Decompression Modeling

[PfcAJ]

The model is sort of the template, then I add or subtract from it to make the ascent I feel is best based on current theory and experience, like o2 window, s curve, gas breaks, etc. The model only takes you so far, the rest is add ons.

 

[gsk3]

So there's really not a model that just works without all the add-ons?

 

[Rainer]

For GUE and UTD divers? Not really. Almost all schedules are going to get tweaked.

So there's really not a model that just works without all the add-ons?

 

[PfcAJ]

I wouldn't say the model doesn't work, it just works better with the add ons. The add ons don't take away anything, but they improve (in theory) the decompression.

 

[gsk3]

For GUE and UTD divers? Not really. Almost all schedules are going to get tweaked.

Got it. I guess that makes sense, since from what we saw of Decoplanner in Fundies, the interface seemed to encourage tweaking.

I wouldn't say the model doesn't work, it just works better with the add ons. The add ons don't take away anything, but they improve (in theory) the decompression.

When you're building a model up from fundamental principles, it should produce something that empirically works. If not, the model is broken. Still might be useful, but it means it will eventually get replaced with a better model that can reproduce what works based on people's experiences, without all the kludges/additions. Not saying that the additions are the wrong thing to do given the state of today's knowledge--they clearly work. Just saying that the model is clearly substantially incomplete in its explanation of the world. "All models are wrong, but some are useful."

 

[TSandM]

GUE focuses heavily on control of bubble formation, and therefore the addition of deeper stops. Pure dissolved gas models penalize heavily for deeper stops, because they do not consider offgassing to occur at that level.

There is some significant question as to whether the deeper stops are actually beneficial -- see the PDF from the DAN symposium on technical diving (available on the DAN website, and it's free, and you don't have to be a member to get it).

Your observation that taking the output of a decompression program and then mechanically adjusting it invalidates expected safety of the profile as a product of that model is completely accurate. The DIR agencies teach the construction of a decompression strategy that is not generated from any single mathematical model, and its validation has been through the success of the dives that are done using the approach.

 

[ScubaFeenD]

For GUE and UTD divers? Not really. Almost all schedules are going to get tweaked.

Can you go more in depth on this. Maybe give an example? I dont mean to make work for you, but I think i would understand beter if there was a concrete example I can toy with in my head.

 

[Rainer]

Sorry, I'm not interesting in posting dive schedules for those not deco trained.

Basically, the tweaks involve adding deep stops, extra time at gas switches for O2 window effects, s-shaping, maximizing time at 20' on O2, and backgas breaks. This is all covered in T1 and T2.

Can you go more in depth on this. Maybe give an example? I dont mean to make work for you, but I think i would understand beter if there was a concrete example I can toy with in my head.

 

[ScubaFeenD]

Sorry, I'm not interesting in posting dive schedules for those not deco trained.

Basically, the tweaks involve adding deep stops, extra time at gas switches for O2 window effects, s-shaping, maximizing time at 20' on O2, and backgas breaks. This is all covered in T1 and T2.

What you covered is sufficient.

 

[liuk3]

GUE current standards for technical dives when using DecoPlanner state that either gradient factor 20/85 be used for Buhlman, and on a conservatism setting of 2 for VPM. Each individual has to take their own responsibility for how they want to execute or modify their own decompression profiles.