Gradient Factors - What is Everyone Using?

[Capt Jim Wyatt]

I use 50/80 on OC and CC.

If I can, which is 99% of the time I remain at the last stop until GFSURF=70%.

Also I keep GFSURF on the screen of one of my computers at all times.

On OC I dive with a Petrel I and a Perdix.

On CC I dive with a NERD2 and a Perdix.

 

[VikingDives]

I use 50/80 on OC and CC.

If I can, which is 99% of the time I remain at the last stop until GFSURF=70%.

Also I keep GFSURF on the screen of one of my computers at all times.

Same. I feel better if I stay to about 70.

If I'm doing a 10 foot/3M stop, and I'm not too cold, I'll leave at about 72 and do a foot a minute to the surface.

 

[Twiny]

For deco dives with air as bottom gas & 2 deco gases, I use 50/70.
I might use 70/70, if I only have 1 deco gas (no travel gas) to avoid doing deeper stops on air.
50/70 for tec dives with air and 40/70 for tec trimix dives seem widely adopted

 

[harvalen]

Since I generally want to surface with GF <= 70, I use 50/70. That way the computer will calculate TTS and I can verify that I have enough gas and won't be too cold. If something happens then I can abort with a SurfGF of 85 or so, but rather not.

 

[tursiops]

Decompression " theory "

You are using theory as if it means "guess." So do you also disbelieve gravity and relativity?

 

[huwporter]

You are using theory as if it means "guess." So do you also disbelieve gravity and relativity?

To be fair, the equations we use to model decompression correlate to reality a whole lot less well than the equations we use to model gravity and relativity.

Although a black hole might beg to differ, I suppose.

 

[EFX]

So do you also disbelieve gravity and relativity?

Well, because of the gravity of the situation it's all relative anyway.

 

[boulderjohn]

Since I generally want to surface with GF <= 70, I use 50/70.

Years ago on ScubaBoard, I mentioned in a thread that when I did NDL dives, I left my Shearwater computers in OC tech mode, ad I didn't change the GFs, which had a high of 70. This meant the computer would go into deco pretty early when compared to other divers, so if I wanted to have a decent-length dive, I had to let it go into deco a little bit. I knew that if I had taken the tiny time needed to change to a GF high of, say, 85, I would still be within NDL, so I wasn't concerned. I understood what the numbers really meant.

Well, that post turned into a real mess. A SB member who seemed to live to attack me started a new thread, because he really couldn't attack that logic in the present thread. In the new thread, he said that he was shocked to see that in another thread (to which he did not link), a scuba instructor (whom he did not name, but left enough hints to make it obvious) was advocating going into deco during NDL dives without taking any of the standard tech diving precautions. He made it sound like I was pure worm scum and implied that I should be banned from ScubaBoard for advocating dangerous practices.

The thread went on for three days before I blundered into it, and of course it had generated pages of posts from people condemning me for my outrageous statements. I stepped in, explained everything, and made a link to my offending post in the other thread. Once my true position was known, of course, the direction of that thread changed dramatically, but lots of people had already left the thread by then, convinced I was scum.

So now I take the time to change the GFs on my computer when NDL diving, with a GF high of 85-90. This gives me NDLs similar to everyone else. On ascent, I pay no attention to safety stop time and just make sure the SurfGF is below 70, however long that takes. I get the same dive as before, but if some no-mind happens to look at my computer, they won't blow a gasket about violating NDLs.

 

[harvalen]

So now I take the time to change the GFs on my computer when NDL diving, with a GF high of 85-90. This gives me NDLs similar to everyone else. On ascent, I pay no attention to safety stop time and just make sure the SurfGF is below 70, however long that takes.

I'd rather let the expensive dive computer I've paid for do the calculation and tell me how long it'll take. Been on plenty of no decompression allowed dives, no one has demanded proof that my computer didn't go into deco. Having GF High set to 70 means I know how long my stop time will be and can ensure that it's cleared by the time everyone else is done with their safety stops.

As long as you follow the spirit of the rule and stay within the limits you're comfortable with, so you can go directly to the surface in a real emergency, I don't see a problem. Personally I have second computer with more liberal settings, but checking SurfGF so it's not too high would work too.

 

[LFMarm]

Years ago on ScubaBoard, I mentioned in a thread that when I did NDL dives, I left my Shearwater computers in OC tech mode, ad I didn't change the GFs, which had a high of 70. This meant the computer would go into deco pretty early when compared to other divers, so if I wanted to have a decent-length dive, I had to let it go into deco a little bit. I knew that if I had taken the tiny time needed to change to a GF high of, say, 85, I would still be within NDL, so I wasn't concerned. I understood what the numbers really meant.

Well, that post turned into a real mess. A SB member who seemed to live to attack me started a new thread, because he really couldn't attack that logic in the present thread. In the new thread, he said that he was shocked to see that in another thread (to which he did not link), a scuba instructor (whom he did not name, but left enough hints to make it obvious) was advocating going into deco during NDL dives without taking any of the standard tech diving precautions. He made it sound like I was pure worm scum and implied that I should be banned from ScubaBoard for advocating dangerous practices.

The thread went on for three days before I blundered into it, and of course it had generated pages of posts from people condemning me for my outrageous statements. I stepped in, explained everything, and made a link to my offending post in the other thread. Once my true position was known, of course, the direction of that thread changed dramatically, but lots of people had already left the thread by then, convinced I was scum.

So now I take the time to change the GFs on my computer when NDL diving, with a GF high of 85-90. This gives me NDLs similar to everyone else. On ascent, I pay no attention to safety stop time and just make sure the SurfGF is below 70, however long that takes. I get the same dive as before, but if some no-mind happens to look at my computer, they won't blow a gasket about violating NDLs.

For the same dive profile, it’s safer to keep a lower GF Hi and do some deco stops than pushing GF Hi up to stay within NDL. I would go back to your initial logic and not be influenced by somebody who likely doesn’t understand deco.