Questions, I gots some questions...

[reefraff]

I'm interested in seeing what some other technical divers on the board are doing/thinking. I've answered my own questions to start the discussion...for many people these questions will not apply and that's okay.

What kind of technical gas diving are you certified for?I'm a TDI Advanced Trimix diver, trained to 330'.
What kind of SAC rates are you using for the working and resting portions of your dives?I use 0.7 working and 0.5 resting. I'm a big guy and I like to allow a little "extra" in case something exciting occurs.
What kind of ppO2 limits are people using for the working and resting portions of their dives? Do you adjust the limit to account for workload and for temperature?For water temps below 50F, I like to use a ppO2 limit of 1.2 during the working portion of the dive, 1.4 if the temperature is over 50F. For deco I use 1.6. I'm lazy enough and concerned enough about CO2 exposure that I don't plan dives where hard work would otherwise imply an even lower ppO2.
What kind of END limits are people using?Personally, I like an END of 100' but there are times when I'm willing to exceed that - if I ever make it to Truk you'll find me groveling about the bottom, END be damned.
A couple of dive plans, both potentially a little dodgy, how would you plan them?

(1) How would you plan a non-penetration dive to 150' for 30 minutes?150'....28.3..(30) TMX 18/45
90'......1.0..(33)
80'......2.0..(35)
70'......5.0..(40) EAN50
40'......3.0..(44)
30'......5.0..(49)
20'.....23.0..(72)
(2) How would you plan a dive to 250 for 15 minutes?250'....12.2 (15) TMX 15/55
160'......1.0 (19)
150'......1.0 (19)
140'......1.0 (20)
130'......2.0 (22)
120'......1.0 (23)
110'......2.0 (25)
100'......2.0 (28)
90'........3.0 (31)
80'........4.0 (35)
70'........5.0 (40) TMX 50/30
50'........4.0 (44)
40'........5.0 (49)
30'........7.0 (56)
20'.......19.0 (75) O2

You'll notice that I've left out how many cf of gas these plans will require - what bottles would you need for a workable plan?

[SLIM]

What kind of technical gas diving are you certified for?

IANTD Normoxic-but then was using all this vodoo gas before I was certified. It is just to a depth, what is the differance once you know the basics. Just means more money for the agencies to make off a person. Learned more at the school of hard nocks(a mentor) then from any instructor.

What kind of SAC rates are you using for the working and resting portions of your dives?

About the same, is more but as a conservitive.


What kind of ppO2 limits are people using for the working and resting portions of their dives? Do you adjust the limit to account for workload and for temperature?

Keep all work at 1.4 for water temps above 40* and all deco at 1.6 no mater water temps.


What kind of END limits are people using?
Depends on the dive plan. Is it a deep OW or a cave, then how framilure am I with the cave or wreck. 130 for most dives.

(1) How would you plan a non-penetration dive to 150' for 30 minutes?
150'....28.3..(30) TMX 20/30
100'for 2 minutes
90'......1.0..(33)
80'......2.0..(35)
70'......5.0..(40) EAN50
40'......3.0..(44)
30'......5.0..(49)
20'.....15.0..(72)(100% if I have it)

2) How would you plan a dive to 250 for 15 minutes?
250'....12.2 (15) TMX 14/58
160'......1.0 (19)
150'......1.0 (19)(18/45)
140'......1.0 (20)
130'......2.0 (22)
120'......1.0 (23)
110'......2.0 (25)
100'......2.0 (28)
90'........3.0 (31)
80'........4.0 (35)
70'........5.0 (40) EAN50
50'........4.0 (44)
40'........5.0 (49)
30'........7.0 (56)
20'.......19.0 (75) O2
Switch from EAN50 to 18/45 at 70' on way down and then at 150 switch to 14/58 and on way back up do just the oppisit.

Even thought you mention in number 1 no penatraion, you still have a overhead environment. Due to that there is still a type of penatraion. Remember that not all overhead is in a cave. You have your mandatory deco obligation as a overhead also.

I hate to say this because I bet some will squeel about it, but as in the above, not having a full trimix card is not a big deal. Once you know the basics and have a good mentor then the Full Trimix class is extra money that could be spent on gas and trips. Some might not like the gas choices but each dive plan can have a differant gas mix. There are what some now call Standard mixes but they may not be the best for the dive. Just bye changing a gas mix can change a large amount of time in a deco schedual. If you go to some places they do not use EAN50 and use only 32 or 36% so they can get on the higher O2 sooner and help with the exchange. There is no right or wrong way to choose a gas. All this is still therotical and still being tested. Each individual takes gas differant. What is on hand and available is what I choose for my gas.

WHat people today use as a END of 100' to me is not that great of a deal. SOme dives I use 150' for my END. I also think about what amount of gas I might use on the dive and what I can do on a top off to help save money again.

SLIM

[steve2281]

I'm nitrox certified
For a 150' dive for 30 minutes:
I just use a little 20/20 homebrew that I'm not certified to use, put 2 wristmout computers in the driver's seat, deco on an air profile, and hope for the best. Wouldn't even worry about the PO2 at 150'.






Uh, JOKE!!!!! Hope yall got a sense of humor. I must be narked or board to post that but it is an interesting topic I would like to hear more about.