Gradient Factors - What is Everyone Using?

[jgttrey]

50/85 here, but I usually extend the last stop and watch SurfGF drop until I'm bored. Usually closer to 70 when I get out. So, 50/85 up to the last stop, then more like 70 to exit. The goal is to be efficient about getting to shallow stops, then extend from there to be more conservative as circumstances allow.

 

[boulderjohn]

I hope everyone realizes that on a recreational, NDL dive, the first GF number does not mean a whole lot.

 

[tursiops]

I hope everyone realizes that on a recreational, NDL dive, the first GF number does not mean a whole lot.

If by "not mean a whole lot" you mean it means nothing, I agree.

 

[NAM001]

I see all sorts of GF settings here. and a lot of difference in the gf low value. for rec diving why is the gf low a concern?

 

[rjack321]

I think you'll find general consensus that GF-Hi of 100 is too aggressive for old, fat, recreational divers, who don't like to see themselves as expendible (compared to navy divers, anyway)

While those of us in the recreational side tend to joke about this and actual service members joke about it too, several ex-Navy military divers have told me they know they're pretty valuable assets and not disposable. Not to mention its hard to get the best out of people who behave like cannon fodder. Having calculated risks doesn't necessarily mean they are any quantitatively worse than those of us on the recreational side who pretty much just guess at how risky a dive might be.

I have had great success with 50/75 for up to 3-3.5 hours of deco.

 

[rjack321]

I see all sorts of GF settings here. and a lot of difference in the gf low value. for rec diving why is the gf low a concern?

because people think it influences their NDL or 5min deco dive when it doesn't?

 

[NAM001]

40/85 for rec dives. This is Shearwater's medium setting and I've never seen any reason to change it.

I looked at my petrel2 and 30/85 is the medium setting IN REC MODE but the custom is default set to 40/85. what version are you using. I was assuming that all the versions were the same. OR poerhaps 40/85 is medium in tech mode.

 

[NAM001]

There is a problem with the use of the word "conservative" in this context. The word became popular with algorithms that used the word "conservative" for settings that created a deeper first stop, with the implication that staying farther away from the M-value line was safer. Stopping deeper on the ascent was believed to be safer.

Current thinking has moved away from that, with the realization that when doing stops deeper, you are adding nitrogen to the slower tissues, gas that must be eliminated later with longer shallow stops. Research indicated that deeper stops are not in themselves safer.

People associate the word conservative with safer, but if by conservative you mean adding more deep water time to your profile, you are likely not making your dive safer.

Here is some reading on this.

good point for me I use conservative in regards to what GF I plan to hit the surface with. that bit of percentage I am away from a chambers door. conservative implying most precaution , least bottom time max deco on the ascent. (all dives being deco dives) such as 25 FPM is conservative ascent rate compared to 30-40 fpm. for the rec world,, what is commonly refered to as deco,,, is not part of the dive.

 

[boulderjohn]

If by "not mean a whole lot" you mean it means nothing, I agree.

We are in agreement. I have a characteristic leaning toward understatement.

 

[NAM001]

because people think it influences their NDL or 5min deco dive when it doesn't?

thanks, I have not come across that before. but most people have no clue what GF's are any way,, in the rec world. they only know low med hi. I do a lot in my dive club and other venues to educate people on gf's and what they mean. IMO GF's are going to become common place in the, some what, near future. I think it will be a major change on how we look at ascents.