Watch with Similar Algorithm for Partner (and buddy)

[KenGordon]

What does this have to do with your original point, But Suunto RGBM is not RGBM?

SB people tend to be fans of a primitive gas content model with one rather ill defined way of applying extra conservatism. They criticise bubble models as they are no longer fashionable even though their favourite, fashionable model was designed to cheaply ape bubble models.

Meanwhile, well a bit later, other people took different approaches that target specific issues, and cobbled them together with the simple dissolved gas stuff. Since bubble models were still fashionable still they gave them a bubbly name. They were not real bubble models.

Your list of criticisms is the list of features added to gas content models to make the various ‘proprietary’ RGBMs. But they are not the actual RGBM.

These criticisms/features are things that let non expert divers benefit from some best practice - longer SIs, more stops for various higher risk, but not necessarily greater exposure at depth, profiles.

 

[scrane]

For all those hanging on the edge of your seats for my decision, I decided to pick up a couple of Geo 4s - the fancy tec computer can wait. We've got a trip booked to Sri Lanka in December so they'll get their first run out then! Thanks again for your help.

One question I do have - the Oceanic website/manual says for the manufacturers warranty to remain valid I have to have bought it from an authorised dealer and get it serviced by an authorised dealer. There is no authorised dealer in the UK according to their website - International - does this mean I've bought it from an unauthorised dealer? Do I therefore (i) have no warranty outside my statutory rights; and/or (ii) have to send it to Europe for a service to maintain my two year Oceanic warranty?

I'm sure you'll be happy with the GEO4s. I have the similar GEO2 and have been delighted by it's functionality and design. The GEOs are still very popular and should hold good value for when/ if you decide to upgrade. Have fun.
The GEOs have a pretty good reputation for reliability. The battery replacement is pretty straightforward. If the product you bought is not covered by Oceanic ask your distributer what options you have.

 

[Jay]

I think a Rec diver can be quite model agnostic now with the advent of RGBM2. I realise that RGBM2 is a Suunto algo, but whether it be Cressi RGBM or Suunto RGBM etc, divers aren't going to buy them (literally as well) once they're aware of a 'better' (newer, more advanced if you believe the marketing) RGBM2.

For Rec, XXXX RGBM sucks (where XXXX = any manufacturer), merely because of its output, aside from its theory, soundness etc.

Two things I find interesting in where models are:

1/ SIs in RGBM2 (et al) vs 16C.

2/ For Tec, with the increasing of GF-lows in a post deep-stop world, how shallow does the pendulum swing, before it settles?

 

[ross9]

I'm sure you'll be happy with the GEO4s. I have the similar GEO2 and have been delighted by it's functionality and design. The GEOs are still very popular and should hold good value for when/ if you decide to upgrade. Have fun.
The GEOs have a pretty good reputation for reliability. The battery replacement is pretty straightforward. If the product you bought is not covered by Oceanic ask your distributer what options you have.

Thanks - good to hear! Turns out the site I bought from are an authorised dealer, Oceanic just don't have it on their website for some reason.

 

[dmaziuk]

He is saying that ZHL16/GF is lacking in a number of useful features such as accounting for extra risk due to repetitive diving (the numbers come out so every day is like you have not dived for a year), short SI, see saw dive profiles.

Even if risk is debatable, you still have to design in some of those things. If you're a vendor, you'd want to hire a deco expert to do this for you. From legal ass-covering perspective if for no other reason. And lo and behold here's one such expert and has the model with all of those things rolled in already for your convenience.

And then you have to consider your target demographic. You know, people who can't figure out what the big beeping and flashing "DECO" on their computer means.

 

[scubadada]

SB people tend to be fans of a primitive gas content model with one rather ill defined way of applying extra conservatism. They criticise bubble models as they are no longer fashionable even though their favourite, fashionable model was designed to cheaply ape bubble models.

Meanwhile, well a bit later, other people took different approaches that target specific issues, and cobbled them together with the simple dissolved gas stuff. Since bubble models were still fashionable still they gave them a bubbly name. They were not real bubble models.

Your list of criticisms is the list of features added to gas content models to make the various ‘proprietary’ RGBMs. But they are not the actual RGBM.

These criticisms/features are things that let non expert divers benefit from some best practice - longer SIs, more stops for various higher risk, but not necessarily greater exposure at depth, profiles.

Sorry to further derail this thread, but this in in direct follow up. So...Suunto, Cressi, and Mares, all allied themselves with the then king, Bruce Wienke, many years ago, and went with a compromised version of RGBM. It was the deco algorithm of choice. Since that time, reverse profiles, and reasonable sawtooth profiles have been debunked as a cause of DCS. Shorter SIs, likewise, are entirely taken into account by modern computers. Fast ascents are still prohibited, as they exceed the limits of the decompression algorithm. Suunto and Mares now plan to or offer Buhlmann as an alternative deco algorithm. Hindsight is very valuable.

 

[dmaziuk]

Since that time, reverse profiles, and reasonable sawtooth profiles have been debunked as a cause of DCS. Shorter SIs, likewise, are entirely taken into account by modern computers.

Short SI between 1st two dives means little, they all account for them the same way. One of RGBM "reduction factors" is the repetitive dive window that Dr. Wienke argued should be as long as 36 hours. Short SIs add to that penalty, you'll start feeling it by day 2 or later. That's what you don't see with other models, there's no "repetitive diving" in ZH-L.

There's been at least one study suggesting that human body may "acclimatize" to repeated decompression stress. If true, that extra conservatism may be as unnecessary as penalties for reverse profiles.

 

[KenGordon]

reasonable sawtooth profiles

What is a reasonable sawtooth profile? So I am ok to pop up and down a half dozen times from how deep doing CBL training?

Shorter SIs, likewise, are entirely taken into account by modern computers

Exactly how? The Buhlmann derived ones just use the same on and off gasing rates and the same m value limits whatever the timing between dives, and if you believe they ignore GF low then at all times within NDL. There is nothing like the Suunto business where the equivalent to GF is lowered for a couple of hours after surfacing.

 

[scubadada]

What is a reasonable sawtooth profile? So I am ok to pop up and down a half dozen times from how deep doing CBL training?



Exactly how? The Buhlmann derived ones just use the same on and off gasing rates and the same m value limits whatever the timing between dives, and if you believe they ignore GF low then at all times within NDL. There is nothing like the Suunto business where the equivalent to GF is lowered for a couple of hours after surfacing.

You obviously have you own philosophy, good for you. A reasonable sawtooth profile is following the topography of your dive, satisfying ascent limits. Your SIs control your next NDL, duh. As your know, GH low applies only to deco dives. What is it that you like about Suunto?

 

[KenGordon]

You obviously have you own philosophy, good for you. A reasonable sawtooth profile is following the topography of your dive, satisfying ascent limits. Your SIs control your next NDL, duh. As your know, GH low applies only to deco dives. What is it that you like about Suunto?

I don’t have my own philosophy. I follow the recommendations of the experts and have a good knowledge of the way Buhlmann/GF works having built an implementation to further my understanding.

Duh? How do the SIs control the NDL? That is a key difference between the Suunto etc RGBM computers and the GF ones. In fact the GF ones don’t really have an idea of a surface interval, just a period of 1 atm exposure to air. As pointed out in the first post of the recent thread about GF values in DIR training, the original research was based on single dives.

Meanwhile the marketing RGBM ones reduce the maximum oversaturation allowed for a while, so short SIs have an extra compensation.

Why do I like Suunto? They are common, relatively cheap, appear to work and encourage better practice. I don’t have to worry so much that divers set them to mad GF combinations, I think that reduces my chances of having to explain GF to a coroner.

I deal with a lot of new divers. I see how their eyes glaze over when you explain tables, tissue compartments, half times, etc. They need something that lets them set the mix, maybe plan dives, and finally know how far away in time the surface is. With the GF computers even the proper IT people that can build you a multi continent web service with failover that actually works and guaranteed transaction resilience eventually ask “what numbers should I use here?’