Gradient Factors - What is Everyone Using?

[Kay Dee]

Let's take a 55m dive on air ............

Oooooooh, dont say that here, you'll be drawn and quartered!

 

[L13]

It seems to be that a serious study is needed to know at which point the trade-off becomes less profitable.

NEDU already did that study. Deep stops (low GF Low) are not good!

I'm far from being a specialist in the matter, I'd like to have references to sources more in depth than the usual one targeting divers ("Deco for divers" for instance)

Deco for Divers is a great reference, but is out of date with regard to the research on deep stops in the last decade.

 

[100days-a-year]

I'll continue with 80/80 to 90/90 on air and lean nitrox until l see or feel damage. Maybe pad a few minutes here and there but that is already conservative to me. Maybe if I was doing big dives I'd consider a little more alleged conservatism.

 

[Wibble]

I'll continue with 80/80 to 90/90 on air and lean nitrox until l see or feel damage. Maybe pad a few minutes here and there but that is already conservative to me. Maybe if I was doing big dives I'd consider a little more alleged conservatism.

Hmm, "alleged conservatism". Any planning with those gradient factors would certainly get you out before others on more sensible GFs.

If you were doing dives outside of NDLs where your SurfGF is well above 100 you may change your mind not least due to post dive fatigue — just see the number of divers sleeping on the boat back from a dive.

 

[L13]

... alleged conservatism.

The research is pretty clear that GFs <80/80 are more conservative, I think someone is in denial.

 

[KenGordon]

It would be nice to see computer manufacturers introduce GFs which can be scaled to depth or total deco time.
NDL 85, then once exceeded that the plan shifts to 80, if more that X total deco shift to 75 etc.

Although with GF99 and surf GF it's easy enough to keep an eye on those. I'm not a tech diver (yet) but I keep an eye on both those pieces of data and will either slow an ascent and/or lengthen a SS based on that information.

GF at surfacing is not really a measure of risk. It is simply the GF of the limiting compartment. That might be one fast compartment, with the rest way behind, for a short deep dive, falling quickly at the surface. At the end of a longer dive it would be one of many similar slow compartments, reducing slowly. The risk is greater for the second case, even if the GF is the same.

 

[grantmac]

GF at surfacing is not really a measure of risk. It is simply the GF of the limiting compartment. That might be one fast compartment, with the rest way behind, for a short deep dive, falling quickly at the surface. At the end of a longer dive it would be one of many similar slow compartments, reducing slowly. The risk is greater for the second case, even if the GF is the same.

So the question becomes whether the ability to select gradient factors by compartment would be beneficial. Allowing higher for faster compartments and lower for slow ones.

 

[inquis]

So the question becomes whether the ability to select gradient factors by compartment would be beneficial

The maximum tolerable supersaturation already varies by compartment. Perhaps not the the ideal way (i.e., iso-risk), but finding better numbers requires testing.

Making them user-configurable also has the same problem as today's single GF: what do you set them to?

 

[dmaziuk]

So the question becomes whether the ability to select gradient factors by compartment would be beneficial. Allowing higher for faster compartments and lower for slow ones.

"Select gradient factor by compartment" is equivalent to selecting the M-value and the slope of the M-value line by compartment. That's exactly what the different models do. If you believe you know better then their authors, go ahead and don't let anyone stop you.

 

[100days-a-year]

Alleged as in research has shown 30/70 is likely not conservative and 100/100 not either. In between is a large gray area with pontificating proponents positing positions perfectly free from fact.