Kindling an interest in rebreathers

[Armymutt25A]

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

You haven't been part of an Airborne Timeline, have you? You want to talk about long and aggrevating. I really don't foresee myself getting far enough into it to require carrying a redundant system.

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.

Just out of curiosity, are the "rules" different for CCR than OC? I figured that if the loop went to hell, the dive was over. From 50 ft, a full 80 should be plenty of gas to reach the surface, and probably enough for a shortened safety stop.

 

[sunkmail]

Just out of curiosity, are the "rules" different for CCR than OC? I figured that if the loop went to hell, the dive was over. From 50 ft, a full 80 should be plenty of gas to reach the surface, and probably enough for a shortened safety stop.

NO, the rules aren't different. At least for myself, the one time I had a caustic, I ended my dive right away.

Going through an 80 in 5 min @ 50' is probably an exageration, but your breathing rate may be increased by getting hit with a cocktail, therefore you will not be using up your gas at the same rate you're used to...

It would depend a lot on how bad the hit was - ie, did you swallow it? breath it into your lungs, just in your mouth, etc. - and how well you handle a stressful situation. With a bad hit and poor stress management, I can see someone going through there gas pretty quick. (I'm Not trying to put down the diver mentioned.)

 

[Mr.X]

You haven't been part of an Airborne Timeline, have you? You want to talk about long and aggrevating. I really don't foresee myself getting far enough into it to require carrying a redundant system.




Just out of curiosity, are the "rules" different for CCR than OC? I figured that if the loop went to hell, the dive was over. From 50 ft, a full 80 should be plenty of gas to reach the surface, and probably enough for a shortened safety stop.

On the Andrea Doria dives in the lates 80's/early 90's, and on some remote technical dives we had secondary CCR backup. It's a total drag when you spend tons of money, a whole lot of diving time, training and enduring a lumpy ride to find out your CCR has bagged out. It happened a few times.

On some deep working dives with large enough of a team we could mix and match rebreather components when the electronics bagged out. This is includes the first and second generation Hammerhead monitors, as well as Inspiration, Megalodon and Cis Lunar units.

Additionally, you sling, or hang enough gas to cover your bailout contingencies. Your buddies, or team would do the same. It's not very pretty when you do a long technical dive and find out the hard way you've got a deco obligation which requires a long hang. Sure you can make it from 50' to the surface unless you've got a long obligation.

X

 

[battles2a5]

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)

That seems like a lot of bail-out for a dive in the 18/45 range. But regardless of the application, one thing that we seem to be missing in the discussion of more vs. less bottles is actually FILLING said bottles. I dive standard bail-out gases so I just go into the garage and pick the ones I need for the dive I am going to do. No need to go to the shop, get fills, and all of the other prep that goes along with it. Just grab the bottles and go.

To make it even easier, get a T bottle of O2 from the gas supplier, fill one your (now unused) sets of doubles and fill it with 18/45, and get a small booster ($1000). Now you just have to get fills about once every 6 months. For deeper stuff, keep doubles of 10/70 and 32% and you can mix anything you want in your garage and get fills twice a year.

I think the build-up/ break-down times are very manageable (especially if you own a rEvo). I just break it down as I am rinsing gear. Let it dry then take 15 minutes to repack scrubbers and build the unit (including pos/neg checks). Calibrate and finish testing the unit and you are ready to go.

 

[matt t.]

That seems like a lot of bail-out for a dive in the 18/45 range. But regardless of the application, one thing that we seem to be missing in the discussion of more vs. less bottles is actually FILLING said bottles. I dive standard bail-out gases so I just go into the garage and pick the ones I need for the dive I am going to do. No need to go to the shop, get fills, and all of the other prep that goes along with it. Just grab the bottles and go.

To make it even easier, get a T bottle of O2 from the gas supplier, fill one your (now unused) sets of doubles and fill it with 18/45, and get a small booster ($1000). Now you just have to get fills about once every 6 months. For deeper stuff, keep doubles of 10/70 and 32% and you can mix anything you want in your garage and get fills twice a year.

I think the build-up/ break-down times are very manageable (especially if you own a rEvo). I just break it down as I am rinsing gear. Let it dry then take 15 minutes to repack scrubbers and build the unit (including pos/neg checks). Calibrate and finish testing the unit and you are ready to go.

As I'm fairly new to this I'm always open to suggestions and changes. What I've been doing to this point is what I've learned in class and what others in my dive group are doing.
My rebreather does not have a BOV, so I can't use any on-board gas for bailout. My bailout is always an 80 of whatever my diluent is. I'm not sure what you would use for bailout, but my preference is to still exit the water as clean as I would have if still on the loop. On a 200 ft dive I wouldn't consider anything less than 2 decos gasses. It may make more sense to take an 80 of 35/25 rather than the 50%, but I wouldn't think about NOT taking the Oxygen as well. In either case it's still 3 bottles.
I'm in complete agreement with you on the filling process. A booster (though I think an AG 30 or 15/30 is more appropriate) is mandatory. I bank 18/45 in my 130's and have a couple different sets of standard gas bailouts, as well as a couple of T's of 02 and a RIX to mix up what I need (infrequently).
I'm fairly new to the rebreather (16 hrs so far) so I'm still slow on the set up and tear down/clean up. It probably takes me 1/2 hr on each end. Maybe not that long to some, but it seems to take forever with all of the steps compared to OC.
The 5 minute draining of the 80 (and subsequent coughing and puking) was not an exageration.

 

[battles2a5]

As I'm fairly new to this I'm always open to suggestions and changes. What I've been doing to this point is what I've learned in class and what others in my dive group are doing.
My rebreather does not have a BOV, so I can't use any on-board gas for bailout. My bailout is always an 80 of whatever my diluent is. I'm not sure what you would use for bailout, but my preference is to still exit the water as clean as I would have if still on the loop. On a 200 ft dive I wouldn't consider anything less than 2 decos gasses. It may make more sense to take an 80 of 35/25 rather than the 50%, but I wouldn't think about NOT taking the Oxygen as well. In either case it's still 3 bottles.
I'm in complete agreement with you on the filling process. A booster (though I think an AG 30 or 15/30 is more appropriate) is mandatory. I bank 18/45 in my 130's and have a couple different sets of standard gas bailouts, as well as a couple of T's of 02 and a RIX to mix up what I need (infrequently).
I'm fairly new to the rebreather (16 hrs so far) so I'm still slow on the set up and tear down/clean up. It probably takes me 1/2 hr on each end. Maybe not that long to some, but it seems to take forever with all of the steps compared to OC.
The 5 minute draining of the 80 (and subsequent coughing and puking) was not an exageration.

Nobody ever died from carrying too much gas For anything in MOD1 depths (160 for me) I carry a 40 of 18/45 and a 40 of 50%. This will get me out of the water with loads of gas to spare on just about any profile I would run at these depths. I can plug the 50% into my unit if I have an oxygen failure. The deco time is longer on 50% alone but with CCR bail-out I don't really shoot for optimal deco time as much as I do flexibility. Another benefit is that I can use T1 ratio deco for bail-out so I have lots of options to get out of the water in case the poop hits the fan.

I would increase my deep bail-out to an 80 and might add a second deco gas depending on the RT I dealing with. Over 250 would definitely involve at least 3 bottles, prob an 80 and 2 40's.

Tear-down and build-up will start to become second nature. I have a rEvo which makes this very easy, but once you get the habit down it will fly by.

 

[Mr.X]

At the end of the day the rebreather is supposed to make life, or the mission easier & safer. Carrying multiple bottles might be necessary for the mission, though at times I subscribe to the 'Alpinist' perspective and when I have the chance I dump bottles and get them going out. Last thing I need is a bottle hanging up inside a wreck with dangling electrical wires, or where I have to squeeze through a major restriction.

Since I've been at the rebreather game for a while - they are only a tool. Going deep on these things, or OC brings added challenges. I've seen far too many of my CCR colleagues die during the decade + and feel particularly blessed for not having died doing the same, crazy deep stuff. I've come close and I would pose this question to folks interested in CCR and those starting out - Is getting a CCR purposeful? If it's just for deep kicks/adrenaline scrap the machine and go simple. Especially if you have a family. You can only do so much of the deep stuff without paying some hard dues at some point.

X