Gas Management Question

[WreckWriter]

too much math for me. I'd turn the dive at 1000 psi.

WW

 

[jeepster0000]

O-ring, do you know the correct sac rate to plan for rock bottom?
Thanks
ADAM

 

[O-ring]

The rule that says we carry 1.5 times the deco gas needed is there to take provide gas for things like increased sac rates or the need to do more decompression than planned.

It was the double your deco gas * 1.5 that I found excessive. Instead of 1.5 * deco gas it would be 2(deco gas) * 1.5 . That seems overly conservative for this type of dive, IMHO.

 

[O-ring]

jeepster0000 once bubbled...
O-ring, do you know the correct sac rate to plan for rock bottom?
Thanks
ADAM

Unless GUE changed it since my DIRF (last July), it was 1.0 for rock bottom calculations. That makes your analysis spot on..

 

[jeepster0000]

WW + O-ring, I do plan dives the lazy way, I figured since we were on a discussion, I would use the correct numbers. Usually i jsut use deco planner, for my gas, find my rock bottom, and plan from there. I do not go through this every dive.
ADAM

 

[ericfine50]

ADAM,

Thanks for the math refresher - My dir-f outline is at home. Rock bttom refresher, very nicely done. I do agree with Mike that if you are swimming around teh bottom, the 1/3 would not apply.

Eric

 

[WreckWriter]

jeepster0000 once bubbled...
WW + O-ring, I do plan dives the lazy way, I figured since we were on a discussion, I would use the correct numbers. Usually i jsut use deco planner, for my gas, find my rock bottom, and plan from there. I do not go through this every dive.
ADAM

I wouldn't have been capable of doing it the way you did in under a couple of hours! I use V-Planner or Deco Planner (usually V-Planner) and sorta errrrrr ....guesstimate..... turn pressures.....

WW

 

[Spectre]

What about having two turn pressures? Having your turning point if there was no penetration involved, and then have your penetration turning point.

You have the extra gas for the penetration; and then upon exit; you revert to your open water turning point?

e.g. using O-Ring's numbers:

2700 - 550 = 2150.

lets say you plan for 200 psi to get to the penetration entry point:

2150 - 200*2 = 1750.

So your "planned" mark to begin penetration is 2500. If you've got less than that, you re-calculate on the fly [much like re-calculating after your s-drill].

So with 1750 usable, you plan 1/3s, or 550 psi.

So you end up with a plan of:

begin dive: 2700
enter overhead: 2500 [200 out]
turn in overhead: 1950 [550 out]
exit overhead: 1400 [550 back]
turn dive: 1100 [300 out]
ascent: 600 [300+200 back]
---------------

So you plan 300 psi out _after_ completing penetration.

If you use your 1/3 reserve in the overhead:

1400-550 = 850. That still leaves you 300 psi for the 200 psi swim back to your ascent point.

So basically... once your done with the overhead portion, using the unused overhead reserve to continue your OW dive.

 

[Rec2Tek]

If you go back and read my post again it was not double your gas *1.5. It was take your required gas *1.5...=...20 for you *1.5 add them together for a total of 50ft3 ........20 for you 20 for your buddy and 10 for comfort.....

 

[O-ring]

Rec2Tek once bubbled...
If you go back and read my post again it was not double your gas *1.5. It was take your required gas *1.5...=...20 for you *1.5 add them together for a total of 50ft3 ........20 for you 20 for your buddy and 10 for comfort.....

My bad...sorry for the confusion..