Request for comments on article - mixed OC / CCR teams

[johndiver999]

As someone who has the most superficial understanding of rebreathers... my conclusion is NO WAY!

That is way too complicated with: do this, but never do that. Get the switches mixed up at depth and you kill the guy... etc.

I assume the discussion is concise and correct, but I had no idea how complicated those things are. No way I would feel comfortable diving with a rebreather diver, unless I spent a CONSIDERABLE time training and studying the unit.

One of the more useful things I have read on this forum.

 

[inquis]

Thanks for that article. I learned quite a lot and felt the level of detail was great. I wish I knew someone who dives a CCR now! Definitely a fair bit of training is required to be a competent buddy.

The DSV vs. BOV was most interesting, as flipping it could be deadly, as could not flipping it (if it were the other). Out of curiosity, is either more common than the other?

 

[doctormike]

Thanks for that article. I learned quite a lot and felt the level of detail was great. I wish I knew someone who dives a CCR now! Definitely a fair bit of training is required to be a competent buddy.

The DSV vs. BOV was most interesting, as flipping it could be deadly, as could not flipping it (if it were the other). Out of curiosity, is either more common than the other?

Glad you liked it!

Like many things in scuba diving, this choice is somewhat controversial. It's beyond the scope of this discussion to go over those arguments, but the main advantage for the BOV is that you can bail out more easily, which is an issue if you are partially incapacitated by hypercapnea. I have heard some divers describe a CO2 hit in such a way that they could barely throw the switch, and don't feel that they would have been able to do the slightly more complex action of closing their DSV and switching to an independent second stage on their bailout. A seizing diver with hyperoxia would also benefit from that feature, since the rescuing diver can supply fresh gas without the need to switch mouthpieces, which is much more likely to fail in that situation. Both of these situations are fairly uncommon.

However, each approach has advantages and disadvantages While initially you might assume that the BOV would always be best, many very experienced divers and very bright rebreather designers have opted for the DSV. I'm not so experienced, but I also prefer that configuration.

But the bottom line is that unless you are in the very rare situation of coming across an unresponsive CCR diver underwater that you don't know, you would have discussed this ahead of time, and you would know whether you were supposed to flip the switch underwater (BOV) or to only flip the switch after the loop was out of the divers mouth (DSV) and they were hopefully on a bailout regulator.

 

[happy-diver]

Having been subjected to obligatory buddying
It is always good to read what people are thinking
I know, a remote nerd for the OC buddy, magnifique
I have been both as a CCR and OC diver, insta bud-died
Why do the proponents of the buddy system even do that
I'm sure the only possible explanation be that they are slow!

 

[KenGordon]

TBH I think you are telling people too much. I would suggest two articles, an intro one and a detailed one. I’d choose a simpler picture for the top of the article, no scooters and no strange dangling stuff.

One of the BSAC Sports Diver lectures covers the principles of CCR and I end up teaching that. Once I took my JJ to the pool and did that part of the lecture for about 20 people, maybe 4 needed it but taking an actual rebreather vs a PowerPoint is a good way to embed the knowledge.

If diving with OC buddies I basically assume I am solo except for when it is a deco dive with experienced people. I explain what to do (make sure I am conscious) in the case of a flashing red computer or HUD and what to do (turn the BOV switch) if I am not. I explain about the flood risk and how essential closing the loop would be. I show them the yellow hose with a regulator and explain that is for them. Before I had a BOV I would explain about a dil flush. I don’t go into the lifting issues with inexperienced divers. They are lucky to be able to lift another OC diver and it is pretty much hopeless to expect them to lift a rebreather diver, especially in a drysuit, without both having an uncontrolled ascent.

In the extended version I explain about the quiet death versus violent death etc. Don’t try doing that on a boat.

BTW “One approach to this problem is to put a second regulator on a long hose on the bailout tank.” I have never seen this done. Generally I see an arrangement where the bailout regulator is either on a silicone bungee, looped somewhat like a hog loop primary (ie round behind the neck and dangling) or just on the bailout cylinder like a deco reg.

 

[doctormike]

TBH I think you are telling people too much. I would suggest two articles, an intro one and a detailed one. I’d choose a simpler picture for the top of the article, no scooters and no strange dangling stuff.

One of the BSAC Sports Diver lectures covers the principles of CCR and I end up teaching that. Once I took my JJ to the pool and did that part of the lecture for about 20 people, maybe 4 needed it but taking an actual rebreather vs a PowerPoint is a good way to embed the knowledge.

If diving with OC buddies I basically assume I am solo except for when it is a deco dive with experienced people. I explain what to do (make sure I am conscious) in the case of a flashing red computer or HUD and what to do (turn the BOV switch) if I am not. I explain about the flood risk and how essential closing the loop would be. I show them the yellow hose with a regulator and explain that is for them. Before I had a BOV I would explain about a dil flush. I don’t go into the lifting issues with inexperienced divers. They are lucky to be able to lift another OC diver and it is pretty much hopeless to expect them to lift a rebreather diver, especially in a drysuit, without both having an uncontrolled ascent.

In the extended version I explain about the quiet death versus violent death etc. Don’t try doing that on a boat.

BTW “One approach to this problem is to put a second regulator on a long hose on the bailout tank.” I have never seen this done. Generally I see an arrangement where the bailout regulator is either on a silicone bungee, looped somewhat like a hog loop primary (ie round behind the neck and dangling) or just on the bailout cylinder like a deco reg.

Thanks! I appreciate the reply... it's hard to strike the balance between too little and too much information. Still a work in progress.

I chose the cover photo because I wanted to use my own photo, and I liked it from a compositional point of view and because the divers eyes are engaged, making it pop a bit. I agree, not the best for illustrating the point of the article in terms of gear, but that's why I chose it. I also don't have that many mixed team photos to choose from!

I have done the extra long hose on the bailout tank myself. The bungeed regulator on the necklace is for me. The long hose is if I had to donate gas to my OC buddy (I'm still responsible for that, even if I'm on CCR). And if have to do that, I don't like the idea of suddenly having no bailout (I have a DSV, not a BOV). I don't have experience with BOVs, but I assume that it's a good idea to also have a second stage somewhere in case you tear or lose the mouthpiece, right?

 

[inquis]

While initially you might assume that the BOV would always be best

Yes, I have, based on my limited understanding. (Your article is the first time I've heard of the DSV.) Would you say that safety when flooded is the main advantage of a DSV?

 

[doctormike]

Yes, I have, based on my limited understanding. (Your article is the first time I've heard of the DSV.) Would you say that safety when flooded is the main advantage of a DSV?

Well, if you don't throw the switch, either will flood the loop if it's out of your mouth. The idea is that when you bail out with a DSV, you have to close it to prevent a flood, since it's now just floating loose in the water. If for some reason you had a BOV but went to an independent second stage (for example, if you tore or lost the mouthpiece), you would still have to throw the BOV switch to keep the loop from flooding.

It's beyond the scope of this thread, so I don't want to get too much into the DSV vs BOV discussion, but happy to do that in DM if you like.

 

[inquis]

Ha, I came back to edit my post to remove that last question after a little googling... but you're quick this morning. It does seem to be a complex topic.

 

[KenGordon]

Thanks! I appreciate the reply... it's hard to strike the balance between too little and too much information. Still a work in progress.

I chose the cover photo because I wanted to use my own photo, and I liked it from a compositional point of view and because the divers eyes are engaged, making it pop a bit. I agree, not the best for illustrating the point of the article in terms of gear, but that's why I chose it. I also don't have that many mixed team photos to choose from!

I have done the extra long hose on the bailout tank myself. The bungeed regulator on the necklace is for me. The long hose is if I had to donate gas to my OC buddy (I'm still responsible for that, even if I'm on CCR). And if have to do that, I don't like the idea of suddenly having no bailout (I have a DSV, not a BOV). I don't have experience with BOVs, but I assume that it's a good idea to also have a second stage somewhere in case you tear or lose the mouthpiece, right?

I think you are planning on one more failure than usual. If either your buddy is OOG or you need to bail out it is the end of the dive. With the bailout routed round the neck then the process is very like primary donate. If on a silicone necklace then it is like regular secondary take or donate.

Yes, with a BOV you need another reg in case of a failure of the mouthpiece.