BOV with MAV and/or ADV - thoughts?

[rjack321]

The other dumb thing about plugging onboard gas into a BOV not already mentioned... Once you suck the itty bitty tank dry - which you will be cause no way are you getting your breathing stabilized in <2mins. Now you have no wing. Especially for OW diving do not run your wing off any kind of offboard, it needs to be from an onboard gas. Trust me on this one you will end up getting in or trying to get out of a boat without gas plugged into the wing eventually. And that is really bad news to have a loop in your mouth, sinking, and no power inflator. About all you can do turn so your neck seal doesn't vent and try to stabilize on suit gas. Or inject O2 and then try to transfer it to the wing, but good luck doing that fast to not crush you lungs or sink into the abyss - or both.

Using onboard dil to your BOV is not just a bad idea from a volume to breath on OC perspective. Its a bad idea additionally because it compromises your buoyancy options.

The entire concept seems to be a legacy from the YBOD days off CCRs. Plug that BOV into offboard with a high flow connector.

 

[stuartv]

The other dumb thing about plugging onboard gas into a BOV not already mentioned... Once you suck the itty bitty tank dry - which you will be cause no way are you getting your breathing stabilized in <2mins. Now you have no wing.

Presuming we're not talking about cave diving, once you go to BO, why would you be inflating your wing? Once you bail, the dive's over and you're going up, right? Plus, you've still got inflation you can put into your drysuit. I'm not trying to argue. I realize I know virtually nothing. I'm just asking the questions that occur to a newbie (me).

As I am understanding all these recommendations, the consensus is, on a big, deep dive, you have a BO of bottom gas in a slung cylinder. If you have a CO2 hit, you bail off the loop and onto that. Having a BOV connected to onboard dil as an intermediate step you CAN use is "bad", even when you also still have the big cylinder of slung BO gas. Even if you are really deep and the dil cylinder only gives you 30 seconds, I am unclear on why that is worse than no BOV and being FORCED to go directly from the loop full of CO2 to the slung BO cylinder.

 

[tbone1004]

@stuartv ever dumped too much gas on ascent? Still have to get back to the anchor line so you have to travel somewhere.
The bigger issue is if you bailout, you have to bailout again. That little 3l bottle, assuming it's 3l, has 23cf assuming it's a full fill, first dive of the day. Now, let's assume you are diving in the salty stuff and dive a perfectly square profile and are 21lbs negative *perfectly reasonable for OW at the start of a dive*. That's .3cf that you have to displace. You're already doing normoxic dives, so we'll assume say 9ata since it was brought up earlier.
You have 23cf of gas available, 3 of which has been allocated to wing inflation, going to have at least 2 used for dil, and 2 is needed as a minimal reserve to keep the reg going at the bottom. Leaves you 16cf of bailout and as said, you're consuming at bare minimum 5cfm at depth, but if you bailed out, odds are you're breathing quick so could easily be breathing 10-15cfm at that depth. You are going to suck that bottle dry REAL fast trying to switch to your other regulators. May as well use the 23cf for wing/suit inflation and plug in your offboard bottle to the bov where you at least have 80cf to play with instead of 16. Doesn't give you much time if doing OW with a single AL80, but you can't be stupid with this stuff.

 

[doctormike]

Presuming we're not talking about cave diving, once you go to BO, why would you be inflating your wing? Once you bail, the dive's over and you're going up, right? Plus, you've still got inflation you can put into your drysuit. I'm not trying to argue. I realize I know virtually nothing. I'm just asking the questions that occur to a newbie (me).

If you are on the surface and not in the best shape for whatever reason after your bailout (DCS, exhaustion, etc...), you really want to be positive with a CCR. If you lose the mouthpiece, flooding the loop will make you very negative. Not having dil makes it very hard to fill your wing if you are not doing well. It's a complicated case with a lot of speculation, but this sort of thing may have contributed to Rob Stewart's death.

As I am understanding all these recommendations, the consensus is, on a big, deep dive, you have a BO of bottom gas in a slung cylinder. If you have a CO2 hit, you bail off the loop and onto that. Having a BOV connected to onboard dil as an intermediate step you CAN use is "bad", even when you also still have the big cylinder of slung BO gas. Even if you are really deep and the dil cylinder only gives you 30 seconds, I am unclear on why that is worse than no BOV and being FORCED to go directly from the loop full of CO2 to the slung BO cylinder.

This kind of setup means that while you still are going to end up on your offboard bailout, now you have paid for that 30 seconds by emptying your onboard dil. Not only does that mean no wing on the surface, but sometimes you go back on the loop after bailing out, need to do a dil flush, need to add dil if you overvent, etc... I don't dive a BOV, but I just don't see the advantage of that configuration.

 

[rjack321]

Presuming we're not talking about cave diving, once you go to BO, why would you be inflating your wing? Once you bail, the dive's over and you're going up, right? Plus, you've still got inflation you can put into your drysuit. I'm not trying to argue. I realize I know virtually nothing. I'm just asking the questions that occur to a newbie (me).

CCR is wonky but you aren't sure why, switch to BOV
Turns out you are flooding, getting heavy fast
But wait you weren't even on the bottom yet, only halfway down
Blowing dil into your wing like crazy to try and stop your descent while also breathing said dil at an elevated rate
Adv is firing as your loop crushes, but its just venting dil out as water comes in, more dil lost
OUT OF DIL nothing left to breathe AND nothing left for your wing
Getting really hard to switch to a proper BO reg fast and then orally inflate too at this flustered point
This is not ending well....

As I am understanding all these recommendations, the consensus is, on a big, deep dive, you have a BO of bottom gas in a slung cylinder. If you have a CO2 hit, you bail off the loop and onto that. Having a BOV connected to onboard dil as an intermediate step you CAN use is "bad", even when you also still have the big cylinder of slung BO gas. Even if you are really deep and the dil cylinder only gives you 30 seconds, I am unclear on why that is worse than no BOV and being FORCED to go directly from the loop full of CO2 to the slung BO cylinder.

Because if you don't bail to it the chances of burning through it and losing your primary buoyancy control are reduced. And if you were diving with 6ft of suit gas that is unlikely, by itself with the dil gone, going to support a flooded unit.​

Smart people haven't plugged BOVs into onboard gas in decade. Just don't.

 

[joshk]

I need to sell you my 3D printed invention:

Hah, well that looks slick. But it's still faster to dry open hoses

 

[KenGordon]

I have a JJ with the DIvesoft BOV, no manual adds or ADV. I have it plumbed in to my offboard bailout, usually a 7 for no stop stuff or an Ali80 for deeper stuff. It isn’t noticeably heavier or more awkward that the regular DSV. Looking down at your chest you can tell it is there as it will restrict movement a bit sooner. The knob could be bigger and is not so nice as the normal JJ one, but who can say they wouldn’t like a bigger knob? I have however had an email informing me I can have an enlarged knob for only £17 plus postage, so I will be ordering one with my next cell.

Other than for a 10 or 20m dip you’d be mad to use your 3l dil as bailout, even then I wouldn’t.

The point of a BOV is to avoid having to take the loop out of your mouth while breathing like a train and with a brain that will not let you. Delaying that by a short time is pointless. Even delaying it by the 10 minutes your Ali80is expected to last still might mean a huge effort of will to swap to a real reg if the accounts people give of co2 hits are to be believed.

I don’t know how the manual adds etc are arranged on a Revo but on the JJ you can disconnect the dil/o2 and plugin bailout instead. This allows a wide range of options to solve issues. I suspect that you’d need to find another way to get those options so really the manual adds would have to stay, or some equivalent plumbing.

I have dived with people who have done wild and crazy stuff to their rebreathers in the name of improving them for some unlikely scenario or other. It makes everything a bit harder as a buddy and is probably counter productive.

 

[lv2dive]

I know several instructors who DO use BOVs - I guess it’s a matter of who you know!

There's a place to plug in off board. But, after you finish getting familiar without a BoV, and get comfortable, I doubt you'll opt for $1600 to switch to a BoV.

I don't think they're necessary. I know VERY few instructors who use them.

BTW, the ADV on the Revo is the worst I've used.

 

[lv2dive]

I take it that is loop hanger? I like it! How much?

I need to sell you my 3D printed invention:

View attachment 474437



I need to call in some Singulair for you.

 

[Superlyte27]

I take it that is loop hanger? I like it! How much?

I want a few also.