Mixed team (cc & oc)

[joshk]

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.

Do you have cam bands going directly from the carbon fiber body to the LP50s? As in, the scrubber tube and base are supporting all that weight directly onto a STA to the backplate?

 

[JohnnyC]

Do you have cam bands going directly from the carbon fiber body to the LP50s? As in, the scrubber tube and base are supporting all that weight directly onto a STA to the backplate?

Noooooo. It's in an RB80 rack. Normally it has steel bands for 85's. I was looking for bands for LP50's and AJ suggested an STA with cam bands bolted to either side of the rack instead of trying to source smaller bands.

You can see my WTB thread here: WTB RB80 rack LP50 bands

Basically, instead of the tank bands directly bolted to the rack, the STA's are bolted where the bands are. I'm flying home from Paraguay tomorrow. Remind me and I'll take a picture of it when I get back CONUS.

 

[joshk]

Noooooo. It's in an RB80 rack. Normally it has steel bands for 85's. I was looking for bands for LP50's and AJ suggested an STA with cam bands bolted to either side of the rack instead of trying to source smaller bands.

Ah, I got it. The “STA” goes on each 50. Will ping you tomorrow

 

[broncobowsher]

Planned Team bailout is one of the worst ideas.

Fixed it for you.

My plans are to have enough to get myself out of trouble. Team bailout is not something I plan for, it is something that happens when there are multiple failures to the point where you should consider a different sport.

 

[flymolo]

I know this is an old post, and not debating the merits of team bailout, but just curious to hear ppl's arguments against team bailout. (disclaimer: I would not consider planning team bailout for a dive)

 

[Jack Hammer]

I know this is an old post, and not debating the merits of team bailout, but just curious to hear ppl's arguments against team bailout. (disclaimer: I would not consider planning team bailout for a dive)

Simply put, if you have a separation and a problem you are likely f*cked.

 

[wedivebc]

I know this is an old post, and not debating the merits of team bailout, but just curious to hear ppl's arguments against team bailout. (disclaimer: I would not consider planning team bailout for a dive)

There are very few people who I would engage in a team bailout scenario. I have done it with a highly reliable team but they are so rare. Dive conditions have to be pretty good too bad vis or current can be a show stopper.

 

[Mod63]

Simply put, if you have a separation and a problem you are likely f*cked.

That.

 

[tbone1004]

I know this is an old post, and not debating the merits of team bailout, but just curious to hear ppl's arguments against team bailout. (disclaimer: I would not consider planning team bailout for a dive)

I think to answer that you have to argue the merits of team bailout and where it may or may not be applicable. I'm sure guys like @Bobby and @kensuf will be able to add some things with their experience and correct anything I missed.

In CCR every diver needs the following
O2-runs the CCR
dil-runs the CCR
Those historically are onboard bottles and in open water, the dil bottle is often plumbed to the wing, drysuit, and a BOV if fitted. That bottle is traditionally 3l that holds roughly 20cf of gas.
The "rule of thumb" says that O2 is consumed at ~1lpm/.035cfm and a 3l O2 bottle at roughly 20cf minus flushes, calibration, etc. so that bottle is good for 6-7 hours of diving or roughly the capacity of most scrubbers. Super convenient eh?
Dil doesn't really have a rule of thumb because there is absolute depth involved for loop/wing/suit compensation, you don't know if the diver is an efficient user of dil *i.e. leaking/fogging mask, not stable with buoyancy, etc*, so we can't go with that, but generally speaking the onboard bottle is enough to run the dive.

Most experienced divers discuss the concept of "rock bottom" to calculate the minimum gas required to make a safe ascent from depth. If you subscribe to this, then you'll realize that the onboard bottle is not big enough to realistically make an ascent. A good "rule of thumb" that I use is 8cf/ata/diver which is enough to solve a problem at depth/traverse back to an ascent line, make a "normal" ascent, and do it all with an elevated sac of around 1.0cfm. Yes that is a lot, but I said it's an easy rule of thumb. It's based on 4ata dive, 3 minutes to resolve, 4 minute ascent, 5 minute safety stop at 15ft. It's too much for shallower, and not enough for deeper, but it's a rule of thumb, so sue me.
So based on this and assumption of failures, you are only planning on getting yourself out, not you and a buddy. Let's stay at 100ft, so no less than 32cf to get up so you carry an AL40 for your own bailout and we will add that to the list of mandatory bottles a diver carries so everyone has their own O2, dil, and bottom bailout.

Any open water non-penetration, non-trimix, no-deco CCR dives would then be done with those three bottles that I think we can all agree are considered mandatory.

So what happens when we get into mandatory decompression? Let's stay in open water and stay in <5ata's of depth. For the rest of this I'm using Deco Planner with bottom gas set to around 1.1 ppO2 and standard gases for decompression and helium mixes, and GF60/80 which is what I am using right now and SAC rates set to 1.0cfm. Obviously the real deco obligations on a CCR are going to be different, but the OC ascents are what we care about and what you have to plan for anyway.
Step 1- Let's look at a deco dive with a reasonable amount of backgas deco, say less than 20 minutes. 100ft for 40mins gives 19mins of deco time and calls for 26cf of gas. 26cf for decompression, plus the "rule of thumb" of 32cf for bottom mix and you're probably going to change that AL40 for an AL80.
Step 2-I used that dive profile because the other option is for you to keep that AL40 of bottom mix, and bring an AL40 of O2 to cut the deco down to 10 minutes.

If we look at Step 2, you can start to make arguments for team bailout. One diver with an AL80, another with an AL40 of bottom mix and O2. It saves 1 bottle going into the water, each diver is capable of getting to the surface, but if they stay together, the guy with the AL80 can grab the O2 bottle and accelerate deco. This dive isn't particularly enticing to move to team bailout, but it's the first example of where there is a potential benefit. As we get deeper and longer, that bottle saving starts to compound and you eventually get to the point that you need to seriously look at team bailout. Team bailout IMO should only really be looked at in teams of 3, and only in conditions where the odds of you getting separated are essentially 0. For me, that means in a team of 3, the decompression gas for 2 full divers will be split between the team of 3. Every diver will have enough bottom gas to get themselves to the first gas switch, and the gases will be split appropriately to where any individual diver should be able to get to the surface. To me that means changing gf-hi to 99 instead of whatever your chosen GF may be and then deal with IWR or surface O2 since being bent is less bad than drowned, but the team bailout for me is balancing the accelerated decompression against the practicality of the bottles. I am not doing dives where I would consider that, but I do know that both Bobby and Ken have done a lot of them, especially while CCR was in its infancy and would be more qualified to talk about it. With most of my diving being in caves, we do have the advantage of being able to do setup dives which removes the pressure to move towards team bailout that is very real in deep ocean diving. Me personally? I'd consider a bailout CCR long before I considered any of the traditional implementations of team bailout.