Feedback on recent two-tank and dive limits

[clownfishsydney]

I am not confused. I operate a fully loaded VR3 which is far more challenging to use. My point is with the new recreational diver just starting out. It appears from the original question that the diver was confused with the information displayed on his computer (resulting in some anxiety) and I have seen similar threads elsewhere where divers are confused with what is presented on their computer. Some believe that they need to do a safety stop on top of decompression stops. It may be that the computer manuals may need to be reviewed to meet the needs of the new recreational diver, in particular with dive computers that cross over from NDL with safety stop diving to decompression stop diving.

Orthogonal issues - is that like another issue (for the benefit of other readers)?

I am amazed that anyone is still using a VR3. They were rubbish when they came out, impossible to understand if a buddy showed it to you. The unfortunate people I know who had them 20 years ago got rid of them within a few years.

 

[Kay Dee]

I am amazed that anyone is still using a VR3. They were rubbish when they came out, impossible to understand if a buddy showed it to you. The unfortunate people I know who had them 20 years ago got rid of them within a few years.

They were certainly challenging to use at times and had a fairly steep learning curve if you wanted to take advantage of all their features, and had their fair, or more, share of shall we say 'quirks'. But it was the only kid on the block for quite some years when it came to helium and CCR and they - from the brick to the puck - served me well for well over a thousand(s?) dives and thousands of hours. Given what's available today though I wouldn't have thought they would be of much use save for making good paperweights, as mine do.

 

[Belzelbub]

I have said many things.

Correct. You've said many things. You've said many things that are just flat out wrong.

You continue to say that GFs are confusing for the recreational diver. There is perhaps some truth to this, if the recreational diver were forced to independently enter the GFHi and GFLo numbers without any guidance. With the computer in question (and many others running Buhlmann ZHL-16C) this is not the case.

I've asked this before, and you've repeatedly ignored it. I can only assume that means that the answer does not fit your stance. Why do you feel that choosing between High, Medium, or Low conservatism on a Buhlmann DC is any more confusing for the recreational diver than choosing High, Medium, or Low or 1-5 on a computer running another algorithm?

The only issue in the OPs case was that the diver was not familiar with the adaptive stop. The OP was not confused thinking this was a Deco stop instead of a Safety Stop. You were. The OP was only confused that the Safety Stop was 5 minutes instead of 3. This is clearly explained in the manual, and can even be turned off. That's all this was. In the grand scheme of things, the extra two minutes should be irrelevant. The extra gas used is likely inconsequential, and, as always, the safety stop is optional, so no issue with stopping it at 3 minutes if the rest of the group only did a 3 minute stop.

 

[boulderjohn]

-Gradient Factors (GF) were originally conceived for technical diving, not recreational diving.

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

-GFs concept is complex and abstract, in particular for the basic level recreational diver.
-GFs are confusing for the basic level diver and are a source of distraction.
-The computer incorporating GFs even at the entry level has too many options for the basic level diver.

Recreational divers do not have to understand GFs to use them. All they have to do is pick one of three levels for their conservative setting, exactly the way it is done in all other algorithms. Do you understand the mathematics of how the conservative settings work on the Oceanic computer?

 

[Blackcrusader]

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

Recreational divers do not have to understand GFs to use them. All they have to do is pick one of three levels for their conservative setting, exactly the way it is done in all other algorithms. DO you understand the mathematics of how the conservative settings on the Oceanic computer?

Old Frogman also claimed that the Shearwater would give a deep stop on an NDL dive. This is false.

The Peregrine does not include the feature of adding extra stops at deeper depths (like 15-18 meters) during ascent from a dive within NDL, according to the computer's manual

 

[boulderjohn]

Old Frogman also claimed that the Shearwater would give a deep stop on an NDL dive. This is false.

The Peregrine does not include the feature of adding extra stops at deeper depths (like 15-18 meters) during ascent from a dive within NDL, according to the computer's manual

Oh, I certainly know that. I have replied to that error at length. See post #196 for my last post on that topic. At least he is not still repeating that misinformation.

 

[Kay Dee]

-Gradient Factors (GF) were originally conceived for technical diving, not recreational diving.

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

Was it Eric Baker that first conceived / first stared generating tables with Gradient Factors? If not, who if I may ask?

 

[inquis]

Was it Eric Baker that first conceived / first stared generating tables with Gradient Factors? If not, who if I may ask?

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.)

 

[old frogman]

Interesting flyfishing exercise so far.

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. 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.

 

[Nick_Radov]

Interesting flyfishing exercise so far.

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. 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.

If one of my children wants to learn how to dive then I would sign them up for a GUE Rec 1 class (or equivalent) where a qualified instructor would teach them the basics of decompression theory and dive computer use sufficient for recreational dives within the NDL. Specifically this topic is covered in the Rec 1 course materials document titled "Dive Computer Use: A guideline for the recreational GUE diver". If the instructor certifies them then I would consider that safe enough.

It seems like you want dive computer designers to make their devices so idiot proof that even divers who were badly trained or haven't read the manual can't possibly make a mistake. While there are perhaps some usability flaws in certain specific models that could be improved, overall that is not a reasonable or achievable goal. The particular deco algorithm used or how the conservatism settings are configured doesn't change that reality.