When does PADI teach gas planning?

[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?

You could do it any number of ways:

1) calculate it by hand- that's what the 5thd-x worksheets are all about

2) print out the spreadsheet and laminate it or put it in a plastic sleeve and throw it in the dive bag. That's what I've done

3) You don't really need the whole spreadsheet, as it shows RB's for all depths and a variety of tank types. All you really need to know or have jotted down are the RB's for your particular tank, or even just some basic numbers. I don't think it's too hard to remember three figures- RB for 60, 100, and 130 feet depths as an example. You could do the calculations with no padding, rememember those, and then just add padding to them in your head on the spot to account for changing conditions.

Really, I don't see how it's impractical to implement this using any of these methods.

 

[LG Diver]

That's a pretty conservative plan considering you are diving in such good conditions with a group of people, all of whom have air. I think he would have a hard time finding a buddy who would dive that plan with him. Which begs the question of altering assumptions based on conditions. 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?

The point of RB calculations are that they are specific to the dive. The calculations above are for rough surf entry/exit, cold water, deep dive, inexperienced divers. Of course I wouldn't use these numbers when diving in 80 degree Hawaiian water with 150' vis.

 

[Sideband]

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?

I have never got on a boat and not known where I was going to dive. It may be open as to one of 2 or 3 sites but I knew what those site options were before I signed up. Diving Nitrox I have to know at least the max depth or I could show up with a mix that means I only get to ride the boat out and back with no dive. I have never seen a boat or shop advertise a mystery dive.

Joe

 

[Cave Diver]

I have never seen a boat or shop advertise a mystery dive.

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

 

[rjack321]

As Stephen mentioned previously, RB rolls with depth- it's not just one number. Using the same set of assumptions in the spreadsheet as before with the 2100 PSI RB at 130, it looks like this:

Depth => RB

50 - 1016 PSI
60 - 1099
70 - 1189
80 - 1452
90 - 1568
100 - 1690
110 - 1819
120 - 1955
130 - 2098

Now certainly you wouldn't want to memorize all of these, but you could jot them on wetnotes or just remember to start up from 130 by 2100, be at 100 by 1700 PSI, be at 60 by 1100 PSI (or something like that). That's how I'd use the spreadsheet to plan it.

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

 

[lamont]

I have never got on a boat and not known where I was going to dive. It may be open as to one of 2 or 3 sites but I knew what those site options were before I signed up. Diving Nitrox I have to know at least the max depth or I could show up with a mix that means I only get to ride the boat out and back with no dive. I have never seen a boat or shop advertise a mystery dive.

Joe

i've gotten on boats knowing only that we were diving in the san juan islands. dive plan is generally always the same -- EAN30-32%, max depth a buck even, max bottomtime 25-30 mins, max runtime ~60 mins, follow instructions for how to not get blown off into high boat traffic areas. with 130s or 119s you don't come close to rock bottom (but 10 psi per foot works reasonably well with those tanks).

 

[friscuba]

So... the obvious question is...

...when do the other OW cert agencies teach gas management? :huh:

I was wondering that myself. It seems like this entire thread is trying to apply tech diving standards to all recreational diving, and singling out one agency for what is common practice.

 

[LG Diver]

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

Yes, I agree that no spreadsheet is required. My assumptions are a little different than yours. 2 divers at a stressed SAC of 1.0 cu ft/min, 1 min at depth, ascent at 33 ft/min, 3 min stop at 15 feet, and the biggie, 300 PSI pad. At 50' the figures work out as:

1 min at depth: 5.03 cu ft
Ascent: 5.33 cu ft
safety stop: 8.73 cu ft

without the padding it would be 716 PSI. With the pad (since this is all based on my original scenario) 1016 PSI.

 

[friscuba]

I have never got on a boat and not known where I was going to dive. It may be open as to one of 2 or 3 sites but I knew what those site options were before I signed up. Diving Nitrox I have to know at least the max depth or I could show up with a mix that means I only get to ride the boat out and back with no dive. I have never seen a boat or shop advertise a mystery dive.

Joe

Probably depends on where you are diving. Every dive op I've ever worked for in Kona generally doesn't pick sites 'til they're on the water, have checked out conditions and what the divers on board have already done.

I suppose if you dive a location that only has limited number of good sites you'd be more likely to know which site you're gonna hit ahead of time.

 

[LG Diver]

I was wondering that myself. It seems like this entire thread is trying to apply tech diving standards to all recreational diving, and singling out one agency for what is common practice.

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.