New diver: Suggested conservatism settings for a Petrel?

[C Dub]

Are you using the recreational dive interface?

Yes, only the rec mode interface.

 

[Capt Jim Wyatt]

If there are only three settings possible use 40/85.

 

[Michael Guerrero]

I'd leave it at the default (medium) unless you thought there was some issue. Like Dr. L mentioned, there's some controversy over the perceived conservatism of a lower GF Lo. If you do accidentally end up in deco, follow the computer derived stops, and find that you feel unusually tired (like you really need to lay down and take a nap), then you could change the settings to the "more conservative" for next time.

Just keep an eye on your computer, do what it tells you, and stay out of deco.

 

[C Dub]

I came home from the office, and fired up the computer. Here are the NDL times from the dive planning function in the computer, at each conservatism setting, for a dive to 60 feet:
High 31 minutes
Med 40 minutes
Low 50 minutes

Interesting comparison, from the PADI tables, the NDL limit is 55 minutes, with a required safety stop at 49 minutes (makes me wonder if I'm reading the table right, Maybe I'm not??lol)

Looking at the settings for safety stops in the computer, it does not have an option for deeper stops, only the standard depth and stops of 3,4 or 5 minutes (unless you slip into full blown decompression mode, then I have no idea what it will do).

 

[Dr. Lecter]

Thus, you should not program a lower number at all. Dive a 75/75, 80/80, or even a 50/50 or whatever. Again, since you are NOT doing decompression dives, any settings for GF are completely irrelevant anyway.

It's very interesting to me you're telling a quintessentially recreational user they need to abandon OC Rec mode and go into OC Tec mode--and start diving radically different GFs than Shearwater sets as a default or even offers as a Rec mode option. The idea one should be diving equal Lo and High GFs for *NDL* diving...is a bit nuts. If your GF lo is 45, you're going to have significantly shorter NDLs than if you're diving 85/85.

I understand what Peter and ADD Helium like to teach, but I think your suggestion is a gross oversimplification (at best) for NDL air diving.

 

[C Dub]

I suspect he is trying to kill me.

It's very interesting to me you're telling a quintessentially recreational user they need to abandon OC Rec mode and go into OC Tec mode--and start diving radically different GFs than Shearwater sets as a default or even offers as a Rec mode option. The idea one should be diving equal Lo and High GFs for *NDL* diving...is a bit nuts. If your GF lo is 45, you're going to have significantly shorter NDLs than if you're diving 85/85.



I understand what Peter and ADD Helium like to teach, but I think your suggestion is a gross oversimplification (at best) for NDL air diving.

 

[mathauck0814]

This is the problem with recreational divers buying technical diving computers. The Petrel will not prevent you from hurting yourself. It will not provide you any warning and it will not advise you against making stupid decisions. Gradient factors need to be understood in order to be set appropriately.

In very general terms, the low/high factor system should be used by technical divers only. If you're diving within NDL then set both numbers to the same amount and any number less than 100% will give you conservatism from the M-value of a controlling compartment.

If you're doing decompression diving, then you'll want to be able to adjust where your stops begin and how quickly you can proceed through them; your instructor can help you understand how your choices will impact the balance of conservatism and time in the water.

---------- Post added August 12th, 2014 at 07:36 PM ----------

I The idea one should be diving equal Lo and High GFs for *NDL* diving...is a bit nuts. If your GF lo is 45, you're going to have significantly shorter NDLs than if you're diving 85/85.

??? please elaborate

 

[Croomrider]

This is the problem with recreational divers buying technical diving computers. The Petrel will not prevent you from hurting yourself. It will not provide you any warning and it will not advise you against making stupid decisions. Gradient factors need to be understood in order to be set appropriately.

In very general terms, the low/high factor system should be used by technical divers only. If you're diving within NDL then set both numbers to the same amount and any number less than 100% will give you conservatism from the M-value of a controlling compartment.

Are you trying to tell us that a recreational diver cannot be safe by selecting one of the conservatism factors that Shearwater programs in for their recreational OC diving mode? Even if you are not getting into deco, the different conservatism choices affect the NDL times allowed at any given depth. They ALL seem to be more conservative than my Oceanic computer!

Mike

 

[mathauck0814]

Are you trying to tell us that a recreational diver cannot be safe by selecting one of the conservatism factors that Shearwater programs in for their recreational OC diving mode? Even if you are not getting into deco, the different conservatism choices affect the NDL times allowed at any given depth. They ALL seem to be more conservative than my Oceanic computer!

Mike

I'm advocating an understanding of the model rather than a blind adherence to a random set of variables.

 

[C Dub]

Would love to see the NDL times of your Oceanic, at whatever settings it allows.

Are you trying to tell us that a recreational diver cannot be safe by selecting one of the conservatism factors that Shearwater programs in for their recreational OC diving mode? Even if you are not getting into deco, the different conservatism choices affect the NDL times allowed at any given depth. They ALL seem to be more conservative than my Oceanic computer!

Mike