Optimal Pony Bottle Size for Failure at 100ft?

[SpaceX Aquanaut]

I don't have an issue with that calculation. And I have figured out gas/ascent calculations for myself "longhand" and built my own spredsheet for fun to more easily play with different variations. I haven't needed much spoonfeeding for about 55 years, but of course things do have a way of coming around.

But that is NOT calculated with the parameters that you have been repeatedly discussing - that is moving the goalposts. The one minute STOP after ascent of EVERY 3m/10' was what I took issue with. The resulting average ascent rate is a quater of the generally-accepted, current "safe" ascent rate.
[I am pre-editing here to be thorough and point out that I went back and you did explain that your procedure is actually a one minute NET ascent and hold cycle which would result in a 10'/minute average ascent rate. You have repeatedly referred to one-minute stops in susequent posts and I believe that variability is significantly clouding the issue here (certainly for me.)]


And that IMO does make the resulting calculations irrelevant to novice divers who would reasonably be expected to ascend at the nominal 30'/minute rate they were trained to.



I actually find your methodolgy conceptually intriguing. It does bind the ascent into an arguably more controlled situation. I do find the length of those stops unnecessarily long at the expense of other important factors - boiled down: more time at depth, less available gas for the unexpected and time at more beneficial offgassing depths.

As I pointed out, a 10 second stop guarantees a maximum of 60'/minute rate. Even if you actually ascend (between stops) at 60'/minute, with the 10 second stop, your average ascent rate is only 30'/minute. And if you ascend (between stops) at 30'/minute your average ascent rate only falls to 20'/minute - a bit safer if you are concermed that 30' is too aggressive, but with far less negative impact (IMO). In other posts you have made much the same profile suggestion.


[Reiterating: There seem to be several different intermixed profiles presented and this has been confusing (again - at least to me - sorry to the extent that my loss of context led to more critical tone. ) The coceptual ascent methodology is worth thoughtful discussion.]

Fair enough. You’re free to “move the goalposts” -to reiterate if you don’t like 1 minute stops, change that factor to 0.3 minute (20 second stop, split into a 10 second hold & 10 second travel between stops in easier practice).

[Go Rams -Beat the Eagles! LAFD Strong!]

@SpaceX Aquanaut
Doing the math isn’t the issue. That is not ascent strategy that makes sense to me or several others. That’s the issue.

You did you use the term ‘min deco’ somewhere in there. May I ask where you got this particular ascent strategy?

 

[SpaceX Aquanaut]

As someone who was attacked by a Kraken (large giant pacific octopus on my head) I can say the buoyancy goes to sh*t and gas consumption is off the charts, although it's hard to distinguish how much is from breathing and how much is from the Octo pushing on the purge button.

This was at Sares Head wall off Fidalgo Island for the locals.

And I like stops to pick up Southern California mermaids. . .

 

[-JD-]

LAFD Strong!

Will strongly agree with that!

Rams, sorry (NS), err - NO!

 

[MarkA]

Fair enough. You’re free to “move the goalposts” -to reiterate if you don’t like 1 minute stops, change that factor to 0.3 minute (20 second stop, split into a 10 second hold & 10 second travel between stops in easier practice).

[Go Rams -Beat the Eagles! LAFD Strong!]

Relevant to the OP. The guy in the video gives an example of a no decompression stop dive to 100 feet. The answer given is 40 cubic feet for 2 divers. So the OP’s AL40 would be more than adequate for the people in this video.

Out of interest. This video is 11 years old. Has the Spizni thing altered the ascent profile described?

 

[SpaceX Aquanaut]

Relevant to the OP. The guy in the video gives an example of a no decompression stop dive to 100 feet. The answer given is 40 cubic feet for 2 divers. So the OP’s AL40 would be more than adequate for the people in this video.

Out of interest. This video is 11 years old. Has the Spizni thing altered the ascent profile described?

IMO if you’re doing mandatory deco profiles over consecutive days, then yes. You gotta do extended O2 time stops to relieve the accumulated N2 load/saturation out of those intermediate slow tissues. But that’s better discussed in the deco/tech forum. . .

 

[rsingler]

Out of interest. This video is 11 years old. Has the Spizni thing altered the ascent profile described?

IMO if you’re doing mandatory deco profiles over consecutive days, then yes. You gotta do extended O2 time stops to relieve the accumulated N2 load/saturation out of those intermediate slow tissues. But that’s better discussed in the deco/tech forum. . .

I think you may have missed the point of @MarkA 's question.
I think his question, and certainly mine is, "Has UTD abandoned making the first stop at 50% of max depth, since the Spisni study?"
Thank you for sharing this video! In doing so, you have proved my point about Normalization of Deviance.
The video starts stops at 50% of max depth. Since Spisni, (not to mention the WHOLE argument about Deep Stops) I no longer think that's safe. But in your post here
your practice has now morphed into stops starting only 10 feet above max depth!!!
That is Normalization of Deviance.
In doing so, you argued that an AL40 was insufficient for emergency ascent. Yet on the video you just cited, 40 CuFt was cited as Rock Bottom Gas.
QED.

Can another UTD diver here on ScubaBoard comment definitively on current UTD ascent strategy? I did find this from DEMA 2022. I can't say I learned anything, and was disappointed to see the Oxygen Window still being touted as real.

 

[SpaceX Aquanaut]

I think you may have missed the point of @MarkA 's question.
I think his question, and certainly mine is, "Has UTD abandoned making the first stop at 50% of max depth, since the Spisni study?"
Thank you for sharing this video! In doing so, you have proved my point about Normalization of Deviance.
The video starts stops at 50% of max depth. Since Spisni, (not to mention the WHOLE argument about Deep Stops) I no longer think that's safe. But in your post here
your practice has now morphed into stops starting only 10 feet above max depth!!!
That is Normalization of Deviance.
In doing so, you argued that an AL40 was insufficient for emergency ascent. Yet on the video you just cited, 40 CuFt was cited as Rock Bottom Gas.
QED.

Can another UTD diver here on ScubaBoard comment definitively on current UTD ascent strategy? I did find this from DEMA 2022:

Then fine. Adjustment of that linked profile to ameliorate the given supply of an AL40 is indicated. . .

Change 1 minute stops to 0.3 minute stops and do an extended safety stop, as subsequently discussed above.

Happy Happy -no more Nrml-of-Dev okay. . .

As for what UTD has done in light of the cited study -I do not know. Do a search in the Tech/Deco Forum and/or start a discussion there.

And again IMO if you’re doing mandatory deco profiles over consecutive days, then yes Deep Stops is an issue. You gotta do extended O2 time stops to relieve the accumulated N2 load/saturation out of those intermediate slow tissues. But that’s better discussed in the deco/tech forum. . .

QED

 

[rsingler]

You clearly have a good understanding of the issues, even if we disagree on implementation. I've been perusing the forums trying to learn more about RD 3.0. I keep seeing comments about using RD in addition to other deco planning tools for tech diving as a sanity check as well as emergency backup.

Honest questions: Do you use a dive computer for planning or diving? If so, do you use one with an RGBM algorithm or Buhlmann? What settings do you use?

 

[SpaceX Aquanaut]

You clearly have a good understanding of the issues, even if we disagree on implementation. I've been perusing the forums trying to learn more about RD 3.0. I keep seeing comments about using RD in addition to other deco planning tools for tech diving as a sanity check as well as emergency backup.

Honest questions: Do you use a dive computer for planning or diving? If so, do you use one with an RGBM algorithm or Buhlmann? What settings do you use?

Shearwater Petrel2 Computer on full Buhlmann algorithm (90/90), for ten years now -for both recreational and tech dives (in which I always bring an AL 40 of Oxygen).

Actually, I think now that UTD indirectly addresses the Deep Stops issue/Spisni Study by offering an Oxygen Clean-up Certification for Recreational Divers regularly encroaching on NDL Limits (or just for good anti-DCS margin for old farts like me), as well as cutting back on intermediate stops in RD3.0 before the first mandatory deco gas switch on Tech dives. . .

 

[rsingler]

Thank you.
For a guy who dives 50/70, and is testing 60/70 for myself, how often do you actually surface from a tech dive with a GF99 above 80?