Safety stop feature request

[KenGordon]

As far as I am concerned, a dive is not a deco dive if it does not exceed m-value. You can stop and offgas from m-value to a lower surface gf for conservatism. That greater conservatism, to me, is a safety margin and the stop is a safety stop.

So dive 99/99 and go directly to the surface. Add a fixed length safety stop for margin. If you are not prepared to routinely go to the surface it is a deco dive.

If your stop length depends on tissue loadings it is a deco stop.

You are ignoring the issue the boat has. It has decided for whatever reasons it does not want deco dives being done. You are doing deco dives and trying to pretend you are not by tweaking one set of numbers to make a long NDL while actually diving another set of numbers to a lower, conventional, limit with actual deco stops.

 

[CWK]

So dive 99/99 and go directly to the surface. Add a fixed length safety stop for margin. If you are not prepared to routinely go to the surface it is a deco dive.

If your stop length depends on tissue loadings it is a deco stop.

You are ignoring the issue the boat has. It has decided for whatever reasons it does not want deco dives being done. You are doing deco dives and trying to pretend you are not by tweaking one set of numbers to make a long NDL while actually diving another set of numbers to a lower, conventional, limit with actual deco stops.

For the last 2 years I have been diving recreational with:
1. Teric on my left wrist set to Rec mode 99/99
2. Perdix on my right wrist set to Tec mode 75/75

For all recreational dives, my Teric on my left wrist has never showed that I was in deco because I have never exceeded m-value. For quite a few dives, Perdix on my right wrist has showed that I am in deco even though I have not exceeded m-value. It is not correct that Perdix is showing that I am in deco just because my surface gf has reached 76. It cannot be that my left hand is never in deco, whereas my right hand sometimes is. The error is that Perdix shows deco when m-value has not been exceeded. Am I prepared to routinely surface when my Perdix shows that I am in deco because my surface gf is 76? Absolutely! Am I prepared to routinely surface when my Perdix shows that I am in deco and my surface gf is 85. Yes, I am because I am not in deco. My preference is to offgas until my surface gf is 75 or less. To me, this is an extremely conservative setting. I can use a more aggressive setting for recreational diving, but that is not my preference.

Recreational diving is non deco diving. Computers can incorrectly showing deco when gf high is exceeded but not m-value. This does not matter in tec diving because m-value will be exceeded shortly after gf high is exceeded, but is an error in recreational diving where m-value is not exceeded.

 

[KenGordon]

For the last 2 years I have been diving recreational with:
1. Teric on my left wrist set to Rec mode 99/99
2. Perdix on my right wrist set to Tec mode 75/75

For all recreational dives, my Teric on my left wrist has never showed that I was in deco because I have never exceeded m-value. For quite a few dives, Perdix on my right wrist has showed that I am in deco even though I have not exceeded m-value. It is not correct that Perdix is showing that I am in deco just because my surface gf has reached 76. It cannot be that my left hand is never in deco, whereas my right hand sometimes is. The error is that Perdix shows deco when m-value has not been exceeded. Am I prepared to routinely surface when my Perdix shows that I am in deco because my surface gf is 76? Absolutely! Am I prepared to routinely surface when my Perdix shows that I am in deco and my surface gf is 85. Yes, I am because I am not in deco. My preference is to offgas until my surface gf is 75 or less. To me, this is an extremely conservative setting. I can use a more aggressive setting for recreational diving, but that is not my preference.

Recreational diving is non deco diving. Computers can incorrectly showing deco when gf high is exceeded but not m-value. This does not matter in tec diving because m-value will be exceeded shortly after gf high is exceeded, but is an error in recreational diving where m-value is not exceeded.

The GF scheme allows you to choose your M values. You have chosen a lower set on your Perdix than on your Teric. The Perdix is correctly indicating that you are in deco. You get to make a (hopefully) educated guess as to what m-value to use.

The whole point of GF Is that 100/100 is too aggressive.

Now 75/75 sounds pretty conservative so you are left with no real idea where you are, other than SurfGF, between the two. You can’t really tell what your TTS is for whatever actual SurfGF you decide to target.

You are also gaming the model. Gaming models is for mugs. You optimise outcomes based on an approximation of reality and not reality.

 

[Tribal]

Am I prepared to routinely surface when my Perdix shows that I am in deco because my surface gf is 76? Absolutely! Am I prepared to routinely surface when my Perdix shows that I am in deco and my surface gf is 85. Yes, I am because I am not in deco.

You do realise that being into deco isn’t an exact sience? The M-line is an estimate to be able so surface in a safe way. To be even safer people use the gf settings. If you set it to 75 you will be “in deco” once you go past that value.
Pretty sure there isn’t much difference in surfacing with a gf of 99 vs 101.

 

[CWK]

You do realise that being into deco isn’t an exact sience? The M-line is an estimate to be able so surface in a safe way. To be even safer people use the gf settings. If you set it to 75 you will be “in deco” once you go past that value.
Pretty sure there isn’t much difference in surfacing with a gf of 99 vs 101.

Yes. I am quite aware that it is not an exact science. That’s why I use a conservative setting of 75 to get well away from 99, or 95, or 90.

 

[CWK]

The GF scheme allows you to choose your M values.

This is were we differ. To me, m-value is set by the algorithm such as Buhlman’s zhl 16c. The gf high allows you to set a conservatism or safety margin away from m-value. But to set a conservative value such as 75 and have the computer say that you are in deco because your surface gf is 76 is, to my mind, incorrect and erroneous.

 

[scubadada]

Do computers other than Shearwater give you SurfGF?

 

[tbone1004]

@CWK my issue with this is that you are in fact in deco, so why not just own up to it and be in deco? Dive the profile you want to dive and just let it go. It is quite easy to raise the GF-Hi while you're on deco if you need to get out earlier, but I don't see why you are trying to lie to yourself and the computer about what you're doing. If they had the safety stop set to GF instead of time, you still wouldn't know what it was until you got to the safety stop because as you said, it's not a deco dive so why would it show you TTS with the adjusted safety stop? You're already in tec mode to get custom GF's, so why not just set it to what you want for GF so your TTS is correct and if you want to go up early, you're looking at the surfGF anyway. If you violate deco, just hit confirm and the notification goes away so the boat would have no idea that you blew deco. I just don't understand what aversion to the term "deco" you have when you are very clearly doing deco dives.

 

[CWK]

@CWK my issue with this is that you are in fact in deco, so why not just own up to it and be in deco? Dive the profile you want to dive and just let it go. It is quite easy to raise the GF-Hi while you're on deco if you need to get out earlier, but I don't see why you are trying to lie to yourself and the computer about what you're doing. If they had the safety stop set to GF instead of time, you still wouldn't know what it was until you got to the safety stop because as you said, it's not a deco dive so why would it show you TTS with the adjusted safety stop? You're already in tec mode to get custom GF's, so why not just set it to what you want for GF so your TTS is correct and if you want to go up early, you're looking at the surfGF anyway. If you violate deco, just hit confirm and the notification goes away so the boat would have no idea that you blew deco. I just don't understand what aversion to the term "deco" you have when you are very clearly doing deco dives.

You and I are talking about different things. I have changed gf high at the end of a tec dive before, and as you say, it is easy.

I have no aversion to the term deco. To me, I’m not in deco until I have exceeded m-value. If I have not exceeded m-value, the computer should not tell me that I’m in deco.

 

[Rechno]

So, if you plan a Deco Dive you use 99/99 as GF Setting?