Poll: Algorithm Type - strong views/preferences?

[Dan_P]

I guess I should have said - I have no idea how what you are saying applies to me. In other words I'm confused. The Icon uses a RGBM model and I've been told that it's very conservative - some say too conservative.

Is this an issue for me? - in other words less effective and somethig I need to be aware of? I don't spend much time deep on any dive and most of my time is spent above 60'. Average depths range 20-40 something.​

I really wouldn't worry about it.
If we look at the context of the studies that are being discussed in the deep stop emphasis-debate, they're much deeper and in some of the most referenced cases, wildly aggrevated beyond what is typically seen in actual diving - and even that would be normal technical diving (50m+), not comfortably within rec diving.

 

[victorzamora]

Is this an issue for me? - in other words less effective and something I need to be aware of? I don't spend much time deep on any dive and most of my time is spent above 60'. Average depths range 20-40 something.

At those depths, no....it won't make much of a difference. Not even enough that I'd worry about it if I were you.

The Icon uses a RGBM model and I've been told that it's very conservative - some say too conservative.

So I guess this is the crux of it - It won't really matter much to you, no. However, this statement is still inaccurate for the same reason I was trying to clarify above. RGBM isn't "more conservative" or "too conservative." It might have shorter NDLs on some circumstances, it might have "Conservatism" (poor wording) settings. However, saying it's "too conservative" is saying it's "too safe." This is simply not the case. RGBM is more and more being considered a less safe algorithm. Heck, there's a nickname for it meaning "Really Good Bends Model."

The way I see it is that the primary (sole?) purpose of having a computer is for it to execute a deco algorithm. Why buy a computer if it's not going to be executing a deco model you consider "good" or "best," even if others "aren't too terrible for my diving"? To me, the algo is the primary and vast majority of my motivation for selecting a computer.

Less applicable to you, but:
My issue with RGBM, and other algorithms I consider "subpar," isn't their "conservatism"....as boulderjohn and I have both stated, this is NOT a valid phrase. I'm all for additional conservatism, and I use settings that are currently/predominantly considered "more conservative" than necessary....but it's a variation of parameters that I personally feel adds to my safety.

RGBM is the main algorithm that I dislike. It's proprietary, and so are all of the variants (like Mares RGBM and Suunto RGBM). This means that you can't actually figure out what they do. RGBM and variants also still incorporate (per Mfg comments) outdated ideologies in their algorithms. For example: reverse profiles were thought to be bad. Now that's been mostly-disproven. They still penalize you at semi-random for that. Heart rate and SAC rate are not thought to contribute in a predictable way to deco needs....yet these are still being incorporated into some of the calculations.​

 

[Rollin]

Do you have links or studies about those reverse profiles being not too bad?

 

[dmaziuk]

How about DSAT for safety? My Oceanic is DSAT and I notice not many computers are anymore. Does anyone know why that is? I want a back up watch and I'm thinking I need Oceanic ( like a Geo2) but with the Huish buy out and the difficulty I had recently buying my Pro Plus 2 that replaced my Pro Plus I'm afraid Oceanic might disappear. And if that happens maybe DSAT will disappear as a computer option. Is DSAT outdated and risky or tried and true, like aspirin vs ibuprofen?

DSAT's been developed for repetitive no-stop dives at sea level on air, and after testing they further refined the definition to "4 tanks/day, 6 is certainly too many, for 6 days straight and taking every third day off is highly recommended". (Don't take my word for it, read the 1994 DSAT report.)

I expect among rec divers it's mostly that "RGBM" options are more and cheaper. In terms of actual risk difference between DSAT and "RGBM", it's probably in the third digit after decimal point... unless you're doing 6 tanks/day for a week.

But it was designed specifically for non-stop dives so I don't see why a tech diver would want to use it.

 

[Dr Simon Mitchell]

But it was designed specifically for non-stop dives so I don't see why a tech diver would want to use it.

Correct. Short no-decompression dives with repetitive diving was its purpose. It was designed with a short half life controlling tissue for surface intervals based on the assumption that it would be used by scuba air divers performing short repetitive dives with little slow tissue loading. It seems to have worked OK for this purpose, but I doubt the algorithm would work with long decompression diving; particularly repetitive decompression diving.

Simon M

 

[victorzamora]

Do you have links or studies about those reverse profiles being not too bad?

This is one of the many: Proceedings of Reverse Dive Profiles Workshop.

Essentially, there is no difference. They put some caveat in there to appease the uber-vocal minority that still held firmly to their beliefs. DAN had an article here on it as well, stating essentially the same thing.

Intrestingly, the recommendation for it was of unknown origins. The main theory, however, is that it had to do more with gas planning and logistics than deco physiology.

 

[dmaziuk]

Intrestingly, the recommendation for it was of unknown origins. The main theory, however, is that it had to do more with gas planning and logistics than deco physiology.

VPM's "crushing pressure", as I understand it, is less on reverse profiles resulting in bigger bubbles and thus more deco. No idea if that came before or after the "reverse profiles bad" meme though.

 

[victorzamora]

VPM's "crushing pressure", as I understand it, is less on reverse profiles resulting in bigger bubbles and thus more deco. No idea if that came before or after the "reverse profiles bad" meme though.

It came after. The "reverse profiles bad" seems to have roots back into the early 70s. As far as I can tell, it was a 1972 PADI manual that stated the suggestion of diving your deepest dive first. VPM wasn't conceived until the mid/late 80s, I think.

 

[boulderjohn]

Just playing with semantics; you could argue that stopping deeper and spending more time shallow would technically be a more "conservative" approach, but a less "effective" one.
...
If that is the case, then added "conservatism" is compatible with deeper first stops, logically speaking.

Similarly, if you eat a mammoth hot fudge sundae and then don't eat anything else for 3 days, it could be argued that mammoth hot fudge sundaes are part of a calorie reduction diet plan.

 

[boulderjohn]

Do you have links or studies about those reverse profiles being not too bad?

This is one of the many: Proceedings of Reverse Dive Profiles Workshop.

The reverse profile workshop essentially asked the opposite question--what is the evidence that reverse profiles are bad? It turns out there is no such evidence.