Mixed team (cc & oc)

[sea_ledford]

Reading all the replies I get the impression that the variations in configs makes what I asked for originally almost impossible unit/bov/dsv. As to my confidence level were I to have to get my buddy out of the water from a ca 30-50m dive with some deco, I'm not sure.
Prob have a look on the handset to see what his ppo2 is doing switch him to oc on the shrimp (off board) and head up.
Guess it's a discussion I need to have in more depth with him and the particulars of his setup, bov is easy it's connecting to his bo (usually one 80 unless we're practicing with multiple stages etc) so no switch from hypoxyic.
As an aside is rescue tackled in rb training or is the focus solely on avoidance rather than dealing with a poop sandwich?

Performing any gas switches on a unconscious diver is going to be next to impossible. If they have managed to maintain the mouthpiece (loop or reg is irrelevant), I would take them up on whatever gas they are on. The level of risk you are willing to personally take (skipped deco) to get someone to the surface is up to you, and probably mostly depends on who you are rescuing. That is one if the primary reasons I don't understand the gag-strap, but no BOV argument. Also a BOV is mostly useless if it isn't connected to an off-board tank.

I think there should be more rescue oriented training in technical classes in general, it is mostly up to the individual instructor to include much of anything beyond air sharing. Cave being the primary exception to that.

-Chris

 

[KenGordon]

I had to do CBL on both MOD1 and MOD2. Personally I found it very difficult with six gas spaces to control and without practice I would say it is not going to work. For a one off buddy on a boat I don’t even bother telling them how to dump the lungs.

 

[rjack321]

Also a BOV is mostly useless if it isn't connected to an off-board tank.

I shake my head every time I hear about someone plumbing an onboard dil tank to a BOV.

 

[DA Aquamaster]

I shake my head every time I hear about someone plumbing an onboard dil tank to a BOV.

I have the same reaction anytime I see or hear about a diver plugging both on and off board diluent into a manifold, rather than a gas switch block.

With a manifold, if the tank valves are all open, which tank actually supplies the gas being used is entirely dependent on the respective intermediate pressures of the first stages involved. For example, if the on board diluent reg has a higher IP than the first stage for the off board dil/out, then the on board diluent will be used first. That's not really a problem until you are donating gas. In that situation the diver on OC bailout will deplete the on board diluent before using the off board dil/out gas, and if he breaths that off board dil/out down to nothing, you've now potentially got a double fatality as the CCR diver has no diluent to complete the exit. At best he's on the ragged edge and if he has to go deeper to exit, he's screwed.

If a CCR diver is doing this, the first action upon encountering an out of gas diver needs to be closing the tank valve for the on board diluent to ensure it is preserved for the CCR diver's own exit.

 

[JohnnyC]

Best practice, in my mind, is to use an actual supply of bailout/dil for backgas. Say what you will about the PSCR folks, but even a pair of LP50's with a small 3L O2 bottle mounted like an inflation bottle will provide pretty substantial dil for the descent, and bailout gas. Plumbed into a BOV the backgas bailout should get you to a stage bottle, although preferably the BOV is just transitional to a better breathing second stage, even if the same gas supply.

One of the things I really like about my SF2 is that I can plug in any outboard gas into either MAV, and with some judicious use of the various shutoffs, I don't have to do constant switching to actually plumb offboard gas into my rebreather, whether that be dil, bailout, O2, travel gas, etc.

Switch blocks scare the hell out of me. Primarily because they're called "switch blocks" out of context. They either need the exact same gas, and utilized to switch from one supply of gas to say, a reserve, or they need to be limited to air and O2 for IWR where you're already using it in extenuating circumstances, and austere conditions where the alternative is pretty less-than-ideal.

 

[tbone1004]

@JohnnyC I run my meg with a RB80-esque rack. 2x 50's for dilout, 3l O2, and 3l inflation. Love the setup

 

[rjack321]

One of the things I always appreciated about Leon at ISC is his requirement to have a donate-able long hose on the CCR diver's BO. I still do that for OW and Cave dives although I don't use a 5 or 7ft hose on deco bottles. Because I rarely carry less than an AL80 of BO I often have more reserve to give to an OOA OC diver than they reserve for me in their 'minimum gas' (aka rock bottom) calculation.

 

[PfcAJ]

Best practice, in my mind, is to use an actual supply of bailout/dil for backgas. Say what you will about the PSCR folks, but even a pair of LP50's with a small 3L O2 bottle mounted like an inflation bottle will provide pretty substantial dil for the descent, and bailout gas. Plumbed into a BOV the backgas bailout should get you to a stage bottle, although preferably the BOV is just transitional to a better breathing second stage, even if the same gas supply.

We’re all over here like “yuh. Toldyaso”

 

[JohnnyC]

We’re all over here like “yuh. Toldyaso”

Hey, I've always liked the idea. But it sucks for most rebreathers. BMCL's it gets twitchy depending on how you handle O2 addition. You're either super wide with it strapped to a tank, sidemounted it compresses the counterlung, or it hangs like a regular stage and isn't very streamlined.

I hate OTSCL's in cave diving. Well, hate them in general. They're annoying and distracting and the WOB isn't that much better.

Now, when I got rid of my Meg and switched to the SF2, I finally have all the room in the world to mount my O2 like an argon bottle to the plate, run LP50's in a rack, still maintain a streamlined profile, and don't have to worry about compromising the counterlung because it's in the can. New favorite setup, and I took your advice with the STA's and cam bands instead of trying to source the hard bands for the RB80 rack. It worked out well.

 

[PfcAJ]

Hey, I've always liked the idea. But it sucks for most rebreathers. BMCL's it gets twitchy depending on how you handle O2 addition. You're either super wide with it strapped to a tank, sidemounted it compresses the counterlung, or it hangs like a regular stage and isn't very streamlined.

I hate OTSCL's in cave diving. Well, hate them in general. They're annoying and distracting and the WOB isn't that much better.

Now, when I got rid of my Meg and switched to the SF2, I finally have all the room in the world to mount my O2 like an argon bottle to the plate, run LP50's in a rack, still maintain a streamlined profile, and don't have to worry about compromising the counterlung because it's in the can. New favorite setup, and I took your advice with the STA's and cam bands instead of trying to source the hard bands for the RB80 rack. It worked out well.

The STA mod is pretty slick!