Safety stop feature request

[CWK]

So if I understand you correctly, you want a countdown to a chosen Surf GF?
But what I don't really understand is what you want to accomplish with that in real life? If you set 99/99 as GF, your NDL will be determined accordingly. If I understand you correctly you are now looking for the optimum safety stop?

Since you want to do recreational dives (no mandatory stops), I'm going to assume 40 meter as a depth limit. If I play with SubSurface and use a 40 meter square profile on air (gf 99/99) I get a max NDL of 10 minutes (10 minutes and 10 seconds puts you in deco). If you ascent in 3,5 minutes (let's call that 4) to 5 meter, you arrive at SS depth with a Surf GF of 92%. When you do your traditional safety stop (3 minutes, 5 meter), you have a surf GF of 73%.
If you really want to go at 75%, you can go to the surface 10 seconds earlier....
Seems like a lot of hassle (and risk of user error) to lengthen your dive with less than 2 minutes in total, just to not break the boat rules.

Yes. Setting gf high and low to 99/99 gets NDL effectively to m-value.

I am looking for a safety stop setting based in surface gf. I am asking for a setting to be able to do this. Say for example that my desired surfacing gf is 75 and my current surface gf is 50, I’d want the computer to say that I don’t need to do a safety stop. However, if my desired surfacing gf is 75 but my current surface gf is 99, I’d want my computer to work out the safety stop required to bring my surface gf down to 75. I’m looking for a safety stop setting that takes into account my current surface gf and my desired surfacing gf. I’m looking to move away from a fixed time safety stop that ignores my current surface gf and is oblivious to where my surface gf will be at the end of the safety stop.

 

[boulderjohn]

I really wish agencies would make a computer course or add it to AOW.

A number of agencies have had computer versions of the OW course for years. The problem is that they cannot teach specifics of individual computer usage because they cannot predict what specific computer the student will use as a certified diver.

The PADI course teaches generic things that computers will do and tells students to learn how their specific computer does them. That includes, for example, staying within NDL and following its guidance in dong appropriate deco if the diver exceeds that NDL. The PADI course includes a simulator showing how a generic computer reacts to changes in depth over time, etc.

 

[rsingler]

So if I understand you correctly, you want a countdown to a chosen Surf GF?
But what I don't really understand is what you want to accomplish with that in real life? If you set 99/99 as GF, your NDL will be determined accordingly. If I understand you correctly you are now looking for the optimum safety stop?

Since you want to do recreational dives (no mandatory stops), I'm going to assume 40 meter as a depth limit. If I play with SubSurface and use a 40 meter square profile on air (gf 99/99) I get a max NDL of 10 minutes (10 minutes and 10 seconds puts you in deco). If you ascent in 3,5 minutes (let's call that 4) to 5 meter, you arrive at SS depth with a Surf GF of 92%. When you do your traditional safety stop (3 minutes, 5 meter), you have a surf GF of 73%.
If you really want to go at 75%, you can go to the surface 10 seconds earlier....
Seems like a lot of hassle (and risk of user error) to lengthen your dive with less than 2 minutes in total, just to not break the boat rules.

That's exactly what he's after. Or at least what I'm after. I want as long a dive as I can do and still surface with a GFHi (in my case) of 70. But diving 70/70 crimps that. And it's not just two minutes. For most rec dives done in the 80-100 foot range, diving GF Hi70 is a more substantial time penalty, air permitting. What I think we're really talking about is using a reverse profile for Rec dives.
Where it gets sketchy is when he asks about wanting to know how long to extend his "safety stop" when his SurGF is showing 102, knowing he will hit 15 feet at 90. That's really a deco dive with a single 15' stop.

But I'm still with him. If you believe safety lies in a lower GF Hi, then wanting to offgas for as long as you need to, to get there, is why I've come up with my TTS workaround. And like it or not, the No-Deco prohibition is alive and well on most boats. So how do you get the most out of your $3,000 vacation safely?
I think it's a legitimate question, even if @CWK's notion of when you're "in deco" isn't quite mainstream.

So, @Shearwater, how about allowing reverse profiles in Rec Mode, like Subsurface does? We know the calculations can be made. There's my feature request.

 

[NAM001]

A number of agencies have had computer versions of the OW course for years. The problem is that they cannot teach specifics of individual computer usage because they cannot predict what specific computer the student will use as a certified diver.

The PADI course teaches generic things that computers will do and tells students to learn how their specific computer does them. That includes, for example, staying within NDL and following its guidance in dong appropriate deco if the diver exceeds that NDL. The PADI course includes a simulator showing how a generic computer reacts to changes in depth over time, etc.

I agree john the idea of teaching computers is not a teaching of specific computers but how they work. what they measure, the results they provide, the assumptions they operate on. how is ndl computed, things they can not take into condsideration, how to deal with altitude diving. what are GF's or other note worthy items relating to computers with their limitations etc. . Training such that when they get a computer of their own they have an basic understanding what they are doing when they set it up and the things to consider prior to a dive that relates to computers.

 

[NAM001]

I'm sure Scubadada will provide more info, but that article is quite misleading. The PZ+ and ScubaPro implementations of Buhlmann have undocumented and proprietary modifications of Buhlmann. The more correct statement is that almost no manufacturers other than Garmin and Shearwater use Buhlmann such that you know what you are getting. Anybody else uses the name as a marketing gimmick more than an explanation.

that is good i nfo

 

[NAM001]

So if I understand you correctly, you want a countdown to a chosen Surf GF?
But what I don't really understand is what you want to accomplish with that in real life? If you set 99/99 as GF, your NDL will be determined accordingly. If I understand you correctly you are now looking for the optimum safety stop?

Since you want to do recreational dives (no mandatory stops), I'm going to assume 40 meter as a depth limit. If I play with SubSurface and use a 40 meter square profile on air (gf 99/99) I get a max NDL of 10 minutes (10 minutes and 10 seconds puts you in deco). If you ascent in 3,5 minutes (let's call that 4) to 5 meter, you arrive at SS depth with a Surf GF of 92%. When you do your traditional safety stop (3 minutes, 5 meter), you have a surf GF of 73%.
If you really want to go at 75%, you can go to the surface 10 seconds earlier....
Seems like a lot of hassle (and risk of user error) to lengthen your dive with less than 2 minutes in total, just to not break the boat rules.

you have a good point here. my view of it is that why do the traditional SS for 5 minutes if 2 or 3 will suffice. although all rec dives should notr require a SS by definition one cann ot exclude the ones that did the ascent at 40 fpm instead of the calculated 30 fpm rate. the safety stop then serves a purpose bopy providing a method for countering an unexpected event. even with that things like GF and I am sure other metrics can be used to define the NEEDED ss time other than hard values of 3 and 5.

 

[wstorms]

well and if you follow PADI definitions (to pick a common recreational example), a SS is required when diving deeper than 30 meter / staying till you're close to NDL.
Also, in my experience, when a boat issues rules, it is usually max depth, no deco and max time. So I wonder what profile you would dive that gives you a significant benefit over a traditional SS, while still being within the boat rules (including max time)?
And when would you consider something significant? 20 seconds shorter? 1 minute?

 

[NAM001]

That's exactly what he's after. Or at least what I'm after. I want as long a dive as I can do and still surface with a GFHi (in my case) of 70. But diving 70/70 crimps that. And it's not just two minutes. For most rec dives done in the 80-100 foot range, diving GF Lo70 is a more substantial time penalty, air permitting. What I think we're really talking about is using a reverse profile for Rec dives.
Where it gets sketchy is when he asks about wanting to know how long to extend his "safety stop" when his SurGF is showing 102, knowing he will hit 15 feet at 90. That's really a deco dive with a single 15' stop.

But I'm still with him. If you believe safety lies in a lower GF Hi, then wanting to offgas for as long as you need to, to get there, is why I've come up with my TTS workaround. And like it or not, the No-Deco prohibition is alive and well on most boats. So how do you get the most out of your $3,000 vacation safely?
I think it's a legitimate question, even if @CWK's notion of when you're "in deco" isn't quite mainstream.

So, @Shearwater, how about allowing reverse profiles in Rec Mode, like Subsurface does? We know the calculations can be made. There's my feature request.

educate me here what does GF lo have to do with NDL dives? am I missisng something. As I under stand It gf lo is moot until NDL is over stayed and only the gf hi is of value of being used. That for a rec ndl dive there is no difference between 30/70 and 70/70. that gf hi of 70 adjusts the NDL so you can directly surface and hit the surface with a GF of 70 with no stops assuming you did not exceed 70 on the ascent. 30 being first stop and 70 being the max allowed GF through out the dive. Max or the highest GF is expected as you hit the surface.

 

[wstorms]

So how do you get the most out of your $3,000 vacation safely?

Wanted to pick up on this earlier but forgot; I would rather extend the SS for as long as possible without annoying the other dives on the boat too much. Be the first in, last out but still within a few minutes of each other so nobody really has to wait.
Safety wise I am happy with the SS, and everything extra makes me extra fit for the next dive.

 

[scubadada]

Yes. Setting gf high and low to 99/99 gets NDL effectively to m-value.

I am looking for a safety stop setting based in surface gf. I am asking for a setting to be able to do this. Say for example that my desired surfacing gf is 75 and my current surface gf is 50, I’d want the computer to say that I don’t need to do a safety stop. However, if my desired surfacing gf is 75 but my current surface gf is 99, I’d want my computer to work out the safety stop required to bring my surface gf down to 75. I’m looking for a safety stop setting that takes into account my current surface gf and my desired surfacing gf. I’m looking to move away from a fixed time safety stop that ignores my current surface gf and is oblivious to where my surface gf will be at the end of the safety stop.

Some of us have been doing this manualy for some time. I happen to dive a GF high of 95, to approximately match a computer running DSAT. I have SurfGF on my home screen. When I get to my SS, I stay there until my GF is what I want. The time to decrease your GF to goal is going to depend on your SS depth, 10, 15, 20 feet, similar to deco time and how close or far you are from your ceiling.

You want this automated so you know your SS time in advance?

I am sometimes on boats with an explicit rule of no deco. However, I have never been asked if I was in deco or asked to see my computer. If I were to sit at 10-15 feet for considerably longer than 5 minutes, that might raise suspicion, whether I was satisfying a deco obligation or waiting for my GF to fall to my goal. In general, I have found operators to have a little flexibility