Split from Exploration dives without a computer

[onfloat]

I think in terms of the 120 rule all the time. 32% gives you a 20% depth advantage.

I guess the question is why would the DIR instructor be leading tourists on a deep air dive? It does create an issue, part of the team mentality is every one on the same gas. If he has to deal with an OOA (giving or receiving), now someone is not on the gas they started the dive with. Now if he's doing it for money and he's got to eat.......

The only thing diving computers measure accurately is time and depth. They don't measure your personal N2 loading. N2 loading is about like drinking beer, somedays it affects you more than others.

 

[onfloat]

You can..but it wouldn't be true.

That's right he's not big.

 

[JeffG]

That's right he's not big.

Yuk it up while you have the chance stroke boy.

(I better put the smily thing in or else a bear might be after me )

 

[onfloat]

Aren't bears #1 on the threat down?

 

[JeffG]

Aren't bears #1 on the threat down?

They are defiantly on the prowl.

 

[Snowbear]

Grrrrrr .....

 

[Charlie99]

So I go into the water with the following Excel produced table:

40 ft 200 min 750 psi
50 ft 100 min 800 psi.
60 ft 60 min 900 psi.
70 ft 50 min 950 psi.
80 ft 40 min 1000 psi.
90 ft 30 min 1100 psi.
100 ft 25 min 1200 psi.
110 ft 20 min 1300 psi.
120 ft 15 min 1400 psi.
130 ft 10 min 1500 psi.

So I’ll go into the water with this data, and my computer. I know that if I make a fairly square dive my computer will stay well within these envelopes (permit less time and/or depth).

So I’m poking along, having decided, pretty much, to go no deeper than 70 ft, stay down no longer than 50 min, and start up with no less than 950 psi. I see something cool at 100 ft. I look at my computer, I’m 25 min in to my dive and it’s giving me 15 min more. I’m at 1200 psi, that’s turn around for 100 ft. No Go!

But let’s say I was 15 minutes into my dive and had 1800 PSI remaining, my buddy had a hair more, I might go. But it’d have to be really cool, it’ll cost me about 25 minutes of bottom time.

Your rockbottom or minimum ascent pressures are pretty clear, and aren't too different than just adding 200psi to the very simple "100psi per 10'" that many divers use for AL80.

But please clarify the deco planning a bit. You are just treating the entire dive as being at max depth. Correct?

A couple of specific examples. Let's say you went down to 60' for 20 minutes and still had 1700psi (that's about 0.6cfm SAC), and then dipped down to 100'.

1. Per your plan, is your stay at 100' limited to 5 minutes max, such that you do not exceed the 100'/25 minute limit?

2. Per your planning, if you start off a dive to 100' for 15 minutes, and then ascend to 60', do you still hold to a total bottom time of 25 minutes? If you do take into account the shallower depth later in the dive, how does that factor into your calculations?

Thanks in advance,

Charlie

 

[PerroneFord]

now that we are over here, can I call jeffg a big sissy?

Would a DIR instructor be able to dive with tourists and lead them on a deep air dive that is not DIR compliant? air to 127 for example? would that create an issue? does anyone understand the question?

It's my understanding that GUE/DIR does not condone air use period, much less deep air. A proper mix would be EAN29 (EAN28 would probably be asked for). If air is all that is avaialbe, then that's a different story.

Also there are many kinds of tourists. I've seen tourists with rebreathers on their backs, and I've seen some who want a "Discover SCUBA" course. I think the DIR thing would be to determine the level of proficiency of the tourists, and then determine if the dive should proceed.

Personally, I wouldn't do a dive to 127ft on air, on a single tank. Too much potential for problems. And I don't think anyone who is DIR would either.

 

[CD_in_Chitown]

I think the DIR thing would be to determine the level of proficiency of the tourists, and then determine if the dive should proceed.

I would hardly consider that specific to DIR, it seems like a no-brainer.

 

[PerroneFord]

GUE/DIR doesn't have an exclusive contract on making safe dives. They just seem to pay it more than lip service. Some other agencies do also.