First Rebreather - Used Prism 2 - Good Instructor - Is it OK ?

[stuartv]

I don't have enough experience to really have a credible opinion of my own on this.

But, one of my main dive buddies did his MOD2 and MOD3 CCR training with Dave Gration, over in the UK. Dave appears to have some pretty weighty credentials, when it comes to tech/CCR diving and teaching. My buddy who trained with him does dives in the 90 - 120 meter range several times per year (normally - not so much this year!). I think Dave has been a regular on some pretty well-known deep wreck expeditions.

The training my dive buddy has gotten from Dave, including at the MOD3 level, is having the BOV plumbed to the onboard (typically) 3L dil. That is not to say that my buddy never uses any other configuration for any dive. But, I do believe his standard config he uses for anything other than special, "big" dives, is just that - BOV connected to onboard dil. As he was trained.

Like I said, I am at the MOD1 level and don't really have enough experience to express an opinion of my own. My point is that there are what appear to me to be well-credentialed, highly experienced technical CCR divers who are on both sides of this discussion. In my mind, it does not seem black-and-white, one way is Right and the other is Wrong.

 

[vitaly]

Using an onboard 2 or 3L tank as your BOV source is a mistake which opens up a whole lot of other potential problems you just don't need on an already bad day.

It's better address this to Hollis not to me.
Anyway I still can't understand why BOV connected to onboard tank is more evil than DSV which is not connected to any tank. At least they both are in the same category. And I personally treat my BOV (plugged to off-board) as DSV.

 

[rddvet]

It's better address this to Hollis not to me.
Anyway I still can't understand why BOV connected to onboard tank is more evil than DSV which is not connected to any tank. At least they both are in the same category. And I personally treat my BOV (plugged to off-board) as DSV.

Because it gives you a false sense of security when in reality at any significant depth you'll get a couple of breaths out of the onboard tank. Regardless of if the manufacturer designed the unit to be that way, it's not a wise choice. That's not even taking into account stress or a CO2 hit which would be even worse.

 

[rddvet]

I don't have enough experience to really have a credible opinion of my own on this.

But, one of my main dive buddies did his MOD2 and MOD3 CCR training with Dave Gration, over in the UK. Dave appears to have some pretty weighty credentials, when it comes to tech/CCR diving and teaching. My buddy who trained with him does dives in the 90 - 120 meter range several times per year (normally - not so much this year!). I think Dave has been a regular on some pretty well-known deep wreck expeditions.

The training my dive buddy has gotten from Dave, including at the MOD3 level, is having the BOV plumbed to the onboard (typically) 3L dil. That is not to say that my buddy never uses any other configuration for any dive. But, I do believe his standard config he uses for anything other than special, "big" dives, is just that - BOV connected to onboard dil. As he was trained.

Like I said, I am at the MOD1 level and don't really have enough experience to express an opinion of my own. My point is that there are what appear to me to be well-credentialed, highly experienced technical CCR divers who are on both sides of this discussion. In my mind, it does not seem black-and-white, one way is Right and the other is Wrong.

There are lots of "famous" divers that do absolutely stupid sh!t. Just because your friend's instructor does deep dives that way doesn't mean that it's a smart idea.

 

[vitaly]

Because it gives you a false sense of security when in reality at any significant depth you'll get a couple of breaths out of the onboard tank

I'm not sure if you read the whole tread but I'm talking about using BOV + onboard tank for air dill dives only. 3l(23cft) tank even at 150' it's way more than a couple of breaths.

 

[rddvet]

I'm not sure if you read the whole tread but I'm talking about using BOV + onboard tank for air dill dives only. 3l(23cft) tank even at 150' it's way more than a couple of breaths.

It’s definitely more than a couple of breaths in perfect conditions. Throw in a CO2 hit and your consumption will go sky high and now you need to move to off board bailout which is added task loading when you’re already task loaded. I took a minor CO2 hit (long story) and was shocked how heavy my breathing got.
You can definitely use an onboard tank as bov bailout, and those that are proponents of it typically say it’s just a stop gap to get you to your off board bailout. I’d rather be able to use my bov to its fullest, and be able to bailout to it without any additional worries or things to do.

 

[stuartv]

It’s definitely more than a couple of breaths in perfect conditions. Throw in a CO2 hit and your consumption will go sky high and now you need to move to off board bailout which is added task loading when you’re already task loaded. I took a minor CO2 hit (long story) and was shocked how heavy my breathing got.
You can definitely use an onboard tank as bov bailout, and those that are proponents of it typically say it’s just a stop gap to get you to your off board bailout. I’d rather be able to use my bov to its fullest, and be able to bailout to it without any additional worries or things to do.

Question. Serious question. Not trying to be snarky. Trying to learn.

Once you ascend to your first gas switch (on the BOV), what do you do to switch gases? Do you unplug from your bottom mix and plug into your deco gas? So, hold your breath or a long, slow exhale during the time that the BOV is not connected to anything? Or do you actually remove the BOV and put another OC reg in your mouth?

 

[rjack321]

Question. Serious question. Not trying to be snarky. Trying to learn.

Once you ascend to your first gas switch (on the BOV), what do you do to switch gases? Do you unplug from your bottom mix and plug into your deco gas? So, hold your breath or a long, slow exhale during the time that the BOV is not connected to anything? Or do you actually remove the BOV and put another OC reg in your mouth?

Remove the BOV and switch to a deco gas just like you do switches in OC tech diving. (every agency has their own acronym for how to safely switch). This should be a calm deliberative process so you don't end up on the wrong gas and die. Scrambling for an offboard 2nd stage because your BOV is OOA is a terrible switch protocol

unplugging gases and replugging gases is like leaving a 2nd stage in your mouth and unscrewing your backgas lp hose and reattaching your deco gas lp hose.

 

[vitaly]

I took a minor CO2 hit (long story) and was shocked how heavy my breathing got.

Did you use BOV or DSV? Were you able to switch to OC reg? Just curious what to expect?

 

[telemonster]

I am a new Prism2 diver (50 hours or so) and my unit has the BOV plumbed to the dil tank.

Are you talking about plumbing the BOV to the bailout? Using a quick disconnect or something? Usually the training process involves handing off and/or ditch + retrieving the bailout tank.