RGBM Algorithm for Technical Diving

[Diver0001]

Remy, that is assuming you are using a suunto recreational computer.

I have never run RGBM from an app or a computer. I have used RGBM paper tables, and I haven't been bent yet. Mind you, this is all on dives between 100-330fsw.

Mark E's issues are beyond RGBM issues. He claims that he dove RGBM "many" times both at relatively shallow depths and obviously at extreme depths...and got bent EVERY SINGLE TIME. One has to question not only why he got bent every time(even though other people have hundreds of dives without issue using the same algorithm), but also why someone that got bent even on shallow dives using RGBM would willingly continue to use it...on pinnacle dives none the less. His own website has correspondence with Bruce...where Bruce flat out tells him to back the hell off of these dives.
My conclusion is that mark is a nut job, and that he's either lying to some extent about his experiences with RGBM or he has a PFO that you could fly the Goodyear blimp through.

I don't know where you heard that but I think you should cite.

Mark told me personally that he's been badly bent using Wienke once and that in response, as I posted above, Wienke blamed everyone else but utterly failed to take any responsibility for the working of the algorithm. Mark also told me that he's pretty sure that RGBM "will do" in the +/- 100m range (with the same tone of voice that old milk-jugs "will do" for controlling your buoyancy) but if you want to dive deeper then you need to take your deco schedule more seriously.

He also said that all of the deco algorithms on the market start to break down as you go 'really deep'.... He told me that all of the "deep crowd" experience some side effects. Mark usually has some signs of DCS, albeit minor most of the time. He said that Nuno goes deaf after every deep dive for a period of time and so on and so on. He knows these guys (I do not) and I have no reason to believe that he's full of anything.

R..

 

[tomfcrist]

http://www.inspired-training.com/RGBM%20Really%20Good%20Bends%20Model.htm

Literally in the first paragraph.

 

[Diver0001]

xD.

Thx

 

[CuzzA]

So I was participating in a thread about a month ago and the Buhlman vs. RGBM discussion came up during a discussion about computers. I didn't take it any further (Basic Scuba forum) because technical diving is beyond my training right now and I hadn't begun to research deco models, m values, etc., etc. But it peaked my curiosity and so I started to do some research.

I too read the aforementioned website bashing Mr. Weinke, but IMO, I didn't see where Mr. Weinke's reply was out of line. Not to mention, some divers will get bent no matter the algorithm or dive plan. So, I'd like to hear more about this subject. I read many of Mr. Pyle's articles and while his personal experience is anecdotal, you have to consider the large number of other divers (mostly commercial) who follow the deep stop philosophy (Which is what RGBM is based on right?) everyday and aren't getting bent.

I'll add some of the articles I've read to hopefully further the discussion.

Mr. Weinke on RGBM
http://www.scuba-doc.com/rgbmim.pdf

Mr. Pyle on Deep Stops
Deep Decompression Stops

---------- Post added January 7th, 2016 at 09:37 PM ----------

I'll add, is it that difficult to reverse engineer an algorithm on a dive computer? I keep hearing about the secrecy of the RGBM, but I would think once the product is released someone smarter than me could figure it out.

Perhaps we need to get the Chinese on the horn. They reverse engineer then steal products/technology everyday.

 

[Centrals]

Mr. Pyle on Deep Stops
Deep Decompression Stops

Plan the deep stop but extend the shallow stop unless someone.... (the last paragraph).

I used to do deep stop but planned it as part of the BT. But I don't do it anymore.
My next experiment could well be changing the GF from 20/80 to 30/70.

 

[DevonDiver]

At least some of the "conservative" stuff is penalties for is fast ascents and short SSs and SIs built into recreational computers... How much of that is part of the deco algorithm per se is questionable, and we'll never know.

This, for me, is one of the major concerns. For technical diving, the algorithm needs to be predictable. Putting 'triggers' into an algorithm which unilaterally modify the mathematic function based on unexplained parameters.

So... I planned my dive. But, for instance, I trigger an ascent warning by moving my arm too quickly and alerting a hair-trigger depth sensor. The computer whips me for it and now I'm diving on on am algorithm the computer adjusted, not me. And that has consequences on my team deco, my gas plan etc etc

The fact that we have to debate RGBM like this is telling. It's secretive. We all have to guess. Guesswork and technical diving are not comfortable bed fellows.

Suunto is a big company. They make compasses. The they made mountaineering instruments. Then they made diving instruments. Recently they started making technical diving instruments. Tech computers are just one tiny product line, that forms part of a huge, multifaceted, design and production machine.

Compare that to Shearwater, XDeep or Heinrich Weikamp.... small manufacturers run by technical divers, who produce products specifically for technical divers based on personal experience and insight.

Suunto also, I believe, protect themselves from liability - especially class action. A big company is a big target... and has a lot to lose. Hence, they control factors to keep divers safer... removing personal control, which could lead to user errors that, nonetheless could result in legal actions.

In contrast, Shearwater are like "Hey cherubs, don't be a dick and kill yourself using our machine... You can.. So get yourself educated please...". They take responsibility for the hardware... but using open-source algorithms... they can defer some liability. Users have the ways and means to research those algorithms, from the source and community, and make their own decisions.

Honest question, if someone has legal insights.... if VPM-B bent you... who would the lawyers go after? Shearwater or Baker/Maiken et al?

 

[CuzzA]

Andy, I can't disagree with that logic.

 

[uncfnp]

This, for me, is one of the major concerns. For technical diving, the algorithm needs to be predictable. Putting 'triggers' into an algorithm which unilaterally modify the mathematic function based on unexplained parameters.

So... I planned my dive. But, for instance, I trigger an ascent warning by moving my arm too quickly and alerting a hair-trigger depth sensor. The computer whips me for it and now I'm diving on on am algorithm the computer adjusted, not me. And that has consequences on my team deco, my gas plan etc etc

The fact that we have to debate RGBM like this is telling. It's secretive. We all have to guess. Guesswork and technical diving are not comfortable bed fellows.
n et al?

Finally! Someone gave the rationale for disliking the RGBM beyond just the fact that it is proprietary. This makes a lot of sense for technical dives. I never looked at it that way.

So the issue with RGBM and technical diving is deep stops and the unpredictability of the algorithmn?

With recreational, this isn't an issue and I have always looked at it from the rec side. I understand here, the idea is to build in an extra margin of safety for the multiday, multidive recreational diver. And it seems logical in this context.

I wonder if a lot of the general dislike for RGBM on SB comes from the tech community, beyond the fact that the vacation diver may see less NDL's on his/her screen.

 

[Sevenrider860]

http://www.inspired-training.com/RGBM%20Really%20Good%20Bends%20Model.htm

Literally in the first paragraph.

This is an interesting read and I do think it provides some historical perspective of the personalities 13 years ago. The first paragraph says a lot. A couple of statements stand out.


"I had used the RGBM algorithm many times before, both shallow (60-90m) and deep (120m-260m), contrary to Bruce Wienke's website I received DCS every time using the RGBM algorithm."


Mark does not indicate a number of dives, but he is saying 100% of them resulted in DCS. My dives using RGBM were in the 40-60m range (which is not as deep as what Mark describes as his "shallow" dives!) and they did not result in DCS. I have to think that if 100% of the dives made using the RGBM algorithm were resulting in DCS, this would have kept him from using that same algorithm on his 260m dive, but I never come close to those depths and do not know the thought process that made Mark use an algorithm that had a 100% failure on his past dives.


The last sentence of the first paragraph is also interesting.


"I have used the VPM a/b algorithms since they became available, also with similar results, only the version using VPMbE (2005) with maximum conservatism provides acceptable decompression times."


Mark is stating he had similar results using the VPM algorithm. I have to assume the VPM algorithm we see in MultiDeco and running on the Petrel today has been tweaked and modified since this statement. Is it possible that the RGBM and VPM algorithms simply do not work with Mark's personal physiology? I don't know, but he is reporting 100% DCS with RGBM and similar results with VPM and I don't think there were similar results happening to every other diver using the algorithms in 2002 and 2003.


Is it possible that it was how Abyss implemented RGBM? That seems to be implied by both Mark and Bruce in the dialog that is presented. There is a lot of personal baggage to sift through on the web page to come to a firm conclusion. It also seems that he turned down an out of court settlement on the basis it would require a non-disclosure of all the case related papers and he states he will make them available. However I did not see links to the papers to get a full picture of both sides of the case.


What is very clear is that RGBM and VPM did not work for Mark, he had/has a personal dislike of Bruce Wienke, he had a lawsuit dismissed after rejecting a settlemet, and had/has a dislike of NAUI which he refers to as a "dubious diver training agency".


It is a very interesting read though.

 

[CuzzA]

Lisa,

I think your right. The algorithm itself may in fact be better than other options, but as Andy pointed out the secrecy of the RGBM algorithm will never surpass the others simply because the operator doesn't know what the device is going to do. This is a bad business decision IMO if the intent is to target technical divers. Furthermore, one could argue that it's riskier to dive the RGBM deco model on a computer because of the fact the user has no way to predict what it's going to do, whereas with other options you know if you do this your computer is going to do that.

I will admit my computer uses the Weinke RGBM algorithum. It's the Mares Icon HD. I love the computer itself. The graphics are killler, the AI has been flawless and I paid 40% of retail brand new. It was a deal I couldn't walk away from. For me right now, it's the optimal computer for my diving. NDL, recreational depths, repetitive spearfishing dives. The wrist screen and AI make it nearly impossible for me to get sidetracked by being task loaded while fishing. It's like a heads up display "with gas info" while holding my gun.

However, as my diving progresses to tech in the future that computer will likely be retired for something like a Petrel, unless Mares offers a firmware update that includes trimix and an open source predictable algorithm.

I'll tell ya, if you could put the Shearwater computing into the Icon that would be the ultimate computer, IMO. But, that's life right. We can't have it all.