Kudos to the Ginnie Staff

[Soggy]

again, what's so bloody difficult about getting a written letter from
an instructor to dive 1/6's of doubles?

Intro instructors can't provide that letter.

The point is that people should not even be IN a cave if they don't know how to use doubles. That is a prerequisite of any overhead dive.

I asked it before and you never answered..do you think that wreck penetration is acceptable on a single tank? Or 'light' decompression on a single tank?

 

[wreckchick]

BTW, not everyone's Intro instructor can sign the paper, that's the issue.

R

 

[H2Andy]

Intro divers can only fill their doubles 1/2 full. That way they
still dive thirds, but the penetration is limited and they still have the ability to
isolate in case of a failure.

:rofl:

ok, you pay half of my airfill costs then!

 

[H2Andy]

BTW, not everyone's Intro instructor can sign the paper, that's the issue.

oh???

is this agency-dependent?

 

[H2Andy]

I asked it before and you never answered..do you think that
wreck penetration is acceptable on a single tank? Or 'light' decompression on a
single tank?

i don't know anything about decompression, so i'll pass on that.


as to wreck prenetration, yes, if it's the same as cave, where you have 1/3's
rule and a buddy at your same level of training, sure, why not?

but i don't know much about wreck diving, so i am thinking of it in terms of cave diving

 

[wreckchick]

You're only paying for 80 cuft, that's one air fill

R

 

[Soggy]

as to wreck prenetration, yes, if it's the same as cave, where you have 1/3's
rule and a buddy at your same level of training, sure, why not?

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.

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.

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.

 

[Soggy]

oh???

is this agency-dependent?

Well, it's ALL agency dependent. GUE doesn't have this stupid rule and teaches divers to dive in overheads the correct way.

But, a *full* cave instructor is required to sign the waiver. Not everyone takes intro from a full cave instructor.

 

[GDI]

The equipment standards for the NACD Intro to Cave program are:

10. MINIMUM EQUIPMENT:
A. Minimum 72 cubic feet gas with dual outlet valve.
.
E. Two single hose regulators, one with five (seven foot strongly recommended) foot hose, one with submersible pressure gauge attached. Some recognized method of securing the seven foot hose must be provided. Octopus inflation system is not allowed.

Now the Apprentice level

11. MINIMUM EQUIPMENT:
A. Double tanks are mandatory, minimum volume 142 cubic feet, manifolds are recommended.

Ok doubles are required here But they do not need to have manifolds let alone one with isolation, manifolds are recommended.

No where do I see that the Intro Cave diver is permitted doubles other than in training under the supervision of an instructor. (see my earlier post- first post of thread ). One can turn and call this limit stupid but then that only shows again a inadequate internet knowledge as to why training was done this way historically and continues this way today. The issue of single cylinder diving is not just to limit ones penetration the thought of which appears to bother some divers whose apparent goal orientation needs to be put into check. It was not used to limit the chance of going into deco. Last I knew I was more then capable of getting into deco whether I was diving a single or doubles and that deco was more an issue of the relationship between depth and time and that an error of deco was the failure to know ones status, not equipment.

A historical point of view

Part of this standard was to give those divers who may have opted to progress onwards to Cave the chance to build their awareness of cave systems, develop their buoyancy and propulsion techniques, and to develop overall general safe habits, reduce their task loading and a multitude of other factors. Doubles were permitted for purpose of training at the cavern and intro levels not so much because of the cave divers but because of those divers who used the cave diving techniques as a means to improve their diving skills. Divers such as this were wreck divers and those who were looking to go deeper depths in open water environments. As a response to this the Cave diving community permitted dive training in doubles to accomondate these groups of divers many of whom had no desire to advance further to cave certification but thought that the techniques used to train cave divers were the apex of the sport and discipline of diving and thus sought out the cave training agencies for training. With this in mind cave diving instructors and the agencys agreed to permit training in doubles up to the Intro level was permissible but that the development of those who requested further cave diver training would be limited to what had proven to be the best course of action, that being a singe cylinder with two regulators. The safety record of this limitation speaks for itself.
The standards of cave training agencies has not become "dumbed down", in fact the training agencies are beginning to tighten up those standards to bring about a return to what the perception of who a cave diver is and was.

This single cylinder limtation is not just a standard of the NACD it is also one of the NSS-CDS. Not all agencies have the same standards, this is a concern. There are other agencies out there and I was asked if I would be willing to provide similar sections to the S&P of the other agency that I teach for. No problem here goes.

From TDI's S&P Part 2
Cavern Course.
The following equipment is required for each student:
1. Primary cylinder - volume appropriate for planned dive and student gas consumption. Students are permitted to use double cylinders, but would be limited to the 1/6 air rule.

Intro-to-cave course
The following equipment is required for each student:
1. Primary cylinder (s) - volume appropriate for planned dive and student gas consumption.
2. Dual-orifice (Y) or (H) closed valve or dual valve manifold.

 

[Soggy]

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.