considering RB

[solocavediver]

Hi,

I think you have to learn all over again that what you are doing is much more dangerous than ordinary scuba. Like you did when you started cavediving, only more so. Rebreather diving is roughly 250 times as dangerous as open circuit, something which used to be true of cavediving but isn't any more now the safety principles are understood and training schemes in place. But it still is true of rebreathers, especially if (as in your case) you are trying to get more of a gas saving than you'd get with an RB80 or other semiclosed rebreather.

Having faced this very same decision myself, I decided to wait for the Open Rev ("Apocalypse") rebreather to come out, and content myself in the meanwhile by playing around every now and again with my homebuild - and carrying on caving and cavediving. This is because it has been designed to a very rigorous safety standard, whose details you can view on the Net. I have been impressed at various points by the generally scientific attitude of Alex Deas, the publicly visible member of the design team. The Apocalypse will be the first rebreather whose plumbing has been designed to the relevant safety standard, and whose electronics have also been designed to the relevant safety standard (EN61508 in Europe). By contrast the Inspo family of rebreathers seem to have excellent plumbing but dangerously unreliable electronics - the first Inspo diver I ever met had a tale of how the unit (admittedly an early inspo) failed to switch on the solenoid and nearly killed him ("Please don't tell my girlfriend"). He felt a little woozy as his PO2 passed down through 0.12, and his quick response to this saved his life. I've heard many other similar tales since. Too many for them all to be mere legends of the past. The problem with CCRs if that you HAVE to rely on "some sort of electronics" to control your PO2 - or at least tell you what it is so you can control it - otherwise you must make do with an SCR so you're back to RB80 etc. If you want some kind of CCR I'd wait for the OR (4 months, they claim). All the others except possibly the KISS have contributed heavily to that overall figure of 250 times more dangerous than open circuit.

That's why rebreathers are not yet mainstream. Read "How Rebreathers Kill People" and think hard before purchase.


Cheers,


Charles.

[Mark Chase]

Hi everyone,

thanks alot for all your suggestions - keep them coming

Mark, my point of view is that you dont have to change much in your protocol to dive a rebreather, and that it should simply be a peace of kit to add between your twinset when needed - without any changes in procedures ( besides having to check po2 and having the loop)
I am leaning alot towards the RB80 as this gives me the opportunity to keep these techniques, and keep a standard rig, that will be intuitive to my non Rebreather buddys in terms of emergency procedures.
also seems like the most "simple" unit to dive, with a great build quality, good scrubber duration and a huge benifit in gas logistic compared to my OC rig

but the COPIS with BMCL inverted cylinders and such does sound like a possibility - I am just not that happy with buying a unit and wanting to modefy it even before it comes out of the box - and I bet it will also be hard to get some training on a non standart unit.

if you are diving anything like this, some pictures would be appriciated

But the sad truth is diving a RB80 is noting like the skill set for diving GUE OC. As a result i see no point in trying to maintain a link outside basic skills and configuration.

The gas switch block is a monster in comparison with the neet and tidy 02 inject of a KISS. So id say the KISS was easier to rig in a DIR way.

Diving protacols are diferent even gas choice is diferent. It realy is start again. Fora a start your not breathing whats in the gas tank. If you have 18/45 in the tank you'r not breathing 18/45. I remember it said 21/35 at 36m was actualy giving you 14% 02 on a RB 80 SCR

Hears some good info

RB80 configuration - YD Scuba Diving Forums

GUE RB80 training - YD Scuba Diving Forums

SCR (RB80) deco - YD Scuba Diving Forums


ATB

Mark

[mempilot]

but the COPIS with BMCL inverted cylinders and such does sound like a possibility - I am just not that happy with buying a unit and wanting to modefy it even before it comes out of the box - and I bet it will also be hard to get some training on a non standart unit.

The Meg is designed to be modular out of the box. Leon wanted it that way. Cylinder size and deinverting them is not an issue with the Meg/COPIS. As for the BMCLs, that is the only MOD considered non-standard; however, I don't think you'd have a problem getting trained. I'd contact someone like Jill Heinerth (Rebreather Pro) and discuss training with her. Another instructor worth discussing this possible setup with is Cederic Verdier. He has been implementing large de-inverted tanks for some time, and he is pioneering the DIRebreather movement in adapting DIR phylosophies in rebreather diving.

Both are highly regarded in the training industry and with ISC.

[Toman]

I've gone through the same path Anders and I don't know if what I've learned (correctly I hope) here within a month can be of any help:

I have decided to go for the Meg because it looks really polyvalent and easy to travel with.

I was also afraid by the electronics but you can use the solenoid rather as an airbag (set it to a low PO2) and run the rb manually. You can even isolate the solenoid if necessary via an oxygen isolator.

Regarding the redundancy, 3 cells on one hand and 2 different electronics (APECS and Sheerwater) on the other seems quite safe to me.

I intend to keep diving with my GUE buddies, explaining to them that I have a few extra checks and drills and also what they should do if I am not responsive.

And I intend to cover my ass even more: BOV, bailout tank, full face mask...

I'm also keen on de-inverting the tanks, mainly for the trim but I'll see when I get my unit, normally any day now

All the Best
Thomas

[trimix]

Like you, I was looking for a rebreather that did NOT rely on electronics to keep me alive - I prefer to be a 'thinking diver' and be in control of my own gas supply, thank you very much.

Something to consider beyond just the equipment is what the rebreather will do for you physically during a dive. You will have less gear to transport, wear and manage. More streamlined, less fatigue. You will be warmer during a dive, and better hydrated, so have less risk of DCS. You will have an optimal mix for any depth at any minute during your dive, which results in shorter deco obligations (like carrying a different bottle for every 3m of your dive). Your buoyancy will be better controlled, no matter how good you are now - it will be better.

For a long time I was set on getting a KISS, but what changed my mind was a 'rebreather experience' session in a pool where I had a chance to try different units and different configurations. I highly recommend that you try to attend one of these demos- I ended up being so impressed with the build quality and ease of breathing of a MEG compared to that of a KISS, I bought a MEG Copis instead (also manually controlled).
The back mounted CLs of a KISS work best with a slightly head-up trim in the water, which I'm sure you wouldn't be happy with. As soon as your position changes to horizontal, head down, or even face up your WOB changes dramatically (ok here's where all the KISS divers flame me). I found the OTS mounted CLs much more comfortable to breathe in all trim positions, when I was able to actually try them each out.

Have you considered flooding? The MEG is designed to allow water from a flooded loop to be drained from the system during a dive, without fear of getting the scrubber wet. The KISS requires bailout.

Another unit to consider is the ReVO - it is an impressive unit, with back mounted Cls, and can be flown manually or electronically.

I think you are making an incorrect assumption that a rebreather is just another piece of kit to support your existing diving. I don't think it is - it is an alternative. The skills required are different, the procedures are different. The gas choices are different, the rigging is different. I think you are mistaken to assume that all your DIR skills will automatically apply with a rebreather - other posts on this thread have already alluded to that. You have to understand that this is not OC diving - those rules are not applicable any more with CCR diving than they are with Surface Supply helmet diving.

I hope you find something that will make you happy - CCR diving has changed everything for me - I honestly hope I never need to go to OC again.

[Anders Knudsen]

.

I think you are making an incorrect assumption that a rebreather is just another piece of kit to support your existing diving. I don't think it is - it is an alternative. The skills required are different, the procedures are different. The gas choices are different, the rigging is different. I think you are mistaken to assume that all your DIR skills will automatically apply with a rebreather - other posts on this thread have already alluded to that. You have to understand that this is not OC diving - those rules are not applicable any more with CCR diving than they are with Surface Supply helmet diving.

I hope you find something that will make you happy - CCR diving has changed everything for me - I honestly hope I never need to go to OC again.

This is where i think my thinking might be different from most of you, maby due to the fact that I am not diving a rebreather, or maby due to my background in the DIR philosophy and mindset, personally I would not even consider a rebreather if I did not think it would allow me to do some of the dives i do/want to do more efficient.

I believe that beside the fact that you are adding some things to the equation ( which you always do when you go deeper, longer ) but that should not change what you have already added, you should simply use a tool that fits into your existing diving, but just adds some possibilities, which is why I dont want a computer controlling Po2 or deco, I dont use one now for my OC diving, then why should I in a rebreather ? - same with OTS counterlungs, the ones I have seen would interfere with the way I wear my stages, my working boltsnap, and my backup lights, and even how I would store my primary light on ascent, besides i like to have my chest free.
I know it can be done - maby it just aint done yet

the flood recovery is a good point, i did not know that - do they flood often ? is this really a factor you would consider important ??

[Hanssing]

the flood recovery is a good point, i did not know that - do they flood often ? is this really a factor you would consider important ??

Hi Anders,
Not to put you off, but besides all the normal critical failures you can have while diving OC-gear the CCR's add several new ways of killing yourself, and they do this with no or little warning. The main ones are:

* Hypoxia - Considered a major contributing factor on many CCR-deaths. Can happen due to equipment-failure (cells, monitoring or bypass on a SCR).
* Hyperoxia - The same reasons as above.
* Hypercapnia - Due to scubberflood, scrubber exhaustion, failure of check-valves in mouthpiece etc.
* Caustic Cocktail - Due to water-ingress into scrubber material, causing a caustic solution to later be inspired by the diver.

All the major scenarious listed above are leathal. Most CCR-divers will have an answer for how they avoid each and every failure you can throw at them, but note, that people still bites it on theese machines.

Something as simple as loosing you mouthpiece can cause water-ingress enough to make a system unusable... But I have never lost a mouthpiece ever in OC or CCR. So the answer is no, they don't flood often. Very rarely in fact, as a lot of checks and procedures are used to ensure they are watertight.

CCR designs are allways a tradeoff, but I have yet to hear about a diver completing a long dive on a rebreather that is having water-ingress throughout the dive - normally the dive would be terminated early on bailout.
My point is that the system has to be water-proof, so the gains you get from being able to have a lot of water-ingress through the DSV, and then recover the system are perhaps not as important as people would think. If the flood is not discovered before it reaches the scrubber the units is toast anyway.

For me after having tried OTS-coulterlungs I knew, that would never work. So I accepted that most units today with BMCL have poor flood recovery, as the "recovery" from wateringress is a feature unlikely to be used for *my* diving. If my breather floods I'm on bailout (If I make it).

However this is where the OR has (on paper) some good features, but they do also add new points of failure. For now I'm happily sticking with my rEvo for shallow Danish wreck-diving from a RIB. My second choice would be an OR.

Some of the main points people use to advertise for CCRs are that they give you time to deal with problems and multiple ways of solving theese when they occur - from a DIR-perspective where procedures are drilled in stone, I would see this as a weakness. So if you're DIR then you probably wont put too much into all sorts of theoretical ways of solving problems underwater with a CCR anyway: Bailout, turn dive, get home.
Recovering the CCR after a bailout is 'nice-to-have', but less important then discovering that you should bail.

I know that the above might read as though I'm putting words in your mouth as DIR diver, but truely I'm not. Just trying to point at things I think you will like to consider.

Regards
Nicolai

[Mark Chase]

This is where i think my thinking might be different from most of you, maby due to the fact that I am not diving a rebreather, or maby due to my background in the DIR philosophy and mindset, personally I would not even consider a rebreather if I did not think it would allow me to do some of the dives i do/want to do more efficient.

I believe that beside the fact that you are adding some things to the equation ( which you always do when you go deeper, longer ) but that should not change what you have already added, you should simply use a tool that fits into your existing diving, but just adds some possibilities, which is why I dont want a computer controlling Po2 or deco, I dont use one now for my OC diving, then why should I in a rebreather ? - same with OTS counterlungs, the ones I have seen would interfere with the way I wear my stages, my working boltsnap, and my backup lights, and even how I would store my primary light on ascent, besides i like to have my chest free.
I know it can be done - maby it just aint done yet

the flood recovery is a good point, i did not know that - do they flood often ? is this really a factor you would consider important ??

Two things. In a previous post the Work of Breathing of the KISS was raised as an issue. It is fair to say a front mounted counterlung unit like the Copis will always have a better work of breathing than the KISS. However I was finding the WOB of the KISS very frustrating until I made several alterations to house routing (keeping standard hoses) and changed the BOV to a low WOB Golum unit.

The difference is staggering. I am now more than happy with the WOB on my rig.


Flooding is a problem on any back mounted counter lung rebreather. Some like the Sentinel and the new Apocalypse have introduced counter lung drains but these are just begging to leak and cause their own flood.

The compromise is flood recovery of front mounted lungs or the clutter of having front mounted lungs against a clear chest area.

Personaly like you I find having a clear chest area to be of prime importance. I have my back up lights stored the same way you do and the only diference on my chest rig to yours is my 02 inject on the right chest D ring.

My attitude is that I always carry bailout and therefore flooding is manageable. I have suffered one flood on the KISS which was caused by a hole in the mouthpiece letting water into the loop so this was not spotted on the pure dive positive and negative checks.


That said if you can put up with front mounted counter lungs then the Copis Meg is a great unit.

Only down side from a cave perspective is crushing the exposed counter lungs when squeezing through restrictions.


ATB

Mark

[Anders Knudsen]

Nicolai thanks alot

at the moment i simply cant find a breather that solves all my problems, without making alot of compromises, the way I see it the RB80 is the one which makes most sence, as that is the only one where I dont have to make any compromises under water, it still does not solve the gas mixing problem entirely, but I guess this could be solved with 4 J´s of premixed gas for the entire team - way easyer than with OC.
it is after al under water it has to make the test - and not "just" because I am bored filling stages and twinsets.

maby I am just not ready for a CCR just yet;)

[Mr_Pyro]

Hi Anders!

There is quite an intresting thread about RB80's and a clone accident here in Sweeden not that long ago. Anyway it is taking up a lot of pros and cons of the RB80. A must read for anyone about to purchase and train on a RB80.
http://www.rebreatherworld.com/showthread.php?t=21515

I'm not trying to bash the RB80 and other gas extenders.
But there are som issues with quite complex decocalculations. And very high drop in partial preassure on accent.
Deco is less efficient on the loop. And general gas logistics get more cumbersome with larger gas volumes to mix and fill. Less room for changed dive plans. That mix you blended last night might be useless on that other divesite the boat decided to go due to bad weather on the preplaned site.

A CCR is more flexible, you get an optimizd PP02 during the entire dive not only the bottompart. This surely must be a huge advantage when diving in caves where the depth can change frequently during the dive.

The way I see it an RB80 gives you most of the added risks and hassels of rebreatherdiving, without giving you all the benefits.

If you decide to go the RB80 route, make sure you add a PPO2 monitor to it.

Cheers
/Johan Fredin