Question Shearwater Teric (GF40/85) goes into DECO on first dive (max depth 25.9m, avg depth 17.6, duration 48mins)

[gmerick]

Perdix 2 has been set to 45/90 for most of a year.
GFlo 45 because if I do get in a situation where I extend the dive somewhat past NDL, I want the computer giving reasonably safe advice. I have noticed the start of getting narc-ed on some of my longer deeper dives. I don't want to overthink things in that situation.
I've also noticed itchy skin on my chest when surfacing at GF99>85 a couple times. No blotches, but it reminds me I'm older and heavier than a navy test diver. I should set GFhi to 80, and be done with it, but I tend to do longer dives, and I got fed up with haptic feedback harshing my mellow during the early deep part of a dive.
Typical shore dive for me is sidemounting a pair of AL80's with air, or a pair of 120's with EAN32. I'm down for 150-210 minutes, and it works out quite well, as my shore dive sites involve a 500+ meter surface swim-out, and that's a bit much for only a small single tank dive. I'll eat up my NDL at 20+ meters then work my way back along and on top of the wall and back to my entry. The last hour or so is spent at 10 meters, so GF99 is 70 or below long before ending the dive.
What I'm saying is, I've learned the Perdix settings, configured GF's to my physiology and dive profile, and set the display to have GF99, GFsurf, and ascent rate readily visible.

 

[grantmac]

Perhaps. I feel free to make a direct ascent to the surface below a GF high of 95 if need be. I'm not sure I would feel the same making a direct ascent to the surface in deco at a GF high of 80. I guess I should be able to figure that out with my SurfGF. We do what we are comfortable with and what has served us in the past.

I think you need to review how GFs work based on this response.

 

[dmaziuk]

I think you need to review how GFs work based on this response.

Think again. Craig is wrong in that he could have Surf GF displayed and then he'd know what the risk of direct ascent to surface would be regardless of his GF High setting. However without Surf GF, if you go into deco at GF High 95, you know you're way too close to clinical DCS for comfort. At GF High 80: maybe yes, maybe not so much.

 

[eja12a]

Perhaps. I feel free to make a direct ascent to the surface below a GF high of 95 if need be. I'm not sure I would feel the same making a direct ascent to the surface in deco at a GF high of 80. I guess I should be able to figure that out with my SurfGF. We do what we are comfortable with and what has served us in the past.

There’s a fundamental misunderstanding of deco here. If your SurfGF is 90, for example, and you choose to surface, you have the same nitrogen loading regardless of what gradient factors you are using. If you’re running a GF high of 95 you’d be under your NDL, and so you “don’t have to do a safety stop” and can surface (although your really should). If you are using GFhigh of 70, you’ll have several minutes of deco. If you choose to skip this deco, and surface, the end result is the same. You are surfacing, either way, with the same tissue loading. And depending on YOUR views on how conservative you want to be, and what you set your GFs to, you are either within your NDL or you are skipping deco. It’s both. At the same time. Schrödinger's deco if you will.

 

[scubadada]

There’s a fundamental misunderstanding of deco here. If your SurfGF is 90, for example, and you choose to surface, you have the same nitrogen loading regardless of what gradient factors you are using. If you’re running a GF high of 95 you’d be under your NDL, and so you “don’t have to do a safety stop” and can surface (although your really should). If you are using GFhigh of 70, you’ll have several minutes of deco. If you choose to skip this deco, and surface, the end result is the same. You are surfacing, either way, with the same tissue loading. And depending on YOUR views on how conservative you want to be, and what you set your GFs to, you are either within your NDL or you are skipping deco. It’s both. At the same time. Schrödinger's deco if you will.

Thanks, a few people have pointed this out.

Please see my post #76. I am diving one computer running Buhlmann that has SurfGF and a second computer running DSAT. I find my strategy the simplest way to dive my equipment. I have considerable experience with this setup.

Question Post in thread 'Shearwater Teric (GF40/85) goes into DECO on first dive (max depth 25.9m, avg depth 17.6, duration 48mins)'

Apr 1, 2025

Probably minor quibble, but then why not dive 80/80? At least then you'll know how long you'll have to hang (you probably know already, from experience).

Good question.

I have been diving a computer running DSAT since 2002, 2,400 dives, and one of my computers is still running DSAT (a 2010 Oceanic VT3). I am very comfortable with this deco algorithm. I did not start diving Buhlmann until 2016 when I bought a Dive Rite Nitek Q, to learn this deco algorithm. The Nitek Q does not have SurfGF or GF99. I have had my Teric since 2019, about 660 dives, and have used SurfGF and GF99...

• scubadada

 

[dmaziuk]

Schrödinger's deco if you will.

I approve this message.

No model comes with a 100% guarantee of no clinical DCS so it's schroedindeco every time: you have to surface to find out if you get an "undeserved" hit or not.

 

[tursiops]

I approve this message.

No model comes with a 100% guarantee of no clinical DCS so it's schroedindeco every time: you have to surface to find out if you get an "undeserved" hit or not.

Nah. The implication of your statement (dead or alive) is a 50-50 chance. Nonsense.
That the model is not 100% accurate does not suddently mean its information is useless.
YOU know that; why do you say otherwise?