Kindling an interest in rebreathers

[Armymutt25A]

It's been a slow week here in the sand box, so I started at the last page of this section and started reading. My interest in rebreathers has grown, but the actual fulfillment is a few years off (most likely). From what I've been reading, diving a rebreather is akin to riding a motorcycle in traffic, or at night on a country road in mating season. You'll be fine as long as you stay alert. I haven't had an occasion to dive one yet - no LDS in the desert, so I'm not clear on the synchronization of hands and eyes (I'm assuming no feet involved in controlling a unit). So, is the motorcycle analogy close? I'm not talking about a modern fuel injected version, but something like a vintage Triumph with Lucas electronics - you know, a model that gives you something else to worry about.

 

[sea2summit]

If an infantry O can do it a si-go should be able to

Big thing is a reason for having one. Do you enjoy diving? Do it a lot? If so "maybe" a rebreather is something you should look at. You do have to maintain proficiency on the unit and your skill set.

What’s drawing you to rebreathers?

 

[Armymutt25A]

I love diving. As far as doing it a lot, well, I've been on the extended field problem plan for the past several years. Got back into diving after a 19 year hiatus, in early '09. Went out the door last August. In the 3 months I was home, I did 6 dives off Wilmington, NC. I think that's pretty good considering the pre-deployment OPTEMPO. I've been doing a little Google Earth recon of some of the springs around my house - nearest public dive park is an hour and a half away, which isn't really condusive to after work diving.

My draw to rebreathers is logistical benefits, as well as the performance benefits. My current scuba goal is diving the Truk Lagoon. Having to carry just the unit plus bailout system vs. a bunch of bottles to do the same depth is a big plus. The extended time in recreational limits is a big draw as well. An AL100 just doesn't last me long enough. Everything I've been reading about the bubbless interactions with marine life is really attractive. The big key will be getting my wife to learn too. She's not quite comfortable on OC just yet, so RBs are a little ways off anyway - not to mention, I have to wait for her to finish her PharmD - Army doesn't pay enough. Seriously though, as long as I'm on the annual CONUS/OCONUS cycle, I can't justify an RB. It's on the 5-year calendar though, and it never hurts to learn new info.

I understand about keeping the skills sharp, but then, that's business as usual for people like us. Everything is a perishable skill to some degree. I don't think I could meet EIB standards on the SAW anymore, and I carried it for 2 years in a previous life.

 

[jlovold]

You are aware that you would have to carry at least the same amount of cylinders as you would when you dive OC, right? At the very least oxygen and diluent, but a decent size diluent-tank, so that you could bail out on it, or offer it to your buddy.

But usually you carry a separate bailout-tank in addition to oxygen and diluent, and if you go deep, you need deco-gases as well.

The reason you would like to dive a rebreather is because of gas-logistics (you wont have to fill deco-tanks and back-gas all the time), and because it´s a very pleasant way to dive, and because it gives you the ability to dive very long recreational dives.

On OC you dive a more forgiving system, you don´t have to worry about sorb (if your destination don´t have sorb, you need to bring yourself), on technical dives, you may have less decompression with multiple deco-gases (because you would run the CCR on a lower PO2, and you would use a helium-based diluent all the way due to isobaric counter-diffusion-issues.)

I dive a CCR, and love it, despite of the added complexity compared to OC-diving.

I dive a manually controlled unit, and find it very rewarding to be in full control of my unit. I dive a Pelagian DCCCR, which is controlled by a needle-valve, which enables me to adjust the flow of oxygen, on the fly, to closely match my metabolism.

The bonus of diving a mCCR rather than eCCR is that not only are they cheaper, but statistics indicate that they are a lot safer too.

 

[Armymutt25A]

You are aware that you would have to carry at least the same amount of cylinders as you would when you dive OC, right? At the very least oxygen and diluent, but a decent size diluent-tank, so that you could bail out on it, or offer it to your buddy.
But usually you carry a separate bailout-tank in addition to oxygen and diluent, and if you go deep, you need deco-gases as well.

Yes, but 2 13 or 19 cf tanks and a 40cf or even an 80cf are considerably less of a burden than 3 100cf tanks.

The reason you would like to dive a rebreather is because of gas-logistics (you wont have to fill deco-tanks and back-gas all the time), and because it´s a very pleasant way to dive, and because it gives you the ability to dive very long recreational dives.

On OC you dive a more forgiving system, you don´t have to worry about sorb (if your destination don´t have sorb, you need to bring yourself), on technical dives, you may have less decompression with multiple deco-gases (because you would run the CCR on a lower PO2, and you would use a helium-based diluent all the way due to isobaric counter-diffusion-issues.)

I dive a CCR, and love it, despite of the added complexity compared to OC-diving.

I dive a manually controlled unit, and find it very rewarding to be in full control of my unit. I dive a Pelagian DCCCR, which is controlled by a needle-valve, which enables me to adjust the flow of oxygen, on the fly, to closely match my metabolism.

The bonus of diving a mCCR rather than eCCR is that not only are they cheaper, but statistics indicate that they are a lot safer too.

The whole prep-phase is rather interesting to me. My wife thinks I'm a little crazy when we do our layout the night before heading to the coast. Everything gets checked and tested. This is probably a hold over from riding vintage motorcycles. It's always embarassing to have to push a bike that's older than you because some locking nut wiggled loose on the clutch cable.

 

[jlovold]

Yes, but 2 13 or 19 cf tanks and a 40cf or even an 80cf are considerably less of a burden than 3 100cf tanks.



The whole prep-phase is rather interesting to me. My wife thinks I'm a little crazy when we do our layout the night before heading to the coast. Everything gets checked and tested. This is probably a hold over from riding vintage motorcycles. It's always embarassing to have to push a bike that's older than you because some locking nut wiggled loose on the clutch cable.

If you dive with 3 100cf tanks, chances are that you are doing a long and/or relatively deep dive, and are doing a pretty long decompression (the last tank should probably be a deco-gas Nx50 or stronger), which means that you should carry at least two tanks of bail-out/deco-gas in addition to the onboard tanks on the CCR, and those tanks should be big enough to handle a CO2-induced breathing-rate.

 

[Mr.X]

The whole prep-phase is rather interesting to me. My wife thinks I'm a little crazy when we do our layout the night before heading to the coast. Everything gets checked and tested. This is probably a hold over from riding vintage motorcycles. It's always embarassing to have to push a bike that's older than you because some locking nut wiggled loose on the clutch cable.

If you want to increase the % of checking everything over and over - a rebreather flight list is longer and at times - aggravating. :blinking:On a key ($$$$) dive we typically bring a redundant rebreather, or head.

X

 

[matt t.]

After being recently certified on a rebreather I did my first "tech" level dives this weekend. After several years of gear intensive OC tech diving I can tell you that there isn't any less gear to bring along when diving a rebreather. There is more preparation before diving and more clean-up after diving with a rebreather. My bailouts were an 80 of 18/45, a 40 of 50%, and a 40 of oxygen (1 more bottle than I would take on the same dive on OC). I'm not pointing this comment at you, but people have all sorts of reasons for getting into rebreathers, and most of them are invalid. They are not cheaper to dive than OC, you still have to own and maintain the same amount of OC gear to go along with the CCR, and as mentioned earlier you do have to maintain the skillset and discipline that go with a CCR. New cells are required on a regular basis (3@ $50-$85 each), and sorb is around $25 a fill (per dive). IMO, a booster is a required when owning a rebreather ($2,000 +). Yes, you can save a little on helium, but how much helium can you buy for $10,000? YMMV.

 

[sea2summit]

and sorb is around $25 a fill (per dive).

Ouch, you need to change your sorb supplier. Mine works out to about $3.25 an hour (warm water) or $18 a fill (2-3 dives).

I'm of the opinion logistics are significantly reduced in terms of safety on a dive. Yes you need to carry extra stages but you would have been carrying the gas on your back so that's negated. Where the CCR really shines is if there is a problem, I have the rest of my life to sort it out which is significantly more time CCR than OC especially at depth. Also if you're carrying all your own gas you probably have 1.5 x what you need and you're buddy probably has the same so if you have a CCR failure you potentially have 3 x the gas it would take to get you to the surface safely vs. OC you only have maybe 1.5 so lost gas profiles are much more important. Just my opinion.

 

[matt t.]

Ouch, you need to change your sorb supplier. Mine works out to about $3.25 an hour (warm water) or $18 a fill (2-3 dives).

I'm of the opinion logistics are significantly reduced in terms of safety on a dive. Yes you need to carry extra stages but you would have been carrying the gas on your back so that's negated. Where the CCR really shines is if there is a problem, I have the rest of my life to sort it out which is significantly more time CCR than OC especially at depth. Also if you're carrying all your own gas you probably have 1.5 x what you need and you're buddy probably has the same so if you have a CCR failure you potentially have 3 x the gas it would take to get you to the surface safely vs. OC you only have maybe 1.5 so lost gas profiles are much more important. Just my opinion.

I'm buying Molecular Products 797 from Add Helium with free shipping. If you know of a cheaper supplier I'm all ears . All of our good wreck diving up here is cold water (40 on the bottom yesterday) which greatly reduces rated scrubber time. I repack for "serious" dives after 1 use. I don't disagree with you at all as far as logistics for local trips and more options in case of trouble. I do disagree that people think "the" reason to get a rebreather is to save $$$ money somewhere or other in the long run (usually helium fills). Lets be honest, most buy them for the technology and "cool" factor. I've also seen to many/most divers carry to little bailout gas. I saw one experienced CCR diver get a mouth full of caustic and run through a full 80 in about 5 minutes at 50 ft. So, while I don't worry about supplying gas for another CCR buddy in my bailout calculations, I'd rather carry an 80 (or 2 or 3 on deeper dives) rather than a 40 and have enough gas if needed. Again, YMMV.