Posted by CalAbDiver on August 21, 2001 at 15:30:33:
In Reply to: Re: so, Im poor! posted by MHK on August 21, 2001 at 14:29:06:
so maybe i am headed in the right direction. But I do plan to keep using my Suunto Vyper in GAUGE mode to record depth and time and monitor ascent rates.
PADI currently has a top secret tech diving school going on that I was invited to join. I checked it out and I passed on it. Too easy. So I do agree with you about that. Dont quote me.
Plus, anybody doing anything new is going to have a few failures here and there so I dont want to be one of them.
I chose TDI because two of the most highly qualified Bay Area Tech Instructors are TDI. These guys are married with kids, and they have every reason in the world to come back home alive from our tech dives together.
I think TDI is like anything else: it depends on the instructor and not on the agency. My jury is still out on Andy V. and the Northern Cal GUE crowd. Someday when I feel ready I may invest the $2000 for their enhanced training classes. That is what the other Tech divers up here are doing. Thats why they invited you up here MHK to meet with them. It is in vogue right now with them.
Technical issues. Here goes. Air as a deco mix contains 79% N2. If you are trying to wash out tissue N2 by inspiring 79% N2 that sounds obviously inefficient. Fortunately we have US Navy tables with all sorts of 79%N2-inspired data. These are at least handy for conversion to EADs for gas mixes, although even TDI encourages users of Navy data to "go to the next deeper depth and the next longer time" since none of us are young Navy SEALs and UDTs.
So any EAN mix would be better than air for deco.
If your bottom mix is 10/50/40 O2/He/N2 then even that would be a better deco mix than air since it is the rough equivalent of EAN60 as a deco gas, for N2 gradient purposes, it seems to me. This could also be your deco gas back up to 33 fsw, after which it becomes hypoxic due to the thin O2 in it.
If you are carrying one single bottle of deco mix which you are also using as your travel bottle, then pure O2 would get you killed between 20 fsw and 33 fsw with a lean mix like 10/50/40.
Pure O2 is not a good bail out mix either, since you cant bail out on it below 20 fsw. Even at 30 fsw you are taking your life into your own hands.
Hell, from 20 fsw I can FREEDIVE back to the surface. I did it from 25 fsw with YOUR GOOD FRIEND seahunt-Mike while abalone diving. In fact, down to and up from 25 fsw is like freediving up from 50 fsw if youre ditching your gear, I would think.
EAN80 is at least good at 30 fsw and "possible" to 50 fsw as deco mix and as a bailout. O2 is not.
EAN40 is good from the surface down to 100 fsw and "possible" as a bailout down to 132.
N2 gradients for the Navy tables on air are doubled when the N2 is halved, to 39%, as with 10/50/40 or with EAN60. The factor becomes 75% on EAN40, so it seems like you could either shorten your deco time by 25% on EAN40 compared with the Navy air tables or go the full time and let the difference become your safety factor.
It seems like it would be nice to have two deco bottles at all times, to help your balance and trim in the water, and so that one of them with the leaner O2 serves as a travel mix and bailout bottle. Also, two of anything equals redundancy to a certain extent.
I know I know, you cant bail out when you have a deco ceiling over you. Well you can still bail out early if trouble develops early.
I like the GUE ideas of limiting air dives only to the swimming pool (with students), and limiting open water dives to EAN32 to 130 fsw, and all diving deeper than that being with helium dilutions of the gas mix.
Deco, the original purpose of EANx, seems like it makes the most sense with EAN40 and EAN80 depending on the depths involved. Almost all deco schedules go from 50 to 10 fsw, and thats way beyond pure O2. And I would not waste an entire deco bottle on O2 for the 10 fsw stop, unless that stop was 40 minutes long.
At least, thats how it all seems to me now, from the shore. I only just finished the reading and homework problems (a whole bunch) for TDI. I havent jumped into the deep, deep water yet. I wanted to be sure to point that out, lest JeffB point it out instead, as he is certain to do.
I have two deco bottles, one is an alum 40 and the other is an alum 63. I might change my mind someday and put 100% O2 in the 40 and use it last, and put EAN40 in the 63 and use it for travel mix and for early deco. Right now I just dont know.
All my tanks have ScubaPro Mark 20 first stages and ScubaPro S600 second stages. 4 of them. and one is O2 cleaned. Thats $2800 worth of regulators alone, just to play this game called deep wreck diving.
Now, what did I do with that gold treasure map???