Kudos to the Ginnie Staff

[H2Andy]

My SAC doubles and my buddy's goes up to .75 cft/min. Now, I'm breathing off his long hose and, combined, we are breathing a 1.75 cft/min SAC * 3 ATA = 5.25 cft/min at depth...on 54 cft of gas.

first, you're over-estimating the stress. OOA is second nature by the
time you get through Intro. the buddies i dive with, i am confident
this will be routine. a little stress, sure... a whole lot of panting,
no... i've had two "significant" situations in a cave, with an intro buddy,
and we managed fine.

assuming a whole lot of stress, we'll calm down shortly, and we'll get shallower shortly.

also, you overstress the difficulty in swimming while sharing a hose.
it's not much slower than swimming by yourself at a reasonable
rate that is not going to wind you or tire you out.

also, you under-compensate for the current. that's going to be big
boost.

it'll be an emergency, yes, but provided we kept to 1/3rds, we'll be ok.
you basically weighed it against reason and in favor of your argument.

and how likely is this going to be? really... how many tanks do you know
just go like that?

as opposed to the more real danger of a new student and his buddy
getting into deco inadvertently and then having a whole series of problems
as a result of that?

i would say the second is more likely, and that's why diving with a single
tank is not, ipso facto, "more dangerous" for student divers.

also, if you're so concerned about this, shop around. make sure you
take your class from a full-cave instructor so they can sign you off.

you get what you pay for.

 

[GDI]

Ok I'm game lets look at this as a training type thing But I would rather not play what if scenarios.

Let's do a little math

We have two divers with al 80s, both w/ 3000 psi in them
thirds is 1000 psi (26 cft), so turn at 2000 psi
To make things easy, we'll assume a .5 SAC rate and that we're diving at 66 ft (3 ATM). That means, we are breathing 1.5 cft/min on a relaxed ride in....
17 minutes later, we turn the dive because we have reached thirds

Oh crap...my tank just exploded and I'm not too happy about it.

When you say the tank explodes I am assuming that you are just talking about a valve and not a regulator that you could just shut down. I am assuming that you are not talking about a actual exploding tank because that occuring would most likely cause a severe injury if not having killed you.

My SAC doubles and my buddy's goes up to .75 cft/min. Now, I'm breathing off his long hose and, combined, we are breathing a 1.75 cft/min SAC * 3 ATA = 5.25 cft/min at depth...on 54 cft of gas. That will last us about 10 minutes on a 17 minute swim (actually, much more than that because we are now swimming while sharing air and may have also silted up the place because of the exploding tank). Yeah, I'm sure the flow will help push us out a bit, but not that much.

In your math did you calculate on the remaining gas in your cylinder that is still available before you decided to breath on your buddies long hose. You turned at 1/3's therefore you would of had a total of 51.6 cu ft of gas still bellowing out of your tank ( I will assume the valve blew because you seem to be alive in your example) and at 66 ft that would most likely give you better then five- eight minutes of breathing gas that you would have just wasted by going to your buddies long hose placing you both at a higher risk then what may have existed, you have air you still breath it. If you had the awarness and proper mindset to handle a problem like this then you would continue to breath your cylinder down until empty perhaps only holding your buddies long hose until you needed it and not wasting valuable air. Then when it was gone you would switch to his long hose and continue the exit with a chance of still possibly doing a safety stop in part or in whole subject to the amount of air he would have available. At that point you would hold out for as long as possible to settle yourselves down.

How far did we get before we drowned?

Don't you wish you had those doubles now?

The next morning there is a post on TDS/SB: "Two Intro to Cave divers die 300 ft inside a cave in High Springs, FL" where everyone is talking about how stupid they were to be diving on singles.

Well you didn't drown because good soild training allowed you to keep skills in mind and to resolve a problem to a successful outcome. Why because since you stayed on your cylinder until it was empty you were able to clear the water and have 2 minutes worth of air to spare (assuming you stayed at 66 ft the full 17 minutes until exiting)

For your information such a very thing occured while Ice diving one day and good training is what saved our asses. Poorly trained skills are the same as not having those skills. Not having good skills and knowledge causes panic and failure

 

[plankspanker]

The history is completely irrelevent.

All that matters is that NACD is telling students that diving in an overhead environment without adequate redundancy or gas requirements is acceptable. It is not. You should not be in a cave or wreck without redundant gas....period. There is *no* justification that can ever get around that simple concept, historical or otherwise.

I am not trying to be a jerk about it but while I think your intentions are good and your arguments are good if I am not mistaken you have no personal experience with this at all and you are coming across (to me anyway) as a know it all.
If you don't agree with the policy and choose to go the GUE route because "they do it the correct way" then that is fine but for you to be arguing about policies and procedures in a section of the sport that you haven't participated in smacks of arrogance. Let the people who live and breath cave diving every day deal with the policies and make your own decisions based on your own reasons but try to refrain from telling everyone else how it should be based on second hand information.

Again I may be wrong and you may be full cave and have been diving in Florida for years and even if you aren't you are certainly entitled to your opinion but I think you need to keep it in perspective when you are telling people they are wrong.

 

[ArcticDiver]

Oh, that explains it. Thanks GDI I just avoid TDS.

With Good Reason.

A Fellow Avoider

 

[GDI]

The history is completely irrelevent.

All that matters is that NACD is telling students that diving in an overhead environment without adequate redundancy or gas requirements is acceptable. It is not. You should not be in a cave or wreck without redundant gas....period. There is *no* justification that can ever get around that simple concept, historical or otherwise.

Sog I'm not against you But I do need to state one more time that it is not just the NACD that has this limitation. I am working with the NACD reviewing standards and this just happens to be one of them under review and it has been for some time. If you want me to go to the table to have it changed then I need better reasons than what I am seeing on any of these chat boards. The safety record of Intro divers on single tanks speaks for itself. and again I can see both sides of the issue.

 

[karstdvr]

The history is completely irrelevent.

All that matters is that NACD is telling students that diving in an overhead environment without adequate redundancy or gas requirements is acceptable. It is not. You should not be in a cave or wreck without redundant gas....period. There is *no* justification that can ever get around that simple concept, historical or otherwise.

I would say if an intro diver on 1/3 of a single staying within the limits of their training is more than adequately safe. If there are no tight passages (can go side by side),jumps,gaps etc then where is the inherent danger? There isn't much I haven't seen in cave diving, but I'd like to get a unique perspective on justification for your stance. I really can't say history is irrelevent,because all of our rules have a historical perspective, and I am trying to come to grips why history says we don't have accidents on a single,but we do on doubles. I appreciate your opinion,my concern is keeping the sport safe,and that is one of my duties,and this will surely be a topic I will have to face soon.

 

[Soggy]

i've had two "significant" situations in a cave, with an intro buddy,
and we managed fine.

Were you at the limit of your penetration? If you had been at the limit of your penetration, would there have been enough gas to get back? How do you know? Did you figure it out or did someone just tell you that thirds is enough?

also, you overstress the difficulty in swimming while sharing a hose.
it's not much slower than swimming by yourself at a reasonable
rate that is not going to wind you or tire you out.

Hey, if you say so. I've done it many times for practice. Even in just open water it slows you down. That combined with the siltout you probably just created when your burst disk blew, and you're likely to have a nice slow swim. I hope nothing else goes wrong, because if it does, you just died.

Getting shallower is irrelevent, by the way. You were shallower when you came in, too, thus your gas usage reflects that. You can just average out the depth from an analysis perspective.

also, you under-compensate for the current. that's going to be big
boost.

I suppose it depends on how strong the flow is. It'll help you, but planning on it helping you a lot is a bad path to go down.

it'll be an emergency, yes, but provided we kept to 1/3rds, we'll be ok.

NO. It isn't. 1/3rds on a single tank might not be enough. Even if you make my example less extreme, it is still not going to be enough to get you out and up safely. You are trying to justify it because 'you were alright'...Lots of people have done stupid crap and survived. It's called luck.

and how likely is this going to be? really... how many tanks do you know
just go like that?

How many people have had burst disk failures or tank oring failures? Many. It can happen. You better be prepared if it happens to you. With doubles, I can preserve half my gas. With singles....well, I hope your buddy was diving a bigger tank than you and is pretty calm. I'd sure be mighty upset if I lost all my gas with no redundancy and was 60 ft underground....

as opposed to the more real danger of a new student and his buddy
getting into deco inadvertently and then having a whole series of problems
as a result of that?

Come on, be real....that is the worst argument I've ever heard. How the heck do you "inadvertently" go into deco? If you are so incredibly DUMB that you accidentally go into deco, you shouldn't even be DIVING and certainly not CAVE DIVING. (by "you", I do not mean you specifically, I mean the general "you").

Hypothetically, say you're right, and that the typical Intro to Cave diver is so incredibly ignorant of how to SCUBA dive that they manage to get themselves into a decompression obligation without any training on how to get out of it.......
If I had a LP120 in cave country, I'd have about 150 cft of gas. Compare that with a set of double 72s...144 cft. Which is safer? Which one is more likely to "accidentally" (good grief!) get me into a decompression obligation? The Intro to Cave rules say I'm better with the LP120. If you agree with that, I just lost all respect for you.

For the record, I will be doing my Intro to Cave class this weekend, which is why I have such a vehement and vested interest in this topic right now. I will be training in doubles. My interest is to expand my overhead skills to make wreck penetrations safer. I'm not particularly interested in the cave diving aspect itself, though I'm told that may change. I wouldn't ever even consider going inside a wreck without doubles strapped to my back and would discourage anyone else from doing so. A cave is the same way...you can't go up, so you are stuck underwater---you better be ready to stay put for a while and handle anything murphy throws at you.

I wasn't even aware that there were agencies that were so incredibly ignorant of basic dive safety rules and so oblivious to basic reasoning that they would, get this, not only ALLOW singles, but specifically DISALLOW doubles. I mean, it seems so incredibly asinine that I can't even comprehend what could possibly be going through your brains or what part you just don't get. Here, by "your", I mean everyone arguing *for* this ridiculous rule along with NACD and NSS-CDS. I just can't wrap my brain around it. Usually, I can at least understand what is going through people's minds, but this seems so incredibly simple to me, I just can't comprehend how people don't "get it."

 

[Jason B]

I agree with Andy. If you want to dive doubles in an overhead at the intro level, don't plan to stop at intro, and get a provisional. Simple as that. If your instructor is not qualified to teach to full cave and as a result can't sign the wavier, maybe they have a full cave instructor they work with that will sign off on it as Rich suggested on TDS.
Have you consider an instructor for full cave? Contact them, they may help you out.

Bottom line is that Intro, as a non-time-limited certification, is a recreational level cave cert and only allowed to dive a single. As long as you plan to advance on in your training, you can get a waiver. You or your instructor may have to do a tad bit of leg work, but you can sure as heck do it.

 

[Soggy]

I would say if an intro diver on 1/3 of a single staying within the limits of their training is more than adequately safe. If there are no tight passages (can go side by side),jumps,gaps etc then where is the inherent danger?

Read my post regarding what happens if a burst disk (I used the term "explode") fails underwater near the limit of your penetration. The math shows that 1/3rds just isn't enough.

I really can't say history is irrelevent,because all of our rules have a historical perspective, and I am trying to come to grips why history says we don't have accidents on a single,but we do on doubles.

My guess is luck...and probably the fact that a lot of intro divers don't stay at that level long enough to kill themselves (they move to full cave or sneak dive doubles), are smart enough to ignore this particularly foolish rule and use doubles, or took the class to beef up their local wreck diving.

 

[H2Andy]

NO. It isn't. 1/3rds on a single tank might not be enough. Even
if you make my example less extreme, it is still not going to be enough to get you
out and up safely.

using this rationale, 1/3's on doubles at the edge of your penetration may not
be enough either

do you recommend that all divers leave stages behind when diving, in case
they have a loss of air at the maximum range of their doubles?

btw, i have refrained from using epiteths to describe you our your argumens.
i ask that you return the favor or i'll stop discussing this issue with you.