what gf do you use and why

[hayden]

What gradient factor do you use and why?

Personally curious about what other divers are using.
Not looking for a bash thread, feel free to post about vpm but it's not really
of interest to me.
Try keep it polite, everybody's post are going to be opinionated.

Let me start, I am using an 80/80 gf on the zhl-b profile.
The low gives me a comfortable gap from my m-value without
going into deep-stop territory. A high giving me a reasonable amount
of conservatism without pushing my stop lengths out too long encouraging
on-gassing of slow tissues.

Edit: I'm diving in sub 12 degree Celsius water

 

[tbone1004]

started on 30/70, felt fine so upped it a bit. Am now at 50/85 but will usually run the last stop over a few minutes. 30/70 seemed a touch conservative especially with deep stops involved that I didn't agree with so that one got upped, and the 85/70 is because I can always make it more conservative, but with 85 I know that if I have to get out earlier than I'd like, I should be ok. I do take it a bit easier at the surface with 85 instead of 70 though.

 

[markmantei]

Started with 30/85 based mainly on what was working for others. Reduced it to 30/70 based on a story I heard about how Shearwater changed their default after seeing the results of dopplers from RB divers at one RB convention or another. My memory on these things is horrible though, maybe someone else here can better relate the story.

Regardless, subjectively I generally feel better / less tired after a day of diving after having reduced the GF High. That is cold water diving however which of course will decrease offgassing efficiency, at altitude to boot. Can't say I would rule out upping the GF for warm water tropical dives.

 

[CptTightPants21]

Does it mean I am not scuba saturated when I see gf and I still think girlfriend? In which case, the answer is inflatable because it doesn't talk.


--seriously 30/70.

 

[nimoh]

I'm currently using 10/80, and comfortable with it...and don't want to get into a deep stop discussion on this thread

 

[Kevrumbo]

GF's 30/85 ZHL-16 with further conservative resetting on-the-fly of the Surfacing GF to 70 or 60, in order to extend the O2 Deco profile time (I really like and found this feature of the Shearwater Petrel Dive Computer most useful along with the @+5min/"predicted deco time remaining to surface staying at current depth for 5 more minutes" function).

 

[LiteHedded]

20/85

 

[PfcAJ]

20/85-30/70 is what I make tables for.

I dig the 30/70 on the longer stuff thus far.

 

[dreamdive]

Actually I dive different GF's - we all do! Just because you dial in a particular number does not mean you dive it unless you ascend at 30 ft/min and do perfect stops (preferably one foot stops)

I think your second question, the "Why" is the more interesting one. Will I dive a 90/90 on a 600 ft dive? Should I dive a 30/85 on a 350 ft dive with a bottom time of 45 minutes?......Think about those questions instead. Why would a given setting actually matter on DIFFERENT dives? What do you know about tissue saturation and how to manage those different tissues. What tissues are you trying to manage on a given dive? THAT's what should determine your GF. Who cares what everybody else dives. Just look at all the different answers you are getting here.

What about Helium penalties? When does it matter to account for Helium being present in the mix? Does it matter for sub-saturation dives?

In closing I will state that MORE IS NOT NECESSARILY BETTER when it comes to deco. The WHERE however does.

 

[hayden]

Actually I dive different GF's - we all do! Just because you dial in a particular number does not mean you dive it unless you ascend at 30 ft/min and do perfect stops (preferably one foot stops)

I think your second question, the "Why" is the more interesting one. Will I dive a 90/90 on a 600 ft dive? Should I dive a 30/85 on a 350 ft dive with a bottom time of 45 minutes?......Think about those questions instead. Why would a given setting actually matter on DIFFERENT dives? What do you know about tissue saturation and how to manage those different tissues. What tissues are you trying to manage on a given dive? THAT's what should determine your GF. Who cares what everybody else dives. Just look at all the different answers you are getting here.

What about Helium penalties? When does it matter to account for Helium being present in the mix? Does it matter for sub-saturation dives?

In closing I will state that MORE IS NOT NECESSARILY BETTER when it comes to deco. The WHERE however does.

The thread isn't about refining my gradient factor, I'm comfortable with adjusting and justifying new profiles for myself. It's just an interesting topic and wanted to know what other people use and their mindset behind it.

---------- Post added July 3rd, 2015 at 01:31 PM ----------

started on 30/70, felt fine so upped it a bit. Am now at 50/85 but will usually run the last stop over a few minutes.

GF's 30/85 ZHL-16 with further conservative resetting on-the-fly of the Surfacing GF to 70 or 60, in order to extend the O2 Deco profile time (I really like and found this feature of the Shearwater Petrel Dive Computer most useful along with the @+5min/"predicted deco time remaining to surface staying at current depth for 5 more minutes" function).

I do love +5'ing on the last stop with my buddy and just hanging out there.

---------- Post added July 3rd, 2015 at 01:32 PM ----------

Does it mean I am not scuba saturated when I see gf and I still think girlfriend? In which case, the answer is inflatable because it doesn't talk.


--seriously 30/70.

gf that doesn't talk? Sounds like i need to invest in this

---------- Post added July 3rd, 2015 at 01:42 PM ----------

Regardless, subjectively I generally feel better / less tired after a day of diving after having reduced the GF High. That is cold water diving however which of course will decrease offgassing efficiency, at altitude to boot. Can't say I would rule out upping the GF for warm water tropical dives.

On a particularly cold day and further into winter, or even if I just have more time to play with I like to drop my high down a bit; cant go wrong with more conservatism.