Burst disk, neck o-ring, valve, dip-tube clogged, manifold breaks...try and think how it MIGHT happen, you seem to be focussed on how it might NOT happen. Down that path lies death.
Cave 1 / Intro Expiration & Limits
- Thread starter CaveSloth
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tmassey
Contributor
You’re *actually* counting the gas your buddy has?!? Really?
This ain’t recreational diving. Sure: my buddy has extra gas. But that gas does not play a role in *my* margin of safety. To paraphrase John Chatterton: you are expected to be self reliant. You can be opportunistic and use a buddy when you can. But any plan that starts with “a single failure and I’m gonna buddy breathe for 1500 feet through a cave to survive” doesn’t cut it.
Wait till you try it. You’ll move 1/3 as fast. Try it with zero viz: 1/10th. Gas sharing cannot make up for a large amount of gas loss. It might make up for the unexpected small holes in your 1/3 gas strategy (like the missing 200 PSI). And I gave a perfectly fine example: block a valve with crud, and a manifold won’t help you. You lost that gas.
Never mind the not unrealistic situation of buddy separation.
Tech diving is a completely different mindset. Your math is fine. Your entire perspective of what is involved is suspect. Normal recreational logic does not apply.
This ain’t recreational diving. Sure: my buddy has extra gas. But that gas does not play a role in *my* margin of safety. To paraphrase John Chatterton: you are expected to be self reliant. You can be opportunistic and use a buddy when you can. But any plan that starts with “a single failure and I’m gonna buddy breathe for 1500 feet through a cave to survive” doesn’t cut it.
Wait till you try it. You’ll move 1/3 as fast. Try it with zero viz: 1/10th. Gas sharing cannot make up for a large amount of gas loss. It might make up for the unexpected small holes in your 1/3 gas strategy (like the missing 200 PSI). And I gave a perfectly fine example: block a valve with crud, and a manifold won’t help you. You lost that gas.
Never mind the not unrealistic situation of buddy separation.
Tech diving is a completely different mindset. Your math is fine. Your entire perspective of what is involved is suspect. Normal recreational logic does not apply.
OP
CaveSloth
Contributor
Thanks. The discussion is definitely thought provoking.
If nothing else it helps the untrained to recognize the importance of good training and being mindful of Murphy.
OP
CaveSloth
Contributor
I am convinced now more than ever that thirds is overly aggressive. Re-framing my whole perspective to get into detailed exploration and appreciation of the first few hundred feet of cave. Why do I really want to go far in anyway? Most of the cave just looks the same as the last part lol.
tmassey
Contributor
No one likes being forced to be limited. To be told “you’re not good enough.” (Yet!
) But if you really have shifted your thinking in this way, I applaud you. That is a much healthier and safer way to think.And if you think that way, then choosing a class based on 1/6’s or 50 cu ft or 2/3 of 1/3 doesn’t really matter. Then you can ask the *right* questions. 1/3 will come...
OP
CaveSloth
Contributor
BTW I’m scheduled for Cave 1 with my teacher in Feb. Wish me luck.
Who is the instructor?
victorzamora
Contributor
The thing that really put it in perspective for me was a combination of a story by Andrew Ainslie and a story by one of my instructors.
The gist of the lesson is: It doesn't matter how much gas you HAVE, it's how much gas you have immediate access to. Read the story linked above by Andrew Ainslie. My instructor's story was about a near-fatality in a well-known, "tourist" cave very near the entrance. I'm talking about easy access for Full Cave divers on thirds, achievable access by Intro divers if the flow is low. Two divers were on scooters with two stages each and they nearly died because ONE reg was off that the diver thought was on.
There have also been a number of fatalities where one (or more) of the victims still had breathable gas in their tank(s).
When you're in a SHTF scenario, you can't always be counted upon to be the most calm, cool, collected, rational diver around. Being excessively conservative can keep you from ever getting in the water, sure....but diving thirds is absolutely "aggressive" in most scenarios. Heck, even in a high-flow cave that "shouldn't take any gas to get out of" isn't that simple. Andrew's story above is a high flow cave he was familiar with. He should've been able to make it out in record time.
You are absolutely right, 1/3rds is not conservative at all, and even the creator of the concept felt that way later.
Distance is one of those false measures of cave diving ability. People like to throw out numbers as a measuring stick, which strokes an ego, than actually having a microperspective of the cave.
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