Oh, that's good to know, I wasn't sure they did or not. I am glad that they do, I wish all other Dive computer companies have the same sentiment.
Gradient Factors For a Rookie
- Thread starter dflaher
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Oh, that's good to know, I wasn't sure they did or not. I am glad that they do, I wish all other Dive computer companies have the same sentiment.
PfcAJ
Contributor
Ulfhedinn
-Skill Collector-
What is the standard or maybe better put what do all the shearwaters come stock with? I know you can change but initially?
Shearwater Teric and Perdix both default to OC recreational mode. On the Teric, the default conservatism for OC rec is 40/85 (pg 27). I don't own a Perdix, but the manual says the default is 30/70, as of 2019 (pg 39). Not sure why there is a difference, or if that is still true today, somebody who owns a Perdix can say for sure.
Ulfhedinn
-Skill Collector-
Thanks I have the Perdix but I'm working so I don't have access to it at this moment. Appreciate the response. lol.. guess I could have looked at the manual. /facepalm
Ulfhedinn
-Skill Collector-
40/85 for Perdix 2
30/70 for Petrel 3
30/70 for Petrel 3
EFX
Contributor
Here is something I posted awile ago on a different thread:
The SurGF feature does provide an "on-the-fly" option to make the dive safer through additional off gassing at the safety stop or another depth. Keep in mind that the NDL calculation takes GFHi into consideration so that an ascent directly to the surface will not exceed GFHi. You can always set your GFHi to a lower value for more conservatism. GF settings have made safety stops superfluous for additional safety. In the days when tables were used or computers without GF's, the safety stop was the only way to ensure additional safety.
See this post for more info on GF's:
scubaboard.com
After clicking on the URL above and viewing that post scroll up to see the preceding post for more info on GF's.
The SurGF feature does provide an "on-the-fly" option to make the dive safer through additional off gassing at the safety stop or another depth. Keep in mind that the NDL calculation takes GFHi into consideration so that an ascent directly to the surface will not exceed GFHi. You can always set your GFHi to a lower value for more conservatism. GF settings have made safety stops superfluous for additional safety. In the days when tables were used or computers without GF's, the safety stop was the only way to ensure additional safety.
See this post for more info on GF's:
What's your SurfGF and how does it compare to your (Rec) GFHi?
But what system should I have used to do twenty-five 80-100' dives in a row, 4-5 a day (counting night dives), as I drank in the sights of the second dropoff on Bonaire last September? It wasn't DSAT, and it wasn't 95/95. I did 27 dives in TCI in 5.5 days in August. Just like you said. Every...
After clicking on the URL above and viewing that post scroll up to see the preceding post for more info on GF's.
That is actually math: since Workman, M-values are greater at depth. So while you're in no-stop time, your M0 values are the limiting ones. What you're seeing is gradient factors make it possible to push it into a degenerate case.
The way it's supposed to work is:
1) check if I can ascend directly to the surface (that's based on M0 aka GF Hi),
2a) if yes, I'm still on no-stop time,
2b) if no: compute the first deco stop based on GF Lo.
What happens when you do this with a really silly GF setting like 10/100 is you might find yourself with a 6-minute deco stop at 9 msw and 500 psi in your Al80. Oops.
So you could at step 1) also check if you would violate GF Lo at any point in the ascent. I can't think of any reason to do that other than the case of overstaying the NDL while using the really silly GF settings, as described above. If your planner is doing that, well, that's uncommon, I'm pretty sure it's not what Herr Dr. Buhlmann nor Erik Baker intended, but as long as you use sane gradient factors, it's six vs half a dozen.
PfcAJ
Contributor
I can make it do it with 40/85 too. That’s fairly sane.
Manipulating gf lo gives you your first stops, the hi value ultimately determines their length as you can’t surface till that has dropped low enough. Manipulating those values will give you various stops of varying lengths. I’m not really seeing how this is controversial? Kind of arbitrary to base the whole thing on the hi value and just…ignore the lo?
Like I said, M-values are greater at depth. NDL is determined by M0 because M0 is the smallest, nothing arbitrary about it. I'll post this again:
If you have a TC loaded to any point on the slope (and have to stop to off-gas it), its load is by definition greater than M0 and you've been past your NDL for some time. Conversely, if you're within NDL, none of your TCs are loaded above their respective M0 values: the line at z = 1 closest to x-axis. (With a caveat that you off-gas during ascent and your fastest TC could be "riding" the line on the way up.)
(If your planner is "doing it" at 40/85, I'd get two more planners and see which two agree.)
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