DPV gas planning

[nakatomi]

There is no way in hell I would ever consider both being on the trigger and sharing gas.
If my dive buddy suggested such a strategy I would take her directly to UF for impending stroke or brain cancer.
It brings shame on our community that people teach such a stupid idea.

Just out of curiosity, since you're so flamboyant in telling us how stupid this method is, please allow two questions.
Are you DPV trained? If so, did you ever try this procedure during your class?

[PfcAJ]

So, how exactly does this work? I've heard it a ton before, but I'm not sure exactly how it works. I also have practically zero DPV experience.....so forgive the question, but can you clarify this?

Do you breathe your stage down to 1700 (assuming AL80) and then exit on your stage, draining it completely but leaving your backgas untouched? Or would you scooter in half+200 before switching to backgas and looking around that room before turning? What do you do if you have two AL80s for stages? How would you plan that?

Not sure if you know how to stage dive, but I don't teach cave diving so I'm not going to get into the details of all the gas management. But pretty much the "+200" is burned up during the gas switch. Stowing hoses, droppin' bottles, etc. So at the end of the dive, the stages are effectively empty. If you have an issue, you can jettison the spent stages since there's virtually no breathable gas in them. Compare this to "thirds" where you've got 1000psi in maybe 2 or 3 bottles. That's a lot of gas totaled up, but its also 2 or 3 bulky scuba tanks that slow you down and the reserve gas isn't with you at all times.

To keep the topic focused on DPV diving, I'd suggest that if its longer range and/or deep, you don't touch backgas (that's your reserve) and breath the stages to half+200 each. Depending on the dive I might use a stage (to half+200), drop it and go a ways on backgas. Its HIGHLY dependent on the cave and the situation. There's no one size fits all method for this.

Much more than 3 or so stages and you're getting some distance under your belt and more considerations need to take place. But still, half+200 on the stages.

[RN]

Why teach it if its not safe (first) and practical (second)?

I use it as a skills exercise as mandated in the standards. I don't teach it as a practical application. Same reason I have my IANTD Trimix students remove and replace their rigs underwater during class. Not only that but they have to remove the rigs, ascend to the surface, dive back down and put the rig back on. Is this a practical or safe thing to do during a non-training dive? Absolutely not. It is required by standards and it is useful as a confidence builder. That's the way I view this DPV skill. Not practical but useful as a confidence builder.

It would seem to me that both students are using DPVs while doing the towing method. Diver 1 is driving it, diver 2 is towing it out. DPVs are certainly being used and you don't end up teaching some "technique" that virtually every poster here recognizes as impractical and dangerous.

Towing a DPV is not the same as using a DPV. It's a matter of interpretation. I may be interpreting the standard incorrectly but if that's the case so are other instructors. Who knows, maybe this thread will get the NSS-CDS Training Committee to review that standard and either clarify it or remove it. None of the other agencies I teach through have a similar standard.

[victorzamora]

Not sure if you know how to stage dive, but I don't teach cave diving so I'm not going to get into the details of all the gas management

I do know how to stage dive, and have taken a class.....I was asking specifically about the DPV aspect of it. I do my stage diving differently than half+200, but I don't want to get this thread onto what stage gas management techniques you use.

[PfcAJ]

I do know how to stage dive, and have taken a class.....I was asking specifically about the DPV aspect of it. I do my stage diving differently than half+200, but I don't want to get this thread onto what stage gas management techniques you use.

What do you do?

[RN]

So, how exactly does this work? I've heard it a ton before, but I'm not sure exactly how it works. I also have practically zero DPV experience.....so forgive the question, but can you clarify this?

Do you breathe your stage down to 1700 (assuming AL80) and then exit on your stage, draining it completely but leaving your backgas untouched? Or would you scooter in half+200 before switching to backgas and looking around that room before turning? What do you do if you have two AL80s for stages? How would you plan that?

Should have been covered in your DPV class. Personally, I require my DPV students to have stage experience because we will be using them during the DPV class.

[Kelly Jessop]

. None of the other agencies I teach through have a similar standard.

Maybe I am confused,but I when I learned this skill it came from NACD instruction.(?)

[Jim Wyatt]

I teach DPV divers to gas share side by side using both scooters. It gets the team out of the cave faster. If the team gets to a place where both scooters will not go thru side by side, then get in one behind the other configuration. This seems like common sense to me. I was taught this procedure by Larry Green who was at the time the training director for the NACD.

There is nothing written in the NSS-CDS Standards about which method should be used in an OOA situation. I did not review the NACD standards in regards to this issue as I am not certified as an NACD DPV instructor.

Rob: If you have suggestions for the NSS-CDS training committee please send them in the proper venue. I do not read this forum daily and will not see your suggestions. I will of course appreciate all suggestions you may have but will appreciate them being sent to me via e-mail to: trainingdirector@nsscds.org

Mdax-> I live close to you, so I will wait at the top of my driveway for my ride to Shands.

[nakatomi]

I teach DPV divers to gas share side by side using both scooters. It gets the team out of the cave faster. If the team gets to a place where both scooters will not go thru side by side, then get in one behind the other configuration. This seems like common sense to me. I was taught this procedure by Larry Green who was at the time the training director for the NACD.

That is exactly how I was taught and based on my experience with it going so smooth, I have high confidence in it being the proper approach for two skilled divers who know how to do this.

[bamafan]

I was thinking about this thread last night. It occured to me last night what this reminded me of. When I was a little kid me and my sister had some huge rubber bands that were over a foot in diameter relaxed. We would hook them over something and see who could shoot them the farthest. Finally one of the broke so we took it and tied the handles of our Big Wheels together with it. We would ride up and down the driveway and steer away from each other and it would pull us back together. One day we were coming down the driveway playing like this. Our garage had 2 seperate doors with a small section between the 2 doors. She went on 1 side and I went on the other as we were going as fast as we could. The rubber band stretched tight and I remember pulling back waiting on something bad to happen. Finally the rubber band broke and it hit my sister and luckily all she got was a big whelp. I am not saying it can't be done but I can't think of 1 instance where it would be better than being connected to the doner. I can just see the hose getting hung on something and the best case scenario is the reg is pulled from the divers mouth. The worst case scenario is something breaks. I prefer to be attached to the diver that is donating gas. Each to there own. Oog sidemount is so far down on my list of worries that it doesn't really concern me. Now backmount and a collision that damages the manifold and causes a total loss of gas might be unlikely but alot more likely than loosing both tanks sidemount. Just look at the ceiling in the duck under in the Lockwood tunnel the next time you go. Everytime I go in there all I can think is this would be a bad place to tear a manifold up but from looking at the ceiling alot of people are hitting it.