Suitability of varying rebreathers for cave diving

AM

I have cave dived with the Inspiration and I do not really consider it a good rebreather for any type of penetration cave diving or smaller caves.

What other rebreathers are people here using for extended cave dives?

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lizardland

I don't think there is any one rebreather. They all have features that are good but I don't think there is one that has all of them.

Maybe the answer is to build one?

Depends what you want. A Rebreather that is good for long, deep dives in big caves may not necessarily be the best choice for a shallow cave with lots of uppy-downy.

I agree the Inspiration is not a good choice for small caves. I once saw an instructor almost drown one of his students by trying to squeeze him through the entrance to the Font de Truffe... the mouth is so narrow it crushed the OTS lungs and wouldn't let them inflate on exhale. It takes a good bit of squeezing on a small twinset, on the box it took forever. He ended up pulling him out by the feet only when someone else pointed out what was happening.

EBT

The KISS is coming with me to france in a few weeks.

Having said that Im very aware that I dont have offboard plugins, or dumpable water traps, so my bailout is planned appropriately.

The fixes to both are easy (I think);

Plugins; Either at manifold (yuk), or via a second gas inlet (like the newer classics)
Dumpable water traps; Im pondering sticking a dump valve in the exhale CL and blanking off the current OPV.

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Mark Chase

I would have thaught the Meg was the ideal cave unit but it would seem the Mk15.5 is the rig of choice for the deep cave boys and girls. Why this is I dont know. The meg seems ideal as it can run the CIS luna scrubber for max duration diving and it can be rigged with any tank configuration . The problems with the OTS counterlungs remain but surley this is better than having to fly a manual unit in chalanging conditions?

ATB

Mark Chase

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schford

I know a large proportion of Leons customers are cave divers.

I think they like it as its so modular, some configurations include it being side slung with a single counter lung...

I believe they reconfigure depending on needs of the dive.

Stuart

Ken

I think it would be interesting to get Curt Bowen's (Advanced Diver Mag.) opinions on here? I know he now uses a Meg and perhaps he's Armadillo'd it by now. Ken

cedricverdier

I just spent the last month cave diving in the Cenotes of the Yucatan Peninsula (shallow dives, very long penetration, low flow).

I tried different configurations with my Meg and definitely like to use the diluent and the O2 cylinders sidemounted. That way, I can use bigger cylinders (up to 80cf) with a bailout 2nd stage on each. So no off-board bail-out and a good trim.

I also used my Inspiration for cave diving but don't like the fact that it's more difficult to empty a partially flooded loop than with the Meg. The position of the OPV makes all the difference.

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Cedric Verdier
PADI Course Director, ANDI-IANTD-PSAI-TDI-DSAT-DAN-NAUI-CMAS Instructor Trainer
Trimix (CCR and OC) and Cave Diving Instructor Trainer

www.CedricVerdier.com
DIRrebreather member

AM

Thanks for sharing that. It's amazing what instructors will do sometimes.

I spent the best part of ten minutes trying to get under the entrance restriction at Goul du Pont and that's not even big! The yellow lump is definitely too big for these type of environments. I also had to squash the lungs, as you said, quite difficult to breathe. The only way to get under eventually was to back in feet first, get my legs under and then leverage myself under while not breathing and holding the lungs in tight. The case was not without a few deep gouges LOL

The KISS is a revelation from the "profile" point of view.

Regards

AnneMarie

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lizardland

This is why I like the sidemount rebreather, undo 2 clips and 2 hoses and push it through ahead of you. The way I looked at it there was either 2 ways of doing it. Either as rebreather all the way or as a gas extender as the DIR folks do. I chose the gas extension tool. For the diving I do in France, I think DIR/Hogarthian rigged OC system is more or less the perfect setup for that kind of cave diving. What I wanted was something that I could carry on top of that system that would magically make my gas go further but could be ditched when necessary without causing a problem. I don't believe the RB80 fits particularly well within the hogarthian framework so I wanted to make what I felt was a Hogarthian CC rebreather. It was heavily influenced by Duncan's D5 which from what I've seen would be my choice for a cave diver's Rebreather.

How realistic my Rebreather is for cave diving I'll find out in a couple of weeks provided Zak doesn't piss himself at it too much. Unfortunately the £300 I've invested in an EDO scrubber was designed for back mount and is not particularly well proportioned for sidemount so it's on the little 90min scrubber

I'll be interested to see how easy/hard a KISS style Rebreather is to dive in a cave. I don't see why this should necessarily be difficult, if you can monitor a handset then you can dive a KISS.

AM

I'll be very interested in your feedback. Have tried a few sidemounts already, I like the concept of dual sidemounts as long as they are feeding from separate gas sources (not the Y valve, I had a tank o-ring go before).

The KISS is infinitely better in small spaces than Inspiration - there was no doubt in my mind to make the switch.

I was planning to go to the congress in France but it depends on my ribs getting better enough. Are you going?

The gas extension concept is an interesting one but I get concerned as soon as I think that there is a risk I can't manage if I have to make a worst case scenario exit. In the gas extension case, if you have used a SCR or CCR to extend your distance (penetration) and then have a failure and have to make OC exit then I guess that's where it gets interesting. In fact if the scooter fails on top then it could get VERY interesting. All my planning is focussed around the absolute worst case, i.e. a very bad day!!

Regards

AnneMarie

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