Diving and surviving with double Rebreather

Marc T

This thread is a reaction when seing the double HH rebreather but dont wanted to highjack the thread so I prefer to put it alone here, specially because Im a little critical with double backmounted Rebreather


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combination of OTS CL and BMCL allows (relatively) streamlined configuration.
The rig also sports the new GolemCCR wing designed to fit HH CCR and most other RBs[/quote]

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Exactly between dream and nightmare!
This back wiew of this naked double Rebreather is the start point of a possible dream, but...
How to connect the feeding hoses to avoid one of the Rebreather to become useless in case of the loss of one reg ( dil or o2 ) will give you ( had given me )lot of headhache. Probably dil are sidemounted, then again problem to place sufficent gaz for the suit and wing inflatiion in a streamline way. then lights cannister
Problem with such a bulky and heavy rig is that you drastically increase the risk of entranglement or impact when scootering and decrease the possibility of self rescue.
If ou add to all of that the fact that you really need two Rebreather for the dive it has been designed for, you must deal with the idea that you have double chance to abort all your dives with this system.
Finally monstruously bulky and unreliable,im afaraid the front wiew of the thing will show you a real nightmare.
I sincerely hope for you Im wrong and youll get fun and safe dive with that.

Speaking of double CCR ( cave )diving, few divers have shown us the way ( double side mounted for Menniscus, one back mounted and a sidemounted for Stanton and Vollanghten ).
The biggest problem is then to learn how to dive with it.
Im sure there is a ( not so small market ) for a good sidemounted, because a sidemounted is not only a back up rebreather, correctly used the WOB is perfect and you can very safely use it with a classic twin which give you many gaz in case of problem.
When you are easy with side mounted Rebreather and twin, then easy with backmounted RB, youll have a chance of being easy with two RB.

Special thanks to John Vollanghten and Xavier Menniscus for their thoughts and help about Sidemounted BOB.

Double CCR is a difficult way but IMHO not only for heros and its a shame not to listen the ones who show us the way and share with us so easily.

Any comment reaction will be very appreciated.

Marc T

Drmike

Have to say Marc I love my back up Rebreather configuration.

It works really really well (once I developed the best techniques to use it)

It is very simple and reliable, the work of breathing feels very good and its just as streamline as a single rebreather. I have a sidemount BOB too but preffer back mount as I dont lose any side mount area for bailtanks/drive gas.

I used it in Song hong II exped to 140m

Drmike : photos : Song Hong II expedition (-140m) - Thailand NOV 07- powered by SmugMug

your 100% right that the hardest part is working out the techniques.

The techiques I developed to enable its reliable use are:-

1) BOB and primary Rebreather ADVs share same gas supply so you can never forget to connect dil to bob adv! so flooding is less likley

2) on descent I manually add gas into the BOB so it in part is part of my bouyancy (for same reason as above - prevents flooding)

3) When using BOB critical gas is now O2 so carry second off board O2 only
connected to BOB

4) in event of flood can see cell reading go ape sh1t so gives warning

5) Pre breathe on surface then quick check at target depth


6) totally manual operation

just my thoughts

ps Dave A and Paul G have been diving twin backmount rbs for years in OZ with sucess, similar configuration, be good to get their input, - paul?

pauls old unit:-
Drmike : photos : France (LOT) cave diving - Sept 06- powered by SmugMug

__________________
Cave diving is a sport
Wreck diving is a sport
Diving in general is a sport

'Rebreather diving' is not a sport
its the delusional obsession with a highly dangerous and often inappropriate piece of equipment

Mdemon

Mine is still evolving and whilst I like the current format (butt-mounted scrubber), it does come with different headaches. Learning to dive it required a lot of care, especially on ascents. The twin-format was much easier from this perspective.

I share dil between the two. Both have ADVs and BOVs.

I carry 7li dil and O2 onboard, and a small off-board O2 cylinder. If I get round to doing demanding stuff, I have room on the case for two more cylinders and could add another pair of 3li with reserve dil and O2. This would be so ridiculously heavy that it would only be useful in certain circumstances.

My BOB is currently 100% manual. I am looking at ways of making it 100% ECCR - electronics isn't the problem but where to put them in the unit is.

When fully ECCR'd up, I'll dive the BOB as the primary (bigger scrubber) and save the "proper" one for emergencies. I was on the verge of buying the Pelagian O2-add for this, but found the Shearwater setpoint controller neatly "upgraded" the BOB for normal use. That means I can leapfrog the current primary (a Classic) and get a better system when available. The Narked@90 Pursuit models looking very likely for this.

The unit case is very robust, so good for overhead stuff. It isn't perfect though and the only way to carry it easily is to wear it.

My dream is to make a small unit out of a solid block of something, with twin axial scrubbers set up for the easiest hose routing. Small, light, redundant, efficient, with every scrap of sofnalime being used and no trouble for those with glass backs. Currently, the only suitable thing seems to be a truck engine block, which would be marginally lighter than my current unit but has O2-clean issues.

__________________
www.southwestmafia.com

"small minds talk about people, Average Minds Talk About Events, GREAT MINDS TALK ABOUT IDEAS!"

The WRONG Attitude will get you killed.

"Once the agenda-monkeys and perfect-worlders have moved on, perhaps we can do some diving?"

Mark Chase

Hears an old pic of one of the evolutionary modes of Johns rig. (Or pile of crap as his freinds refer to it )

The fact hes still alive is testiment to an amazing level of diver skill

__________________
See my "Doing It Chasey" video where I'm locked into a padded room, naked, with two ball bearings and within an Hour, I manage to lose one and break the other!!!

Kevin Juergensen 16/11/08
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Marc T

In fact this sort of double rebreather is rather easy to dive because the "buoyancy center" is closed to the "gravity center".
But mounted of the second scrubber seems to became over the last five years a "standard" that I cant used on my double Rebreather because the main was/is a RB80 clone, but I could appreciate the back mounted CL "a la Kiss" for the backup loop.

Problem is the size, weight and complexity of the Rebreather that you cant even turn easily in a simpliest config for "usual dives" (where double RB is not absolutely necessary ).

Thats the reason I went to sidemount BOB and AFAIK its what Paul G done.

Dil feeding prob is the same and I choosed to use a gas block thats allow to feed both breather and OC reg, but IMHO this gas block immediatly disconnectable to avoid gas loss in case of any MP hose rupture.
All my dil are external and sidemounted (actualy two 7 liters ).

Back mounted on my mCCR EDO 04 are a 4 liter Oxy a 4 liter dil for wing/suit/occasional dil for Rebreather
à 1 liter oxy for "deep" backup but I often put an other 6 liter oxy at the deco stop ( in fact loss of oxy become one of the main risk ).

So in fact the whole system is modular and easy to carry compared to a double breather.

buoyancy problem have been solved that way:
1 / my Sidemounted is neutral in water when half full so he float other my ( left) shoulder along the back mounted cylinder and so the WOB is perfect in any position.
2/ after pre breath I use my back mounted on descend and most of the time in horizontal travel
3/ from time to time and everytime on ascent I go to my sidemounted so no buoyancy problem as my backmounted is heavy enough for not having to deal with even if he his full of gas ( exhaust valve does its job and thats all ).
4/ O2 add is mCCR hydrogom with quick disconnect andeasily changed from one Rebreather to the other to avoid mistake and also to avoid the use of the back up O2 ( but you have to try it from time to time too, dont forget that if you loose your O2 your dead )
5/O2 control is by rEvodream for each loop plus a backup display for the EDO.
6/ using double Rebreather youll certainly notice that your dil comsomption is twice, and I also noticed that being necessary heavy to help buoyancy control you need more gas for the wing

I Anyway I must say that Im very pleased with this system because not so difficult to dive with ( at least in cave ), easy to wear and service, possibility to use separately the sidemount, the EDO.

Just playing with the idea to go to a rEVO for back mounted because the EDO 04 beloved for his reliability, become heavier with the years.


And ho hum as I cant stop dreaming I started to build a double breather from scratch, but a very compact one just for my really old days

Mdemon

Or "triumph of hope over experience"

That's quite an old pic now, but it shows the bottom scrubber quite well.

Modular is an excellent system and one I hope to copy one day. By that, I mean something which just clips on and off. Currently it takes about 30 mins to add the second loop and get it all tested, but splitting the unit doesn't make it easier to carry unfortunately.

I think this is an excellent idea, and look forward to seeing the results. My vertebrae are especially interested, having prolapsed two discs in the past!

__________________
www.southwestmafia.com

"small minds talk about people, Average Minds Talk About Events, GREAT MINDS TALK ABOUT IDEAS!"

The WRONG Attitude will get you killed.

"Once the agenda-monkeys and perfect-worlders have moved on, perhaps we can do some diving?"