Shearwater - Update GF During DIve

[biggpa]

Several posts about John Chatterton's classes brought up the idea of changing GFs during a dive (please don't debate if this is a good idea or not). However, I cannot find any information about it, so I tried it on a recent recreational dive.

Perdix AI GFs set to 50/85 - on the dive at 60ft, Surf99=72%, I tried to update the GFHi to 95, I got "error". I was able to update to HI to 90. GFLow was grayed out.

Does anyone know the rules for what values are valid or not? Maybe my google skills are poor, but I cannot find any information about this...

 

[Jay]

This was on a Perdix?

 

[KenGordon]

Several posts about John Chatterton's classes brought up the idea of changing GFs during a dive (please don't debate if this is a good idea or not). However, I cannot find any information about it, so I tried it on a recent recreational dive.

GFs set to 50/85 - on the dive at 60ft, Surf99=72%, I tried to update the GFHi to 95, I got "error". I was able to update to HI to 90. GFLow was grayed out.

Does anyone know the rules for what values are valid or not? Maybe my google skills are poor, but I cannot find any information about this...

If GF lo is too high you can only set GF hi to 90. So max aggressiveness is either 49/99 or 90/90.

I want to set my CCR bailout Gf to 100/100 as I am mostly worried about running out of gas after a CO2 hit. That is not supported. I’d also like to be able to set different values for CCR mode and bailout, and have both TTS available. As it stands I have to guess (ok precalculate before the dive) that my CCR mode TTS is a reasonable approximation of my bailout TTS and so that I am still within my bailout limits.

 

[biggpa]

This was on a Perdix?

Yea - Perdix AI firmware v71. Original post updated

 

[biggpa]

If GF lo is too high you can only set GF hi to 90. So max aggressiveness is either 49/99 or 90/90.

I want to set my CCR bailout Gf to 100/100 as I am mostly worried about running out of gas after a CO2 hit. That is not supported. I’d also like to be able to set different values for CCR mode and bailout, and have both TTS available. As it stands I have to guess (ok precalculate before the dive) that my CCR mode TTS is a reasonable approximation of my bailout TTS and so that I am still within my bailout limits.

Did you just figure this out by pressing the buttons or talking with someone? I am kinda looking for official documentation about what the values can be.

Changing in "System Setup" while on the surface, i get the error with "Lo>50. then Hi<90". Dive Setup only says Error

Do you know why GFlo cannot be set above some value (50?) - is there a ZHL algorithm limitation?

 

[KenGordon]

Did you just figure this out by pressing the buttons or talking with someone? I am kinda looking for official documentation about what the values can be.

Changing in "System Setup" while on the surface, i get the error with "Lo>50. then Hi<90". Dive Setup only says Error

Do you know why GFlo cannot be set above some value (50?) - is there a ZHL algorithm limitation?

This is an arbitrary design choice by Shearwater.

I have tried it on several versions of firmware. If you look at past posts here you will find it discussed, if might have been commented upon by Shearwater or that might have been relayed by StuartV. There have been claims they would change this behaviour but it has not happened yet. Once upon a time a GF lo > 50 was heresy, however there are no limits in the scheme, indeed proper ZHL16 (as in designed by a proper deco scientist) is 100/100.

 

[Blackcrusader]

Mine is set to 45 / 95. I also often do 10 - 15 minutes ending the dive around 5m off gassing.

 

[Protondecay123]

I haven't tried this. But in this article Gradient Factors in a Post-Deep Stops World the author uses 70/85. So maybe if you bring the GFhi below 90, you can then bring GFlo above 50? Personally I would like to see Shearwater make the Thalmann Algorithm available rather than the $60 upgrade to VPM.