Kudos to the Ginnie Staff

[Soggy]

BabyDuck, there are a couple issues here. The first is, why aren't doubles allowed at the intro level and the second is why are singles allowed at all. My opinion is that no one should be in a cave (or other overhead) with a single and no one should be in a cave without doubles and to teach otherwise is irresponsible.

Karstdvr, With regards to 1/3rds on doubles and a huge loss of gas...I agree, it might not even be enough there, but your odds of getting out alive are close to doubled since you will be able to save half of your exit and emergency gas, leaving you with close to 1/3rd of your original gas supply left.

 

[lamont]

You know Sheck used to say 1/3s was a (bare) minimum,and he used to say the same scenario that if you had a failure on doubles at maximum penetration and had to air share you more likely were not going to make it out. Even if you have the ability to isolate you have 2/3 of a buddy and a partial of a single tank at that maximum penetration point. Now the team will have elevated breathing rate and will have to swim and negotiate restricitions on a 7ft hose-will the team make it out,let me contact Las Vegas because the odds aren't real good.

One of the dives in Caverns Measureless to Man that he almost didn't come back from involved catastrophic gas loss of his buddy's gas at max penetration and on 1/3rds they barely made it back to their stage bottles.

Yeah, page 145 of my edition, at 4,518 feet in Atlantida with Ken Fulghum

 

[notabob]

I happen to agree that use of singles in overhead environments is unacceptable, H-valves or not. Be it cave, wreck penetration, or deco. What bugs me, is that the main justifications that some agencies seem to have for requiring a single at intro level is to limit the diver's gas "so they have less chance to get into trouble by penetrating too far" and "because requiring an intro diver to wear doubles unnecessarily taskloads them." I'm not going to rehash the same points that people have been quarreling over for the last four pages, but here're a couple of thoughts that I don't see many bring up, whether in the discussion on TDS or here.

First - if someone wants to break the rules, restricting them to a single and 1/3rds will not stop them!! The same intro diver that would dive doubles to 1/3rds, will be the same diver that will also be doing jumps, gaps, traverses, go below 100ft, and who knows what else - whether they're on a single or doubles. To expect otherwise, is foolish, IMHO.

Second - if the intro diver feels too taskloaded wearing doubles - what the hell are they doing inside a cave!?!? Learning to dive doubles should be a requirement for intro. Just as the requirements to learn proper buoyancy skills and proper trim. Agencies state that good buoyancy and trim are prerequisite for going inside a cave. Doubles should be too. And those of you saying that if someone wishes to dive doubles in a cave, they should continue on to full cave - stop and think for a second. A diver is 1200ft inside a cave. We don't know if the diver is full or intro. Just a diver, 1200ft in. Is the cave going to be more forgiving if the diver is at the intro level vs. full? I doubt it. It's the same cave. Same flow, same vis, same conditions, and just as capable of killing a less-than-prepared diver. It's the same unforgiving cave, hence equipment requirements for an intro diver should be exactly the same as for full cave. The only limits placed on the intro diver should relate to actions they are not yet allowed to perform - penetrating too far (hence only 1/6 on doubles, vs. 1/3rds), complex navigation, and complex gas planning (i.e. stage diving) - not on their life support equipment.

-Roman.

 

[H2Andy]

I happen to agree that use of singles in overhead environments is unacceptable, H-valves or not.

how many cave fatalities involve students in single tanks?

 

[notabob]

how many cave fatalities involve students in single tanks?

I'm aware of the stats. By the way, I'm going to assume that you were referring to intro divers in singles, not students in singles. The numbers I've heard are minimal. However, statistics can be spun very easily. This particular one holds almost no water, unless you or any other person that references it can tell me the ratio of intro divers that are actually diving in singles vs. doubles. Not just "certified" and making a trip or two a year, but actually actively diving. I confess that I don't know the actual numbers, but I'd be willing to bet that the overwhelming majority of intro-certified divers that are actively diving in caves, are doing so in doubles. Hence, a higher number of intro divers in doubles that have died. That would be my explanation for the statistics. I'd also expect the majority of the single-tank intro divers to be only occasional cave divers, though I'm afraid I don't have any hard statistics to put behind that theory.

-Roman.

 

[notabob]

how many cave fatalities involve students in single tanks?

Incidentally, I happened to notice you wearing doubles in your profile pic. If diving a single is so safe in caves, how come you're diving in doubles? Do tell...

 

[Soggy]

how many cave fatalities involve students in single tanks?

Once again, wholly irrelevent to the discussion. The issue revolves around what the potential failure points are. Without realizing it, you are making an argument against isolation manifolds altogether, since you do not see burst disk failures as something to be concerned with.

Which is more likely to get you back to the surface alive with a burst disk failure at maximum penetration?
a) 1/3rds on a single tank
b) 1/3rds on doubles

Or even better, since we are INTRO divers
c) 1/6ths on doubles

I notice you are an intro level diver and are wearing doubles in a cave in your profile. Are you a hypocrit or are you willing to put your life where your proverbial mouth is?

 

[H2Andy]

Once again, wholly irrelevent to the discussion.

quite relevant. you're creating a problem (failure of single tanks as a significant
danger) where one doesn't exist.

if it does, please show me the data

Incidentally, I happened to notice you wearing doubles in your profile pic. If diving a single is so safe in caves, how come you're diving in doubles? Do tell...

simple: i am working my way up to full cave (slowly) and wish to do it in doubles
since it's what i will be ultimately using. nothing like doing tons of dives in the
config of your choice.

i did cavern and Intro. on singles and didnt' have a problem with it.

Are you a hypocrit or are you willing to put your life where your proverbial mouth is?

ok, that's it. i'm not talking to you again until you can show me you can
have an argument without resorting to name calling and with a little bit
of respect.

by the way, it's spelled "hypocrite"

 

[notabob]

simple: i am working my way up to full cave (slowly) and wish to do it in doubles
since it's what i will be ultimately using. nothing like doing tons of dives in the
config of your choice.

so doubles is your config of choice. why? what makes it a preferred configuration for your current diving as an intro diver inside a cave?

 

[H2Andy]

so doubles is your config of choice. why? what makes it a preferred configuration for your current diving as an intro diver inside a cave?

ok, tell me what part of my previous answer you don't understand, and i'll try
to clarify eyebrow

i am working my way up to full cave (slowly) and wish to do it in doubles since it's what i will be ultimately using. nothing like doing tons of dives in the
config of your choice.

why will i be doing post-full-cave diving in doubles? because i don't want to be limited to a very small penetration window (i.e. a single)