Feedback on recent two-tank and dive limits

[inquis]

they have just completed their basic open water course

Do you understand that class covers computer use?

Initially, I'd say, "When this number [NDL] hits 5, start to shallow up." They should also be checking their gas pressure, and that will typically be the limiting factor in my experience with new OW divers.

 

[Kay Dee]

Nope. It applies to the entire Buhlmann algorithm. It was used early on by tech divers. So what? What difference does this make?

old frogman:
Conclusion, Erik Baker did not have recreational diving in mind when he developed gradient factors.

Wasn't OF opining that using GF was not suitable for new divers let alone recreational diving?

Yes, gradient factors were conceived of by Baker to

1) add conservatism in the surfacing tissue loading -- applicable to both NDL and mandatory stop diving​

2) increase the depth of the first stop on a mandatory stop dive (to better align with the bubble models in vogue at the time)​

(That is why there are 2 numbers and the first number does apply to NDL diving.)

I thought it was Eric. And if he is, and ‘they are’, the person / tables I am thinking of, then @old frogman and @Blackcrusader are correct, they were originally, repeat originally made specifically for technical diving.

Let me clarify; 'back in the day' (94/95?) I was staying with deep caver Larry Green up in Cave Country and Eric was there doing his thing working on what at the time were his prototype tables. (It was rather funny actually, he was so protective of his 'baby' that he would sit at his laptop with a sheet covering his head and laptop so no one else in the room could see exactly what was doing with the tables. I s%&t you not!) And those tables he was working on at the time were specifically for deep cave dives. He offered to cut us some tables for OC deep dives we were doing, and proposed to do (USS Atlanta) in the Solomon's, but we only used them once (on Atlanta) as riding that long curve up with all those incremental stops (from very deep) just ate up the gas. And we just didnt have the support then to have that much OC gas in water as we had to carry all our own until very shallow, so we fell back on what at the time were the tried and trusted tables that Kevin Gurr had come up with, i.e. ProPlanner IIRC. So while Eric's tables, at the time, may have been good for deep cave diving where you could stage deco cylinders along the way, they were not so much at the time for 'vertical ascent' deep wreck dives in 'remote' locations.

So if, repeat if those tables were the early Gradient Factor tables - which it was my understanding they were, or became the GF tables - then they were definitely conceived for technical dives / divers to begin with, although I do realise that if they are the 'same' tables there has been a lot of tweaking (no, not twerking!) since then, especially given the fact that the deep stop 'theory' prevalent at the time has since, shall we say, fallen out of favour.

 

[JMarc]

Excepted the range of depths and durations (and the effects on repetitive dives determined by assumptions about those), what makes a deco model a rec or tech one? I don't see the relevance of such classification for determining the deco obligation or absence of them for a given dive profile.

 

[Belzelbub]

Let' look at a scenario. You have a son or daughter somewhere between 16 and 18 years of age and they have just completed their basic open water course, and you are going to give them an entry level Shearwater Peregrine dive computer or one similar with Buhlman and GF algorithm.

Perfect. I can relate to this very well. I have two daughters, and both are divers. Youngest is still in that age range. When they first got certified, I absolutely would have gotten them a Peregrine TX. Unfortunately, it hadn't been released yet, so they did their courses and first few dives with Oceanics running DSAT. I have since bought them both Peregrine TXs.

What precautions are you likely to take to make him or her safe when using this dive computer? Or are you just going to give him or her the dive computer and just say read the user manual and figure it out.

What I did is help them to set up their computers and Shearwater Cloud. For familiarity, I had them use the same layout and conservatism settings as I use, and showed them how to navigate the computer including changing gas mix, etc.

There is nothing special they need to be worried about by simply running Buhlmann vs. DSAT. Honestly, it's just easier. The UI on the Peregrines are so much better than the UI on the Oceanics they were using. From there, it's just a quick tutorial about what each of the sections of the screen are for, and what the information means. Exactly like I did when I showed them how to dive with their Oceanics.

Despite your claims to the contrary, there is nothing mysterious or dangerous about their Peregrine TXs running Buhlmann as compared to the Oceanics running DSAT. Big difference is that they won't need to consult the manual each time they want to change a setting. It's just that much more intuitive.

 

[boulderjohn]

What precautions are you likely to take to make him or her safe when using this dive computer? Or are you just going to give him or her the dive computer and just say read the user manual and figure it out.

How would the precautions taken for a Buhlmann computer be any different from the precautions taken for a DSAT, RGBM, or any other type of computer?

 

[boulderjohn]

I thought it was Eric. And if he is, and ‘they are’, the person / tables I am thinking of, then @old frogman and @Blackcrusader are correct, they were originally, repeat originally made specifically for technical diving.

Are you saying that the GF system he created is accurate for technical diving but not accurate for NDL diving? Please explain how this would make one iota of difference?

 

[Kay Dee]

Are you saying that the GF system he created is accurate for technical diving but not accurate for NDL diving? Please explain how this would make one iota of difference?

Not at all. Where do you get that from? Just letting you - and any others that might not have been aware of GF's actual origins - that both @old frogman and @Blackcrusader were right in saying that the GF tables as originally conceived by Baker were for technical diving.

 

[boulderjohn]

Not at all. Where do you get that from? Just letting you - and any others that might not have been aware of GF's actual origins - that both @old frogman and @Blackcrusader were right in saying that the GF tables as originally conceived by Baker were for technical diving.

And he was saying that to prove that GHFs should not be used for recreational diving.

 

[Kay Dee]

And he was saying that to prove that GHFs should not be used for recreational diving.

Well that is his prerogative, although I do not necessarily agree with what he says with regards to "should not be used for recreational diving". But that doesnt make him any less right in saying what GFs were originally conceived for though.

 

[Blackcrusader]

And he was saying that to prove that GHFs should not be used for recreational diving.

Yes Old Frogman was but not I. I write that GF's are great for NDL diving as well as DECO diving.