Multi deco vs V-planner vs GUE Deco Planner

[tbone1004]

Bruce developed that model for a very, very select audience. If your job doesn’t involve the possibilities of deep dives to recover a nuclear weapon and then immediately needing to fly in a mc-130 you are probably not that audience. It might well work better for that need, but as a general purpose model it’s been shown to be not ideal.

and yet he and NAUI promoted it as a superior model for diving and continue to do so otherwise they wouldn't be used in their literature...

 

[Wibble]

and yet he and NAUI promoted it as a superior model for diving and continue to do so otherwise they wouldn't be used in their literature...

Meanwhile the rest of the world has standardised on Buhlmann + GF

 

[rongoodman]

but as a general purpose model it’s been shown to be not ideal.

Shown not to be ideal because of specific issues with RGBM, or problems with bubble models and deeper stops in general? Leaving aside the marketing hype of Suunto and others, has it ever had much use in the recreational community? I remember an aftermarket implementation for one of the Liquivision computers and vaguely recall a desktop version and tables.

 

[dmaziuk]

Shown not to be ideal because of specific issues with RGBM, or problems with bubble models and deeper stops in general? Leaving aside the marketing hype of Suunto and others, has it ever had much use in the recreational community? I remember an aftermarket implementation for one of the Liquivision computers and vaguely recall a desktop version and tables.

What do you mean by "much use"? -- Until recently entry-level computers came in RGBM or DSAT/PZ+, with the former usually being the cheaper option. I've seen a lot of Suuntos on recreational dive boats.

 

[huwporter]

I thought it was common folk knowledge that "Suunto RGBM" isn't actually RGBM - with the understanding that regular wrist computers aren't even close to being capable of running the full RGBM algorithm; that requires access to more serious computing power - but is instead a standard dissolved gas compartment model with some tweaks to make it do deep stops and excessive deco times, and a license fee paid to BW for the name.

I remember a list thread from the early 2000s where BW was challenged on this and smokescreened something about 'folding' RGBM into the Suunto algorithm, but it was never clear what exactly this meant. Suunto, of course, aren't saying.

What did Uwatec Aladdins run?

Edit: the Wikipedia article on RGBM describes Suunto RGBM as "Some manufacturers such as Suunto have also devised approximations of Wienke's model. Suunto uses a modified haldanean nine-compartment model with the assumption of reduced off-gassing caused by bubbles." Reduced gradient bubble model - Wikipedia

 

[rongoodman]

I mean the actual full iterative RGBM algorithm, as opposed to all the various proprietary schemes which have licensed some variation of the name. Some versions were touted as running on cheap DCs which wouldn’t have had the computational power required to run the real thing. As I recall, the Liquivision X1 was the first to run VPM-B, which I assume to have similar computational requirements and was certainly more expensive than recreational computers of the time. Early versions of “Suunto RGBM “ were believed to be simply dissolved gas models with some tweaks applied, but there’s really no way to know. Suunto now claims to include the full algorithm as part of their Fused RGBM but only on deeper dives, if I read their advertisements correctly.

 

[dmaziuk]

IIRC "RGBM-specific issues" included e.g. 36-hour window for repeated dives; that would be something you could bolt on to any algorithm and still claim there was a little BW in there.

I don't believe entry-level "recreational RGBM" devices ever ran the full iterative bubble model. However if their simplified approximation is close enough to the real thing, what does it matter? We pre-compute stuff and stick it in production code as constants all the time; as long as the user doesn't take it past the limits, it works just fine.

 

[rongoodman]

It probably doesn’t matter all that much, but it makes it hard to discuss. We never seem to have to speculate as to what Buhlmann GF or VPM-B ”really mean.

 

[boulderjohn]

As I recall, the Liquivision X1 was the first to run VPM-B, which I assume to have similar computational requirements and was certainly more expensive than recreational computers of the time.

I am pretty sure that the Liquivision VPM-B was created by Ross Hemingway. I then asked Shearwater if their version of VPM was created by Ross, and they said that, no, they had created it themselves.

 

[scubadada]

Scubapro runs a proprietary version of Buhlmann, ZH-L 16 ADT MB. The variables in the base algorithm are not known, The variables in the "human factor" adjustments are not known.