MOD marking for 21/35

[AndrewJD]

Duct tape and a black magic marker are more then adequate to mark your MOD on a stage bottle. It's cheap, easily changed and robust enough to last for the duration of at least one dive.

Besides, it was Joe T who taught me the "right way" to mark my stage bottles...

 

[rainman_02]

Alright. So, apparently this discussion was bothering me on a subconscious level because I woke up from a dream and this was my thought:

If everyone is blindly accepting the "hard MOD" of 1.2, then why is 32% not limited to 90 feet?

1.4 ppO2 is plenty fine for a nice relaxed dive. If conditions dictate otherwise, then on-the-fly start adjusting to the conservative side.

 

[rjack321]

Alright. So, apparently this discussion was bothering me on a subconscious level because I woke up from a dream and this was my thought:

If everyone is blindly accepting the "hard MOD" of 1.2, then why is 32% not limited to 90 feet?

1.4 ppO2 is plenty fine for a nice relaxed dive. If conditions dictate otherwise, then on-the-fly start adjusting to the conservative side.

I feel 21/35 is fine for most 160ft dives. Ditto 30/30 at 110ft. But I won't ride a ppO2 of 1.4 for the whole dive on any mix. I still aim for 1.2 average. Apparently this is not what's currently being taught now though, or it is but its contradicted by the handouts/published MODs.

 

[Jason B]

Where did the hard MOD of ppo2 of 1.2 come from? When did this change come about? Is this a real change or some speculation made on the internet?

I was taught an avg ppo2 of 1.2 (class in the last 5 months).

 

[rjack321]

Where did the hard MOD of ppo2 of 1.2 come from? When did this change come about? Is this a real change or some speculation made on the internet?

I was taught an avg ppo2 of 1.2 (class in the last 5 months).

Revisions to the MODs of 30/30 and 21/35 (MODs of 100ft and 150ft respectively). They are listed this way in current class handouts, and Limeyx asked Gideon and got the same answer (on which JJ was CCed), it in one of his earlier posts but I can't find it.

 

[Jason B]

Revisions to the MODs of 30/30 and 21/35 (MODs of 100ft and 150ft respectively). They are listed this way in current class handouts, and Limeyx asked Gideon and got the same answer (on which JJ was CCed), it in one of his earlier posts but I can't find it.

I was taught 30/30 and 32% depth range was 0-100 and 21/35 depth range was 101-150 as well.

Since the MOD of 32% is still 100ft, I don't see how the max allowable can be 1.2. I was taught avg to be 1.2.

 

[rjack321]

I was taught 30/30 and 32% depth range was 0-100 and 21/35 depth range was 101-150 as well.

Since the MOD of 32% is still 100ft, I don't see how the max allowable can be 1.2. I was taught avg to be 1.2.

32% is 1.29 at 100ft
30/30 is 1.21 at 100ft
21/35 is 1.16 at 150ft
18/45 is 1.27 at 200ft

So 32% and 18/45 don't conform to the <=1.2 exactly but close. Then again those 2 mixes didn't get new MOD guidelines like 30/30 and 21/35 did.

 

[Jason B]

I agree that something is odd and am curious why the change. But it seems to me that your math proves it doesn't have anything to do with maintaining a max PO2 of 1.2. That's my take anyway.

 

[rjack321]

True, Limeyx and myself may have jumped to a false conclusion that the shift was due to a new max of 1.2 ppO2 for 30/30 and 21/35. Any ideas on why if that isn't the reason??

 

[limeyx]

True, Limeyx and myself may have jumped to a false conclusion that the shift was due to a new max of 1.2 ppO2 for 30/30 and 21/35. Any ideas on why if that isn't the reason??

The official word is that there has been no shift (which I find somewhat interesting in the case of 30/30 -- in fact I am wondering how Triox as a class makes any sense at all if you are limited to 100 feet on 30/30 or very short dives on 21/35)

I was told "we've always been at war with Eastasia, we have never been at war with Oceania "

The MOD for 21/35 has apparently and always will be 150, anything else was a figment of our collective imaginations.

I am still generally fine with the average, and I will even be a rebel and dive 30/30 to 120. I guess I am just a non-DIR str0ke these days.