OC/DSV - essential or toy? Multiple choice too!

Mdemon

Sorry mate - never met you... La la la...

[fingers in ears /on]

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wizbang

Not essential but very handy. Just like ABS. (is my view)
I think without an offboard system that can supply enough gas, it has limited scope.
I would rather engrain myself to go for the proper bailout reg than one that has a very limited duration. (such as at 100m etc)

Don't get me wrong, I would have one tomorrow (given the right price and a choice) but then again I have an off-board system so I don't need to take the reg out of my gasping mouth to change to something that will last.

Also if I am not gasping (not CO2) then I have time to take a refreshing/sanity breathe from my bailout reg just under my chin.

All redundent really, once we finalise the BOB in the other thread.

Underwaterbear

Hi Wiz,

I guess I dissagree slightly with your thinking on this one. I think an OC/DSV is an essential due to the nature of a CO2 hit and in particular the often cited "innability to get off the loop".

I have to admit I have not experienced a hit and was a sceptic regarding this aspect of what I considered "self-control" or will power. That is pretty much until very recently when a good buddy of mine related his recent experience of having a hit due to a flooded scrubber. He was at 40m and noticed anxiety, shortness of breath and shallow breathing. He thought it was just because he was in a dark, cold spot he didn't particularly like and after a conscious effort to breathe deep (and then realising he was managing that, but it wasn't helping) he realised he was having a hit. He related a near-innability to hold his breath long enough to go for his necklaced occy, and he thinks that it was only because he was on helium that he had the sense to recognise the symptoms early enough, that the necklace was possible. Once OC, he reported calming down quite quickly. It's worth noting that he also was a sceptic about the self control needed to get off the loop.

His story is really one of complacency and the error cascade when you boil it down. But following a principle of redundant safety systems would suggest to me that anOC/ DSV would given him the easiest access to a sanity breath at the time it was most critical.

It is a secondary contingency whether it is practical to have that OC/DSV connected to your on-board dil or a stage. For intermediate depths and simplicity I think the DSV should go to onboard gas. Your options, once sane, then become go back to the loop, go to bailout scenario which will obviously for all but simple bimbles involve off-board gases. A quick disconnect on the OC/DSV is a must for more advanced profiles given that it allows such flexibilty in utilizing a partially functioning loop.

Cheers
UWB

Steve

Write this down guys. This is exactly what this whole issue boils down to. have some Green UWB.

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decoweenie

Excellent, I never expect anyone to pay attention to what I say/write anyway.

No liability...

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decoweenie

Sorry, what I REALLY meant to say that is don't take everything said on the Internet as gospel!

I have read someone quoting links of something someone said somewhere to prove their point. When someone said something to good to be true, and no one else substantiate the claim, I don't trust it and I don't care what credentials they have.

For that same reason, when I write something, I try to stay within where I could always have proofs from another source if someone ask for it. When I don't (even when it did happen) I leave it off.

The reason for the negativity (if you think it is) is I have met people who made wild claims on the Internet yet have done nothing. I even have dive buddies lied about what they do on the same dives that they dive with me because they don't think I am on the same forum/list.

All fail, I could always claim that I am a pessimistic person by nature...

EDIT: Yes, I agree totally that the discussion is great to get the thought flowing, but not to follow blindly!

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nmanfield

Got a nemotech and very impressed with it. I bougt mine just under a year ago and had no problems with receiving it. Filip kept in touch and was very helpful - received it in less than a month after ordering. The benefits I have found is that it leaks less than my orginal DSV and I find that when starting a dive I can completely empty the counterlungs, dive down on OC for the first few metres, then switch back to CC once I'm sinking (slightly lesser weight needed). I also go to OC when back on the surface as I don't have to monitor handsets when getting back on a rib.

I am prebreathing and carry out all checks prior to going under, I only go to OC for the first 2 metres. Anyone else with thoughts about this or am I doing something very stupid?

Mdemon

Wizbang, I think the previous posts should have cleared up a misunderstanding; the OC/DSV can be plumbed inboard or offboard.

In my case I have GCS connectors so can swap mid-dive, but I tend to do the following:

For the shallow stuff, I use 6li drive tins and both ADV and OC/DSV ('BOV') are plumbed into it - ADV via manifold, BOV from 1st stage.

For deeper stuff, the ADV is plumbed into the inboard drive tin (Open Loop will therefore be a hard trimix correct for depth e.g. 10/52) and the BOV plumbed by GCS into the offboard bailout (e.g. 18/35). I plan to go Open Loop if the hit is debilitating, DSV for all other circumstances - I will be starting my ascent immediately anyway.

I have regs on all tins, but if I feel like it, I can obviously plumb all gasses into the BOV on-the-fly, so never have to remove anything from my mouth or risk a reg failure if I don't want to. To be honest, swapping to the correct regs is probably easier and safer than messing about swapping hoses, but the option is there if required.

HTH!

__________________
www.southwestmafia.com

"small minds talk about people, Average Minds Talk About Events, GREAT MINDS TALK ABOUT IDEAS!"

The WRONG Attitude will get you killed.

"Once the agenda-monkeys and perfect-worlders have moved on, perhaps we can do some diving?"

Philippe GERIN

I don't see why it'd be stupid as long as you check the loop is good to breath before you switch to it.
Sort of the same here, but on CC. Exhale off-board => empty CLs => down. At about 2m, manual O2 inject (Classic Kiss) to get SP up to whaterever I need for the targeted depth (0.5 to 0.7). Sort out checks (hoses, bubles...) and go.
I think what you do works because your ADV (mine too) is a demand valve so the CLs can collapse.
Just curious if that would work with the Meg or the Prism ADV as it's a schraeder valve that kicks in when the CL collapse.
Best
Philippe

ROB DAVIE

Tom Mount of IANTD uses a trombone-valve (slide shut-off valve) in the plumbing to his ADV on his Meg. He typically reaches his desired depth, and then shuts the trombone valve.

JFYI

Rob

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