Gradient Factors - What is Everyone Using?

[cathal]

I typically run 50/60, sometimes 50/70. It is ultra conservative I know, but I am the sole bread winner in my family and with 4 kids I am trying to buy down risk a bit. If I get a hit and need a chamber ride, Mrs. Tomcatbubba will put one foot up my butt, and the other squarely on my dreams of ever diving again.....

Besides, O2 is cheap and I find deco stops relaxing (usually). Plus, I typically have older students in Tec classes from the local Navy base and I like the conservatism with them as well.

You have a great approach to this!

 

[Rollin Bonz]

He spoke to it in this polish conference just 2 months ago:


He mentioned 50/70 at around the 1:40 mark for more isolated locations. 50/80 in other standard conditions I guess.

I'm just a beginner but find the theory interesting.

GREAT (as always) presentation and simplification of the subject by Dr. Mitchell.

But the best part is at 1:23:01

I almost spit my coffee out.

 

[exodusmaximus]

I'm interested in what gradient factor settings everyone is running and why? Does the type of dive you're doing affect your settings (e.g., cold vs. warm water, technical vs. recreational, clear vs. silty, other)? I've heard everyone is all over the map with regard to the settings they are using and I'm curious to hear if there's any sort of consensus.

I've been reading some of the past threads regarding gradient factors and decompression theory but didn't see this aspect specifically addressed, though admittedly I didn't read back super far. However, some of the threads regarding the efficacy of deep stops have been super interesting.

One thing that came to mind while reading those threads is it would be super interesting for Shearwater for example to sponsor some deco research. Many people upload their dive profile and data to their cloud based app. It might be interesting to have a short survey people could fill out after their dive with questions related to how they felt post dive, if someone had skin bends, other DCS symptoms, etc. You may only get people that have issues filling out the surveys, but I wonder if you would see some strong correlations between certain gradient factor settings and problems with DCS or even just feeling lousy after your dive (sub clinical DCS maybe?).

50/75 when I'm rested and will not do dives past 30m, 30/70 for multiple days of diving to 40m. Anything more technical, depending on the dive plan (usually between 30-40/60-75)

 

[exodusmaximus]

You have a great approach to this!

50/70 is not ultra conservative for deeper dives (dan recommended default is 30/70)

Yes, air is cheap.

 

[VikingDives]

50/80, but I'll sit at my last stop until I hit 70. Then 1 foot a minute (if possible) from 10' to the surface, which usually puts me under 60 at the end of the dive.

 

[JMarc]

dan recommended default is 30/70

I'd be interested in a source for this affirmation.

 

[inquis]

50/70 is not ultra conservative for deeper dives (dan recommended default is 30/70)

Those are equally conservative for no-stop (NDL) dives.

If that is truly DAN's current guidance, they are woefully out of touch with that of the researchers in the field. 30/70 is viewed as LESS conservative than 50/70 for mandatory-stop (deco) dives. See the videos and articles linked previously in this thread for more details.

 

[inquis]

It appears I didn't weigh in the first time this thread came around. x/85 for recreational diving, surfGF typically under 70 after waiting for the boat ladder to clear. 65/80 for deco dives down to 65 m. 60/75 for deeper.

Some other threads have indicated a fixed GF has increasing risk as depth increases. I highly doubt my choices are theoretically iso-risk, but I believe it's a step in the right direction.

 

[OTF]

40/70 is the default I now run for everything including several hour CCR trimix dives.

However I will sometimes do extra time at the 10 and 20 foot stops to let the surfacing GF come down to 60 or occasionally even 50 depending on the dive and conditions. Though that's not always easy in cold water.

 

[grantmac]

It appears I didn't weigh in the first time this thread came around. x/85 for recreational diving, surfGF typically under 70 after waiting for the boat ladder to clear. 65/80 for deco dives down to 65 m. 60/75 for deeper.

Some other threads have indicated a fixed GF has increasing risk as depth increases. I highly doubt my choices are theoretically iso-risk, but I believe it's a step in the right direction.

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.