Find the screw-ups

[huwporter]

In the spirit of the thread, here is my dive from last weekend:

I see one major criticism, one minor procedural omission and probably a number of 'why...?' questions that will hopefully make more sense in context.

 

[PfcAJ]

In the spirit of the thread, here is my dive from last weekend:

View attachment 532432

I see one major criticism, one minor procedural omission and probably a number of 'why...?' questions that will hopefully make more sense in context.

Ascent was very slow. Why?

 

[huwporter]

Ascent was very slow. Why?

This was a warmup dive for a bigger dive coming up, so we were running through a full set of procedures that weren't really necessary for this actual profile. Hence the 35/25 deco bottle procedures that weren't really needed for the actual dive - 9m/min to 36m, gas switch, then 3m/min up to 24m, then another switch to backgas before getting to the 50% switch. Leaving out the 35/25, I'd be expecting to arrive at 21m about 5 mins earlier.

Also, GF70/85 is my 'get out of dodge' backup setting on the Perdix, I do a whole lot less deep stops than I used to but I'm not quite ready to go that far yet

(That was one expected 'why?' question since it was a deliberate choice rather than a stuffup)

 

[rjack321]

Rjack, I aim for 9/10m a min but if there are divers on the line it can look a bit out of control so you end up compromising.

I pad the shallow anyway but computer should adjust stop times too surely to compensate for greater loading?

yes but if you look at all the heat diagrams posted as part of those myriad of NEDU study threads you end up with more tissues loaded up to (eg) the 75% of the m value. Those intermediate tissues are the ones that are going to take a hit most of the time. The less you dilly dally below your first stop the more your higher GFlow is actually the target.

9m/min is good! 5m/min (in mine) wasnt so good. It can be hard to accelerate divers who aren't accustomed to moving faster to do it. 10m/min feels really fast when your whole diving career you've been trying to move slower.

 

[rjack321]

In the spirit of the thread, here is my dive from last weekend:

View attachment 532432

I see one major criticism, one minor procedural omission and probably a number of 'why...?' questions that will hopefully make more sense in context.

Do you always go deco gas to deco gas?

On OC I always go deco gas- backgas - deco gas. Not so much for the gas break although sometimes I extend the time. Its just a whole lot safer and less of a CF to verify gases for me. Perhaps you just skipped resetting the predix in between though.

Second what's up with the EAN50 stops? those look rough. lots of waves or crazy currents that deep or something else going on?

 

[JohnnyC]

I go deco to backgas so that I can clean up my first deco bottle and the whole thing is a little tidier. I've gone deco to deco before, but then you end up having to admin your bottles with a less tidy workspace. I'd rather take the 30 seconds to get the reg stowed and the bottle out of the way. Just makes it less likely to flub the switch if you've got a bunch of bottles.

 

[huwporter]

Do you always go deco gas to deco gas?

On OC I always go deco gas- backgas - deco gas. Not so much for the gas break although sometimes I extend the time. Its just a whole lot safer and less of a CF to verify gases to me. Perhaps you just skipped resetting the predix in between though.

Yeah, I switched to backgas at 24m before ascending but failed to also reset the Perdix. That was the minor procedural omission.

Second what's up with the EAN50 stops? those look rough. lots of waves that deep or something else going on?

Yep, that is the major criticism - I was all over the place on deco, particularly on the 50% but there are also a few unflattering wobbles at the end of the 6m stop. I felt off-balance the entire dive, it wasn't until afterwards that I realised I'd forgotten to remove the extra weight when changing from double 12s the previous day to double 18s on this dive. Add in a much thicker undersuit than I'm used to plus all tanks were much fuller and so heavier than they would normally be at this point, I was not handling it with the aplomb that one might aspire to...

 

[JonG1]

I thought the major criticism was using helium OC!

 

[huwporter]

I thought the major criticism was using helium OC!

Forgive me. I probably only have a decade or so tops of hypoxic diving left, and I don't want to lose a couple of the few years I do have to retraining on CCR and building up back to the same level... maybe when my hypoxic days are over I'll do CCR and get another decade of normoxic out of it.

 

[JonG1]

yes but if you look at all the heat diagrams posted as part of those myriad of NEDU study threads you end up with more tissues loaded up to (eg) the 75% of the m value. Those intermediate tissues are the ones that are going to take a hit most of the time. The less you dilly dally below your first stop the more your higher GFlow is actually the target.

9m/min is good! 5m/min (in mine) wasnt so good. It can be hard to accelerate divers who aren't accustomed to moving faster to do it. 10m/min feels really fast when your whole diving career you've been trying to move slower.

So are you thinking the loadings with a slow ascent might exceed what the pdc might account for in its algorithm, or looking for cleaner less sub-clinical impact for the long haul?