Deep Stops Increases DCS

[UWSojourner]

@UWSojourner

Could you share some thoughts on how the NEDU study results should be treated by recreational divers?

Take 30 meters for 20 minutes at 21%. The RDP considers this profile as a no deco dive and within the RDP NDL for recreational diving (with safety stop required). However, using ZHL16 with 40/70 GF, the following are the required deco obligations for the same profile:

9 meter @ 1 min
6 meter @ 3 min
3 meter @ 6 min

So, ZHL16 with 40/70 is more conservative than the RDP. Is it more prudent for recreational divers to follow the stops above as compared to following the RDP which listed this profile as a NDL dive?

The NEDU study relates to decompression diving. There's no need to modify NDL diving based on anything in the NEDU results.

Also, I'd say the results really apply to substantial decompression. A minute or two here or there in relatively shallow depths really isn't going to create a large enough difference in gas loadings to manifest the issues addressed by the NEDU study. This was brought out in Doolette's presentation here.

 

[rossh]

Any model needs real data for validation, that's modeling 101. As far as I know, the Bühlman models are based on and have have been validated by experimental data. However, I can't remember reading about the experimental data behind the bubble models, so I'd really like to hear about that.

You speak like this is a competition - its not. Perhaps you could read our web site for the updated state of VPM Model test data. That text has been there for 14+ years now.

Yes, real original ZHL was man tested, but no one does those profiles much anymore. Instead its headed to grossly exaggerated and stretched out profiles. Hence all this extra long GF stuff has abandoned the concept from where it came. Its not "decompression" profiles anymore - its just over-inflated waste of time profiles. How boring.

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[UWSojourner]

You speak like this is a competition - its not. Perhaps you could read our web site for the updated state of VPM Model test data. That text has been there for 14+ years now.

Yes, real original ZHL was man tested, but no one does those profiles much anymore. Instead its headed to grossly exaggerated and stretched out junk profiles. Hence all this extra long GF stuff has abandoned the concept from where it came. Its not "decompression" profiles anymore - it just stretched out, over-inflated waste of time profiles. How boring.
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Perhaps you've discovered your new tagline.

"Use V-Planner's VPM-B! Because a deco hit is so much more exciting!"

 

[rossh]

The NEDU study relates to decompression diving. There's no need to modify NDL diving based on anything in the NEDU results.
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How interesting. So we should fiddle the GF to suit the dive situation then? Is GF not consistent then? Does it have issues with making properly scaled plans across the dive spectrum?

If I make a plan in GF to match the nedu one, I'd need a GF of 40/55. Should I apply that to the NDL dives too?

How am I going to transition from 100/100 on NDL dives, to 40/55 in my air decompression dives? It sounds impossible.




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[UWSojourner]

How interesting. So we should fiddle the GF to suit the dive situation then? Is GF not consistent then? Does it have issues with making properly scaled plans across the dive spectrum?

If I make a plan in GF to match the nedu one, I'd need a GF of 40/55. Should I apply that to the NDL dives too?

How am I going to transition from 100/100 on NDL dives, to 40/55 in my air decompression dives? It sounds impossible.


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No. Dive your NDL. When you've exceeded it, dive your GF setting. Not rocket science, but perhaps beyond your pay grade.

 

[rossh]

No. Dive your NDL. When you've exceeded it, dive your GF setting. Not rocket science, but perhaps beyond your pay grade.

So answer the question please...

"How am I going to transition from 100/100 on NDL dives, to 40/55 in my air decompression dives? It sounds impossible."

That's an enormous jump and would make any air deco dive, really, really, really ,really ,really long. Surely we can't go straight to 40/55?


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[UWSojourner]

So answer the question please...

"How am I going to transition from 100/100 on NDL dives, to 40/55 in my air decompression dives? It sounds impossible."


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I'm not your dive instructor. But if it was me I'd look at the NDL. When I exceeded it I'd look to my tables/computer. For me GF50/75 would be more like it, but you can dive any GF you want.

 

[igor p]

Any model needs real data for validation, that's modeling 101. As far as I know, the Bühlman models are based on and have have been validated by experimental data. However, I can't remember reading about the experimental data behind the bubble models, so I'd really like to hear about that.

Unfortunately the truth is no GF adition to ZHL has been validated.

Does anyone here check graphs and data presented on forums or you blindely believe them?

Kevin if you are so sure your graphs and math behind are correct why dont you publish the excel file you make graphs in? So we can check it is ok.

I would be wiling to check it and conferm it if ok.

 

[UWSojourner]

Unfortunately the truth is no GF adition to ZHL has been validated.

Does anyone here check graphs and data presented on forums or you blindely believe them?

Kevin if you are so sure your graphs and math behind are correct why dont you publish the excel file you make graphs in? So we can check it is ok.

I would be wiling to check it and conferm it if ok.

I know you code. Why don't you just code it up and repeat the charts? That would be the best check if you're concerned. I'm not. I'll help along the way if you get stuck or something doesn't seem to be working for you.

None of this is proprietary; to do the charts you're not even required to do any deco calculations. Those come from the model providing the profile. Once you have the profile its just a matter of following the tissue compartments through to however long post-dive you want to display. It would be a good project for you.

 

[igor p]

I know you code. Why don't you just code it up and repeat the charts? That would be the best check if you're concerned. I'm not. I'll help along the way if you get stuck or something doesn't seem to be working for you.

None of this is proprietary; to do the charts you're not even required to do any deco calculations. Those come from the model providing the profile. Once you have the profile its just a matter of following the tissue compartments through to however long post-dive you want to display. It would be a good project for you.

If you would be sure you would post it without hesitating. But you do not. That tells it all.