Where should I start to approach the rebreather world
- Thread starter Nico-ITA
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I wish people would just be honest about the time it takes to prep a rebreather. There is no way you are filling both scrubbers, analyzing all your gases, checking your batteries, flow check on your MAV if a mCCR, doing a stereo check, build, positive-negative, calibrate etc in 30mins on any CCR. A full 5mins each at positive and negative alone are minimum 10mins
If you have a bunch of stuff done ahead of time or you skip steps, then sure you can get it down to under an hour. But from scratch let's not mislead people. 60mins is fast, 90mins is normal, 2 hours isnt anything to be ashamed of.
broncobowsher
Contributor
I keep bottles pre-filled and don't count that as part of my build time. If you want to add fill times with the booster, that is way more time than actually building the breather.
Truk is a great example. The bottles are handed off. They come back filled. As they are filled you build the breather. Analyze and program. You may not get them back until the next day. But the overall build is fairly fast.
You don't count the time you spend prepping OC gear for a dive to include compressor time. Why count it with a rebreather? If you really want to be fair about build times. You would need to add the time to drive and get the fills. Which was 4 hours for me before I got the booster. Or a couple hours just for air fills.
Truk is a great example. The bottles are handed off. They come back filled. As they are filled you build the breather. Analyze and program. You may not get them back until the next day. But the overall build is fairly fast.
You don't count the time you spend prepping OC gear for a dive to include compressor time. Why count it with a rebreather? If you really want to be fair about build times. You would need to add the time to drive and get the fills. Which was 4 hours for me before I got the booster. Or a couple hours just for air fills.
Even prefilled its still twice as much gas to analyze as an OC dive - just one example.
OC = backgas and deco gas
CCR = dil, o2, deep BO, deco gas.
Ok maybe you don't analyze your BOs because you did yesterday and your regs and analysis tape are still right there on them and nobody has topped them off or touched them. That is still a shortcut. 4x analysis alone takes me 15mins.
And pulling positive and negative is 5 mins each = 10mins. That's 1/3rd of this magic 30mins prep time right there - which I think is unrealistic as a "from scratch per the checklist" build time for any unit.
"30mins more than my 45mins of OC prep time" ok maybe that's legit but that's not what was said. Implying that wham bam 30mins start to finish and you're ready to CCR dive is misleading (unless you are skipping steps or checks)
broncobowsher
Contributor
Analyze is maybe a minute of pull out/put away and another minute to pull the old tape off and put new tape on and write down the numbers that were analyzing while you were changing the tape.
I don't spend 2 hours doing prep work unless you are adding in running the booster time. And the booster time is running it slow to keep the heat down.
When I was shopping for a rebreather I do remember watching a build video (forgot the brand) that was a complete cluster and had layers of complexity/ engineering band-aids on top of band-aids of other fixes. That was a huge build process routing everything just right. Easily twice the build work/time of other rebreathers.
I don't spend 2 hours doing prep work unless you are adding in running the booster time. And the booster time is running it slow to keep the heat down.
When I was shopping for a rebreather I do remember watching a build video (forgot the brand) that was a complete cluster and had layers of complexity/ engineering band-aids on top of band-aids of other fixes. That was a huge build process routing everything just right. Easily twice the build work/time of other rebreathers.
There is a big difference between the overheads of a single day and multiple days. It also depends on the place. can you leave the rebreather on the bench (like in Scapa) or do you need to take it back to a hotel/b&b?
I try to do all the prep the night before, maybe days before for a Saturday with a Friday evening drive.
Gas analysed, scrubber filled, cells vaguely checked by doing a calibrate, dates checked while doing the scrubber fill If the first dive for a while. Even though I will probably take the loop (Ie the two hoses and the BOV or DSV) off for transport, I will do a positive and negative test at prep time in case something weird is happening.
On the day all I have to do is check the mushroom valves (one minute) attach the loop, negative and positive tests (10 minutes) and turn on the gas. I am usually done before the OC people have finished arguing with their integrated weights
Between dives there is nothing to do, except maybe drain the gloop from the loop while it airs and so another negative/positive.
There is a bit of work at the end of the day emptying the sorb, getting condensation off the head and refilling (unless left to before breakfast for a longer drying out) putting fresh cylinders on. At the end of a week then it is time to rinse everything.
The worst way to use one is every Sunday, best is a week or more at a time.
From my experience on boats a JJ is simpler in this respect than some others.
CCR try dives seem like to make you do the prep.
if you like we could borrow these Take a rebreather Try Dive and get one of the region people who is qualified on them to run a try dive. It is a moderate faff but maybe easier than going to NDAC or Vobster. Sounds like a DP2 exercise
I don’t have one but I don’t expect it would be fantastically effective as I find it is suspended muck that gets to the o ring. I don’t think it it big lumps I knock off the ceiling. If there is stuff in the water I guess it will still get there.
Having said that, it has never been an awful problem for me.
broncobowsher
Contributor
The mention of a try dive. The first one I did they had them built up before we arrived and took them off to clean them later. I realized this was BS. After that I did more and had them build up and tear down in front of me as I asked questions. That gives a much better idea of what you are getting into. Even if you don't get that unit, you have an idea of what your buddies who have it will be going through.
The act of a try dive is a different debate.
The act of a try dive is a different debate.
I have done a pool dive with an AP CCR but it was only a 1m deep pool at a dive show so you couldn’t get a feeling of how CCR works with buoyancy and the unit was already assembled.There is a big difference between the overheads of a single day and multiple days. It also depends on the place. can you leave the rebreather on the bench (like in Scapa) or do you need to take it back to a hotel/b&b?
I try to do all the prep the night before, maybe days before for a Saturday with a Friday evening drive.
Gas analysed, scrubber filled, cells vaguely checked by doing a calibrate, dates checked while doing the scrubber fill If the first dive for a while. Even though I will probably take the loop (Ie the two hoses and the BOV or DSV) off for transport, I will do a positive and negative test at prep time in case something weird is happening.
On the day all I have to do is check the mushroom valves (one minute) attach the loop, negative and positive tests (10 minutes) and turn on the gas. I am usually done before the OC people have finished arguing with their integrated weights
Between dives there is nothing to do, except maybe drain the gloop from the loop while it airs and so another negative/positive.
There is a bit of work at the end of the day emptying the sorb, getting condensation off the head and refilling (unless left to before breakfast for a longer drying out) putting fresh cylinders on. At the end of a week then it is time to rinse everything.
The worst way to use one is every Sunday, best is a week or more at a time.
From my experience on boats a JJ is simpler in this respect than some others.
CCR try dives seem like to make you do the prep.
if you like we could borrow these Take a rebreather Try Dive and get one of the region people who is qualified on them to run a try dive. It is a moderate faff but maybe easier than going to NDAC or Vobster. Sounds like a DP2 exercise
I’ll look into this, thanks. Would be useful to do the prep so I know what I am getting into before to pay anything.
OC prep is two discrete phases, days apart. First is to get the gas fills: driving to the gas shop and waiting. Half a day! The build takes minutes in the boot/trunk of the car.
Oh the misery of the wrong gas for a change of plans.
On CCR the gas mixing and top up is done in my garage using three twinsets of air, oxygen and 10/75. I’ve a couple of sets of 3litre tins. From those banks I can mix pretty much any gas.
As that mixing is simple, it’s left to the night before when I know the dive profile. The CCR build still needs an hour in case of problems.
