Twin Setup for Cave Diving...

All,

I am currently looking at gearing up for some cave diving and have come to the conclusion that twin 100cf steel cylinders with a left and right hand valve are my best option.

I have reached this conclusion because I can manifold them if I want, I can run both the left and right hand valves inside if I desire to avoid roll off and because no one has ever 'died of too much air'.

If anyone feels strongly about this kind of set-up or my line of thought then please let me know NOW to avoid any costly errors!!

Thanks in advance, and I hope to be of use in future discussions.

Dave

PS// Can anyone recomend a particular cave diving instructor at Mt Gambier (South Australia) or are they all on top of their game?

g'day Dave,

Once the rest of the people on this board wake up, you'll get some more definitive answers, but why wouldn't you start off with a manifold? Sounds like you are describing independant doubles.

Where's the cave diving in SA? I think I read about a couple of places on the Nullarbor once, or were you thinking of ducking up to Coober Pedy and taking a dip in an old opal mine?

Ben (SF)

...that's where I'm intending to start off on the cave diving thang. Having spoken to a couple of local cave diving people regarding the manifold setup I'm not convinced it's the way to go. Most people here use independant twins to avoid roll off of the left post (i.e. they use two right hand posts with the left sided cylinder post sitting on the inside).

FYI - currently have a MK20 with Yoke connection, S600 primary on long hose with a G250 as backup on a necklace. Anything wrong with these, should I be looking at converting to DIN (definately getting DIN fitting cylinders with Yoke converters, but how important is it to use the DIN 1st stages?).

Also intending to get another MK20 (or 25) for my second 1st stage - seems like a good idea to keep things simple from a maintenance point of view.

Hmm just thinking - if I'm running a long hose and independant twins then this is a bit stupid! I'll have to do reg swaps and therefore deploying the long hose could prove complicated. I wonder if the independant guys use two long hoses bungied to the tanks (yep I know the DIR guys aren't going to like this!).

Keep the views coming it certainly makes me think and will hopefully help me see the light at the end of the tunnel (or should that be cave?).

Later - Dave.

PS// The guys here also don't use manifolds because of the effort involved in taking them apart to change a configuration - now if money grew on trees perhaps they'd change!?

Ok, I'm DIR so you can guess what my feelings on the independent doubles is, so I won't touch that subject.

As far as going to DIN firststages, I think that you should. The reason is that a yoke style fitting can be knocked loose if you hit the ceiling. A DIN fitting is more secure.

I wouldn't worry much about roll-off if you're using yokes... if you're banging into the overhead enough to roll the valve off you'll destroy the yoke anyway. And then the valve position won't make any difference since with independent doubles you lose that tank's gas with the first stage.
Rick

Why on earth would you opt for complexity when complexity is the last thing you want on a technical dive?

I would be very wary of the advice you are receiving from whom ever you have talked to -- they are an accident waiting to happen, IMO. The disadvantages of independent doubles as compared to manifolded doubles are so great that it's mind-boggling why someone would choose independents. You may as well invert them while your at it .

Not having the money or effort to do this type of diving correctly is not an excuse. That type of reasoning will likely get you killed. In the end, it's your life and your team member's lives at stake. What are they worth?

I know a lot of us feel strongly that what you are contemplating is beyond the realm of sanity. Take a good look at what the most elite group of cavers are doing and ask yourself if what they are doing is really inferior to your ideas (be honest with yourself).

Good luck to you.

Mike

If you run both a left and right valve inside all you’ve done is moved the roll off “problem” from left post to the right post.

That said, roll off is something to be aware of, not to fear. On the other hand, the problems introduced by trying to solve the roll off “problem” (gas management, OOA situations, etc.) ARE something to fear. Just look at the progression of convolution of your kit from your posts: You figured out that gas management/OOA is a problem so you’re thinking about introducing another long hose. Now that other long hose is a problem, so you’re thinking of using a bungee to anchor it. Then you realized that as you swap back and forth between the independent doubles to balance your gas usage that you’ll have to unstow/restow the long hoses or, heaven forbid, add short-hosed second stages to both cylinders.

Good technical gear is simple, simple, and simple. The moment you “solve” a problem that gives you another problem to solve, you should stop right there and look for the root problem, not continue down that road.

The real solution to this problem is to get your technique to the point that you’re not bumping the cave and when you do a quick reach back will make sure you don’t have a roll off. If your passages are so tight that you can’t help but bump the cave ceiling, you should consider going sidemount.

As for a cave instructor, get a bunch of folks together who are interested in caving, technical diving and fundamentals and fly in a GUE instructor (www.gue.com).

You asked

Roak

My advise is to choose the instructor. Depending on the instructor and the agency you may not have a choice in the configuration you use. I agree with others here that manifolded (with an isolator) doubles are the way to go. However, in different parts of the wold they do things differently so see what the instructor says. Roakey is correct rolloff is not a problem. Don't bump and if you do reach back and check. I would'nt fly anyone in. It's hard to teach in a cave you don't know. Somewhere on the continent there is a good cave instructor. I just completed a NACD course, I think it was great. The NACD has been cave diving a long time, they know how.

All,

Thanks for the replies. Having read the info here and in the thread above I have decided to contact a local Cave Diving instructor and see what their opinion is - just gathering more info.

The cave instructor has been recommended to me by Richard Taylor (TDI Aust) and I therefore suspect that the manifold system will be used - that's what he tends to use but I'll let you all know what the instructor here decides and give you the reasons if it's independant twins!

Later - Dave.

Anyone have an opinion on a Transpac II over a backplate and harness (talk about opening up the flood gates!)?