Thoughts on Deep and Wreck Diving

[TheRedHead]

If you want to know how Gentile plans, read "The Technical Diving Handbook." You can order it from Amazon.com. You will be surprised that he makes a lot of minor deco dives using a dive computer. He's very pro computer.

 

[LavaSurfer]

but his questions and interest is well founded and the input from fellow SBers will be I am sure interesting to read.

Thanks for the support, it should be fun.
As for gas planning, I am certain they plan, but for who, them or them and a team mate. It will be interesting.

Kevrumbo
Thanks for the links, I have seen the post from Lamont way back, the second link did not work and the battlefield article is very interesting. I do like metric, it makes life much easier.

 

[DEEPLOU]

Haven't read:

by Gentile in Deep, Dark and Dangerous

But, NE wreck divers ala: Gentile etc. are the pioneers of tec diving.
I have learned from many of them (not Gary only met him once at a talk he gave). But considering what we do, I would call NE wreck divers "Mavericks".
Whether you have a buddy or not, the emphisis is on self reliance.

Can they then rethink the tables in their head and make adjustments or do they throw out the tables and just hope the computer is right, And how about computers that calculate DECO and deep stops like the VR3?

You don't "hope the computer is right", why wouldn't it be right?? Yes they do malfunction but it is usually obvious when it does. On deep or just long dives w/deco carry two in addition to tables.
What about computers that calculate DECO and deepstops like VR3?? All computers calculate DECO while not necessarily deepstops like VR3. They work, and people are not getting bent on them

The solo self-sufficient Northeast Wreck Diver a la McMurray's book Deep Descent and others, is so Old School. New & improved is DIR and the concept of the Unified Team

.
Maybe in Yuppyland, but not in the Northeast.

 

[LavaSurfer]

You don't "hope the computer is right", why wouldn't it be right?? Yes they do malfunction but it is usually obvious when it does. On deep or just long dives w/deco carry two in addition to tables.
What about computers that calculate DECO and deepstops like VR3?? All computers calculate DECO while not necessarily deepstops like VR3. They work, and people are not getting bent on them

Kinda along my way of thinking.
If the tables I were to choose are calculated say from VPM/B and the dive computer(s) I choose use the same algorithm then I should get a similar result other than the computer is calcing in real time where tables are somewhat static.

In the case where you don't follow the plan perfectly, maybe a snag held you up for two minutes, then the computers would "theoretically adjust.

Sure I could have a set of table that covered contingencies but a computer should be accurate. I am a software engineer and totally understand the flaws (BUGS) that could exist. But in general, I trust software.

 

[Kevrumbo]

Thanks for the support, it should be fun.
As for gas planning, I am certain they plan, but for who, them or them and a team mate. It will be interesting.

Kevrumbo
Thanks for the links, I have seen the post from Lamont way back, the second link did not work and the battlefield article is very interesting. I do like metric, it makes life much easier.

Here's Lamont's follow-up link to Delia's Battlefield Calculations again:
http://www.scubaboard.com/showpost.php?p=1640508&postcount=61

Compiles the concepts laid out in the article in a nice easy-to-use formula. . .

 

[lamont]

I see a disconnect or shift that takes place somewhere in the move from “Recreational Diving” to “Technical” diving. This shift is away from the reliance on a “Buddy” to viewing a “Buddy” as a liability.

That's one opinion, DIR is basically a bunch of divers fleeing in exactly the opposite direction in terror...

Another point I seem to see is that they wear only enough back gas to complete the depth portion of the dive and then a partial deco.

At some point you can't deco on backgas. Losing a single bottle is generally the contigency plan (and with DIR diving in a gas loss situation on a serious dive you have support divers to get you additional gas).

Then they pick up deco gasses on the line to complete their debt.

GUE teaches carrying all your gas on wreck dives. There are divers in the PNW that do 320 fsw dives with 2 bottom stages and 3 deco bottles (and a scooter) and carry all that crap around with them on the bottom...

 

[TheRedHead]

Here's Lamont's follow-up link to Delia's Battlefield Calculations again:
http://www.scubaboard.com/showpost.php?p=1640508&postcount=61

Compiles the concepts laid out in the article in a nice easy-to-use formula. . .

I think a lot of us are familiar with rock bottom. How do you factor in more than 1 gas? You are not making a direct ascent to the surface in decompression diving. It doesn't account for deco gas either, at least Lamont's original post doesn't.

 

[lamont]

Here's Lamont's follow-up link to Delia's Battlefield Calculations again:
http://www.scubaboard.com/showpost.php?p=1640508&postcount=61

Compiles the concepts laid out in the article in a nice easy-to-use formula. . .

Messy writing, though. How about this:

Al80:

Rockbottom: 300 psi + 10 psi / ft ( min 500 psi )
0 fsw SAC: 300 psi / 10 min
33 fsw SAC: 600 psi / 10 min
66 fsw SAC: 900 psi / 10 min
100 fsw SAC: 1200 psi / 10 min

HP130/120:

Rockbottom: 10 psi / ft ( min 500 psi )
0 fsw SAC: 200 psi / 10 min
33 fsw SAC: 400 psi / 10 min
66 fsw SAC: 600 psi / 10 min
100 fsw SAC: 800 psi / 10 min

So, for every 10 mins at 100 fsw, knock off another 1200 psi from an Al80, while reserving at least 1300. Or to project run time from a full Al80 at 100 fsw:

3000 - 1300 psi = 1700 psi usable
1700 psi / 1200 psi ( * 10 mins ) ~= 15 mins

Take your starting pressure and subtract your SAC at your depth and you should get roughly where your pressure will be 10 mins into the dive. Or 10 mins into the dive do that calculation based on your actual profile and compare to your SPG reading.

 

[lamont]

I think a lot of us are familiar with rock bottom. How do you factor in more than 1 gas? You are not making a direct ascent to the surface in decompression diving. It doesn't account for deco gas either, at least Lamont's original post doesn't.

No this is all recreational. And the rules of thumb (at least the rockbottom rules) become quickly invalid beyond recreational depths and recreational dives.

Another interesting rule of thumb I read recently is that you shouldn't dive a cylinder which is smaller (in cu ft) than your max depth (in ft). Which means max depth for an Al80 is 77 ft and you need at least an HP100 to go to 100 fsw -- not a horrible rule of thumb for new divers.

 

[Kevrumbo]

I think a lot of us are familiar with rock bottom. How do you factor in more than 1 gas? You are not making a direct ascent to the surface in decompression diving. It doesn't account for deco gas either, at least Lamont's original post doesn't.

See Lamont's post above #16, and pp12-13 of AG's Ratio Deco/The Theoretical Aspects: http://www.5thd-x.com/xducation/pdf/ratiodeco.pdf