What is the quietest DPV?

[tbone1004]

Nonsense.
And dpv bailout and CCR bailout are easily equally calculated. But I have sat in with MANY instructors who do not do it accurately in my opinion.

which agency in which textbook has something written other than that? Same with CCR bailout

I'm aware that it's calculated the same way, know your kick speed, know your sac, know your avg depth, but I have yet to see anything in writing other than "always carry at least 2x what you need to kick out" for CYOA reasons

 

[Superlyte27]

This is actually a frustrating topic for me. I've actually outed some pretty big names on this board regarding their inability to plan bailout for DPV or CCR properly. Recently, I witnessed one of the biggest (if not the biggest) name in diving telling someone that 80cu' is enough bailout for X amount of penetration. No consideration on flow, depth or sac rate or swim speed. Just 80cu' should be good enough for 2000' of penetration. Try that at Indian or Eagle's Nest or P3 where it siphons.

I agree a proper dpv cave class is needed for most. Find a good instructor that knows how to do it. *Hint* if they don't take into account the features of the cave, your sac rate under stress, your likely average swim speed on exit under stress, in possibly (and likely) reduced vis, and depth/flow of the cave, find another instructor. The same goes for CCR bailout planning.

 

[Superlyte27]

which agency in which textbook has something written other than that? Same with CCR bailout

I'm aware that it's calculated the same way, know your kick speed, know your sac, know your avg depth, but I have yet to see anything in writing other than "always carry at least 2x what you need to kick out" for CYOA reasons

I've yet to see any literature from the three agencies I've taught for that give proper planning. I know two instructors that actually do/teach proper planning. I am one of them.

 

[Superlyte27]

I'm aware that it's calculated the same way, know your kick speed, know your sac, know your avg depth,

And that is where the problem originates. What sac, what kick speed? I know people who are planning their bailout on best case scenarios. Sure, in crystal clear vis with flow at your back and no stress you have a .5sac and a 100fpm swim speed. But is that what happened to Evelyn’s buddy in Ginnie? Vis was crap. His sac was crap. Did he make it out?

I plan for worst case, not best case. In 22+ years of cave diving, don’t you think I’ve been in some hairy crap? It’s ludicrous to believe that I can maintain 100fpm in 5’ of vis. It’s stupid to believe my sac won’t double or more depending on how bad the situation is.

A few years ago I got wedged in a section of Madison for a solid 30 minutes. 30 Minutes!!! Don’t you think my sac rate was elevated beyond it’s normal .4? And when I finally got free, vis for Madison was zero for the next 1500 feet. What do you think my swim speed was?

The other problem is, that us CCR divers might go years between our OC dives. Some of us have no idea what our sac rate is, because it’s been so friggin long since we had to worry about it. Is it a .4 still? Or, because it hasn’t mattered for so long on CCR, is it up to 1.0? I’d venture that most people don’t know.

These are questions DPV and CCR students need to be asking. If your instructor doesn’t see the benefit in these questions being answered, you’ve found the wrong instructor.

 

[tbone1004]

@Superlyte27 my DPV and CCR instructor both made me doing SAC swims. They were suprised when I told them before we went in what it was going to be. Lo and behold, 70fpm and .65cfm rate for my "need to get out of here" SAC, and 50fpm, .45cfm for my leisurely pace. Needless to say my bailout calculations are 1.0cfm/50fpm
Apparently they don't get many students that keep track of that sort of thing.

On the no o/c for a long time, it is something I'm painfully aware of with several CCR buddies, but they've thankfully taken to doing at least one real cave diver per year on OC to validate everythin

 

[Superlyte27]

@Superlyte27 my DPV and CCR instructor both made me doing SAC swims. They were suprised when I told them before we went in what it was going to be. Lo and behold, 70fpm and .65cfm rate for my "need to get out of here" SAC, and 50fpm, .45cfm for my leisurely pace. Needless to say my bailout calculations are 1.0cfm/50fpm
Apparently they don't get many students that keep track of that sort of thing.

On the no o/c for a long time, it is something I'm painfully aware of with several CCR buddies, but they've thankfully taken to doing at least one real cave diver per year on OC to validate everythin

That’s good to hear. I hope more and more start doing this. Another thing I would state is to quit relying on your buddy’s gas in your calculation. I’ve had a handful of close calls. In every single instance, my buddy was no where to be found. In one instance, my buddy was a person that I believe is probably one of the top 5 cave divers in the world.

 

[Jack Hammer]

@Superlyte27, Pete, Same as Tom, my cave cave DPV instructor had me doing SAC swimming and planning for worst case scenario.

 

[DA Aquamaster]

Pete, I had different Cave DPV and Cave CCR instructors but both had us doing SAC swims to confirm how far bailout would last under ideal conditions. And emergencies almost never involve ideal conditions.

My regular team mate and myself both have SAC rates around .65 at a 75 fpm swim rate. For bailout purposes I double the SAC to 1.3 and assume only 50 fpm on exit. With those numbers, an AL 80 in a shallow 60' cave gives only 20 minutes and 1000' of distance. At a 100 ft depth, those same assumptions provide for just 14 minutes and 700' and we drop bailout accordingly based on the actual depths.

If we are in a side mount passage where both the need to find a place to turn around and then tight passage and restrictions during the exit make anything close to an average of 50 fpm impossible, we adjust the bailout accordingly.

I'm as shocked as you are at the suggestion that an AL 80 will provide 2000' of bailout. It's an assumption that is at best very optimistic, even in a 60' deep cave and would most likely be fatal in a 100' deep cave.

 

[drbill]

For me the most silent DPV is the one being used a few miles from where I dive. It irks me when I dive our park and have first time snorkelers and DPV users zooming around above me.

 

[lv2dive]

Off the top of my head I can think of four who talk the talk AND walk the walk - Ted McCoy, Ken Sallot, Dan Patterson, and another Ken (not sure if he is active or not). And those are just the guys I’ve actually seen/heard teaching dpv gas planning (or referencing dpv gas planning training they conducted) - without thinking very hard I can come up with s half dozen more I’d trust in a heartbeat, and that’s before i start counting GUE instructors. The instructor situation may have some challenges but there are very good ones around.

I've yet to see any literature from the three agencies I've taught for that give proper planning. I know two instructors that actually do/teach proper planning. I am one of them.