Why do you dismiss DIR?

[jimholcomb]

"I have been following this thread and to date have avoided jumping in on the old my team is better than you team stuff that is so prevalent on this board."

Now, who said that?!?!?!? I've made it a point to clarify that it's none of my business how other people dive and that people should just keep an open mind to the philosophy. YOU and other anti-DIR folks are the ones that seem to want to keep this an "us against them" debate. The DIR advocates participating in this thread have gone to great lengths to avoid such a discussion. The anti-DIR coalition seems to enjoy calling us "close-minded, a cult, mindless drones, ect,ect,ect....". I contend that the opposite is true and has become evident in this thread.

 

[VTWarrenG]

jim,

Don't worry, you're not the only one who notices such things. AquaTec prides himself on babysitting others so they can have nice discussions the way he would like them to proceed. He also likes to read a calm, rational response, and respond to it as if it was actually a vengeful attack.

- Warren

 

[AquaTec]

Well I jumped in with both feet didn't I
Uncle Pug
Your point is well taken, and you are right this is just a conversation about scuba and not a classroom. I enjoy the converstaion, I am just a sponge for knowledge and I tend to turn any conversation into a learning experience.

I will remeber in the future about it being a conversation.
as for the rest of your post I will discuss these thoughts with you when i get home from work.

Jim Holcomb
In my opinion your contributions here have been fruitfull.
I would definetly not call myself antiDIR I lean more towards DIR than away from it.
If you are DIR thats great, i doesn't matter to me one way or another. Warren was right I was just babysitting, trying to find someone saying why they were one way or another and the reason behind it. UP was right in the fact that it is just conversation and by reading this you might not find out anything about why a person prefers a certain style et al. [that being said there have been some post that do point this out]

VTWARREN
Last time we had post in the same area I pissed you off so I would expect a reply such as you gave here.
I personaly think you will fit right in with the GUE group you are so worried about, you appear to have the right attitude, keep working on it and soon you will be an instructor.

UP we will chat tonight about 32% vs ??

I should know better than to jump in on these types of threads .

I will hand shake UP he is the only one who got past my babysitting and is willing to discuss why he uses a certain technique, that happens to also be a DIR technique
Just like i cant get past the bantering some of you can't get past the babysitting

 

[jimholcomb]

"To clarify the DIR standards for this discussion:
0-100 EAN32
80-120 30/30
120-160 21/35

What gas selections would you suggest and why?
Are you in favor of standard mixes?
Do you have objections to standard mixes?
Which specific points do you disagree with in my list?
Do you do your own blending?
Do you bank certain mixes? "

I'll play.
I have always wondered why 32 is the 0-100 gas. 34 still keeps you at 1.37. The only think I can think of is on extended dives the 34 will work on the clock a little faster.

I am in favor of stanardized mixes, expecially within the team. Know what everyone has in every bottle through stanardized mixes AND standardized marking of the bottles is just common sense.

I do blend my own from time to time.

No, I do not bank, anymore.

 

[newton]

Originally posted by Uncle Pug
(and not some other *mix de-jour*)

My post is really about EAN32 vs. EAN34 as the chosen *mix-du-jour* for DIR.

Several issues:
1. standardization of gases
a. easier PP mixing
b. easier filling from pre-mixed banked
c. easier to remember NDL or deco schedules
d. lessens chance of using wrong mix

Any standard mix has these advantages. This doesn't make EAN32 any better (or worse) than EAN34. Especially when you consider that EAN34 is also safe to 100'.

2. EAD advantage:
a. 20% advantage with EAN32
b. easy to figure EAD
c. no significant planning advantage between 32~36

a) ??? I don't understand what you mean by this. Are you implying that EAN32 has a 20% advantage over air? If so, isn't that wrong? I get .68/.79 ~= 14%, not 20%. Help out a newbie who is trying to learn. (FWIW, EAN34 has a value of ~17.5%). (We didn't discuss any of this in DIR-F.)

b) Again, the calculations don't seem that easy to me. The formula is EAD(32) = ((Depth + 33) * .68 / .79) - 33). This doesn't seem easy to calculate at all

c) This is where I'm really confused. I was under the assumption that dives from 0-100 fsw were done on Nitrox to avoid taking the N2 hit. However, most dives to this depth do not involve *significant* deco obligations, so while I agree there are no planning advantages, the choice of EAN34 would give the same advantage. (Again, having a 'standard' gas is the advantage).

Basically, I see 2(c) as belonging to the same class as 1. However, I'd like more clarification on 2 (a) and (b).

3. Lower O2 exposure:
a. for dives that will require exposure to elevated PO2s in deco
b. for dives that will be followed by dives with elevated PO2s
c. for cold, stressful dives where CO2 build up is a possibility

3a) is easy to accept. However, because the diver can't dive it below 100', won't the additional deco obligations vs. using EAN34 make it a wash. In short, you'll end up having the same O2 exposure since the extra 2-3 minutes to deco would end up giving you the same O2 exposure.

3b) Again, do the differences between EAN32 and EAN34 make *that* much difference.

3c) I would think the higher O2 level would decrease the posssibility of CO2 buildup.

For 2.c.
***try this with a 60 dive on 32 & 36 - what EAD would you use for each... remember the tables?***

EAD(32)@60 = 47'
EAD(34)@60 = 44'

I agree that it doesn't make much differnce, but I also don't see why this makes EAN32 easier to work with (calculations, etc..) than EAN34.

Please enlighten me.

 

[Uncle Pug]

Originally posted by jimholcomb

I'll play.
I have always wondered why 32 is the 0-100 gas. 34 still keeps you at 1.37. The only think I can think of is on extended dives the 34 will work on the clock a little faster.

I hate to start without AquaTec as he is interested in learning also...
but:


You can use 34%... but what advantage does it give you over 32% using EAD and tables? Check it out. I mean, really, get out your tables and check it out.

You will find that 32% is very easy to figure your EAD... just subtract 20% from actual depth to get EAD.

32% to 100' gives you a conservative 1.3 PO2
whereas 34% takes you to right to 1.4 PO2 @ at 100'

As for PP blending... Let me go ahead and use a comparision between 32%, 34% and 36%

PSI O2 to add to a 3000 psi AL80:
32% add 420
34% add 494
36% add 570
Assuming a 300cf T of O2 @ 2400 psi -
you will get 22 fills of 32% and return 420 psi unused
You will get 18 fills of 34% and return 494 psi unused
you will get 15 fills of 36% and return 570 psi unused

Please DO NOT TRUST MY MATH.....
This is not a recommendation to mix or dive EAN without proper instruction and certification and is meant for comparison purposes only.

 

[Uncle Pug]

Originally posted by newton
Especially when you consider that EAN34 is also safe to 100'.

But 32% gives you the edge and in case you need to make the drop to 120 to pick up that item....

a) ??? I don't understand what you mean by this. Are you implying that EAN32 has a 20% advantage over air? If so, isn't that wrong? I get .68/.79 ~= 14%, not 20%. Help out a newbie who is trying to learn. (FWIW, EAN34 has a value of ~17.5%). (We didn't discuss any of this in DIR-F.)

You are really going to like this... you are right the O2 difference in the mix is 14% .... bingo... now you know how much O2 to add to the cylinder before topping with air to get EAN32

The 20% I was referring to was the EAD... check your table or
use your formula if you want to do it the hard way(s)

For example a dive to 100' on EAN32 is 80' EAD
Or you check your table and find that it is 80'
Or you do the formula and find that it is 81'

b) Again, the calculations don't seem that easy to me. The formula is EAD(32) = ((Depth + 33) * .68 / .79) - 33). This doesn't seem easy to calculate at all

No kidding... I hate math... but subtracting 20% from my depth is a piece of cake.... now if I had to subract 22% because I was using 34% that mind overload my poor old brain...

BTW notice that the advantage in EAD of 34% (78' for 100') is not a big deal over 32% (80' for 100')

c) This is where I'm really confused. Please enlighten me.

Sorry I gotta go right now... play with this and I'' get back to you

 

[Uncle Pug]

Originally posted by newton
My post is really about EAN32 vs. EAN34 as the chosen *mix-du-jour* for DIR.
c) This is where I'm really confused. I was under the assumption that dives from 0-100 fsw were done on Nitrox to avoid taking the N2 hit. However, most dives to this depth do not involve *significant* deco obligations, so while I agree there are no planning advantages, the choice of EAN34 would give the same advantage. (Again, having a 'standard' gas is the advantage).

Please enlighten me.

Nate,
Since there is no real advantage to 34%
Since 32% is already a recognized standard
Since 32% is (as you now see) easy to figure EAD in your HEAD
And since 32% is cheaper to blend....

It is the DIR mix of choice.... but anyone is free to choose differently!!

However when you walk into your LDS and say, "Gimme a jug of 34, Bubba!" you will probably get back a tank that analyzes out to 33.4% or 35.1% or whatever so the point is probably moot

 

[Uncle Pug]

Originally posted by newton

3c) I would think the higher O2 level would decrease the posssibility of CO2 buildup.

Please enlighten me.

You were thinking at it backwards Newt:

Cold water + exertion = CO2 buildup
CO2 build up increases the chance of an O2 hit.

So keep the PO2 lower.

Out here in Puget Sound it is cold....
You were definitely under stress in the class....
Sure 36~38% was OK for your depth....
But 32% was better for your dive.

 

[newton]

Originally posted by Uncle Pug


But 32% gives you the edge and in case you need to make the drop to 120 to pick up that item....

Actually, it gives you an extra 9' over EAN34.

PPO2 1.4 @ EAN32 = 111'
PPO2 1.4 @ EAN34 = 102'

Yes, it's 9', but if you're worried about dropping down, why not just got EAN30? (I know, I know, you gotta make the mark somewhere).

You are really going to like this... you are right the O2 difference in the mix is 14% .... bingo... now you know how much O2 to add to the cylinder before topping with air to get EAN32

Cool!

The 20% I was referring to was the EAD... check your table or
use your formula if you want to do it the hard way(s)

For example a dive to 100' on EAN32 is 80' EAD
Or you check your table and find that it is 80'
Or you do the formula and find that it is 81'

Right. Here's a table from formulas
(hope this comes out right, I'm not sure how to do tables here

Real Depth(sw) <+> EAD@EAN21 <+> EAD@EAN32 <+> EAD@EAN34
============== <+> ========= <+> ========= <+> =========
20 <-------------> 20 <--------> 13 <--------> 11
50 <-------------> 50 <--------> 38 <--------> 36
80 <-------------> 80 <--------> 64 <--------> 61
100 <------------> 100 <-------> 81 <--------> 78

Seems like 20% would work for both mixes. Neither is perfect (how about EAN33? )

No kidding... I hate math... but subtracting 20% from my depth is a piece of cake.... now if I had to subract 22% because I was using 34% that mind overload my poor old brain...

It's not quite 20%. 20% is a *tiny* bit aggressive until you get below 80' for EAN32. 20% is a *tiny* bit conservative for EAN34 for all depths, because of high PPO2.

BTW notice that the advantage in EAD of 34% (78' for 100') is not a big deal over 32% (80' for 100')

True, but the decrease in PPN2 over the lifetime of the dive may decrease the risk of DCS. Especially if you use the 20% rule. (Again, I'm assuming that the O2 CNS clock is *rarely* an issue for the types of dives that are done with EANXX, vs. the use of tri-mix or heliox).

So, in summary I believe that EAN32 is a *good* choice for a standard mix, but I don't believe that it's a better choice than EAN34 is, from a technical perspective. From a monetary perspective it's certainly a better choice, and if you have to roll-your-own, it may be a tiny bit easier to mix, but my guess is that if you've standardized on a mix, it really doesn't matter *what* the mix is, it's easy to figure out what to do (using a program or otherwise).

Just to bring things back to DIR, I did see someone mentioning the use of EAN34, and GI3 did rip them a new one with the defense that they didn't have any idea what they were talking about. Oh well, I think I understand a little bit better why EAN32, but I'm still not convinced it's any better than EAN34. I believe they could have chosen one over the other, but happened to choose EAN32.

(My suspicion for the choice is that some of the caves the WKPP folks were diving had a hard bottom that was slightly lower than 100', so EAN34 may not have been a great gas early on for some of the support divers, so they standardized on EAN32. Then again, I'm probably completely out to lunch.