Past NDL. And then this???

[Slow]

Thanks everyone, especially the OP, for this discussion. I have taken the OP's dive logs and pulled them into Subsurface in order to learn as much as I can. I believe I set Subsurface to calculate using 30/70 (Shearwater default I believe and what I'm diving currently). I'm a new user on Subsurface...am I reading this right when I see the green stuff at the top indicating a ceiling? Does any green at the top at all mean the diver would see "deco" on their computer if their computer was set to 30/70?

If so, I'm seeing 12 of the included 15 dives having some "deco." The "worst" one being the first dive the day after the dive being discussed so far here...

Am I reading all this right?

 

[DevonDiver]

I notice curious effects and trends as new technology and tools become available to the diving facilities public.

In this instance:

Novice Diver + Subsurface App = Decompression Science Expert

 

[Slow]

I notice curious effects and trends as new technology and tools become available to the diving facilities public.

In this instance:

Novice Diver + Subsurface App = Decompression Science Expert

Should I interpret this response as implying that I shouldn't be trying to learn using Subsurface until I am a certified Deco Science Expert? I actually was just trying to see if I could learn something about how I dive with my computer...not claiming any level of expertise.

 

[RainPilot]

Thanks everyone, especially the OP, for this discussion. I have taken the OP's dive logs and pulled them into Subsurface in order to learn as much as I can. I believe I set Subsurface to calculate using 30/70 (Shearwater default I believe and what I'm diving currently). I'm a new user on Subsurface...am I reading this right when I see the green stuff at the top indicating a ceiling? Does any green at the top at all mean the diver would see "deco" on their computer if their computer was set to 30/70?

If so, I'm seeing 12 of the included 15 dives having some "deco." The "worst" one being the first dive the day after the dive being discussed so far here...

Am I reading all this right?

At the point of a deco obligation being incurred you would see a green ceiling line up top and the computer if set to same as Subsurface would show that depth as a ceiling.

Bear in mind that 30/70 is WAAAY more conservative than any rec computer setting especially on a first dive. A GF Hi of 85-95 would more closely reflect a DSAT/ PZ / RGBM type DC. Some of them even run up to an equivalent of 100+

 

[KeithG]

I think the discussion was born because the profile given by the OP's DC varies significantly to that predicted by something like subsurface.

The behaviour seems to match pretty close to Subsurface Buhlmann 30/90.

 

[Edward3c]

Should I interpret this response as implying that I shouldn't be trying to learn using Subsurface until I am a certified Deco Science Expert? I actually was just trying to see if I could learn something about how I dive with my computer...not claiming any level of expertise.

No. What it means is Subsurface does not replicate the computer's algorithm, including added penalty settings for ignoring warnings about exceeding no-stop limits. Therefore, a comparison between the two is meaningless.

 

[KeithG]

No. What it means is Subsurface does not replicate the computer's algorithm, including added penalty settings for ignoring warnings about exceeding no-stop limits. Therefore, a comparison between the two is meaningless.

Interesting idea. Do we know of any computers that penalize just for going into deco? I realize there are some (many?) that will lockout if you ignore a deco obligation.

I have been told that Suuntos will shorten your NDL on a dive if your surface interval is less than 60 minutes.

 

[DevonDiver]

I actually was just trying to see if I could learn something about how I dive with my computer...

Pumping dive data incoherently into Subsurface and 'marvelling' at the varied outcomes isn't a particularly good education without having some context on why different algorithms create different results.

In the case of this thread, the obvious learning advantage would come from doing a little research and reading on the RGBM algorithm.

RGBM isnt an open source algorithm (like Buhlmann or VPM) but there's still a plethora of online resources and articles describing it.

What I'd suggest, in respect of learning benefit, is to RESEARCH and READ before trying to EXPERIMENT.

 

[Centrals]

If you do not like the car that you are driving then change it if you can afford one. But the new car won't make you a better/safer driver.
The OP ignored/misunderstood the instruction given by his dive computer and paid the price(very long deco obligation).
No algorithm is 100% safe!

 

[KeithG]

I think there's an important distinction between computers that implement algorithms which:

1) Are intended to best facilitate no-stop diving within typical recreational parameters (multi-day repetitive diving in shallow water with minimal surface interval). That also provide emergency decompression should the no-stop limits be accidentally exceeded. Emergency decompression may prioritise simplicity over efficiency, and may favor shallow deco stops where recreational divers will use least gas and can easily CESA etc if gas were fully consumed while attempting the deco.

Basically, KISS deco to get muppets safely out of the water when they screw up...

2) Are intended to best facilitate technical decompression diving, where dive repetition, surface intervals and other factors are subservient to the dive undertaken (not vice versa). Decompression is planned and calculated for optimal efficiency with an assumption that complex ascent plans are fine, comprehensive gas planning has occurred and there are no issues on that basis.

Basically, complex deco to get highly supersaturation saturated divers to the surface with a reasonable degree of confidence.

Interesting distinction. I am not sure that there is such a clear line?

I have a "sport" computer that I claim matches 1) above. It's manual says "do not do deco" and the computer does not support planning of deco dives. The manual has lots of warnings about staying above 130 feet and not going into deco.

I also have a deco computer that matches 2) above. It is advertised as a sophisticated deco planning computer.

They are from the same manufacturer and both run the same algorithm. They both support deco dives and behave exactly the same in my pressure chamber tests.

Maybe it makes sense to separate the world into "good" and "less good" decompression algorithms based upon your intended use?