What's your SurfGF and how does it compare to your (Rec) GFHi?

[Jay]

Is this why some who have this type of computer seem to 'ride' the NDL as they are using GF99/SURFGF to determine their exposure risk?

I wouldn’t say that’s correct/the general case in either aspect, but if “some” = a small minority then perhaps. Especially if GFHi is set to a low (rec) number, perhaps equal to a desired SurfGF like 75 say.

Also one could ride Ndl on any computer to a point until gas supply becomes an issue.

In theory you could ride NDL and then ride SURFGF when NDL becomes irrelevant (displayed as NDL=99), but that’s akin to Tec targeting GFHi and would be an aggressive N loading and playing with fire given you’re likely using a Rec magnitude for GFHi. Hence this survey .... to see what’s being used/done and the ‘risk’ at depth versus at surface

 

[Fastmarc]

I wouldn’t say that’s correct/the general case in either aspect, but if “some” = a small minority then perhaps.

Yes, I really should have put "few" as "some' really wasn't in keep with what I had in mind.

Thanks for the reply (you too @stuartv ).

 

[Jay]

If I had more survey options it would have been interesting to see how often NDL gets to zero yet SurfGF is sensible (say 75).

Also interesting would be where NDL was in the above comparison vs unmodified M-value.

Part of that puzzle would be dive depth vs SAC.

 

[Shearwater]

@Jay and others, thank you for starting this thread and contributing to it. It is very encouraging for us to see divers discussing and gaining a deeper understanding of decompression stress while using tools that we developed. Our efforts get validated when we contribute to make diving safer. It tells us we are doing something worthwhile.

Regarding the SurfGF coloring, this was brought up to our attention by divers. They gave us the feedback and we agreed with it. Up to this point, seeing something red in your Shearwater screen has meant that something bad is going on and it requires the diver's immediate attention. For the reasons explained before by others it didn't make sense to have SurfGF appearing in red.

...Also one could ride Ndl on any computer to a point until gas supply becomes an issue.

In theory you could ride NDL and then ride SURFGF when NDL becomes irrelevant (displayed as NDL=99), but that’s akin to Tec targeting GFHi and would be an aggressive N loading and playing with fire given you’re likely using a Rec magnitude for GFHi. Hence this survey .... to see what’s being used/done and the ‘risk’ at depth versus at surface

Tec diving has many risks. As divers we manage those risks. Decompression stress is just one of the many risks. Rec diving has less risks. But if we were to focus only on DCS stress by itself, it is quite possible to have a Rec diver incurring into higher DCS stress than a Tec diver. My GFHi is set at 70. I've been going over my dives in the Shearwater Cloud PDF printouts and the End Surface GF for a lot of them is in the 50s range. My last one was at 45% (see image below - highlighted in yellow). If a Rec diver using Med conservatism (40/85) were to ride the NDL and surface with a GF of 80, his simpler Rec dive is riskier than my more complex Tec dive that ended in 45%; at least in terms of DCS risk.

The key difference is awareness. It is more likely that the Tec diver will be more aware of these nuances. Rec divers might be under the impression that their diving is less risky but in terms of DCS risk that may not be the case. They are simply not aware. This is why I find the Rec context of this thread so encouraging. You guys are bringing awareness to Rec divers.

 

[Jay]

One feature-request idea I was having, based on an earlier comment from @stuartv, was for a new Rec (only) feature to answer this question: Do I have enough gas left to get my SurfGF down to my desired cap/maximum value? (assuming we can also input a target cap/max SurfGF). i.e. a Gas_to_target_SurfGF symbol/number/etc ...

I'm would propose this only for OC Rec mode mainly because of gas management arguments / Tec gas planning.

There's a lot of ways to implement the idea (that's a discussion for later) .... the question is, would that feature be worthwhile?

 

[Shearwater]

Noted and submitted. We'll take it into account. We can't promise implementation or timelines, but will take into account. Thanks again.

 

[Mike1967]

Teric

Don't forget the Perdix

 

[stuartv]

One feature-request idea I was having, based on an earlier comment from @stuartv, was for a new Rec (only) feature to answer this question: Do I have enough gas left to get my SurfGF down to my desired cap/maximum value? (assuming we can also input a target cap/max SurfGF). i.e. a Gas_to_target_SurfGF symbol/number/etc ...

I'm would propose this only for OC Rec mode mainly because of gas management arguments / Tec gas planning.

There's a lot of ways to implement the idea (that's a discussion for later) .... the question is, would that feature be worthwhile?

I appreciate being included in the conversation. But, I’m not sure what I said that contributed to this particular feature request.

What I would really like is:

GTR that reflects all stops that the computer will prompt for. I.e. still show an accurate GTR when in deco. Even if it’s only when you have only 1 gas configured.

And, SurfGF that reflects ascent time (including prescribed stops). I am NEVER going to ascend to the surface instantaneously. A SurfGF that reflects the ascent the computer will expect would be more useful.

 

[Jay]

Agreed re GTR and SurfGF, and that change would align methodology with TTS.

The GTR change might need a new thread for Rec divers in OCRec mode

 

[Fastmarc]

er... what is GTR?