When does PADI teach gas planning?

[LG Diver]

I wouldn't get out of bed for a 9 minute dive. Nitrox would help - but I'd much rather bring some gas and do some deco.

I would!! I'll take that over sitting at a desk monkeying with Excel spreadsheets any day. I'd rather do some deco too, but with all of 24 dives under my belt it ain't happening any time soon. It will happen, though.

 

[JimC]

I would!! I'll take that over sitting at a desk monkeying with Excel spreadsheets any day. I'd rather do some deco too, but with all of 24 dives under my belt it ain't happening any time soon. It will happen, though.

I'd just pick a different dive given your training and experience level.

 

[Sideband]

I chose the 500 PSI pad since the PADI motto is "get to the surface with 500 PSI" but there are a lot of reasons why you'd want some sort of padding. 500 PSI is probably a bit much, but SPG error alone should dictate a pad of at least 200-300 PSI. If you need air once on the surface for whatever reason (like needing to get on air for a rough surf entry) then you'd want an appropriate pad.

I'd kind of like to watch 2 divers using standard rec rigs (not long hose) do a rough surf exit while sharing air. Only thing better would be to have them try to buddy breath.

Joe

 

[LG Diver]

I'd kind of like to watch 2 divers using standard rec rigs (not long hose) do a rough surf exit while sharing air. Only thing better would be to have them try to buddy breath.

Joe

Yes, that would be quite a feat. Even with a long hose (which I use) I wouldn't attempt to air share exiting this particular site in the conditions we had last week. However, with the padding at least one diver can still be on air for the entry- better than zero divers on air. It gives you some options- diver on air exits first, strips gear, and is prepared to assist the other diver if needed, as an example.

 

[TheRedHead]

All I mean is that if you're doing a multilevel dive where you just go down and touch 130' and then come up from there your no-deco time would be longer, your RB would be smaller (as you pointed out, it rolls with current depth) so you could have a plan that has 30 minutes bottom time and be gas-limited with an Al 80, whereas you wouldn't necessarily be gas limited on a square profile dive to 130'.

This is exactly the way a lot of diving is done IRL. You've come out of Devil's Throat in Cozumel at 125 feet and you've got 2100 psi. If you decided to make an ascent to the surface, everyone would think you were crazy. You've got a long multi-leve dive ahead of you with viz in excess of 150 feet over beautiful reefs. You're drifting along and don't have to work. How do you plan this dive with your spreadsheet? What assumptions do you use?

 

[LG Diver]

This is exactly the way a lot of diving is done IRL. You've come out of Devil's Throat in Cozumel at 125 feet and you've got 2100 psi. If you decided to make an ascent to the surface, everyone would think you were crazy. You've got a long multi-leve dive ahead of you with viz in excess of 150 feet over beautiful reefs. You're drifting along and don't have to work. How do you plan this dive with your spreadsheet? What assumptions do you use?

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.

 

[Charlie99]

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

Just remember that even the most conservative plan is useless if you ignore it.

 

[TheRedHead]

Just remember that even the most conservative plan is useless if you ignore it.

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?

 

[TheRedHead]

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:

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?

 

[Cave 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?

She asks some thought provoking questions, no?