When does PADI teach gas planning?

[JimC]

If your an experienced diver, and have dealt with a number of intense situations under water and are confident in your and your buddies ability to handle whatever the dive can throw at you in a calm, stress free manner. Then by all means use your true SAC with a bit of padding.

But remember, drowning is drowning, bent is bent. Clear and warm or green and cold.

 

[limeyx]

OOH, OOH!! I just thought of an even better way! I'll just save the spreadsheet to my PDA and get an Otterbox waterproof case for it. That way I can take it on the boat and have 0n the spot calcs Some crazy dude shows up with a Heiser 190- no problem. Change two numbers in one of the columns and I've got his RB's. Sorry, Silicon Valley geek.

The really easy way is to write down (or memorize) your RB's in cft not PSI.
Then simply use the tank factor of the tank you are diving and the RC in cft for that depth to calculate PSI.

f.ex on a tech dive, I need 48cft RB. My tanks are LP80, TF = 6 (3x2 for doubles)
so the RB PSI = 48/6*100 = 800psi. For a different tank, just change the TF
(TF is number of cubic feet in 100 psi in a given tank - so in my double LP80's 100psi=6cft -- makes all kinds of things really easy)

 

[limeyx]

You've got a mistake in that spreadsheet somewhere. Unless you're using a 13cf pony or outrageous consumption numbers, there's not way 2 divers at 50 ft have a RB of 1016 psi.

1 min 50 ft
1 min to 30
1 min @ 30
1 min @ 20
1 min @ 10
5 minute ascent

ave depth 30 ft (2 ATA) * 1 cf/min stressed consumption = 2 CF/min

2cf/min * 5 mins = 10 cf

10 cf / 2.56 cf per 100 psi is about 400 psi, round up to 500 psi (never using less than 500 as RB) The other end (130') looks about right.

No spreadsheet required

Yeah, the lower numbers are high. Usually 500psi at up to 60 feet does it (for a reasonable tank) and then at 100 feet, it's (for me) about 1400psi in an LP80

I dont take singles below 100 so I have no idea about those numbers (not saying I've never dipped my head below 100 for a minute or two in a single tho

 

[Cacia]

I like cheat sheets on little stickers inside my housing, facing out.

 

[limeyx]

Much of what he has reserved is for a series of what I consider to be desireable deep stops, but ones that I am willing to blow off if having to ascend while sharing air. Cold water, bad viz, and drysuit don't have much effect on the gas consumed by a panicked diver.

Surface conditions might effect rock bottom in that one wants a reserve of gas for either hanging out on the surface or for a rough surf exit, but I look at those as a separate adder to be put on top of the depth-dependent rock bottom.

As in many areas of life, maintaining a distinction between "nice to have" and "required" aids in clear thinking and planning. I'm willing to wager that LG Diver will not treat those RB numbers as sacrosanct numbers not to be violated.

I agree in "nice to have" etc. but IMO RB should be minimum for a comfortable ascent.
If you can (safely) shave stops off then really that should be in the RB calculation.

I would actually be inclined to do the 1st deep stops, miss the middle ones and do more time in the shallow ones if I got an OOA when someone was at or near rock bottom.

You want to make it really simple when you are in a bad situation. The last thing you want to do with an OOA diver is start recalculating rock bottoms on the fly (in my opinion)

 

[limeyx]

It doesn't have to be that complicated. There is no need to plan an RB down to 1 psi. Just get in the ball park and add a buffer when appropriate.

ASSUMING that we have agreed to dive Punta Sur on a single AL80... I would plan this as a two or even three level dive.

130 RB 1500
60 RB 800
30 RB 500

Those numbers live in my head but if they got lost I could conjur them up with the simple 10% plus 200 rule.

I would remind my bud that we shouldn't come close to our RBs but if one of us should, then we will signal a move up to the next level.

I would ascend to the top of the reef (about 60 feet IIRC) immediately after coming out of the throat. I would plan to spend as much as half the total dive time drifting in OW at 30 feet. Even though this is well above the reef, it is the price I'll have to pay for a decent profile.

Personally, I would say, "Forget Devil's Throat. Let's stop the boat and hit Columbia Deep, instead!!"

They look like good numbers.

 

[GreenDiverDown]

They look like good numbers.

I agree with your cubic foot deal.

But, I mostly use AL80s (singles/twins) so it's very easy to remember the minimums in psi.

 

[TheRedHead]

If your an experienced diver, and have dealt with a number of intense situations under water and are confident in your and your buddies ability to handle whatever the dive can throw at you in a calm, stress free manner. Then by all means use your true SAC with a bit of padding.

I don't use my true SAC rate or my buddy's either and I use different RBs depending on the circumstances. I get more anxious in bad viz where I need to find an anchor line. I account for that. We've done a couple of real air share ascents both times were 1st stage problems. It was no big deal in warm clear water. We practice sharing air frequently. In our tech classes, we practiced sharing air with no mask and even buddy breathing with no mask, which is the most stressful thing I've ever done underwater. The no mask plus no air is a creepy feeling.

To me, there is a huge difference between stress and panic. I've experienced stress underwater such as vertigo at 100 feet from an ear problem and didn't panic. I'm generally very careful with my profiles and don't take risks. I'm not saying that I will never panic, but I consider panic to be the absolute worst failure of training.

BTW, I found my SSI Deep Diving book and there is an entire chapter on gas planning including reserves. Their recommendation for deep diving is 100 psi per 10 feet plus 500, which is extremely conservative and very close to the RB of GUE. It's laid out in much simplier terms, but in practical application, it works about the same.

 

[tedtim]

BTW, I found my SSI Deep Diving book and there is an entire chapter on gas planning including reserves. Their recommendation for deep diving is 100 psi per 10 feet plus 500, which is extremely conservative and very close to the RB of GUE. It's laid out in much simplier terms, but in practical application, it works about the same.

Not to hijack, but I just have to ask. Is this the source of "back on the boat with 500 PSI."

 

[TheRedHead]

Not to hijack, but I just have to ask. Is this the source of "back on the boat with 500 PSI."

I don't think so. That seems to transcend any particular agency.