When does PADI teach gas planning?

[TheRedHead]

I dunno, the idea of a "mystery dive" sounds pretty cool.

In Coz you never really know. Usually the first dive is deep on air and the 2nd dive is Nitrox 32. You can have great conditions on one reef and blowing sand on another.

Got on the boat one day and the DM informed us that we were diving Barracuda and San Juan. That was an adventure.

One day, the Harbor Master closed the Marine Park to divers and the dive shop called and asked if we wanted to dive the windward side (outside of the marine park). We said sure and drove over there. We had to dive off a 27 foot fishing boat. There was no place for tanks so those were stored in boat well. We get to this spot and I ask where we are diving and the DM said, "I don't know, no one has ever dived here." :lol:

 

[LG Diver]

In real life, you may not know where you are going to dive until you get on the boat and you are not going to have your spreadsheet. How do you do it on the boat?

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.

 

[Charlie99]

Is it reasonable to dive the same way in cold water, bad viz with a drysuit as it is to dive in almost perfect conditions?

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.

 

[Charlie99]

I have never got on a boat and not known where I was going to dive.

You have lived a sheltered life. It's a common situation in many areas.

 

[TheRedHead]

Why is it that only tech divers should know how to save enough air to be able to get to the surface in an emergency? My OP was asking whether PADI taught it anywhere in rec courses, and if not where could I go to learn it. That's been answered to my satisfaction.

If you can calculate your SAC (keep a log over a period of time) then you can learn what your gas consumption is by tracking the amount of gas you used on various dives in various conditions. I learned the rudiments of gas planning in SSI deep diving course. I normally dive a E7-100 and use 100 psi per 10 feet. My tar baby is always NDL, not gas. The assumptions you use diving in cold water and poor viz are far more conservative than the assumptions you would use drift diving in Cozumel.

 

[TheRedHead]

Cold water, bad viz, and drysuit don't have much effect on the gas consumed by a panicked diver.

My SAC goes up in cold water and bad viz. I'm not going to assume that my buddy is going to panic.

 

[LG Diver]

If you can calculate your SAC (keep a log over a period of time) then you can learn what your gas consumption is by tracking the amount of gas you used on various dives in various conditions. I learned the rudiments of gas planning in SSI deep diving course. I normally dive a E7-100 and use 100 psi per 10 feet. My tar baby is always NDL, not gas. The assumptions you use diving in cold water and poor viz are far more conservative than the assumptions you would use drift diving in Cozumel.

You're absolutely right. In my case, I don't have enough logged dives, and I've changed gear configs so many times (moving from various rentals to my own gear) that I have no good knowledge of my SAC. As a result I'm using a generic 1.0 cu ft/min stressed diver SAC. It's better than nothing, but it doesn't vary according to conditions. I would use the padding number to adjust for conditions. If I had the knowledge of my own SAC rates like you do, I'd take 1.5 of that and use that as my stressed rate and it would be much more accurate.

 

[GreenDiverDown]

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!!"

 

[LG Diver]

It doesn't have to be that complicated. There is no need to plan an RB down to 1 psi.

I agree. I was just throwing out raw spreadsheet numbers. I'd never try to remember anything not rounded to 100 PSI.

 

[TheRedHead]

You're absolutely right. In my case, I don't have enough logged dives, and I've changed gear configs so many times (moving from various rentals to my own gear) that I have no good knowledge of my SAC.

I did the progressive chicken method of diving deeper and deeper over time. I didn't take AOW until I had 100 dives.