DPV Gas Planning Golden Rule

[LiteHedded]

You got that right. Imagine you're 3000' back at 300' deep and your dive plan is already pushing the limits of your thermal protection. So what if you got enough gas to swim out, are you going to get bent like a pretzel because you can't handle the cold from a crap load of additional deco swimming versus additional scooter.

well say you've gone out to the end of upstream eagle's nest. pretty straight forward dive that takes 30 mins or so. now you have a failure and your 30 minute exit is now 90 minutes and your bottom time has doubled to 2 hours
i would say most people i see dumping gas on the log there have not brought enough gas/light/heat for a scenario like that

[Dsix36]

well say you've gone out to the end of upstream eagle's nest. pretty straight forward dive that takes 30 mins or so. now you have a failure and your 30 minute exit is now 90 minutes and your bottom time has doubled to 2 hours
i would say most people i see dumping gas on the log there have not brought enough gas/light/heat for a scenario like that

This is one of those instances when a rebreather can save your butt (or mine, since this sounds like my story).

[Pavão]

... So, that's assuming two failures. The rebreather has failed at max penetration and my scooter died, and my buddy is nowhere to be found. How many failures do you want to plan for? ...

Sounds like three failures to me

[Nitrogenius]

First of all, what are these "buddy bottles" you speak of?

Lol.. I was thinking the same.. I think a buddy bottle is referred to as a tank you put on a dive plan as extra safety cushion but not include in the calculation..
To me that is BS. Id rather decide on which safety level I overall want to achieve in a dive depending on external circumstances like complexity, cave known unknown, restrictions etc. etc. and then drive, calculate and plan it from there. So all the gas I am taking or staging is being accounted, therefore I will also know how much I need and wont guess whether one or two buddy bottles will be enough..

Secondly, my golden rule of DPV diving is very simple.... Always have enough gas to swim out.

True for hopefully all of us, but then I can see that some may want to even push that..
Main question here and biggest spread probably is going to be: How much gas is enough gas to swim out

[Superlyte27]

Do the math. It's simple math and it is what it is.

[Draker]

and dives more than ginnie and jackson blue, is a great one.

Fortunately there is also Little River...

[LiteHedded]

Fortunately there is also Little River...

Forgot about that one. But it is a very forgettable cave

[Nitrogenius]

Do the math. It's simple math and it is what it is.

The math is very simple..
It is the assumptions like exit speed, SAC, elevated SAC, CO2 elevated SAC, etc. that go into the math that need be well thought of..
And valued realistically.. Then on top of that math you add your safety margin you need to be comfortable with..
As to a back up scooter being a remedy for swim out gas as mentioned by Brian.. Well it again all comes down what level of redundancies you want to plan for 1 catastrophic failure, 2? etc etc... The more complex the dive gets the more interdependent the failure modes get..
At this point I simply could not imagine getting comfortable on a plan with not enough gas to swim out, same as I have troubles with the concept of a bailout rebreather instead of OC bailout.. latter is probably mainly driven that I already had a CO2 incident and the thought of having to bailout to another breather in that state simply scares the hell out of me..
I also have quite concerns of a BO breather being effective in a CO2 event due to the extremely elevated SACs, I simply think the scrubber wont be able to cope with the induced flow rate and thus even accelerating the issue..On the other hand the increased WOB on a BoB vs OC in combination with instant scrubbing might actually help to bring back the SACs to normal levels faster.. who knows..
So with my current attitude all my diving is definitely limited in comparison what other folks are accomplishing and doing, but I have lots of time to get there as so far my deepest dives are 300 feet and my longest single line penetration is about 6000 feet in lo flow (mexico)..
With the scooter I have only been in high flo and new (to me) caves so I did not even penetrate half of that yet..
Overall plenty of playground until I would have to adjust my planning perspectives as I have reached physical and logistical limits..

[floridabob]

Quite. Also, there is no substitute for experience, gained slowly enough that you can make some 'educational' mistakes and survive to learn from them. Same as a lot of areas in advanced cave diving that you cannot learn from an instructor. A good mentor is probably much more useful.

One of my many soap boxes is that an instructor should be advancing the sport so he may both teach and mentor. Both with experience and application rather than theory and standards alone.

And with only a few notable exceptions, people that plan and execute truly advanced dives (not 4k dives in Ginnie, JB or LR) are quite comfortable doing just that: Planning and executing. The exceptions mathematically plan them but are incapable of executing.

Some are gathering experience alone and others are creating mentoring relationships to further skills. Noble pursuits.

It should be noted we all start somewhere and end elsewhere and there is no shame in learning. But you cannot get the required knowledge and experience here...only in water and in execution--preferably with an asinine friend carrying a Go Pro and a grudge.

Bob

[Draker]

One of my many soap boxes is that an instructor should be advancing the sport so he may both teach and mentor. Both with experience and application rather than theory and standards alone.

And with only a few notable exceptions, people that plan and execute truly advanced dives (not 4k dives in Ginnie, JB or LR) are quite comfortable doing just that: Planning and executing. The exceptions mathematically plan them but are incapable of executing.

Some are gathering experience alone and others are creating mentoring relationships to further skills. Noble pursuits.

It should be noted we all start somewhere and end elsewhere and there is no shame in learning. But you cannot get the required knowledge and experience here...only in water and in execution--preferably with an asinine friend carrying a Go Pro and a grudge.

Bob

Whoa! Hold on. An instructor has to both teach AND mentor? AND scooter somewhere other than goldmine??? Blasphemy.

Thankfully I do have the "ass"inine friend with the camera.