Find the screw-ups

[rjack321]

This should be fun... There are a couple of cockups in this RB profile (at least 3 I would call out without knowing much about it). What do you see?

Will discuss as we go. I'm tough, I can take it lol

 

[grantctobin]

I’ll bite to start it. Too rich in O2 and light in He for given depth. 1.3 PO2 dil flush and 115END make me uncomfortable.*

*Assuming that was the intended wreck/depth and not a last minute change of plans and the ability to adjust mixes

 

[rjack321]

Good catch, agree the dil was too rich. It started out as 18/37 and they pumped some more helium in there to try and fix it. So 16/45 is what I ended up with (at 3600psi in a 3L steel). Dumping and continuing to "fix" it seemed a bit of a stretch. 16% O2 is a PPO2 of 1.25 @230ft, not common for wreck dives, but "hot dil" is very common cave diving so it didnt bug me too much. In my ideal world I would have taken 12/65.

 

[RainPilot]

Hard to tell on the scale, but was the set point 1.4? If so, that's a bit more than I would use. Also, the descent rate seems pretty high initially?

I can't see anything else, unless its the amount of "unnecessary" deco at the end, but that could be padding or just a shallow putter around to continue the dive?

 

[JonG1]

Stop depths weren't hugely stable, and can't quite see but it looks as if some of the ascents from 1 stop depth to next may have been in excess of 3m/min?

Slightly fast ascent to first stop, looks like 12m/min as opposed to 9m/min?

 

[huwporter]

Why the sudden drop in PPO2 just before the final ascent? Wouldn't that be a point where you would push the PPO2 high because it is going to drop as you ascend anyway?

(edit - thinking, I guess changing setpoint to less than PP1 to avoid the solenoid overcompensating. I would have still thought you'd want to O2 flush at that point anyway.)

 

[JohnnyC]

Hot dil, but it’s not so bad that it’s something I’d be too concerned about.

Where was this? Cave? Open water? Cave would explain a 25 minute swim at 20 feet after the deco cleared. Curious what that was about. A lot of people hang out in the shallows, but that seems a lot longer than most people pad their last stop.

I’m assuming that last setpoint change was in preparation for you last ascent and didn’t want the thing pissing O2 to try and maintain 1.whatever on top?

Personally I probably wouldn’t be running my bottom setpoint that hot but that’s more of a personal choice.

I’m on my phone so it’s kind of hard to see too much detail.

So what issues do you see beyond what’s already been covered so far?

 

[rjack321]

Hard to tell on the scale, but was the set point 1.4? If so, that's a bit more than I would use. Also, the descent rate seems pretty high initially?

I can't see anything else, unless its the amount of "unnecessary" deco at the end, but that could be padding or just a shallow putter around to continue the dive?

Setpoint was 1.3 but is hovered around 1.32-1.34 on my shearwater compared to the 1.3 on the controller. I think that was due to altitude compensation during the shearwater calibration but none on the meg handset. Surface elevation was about 600ft. Wasn't really that concerned about that for a ~90min dive.

The "unnecessary deco" was actually waiting for my buddy. Wasn't clear to me how he ended up with more than me although part of it was him running a setpoint of 1.2

Stop depths weren't hugely stable, and can't quite see but it looks as if some of the ascents from 1 stop depth to next may have been in excess of 3m/min?

Slightly fast ascent to first stop, looks like 12m/min as opposed to 9m/min?

I was swimming around in midwater, those squiggles are about 2ft. It was a little bit wavey and the line was jerking around. So it was hold on and flop or float and swim.

Flaw #2 (to me) is actually that the initial ascent to the first stop is far too slow. We left the wreck at 190ft at min 24. Arrived at the first 70ft stop at min 31. That's 7mins to do 120ft or about 17ft/min. Basically we should have been almost 2x faster. Part of that was my buddy running GF 30/70 compared to my 50/75. Part was just moving too slow.​

Why the sudden drop in PPO2 just before the final ascent? Wouldn't that be a point where you would push the PPO2 high because it is going to drop as you ascend anyway?

(edit - thinking, I guess changing setpoint to less than PP1 to avoid the solenoid overcompensating. I would have still thought you'd want to O2 flush at that point anyway.)

Flaw #3 found: That's me dropping the SP on the machine to 0.7 (somewhere around min 97-98), then at minute 100 accidentally realizing the ADV was still on as I breathed the loop down. I didn't make an effort to manually bump it back up beyond about 0.8 (was getting tired of hanging around, knew I was going up, and did so much extra deco I got lazy)

Where was this? Cave? Open water? Cave would explain a 25 minute swim at 20 feet after the deco cleared. Curious what that was about. A lot of people hang out in the shallows, but that seems a lot longer than most people pad their last stop.

I’m assuming that last setpoint change was in preparation for you last ascent and didn’t want the thing pissing O2 to try and maintain 1.whatever on top?

Personally I probably wouldn’t be running my bottom setpoint that hot but that’s more of a personal choice.

This was a wreck dive in Lake Superior off a charter with a mooring. Yeah I was trying to be mindful of the O2 consumption. On the meg its either 0.21(not for diving use), 0.5, 0.7, or 1.0+

For ~90min wreck dives in 38F water I usually run a SP 1.3. Over 2 hrs I start thinking about dropping that to 1.2

To me there's one more thing in the profile I would/should etc do different. Hint its something that many divers do but is actually <missing> here.

 

[JohnnyC]

To me there's one more thing in the profile I would/should etc do different. Hint its something that many divers do but is actually <missing> here.

I always spike my O2 on the descent to over 1.6 to make sure they're not current limited but I understand that not everyone does that, hence I didn't point it out. Do I win the prize?

 

[rjack321]

I always spike my O2 on the descent to over 1.6 to make sure they're not current limited but I understand that not everyone does that, hence I didn't point it out. Do I win the prize?

descent, ascent, at some point that woulda been a good idea