives in very cold water, dives in strong current, dives with difficult shore exits, and dives with an entanglement or entrapment risk. Beyond a certain point, I believe a twinset is the best answer, with the skills and equipment consequences that entails).

If I go out of air at 180', or even 130', I would certainly prefer to have an AL13 to nothing. But, I also would prefer to plan for such a contingency, if I am going to be diving alone (as he was), and carry a redundant air supply of sufficient volume to avoid being in the position of DD in the video, 'inflating the BC, and Trying to get shallow ASAP'. But, he didn't go out of air at 180'. It is notable that he made much of his ascent on his (leaking) backgas, and only after he was shallower switched to his AL13, after which he made a slower, controlled ascent.

I agree with all that. I would like to point out that an AL13 would have sufficient capacity for him to have used it for the entire ascent in the video had he chosen to do so.

DD is a good diver, with considerable experience, and I am not surprised that he successfully reached the surface.

Skills wise, he started an immediate, controlled ascent without finning (which could have triggered severe narcosis at that depth), and then maintained control of his ascent despite the distraction of the regulator failure.

I have no interest in diving to even 130', much less 180', on a single back-mounted cylinder (which I have periodically done in the past), without a reasonable redundant air supply.

On that, we agree.