Suunto Tech RGBM vs Fused RGBM

[DevonDiver]

The guy from the Phillapines? has a website with an article assessing tech capable computers. Well worth looking at in your case.

The Best Technical Diving Computers 2016

 

[scubadada]

The Best Technical Diving Computers 2016

Amusing write up. Even my $400 Nitek Q backup computer is ranked above the Eon Steel.

 

[Diver0001]

Deepstops are already turned off for both plans...
I found a document with more information about Suunto's Fused RGBM - http://ns.suunto.com/pdf/Suunto_Dive_Fused_RGBM_brochure_EN.pdf
On page 12 you can find a graph comparing a diving profile to 80m with Fused RGBM and Buhlmann. Suunto claim that their algorithm gives shorter ascent time than Buhlmann's!
View attachment 400528

The claims of shorter total decompression are things that Bruce Wienke has been saying for years, but it is incorrect.

The gradient factors being used in that comparison are also not gradient factors that informed technical divers would use. That is a manipulation to make the profiles look similar but is not realistic. What it proves is that by using ill chosen gradient factors you can "break" Buhlmann too.

And as I said above since the NEDU study almost all informed technical divers have stopped using RGBM and other bubble models for safety reasons. It was beginning to become clear around 2004 that there was something wrong with it. By 2007 (or so) NEDU was starting to do some interesting comparative studies and by 2011 it was pretty much proven to everyone's satisfaction that RGBM and other "bubble models" are basically broken in terms of how they work.

Take a look at this article. https://www.johnchatterton.com/wp-content/uploads/2013/03/NEDU_TR_2011-06.pdf. You can find it rubicon too if this link stops working.

You may need to read it a few times before it becomes clear what they are saying (at least I did), but take the time to really absorb this and take time to read some more of what NEDU and even DAN are saying about it.

In my personal opinion if Suunto and Bruce Wienke are in bed together then as a technical diver you should avoid their products. Bruce Wienke is one of the few (I only know of 2) model makers who rejects the NEDU study. IN both cases that I know of, the model makers are rejecting the study because they have commercial interests in mind, not the interests of divers. The rest of the scientific community and most technical divers are onboard with NEDU and we are updating our procedures to account for the conclusions of that study.

R..

 

[scubadada]

Do you remember what Simon said he was using?

R..

Hi @Diver0001

I believe @Dr Simon Mitchell dives 50/80

 

[scubadada]

Hi @Diver0001

I believe @Dr Simon Mitchell dives 50/80

A dive to 62 m, 203 ft, on air, with a minute on the bottom, as @3dfx outlined in post #7, would have a run time of 16 minutes with GF 50/80. The two run times 3dfx quoted were 15 and 34 minutes using the two versions of Suunto RGBM

 

[KenGordon]

I was initially very surprised by this. I have used a Helo2 for a long time and was considering an Eon Steel. My experiments indicated that the Steel was more or less the same. However I realise that all those experiments were for actual mixes I actually dive. Air at 62m is not one I considered.

For the Helo2 you ought to plan with deep stops as they cannot be turned off, although they can be ignored.

Change the mix to something like 18/35 with 50% and 100% and the plans compare to 45/80. The Helo2 is near enough the same, the Eon a bit quicker and deeper, by the time you do the safety stop then I doubt it is terribly more aggressive. I didn't try to match to 45/80, that is just how my multideco was set.

For a 35m 30 minute dive on 30% the steel is slightly slower (3 minutes).

It is impossible to represent the curves generated by these with GF numbers. To say 'oh, this is the same as xx/yy" is nonsense. For any given dive you may be able to approximate the same curve, but for another dive the approximating GF will be different. There are a lot of numbers involved, squashing them into two loses too much information.

 

[100days-a-year]

I would dive my EDGE before diving any Suunto,anywhere and at any depth it would read to.

 

[3dfx]

Thanks everyone for your valuable inputs.
Since the beginning of the discussion I read a lot about Buhlmann's model and the comparison between RGBM and gas content models - so it was very useful for me
Unfortunately the Fused RGBM remains a mystery - it is too far away from what I've dived so far and I couldn't find information about where this difference comes from.
I wrote an e-mail to Suunto (no answer so far) and I'll keep you updated if they say something.

 

[3dfx]

So, after two months of waiting I received the following answer from Suunto:

"The difference variate between depth and gasses your using. for example with Trimix it is more in favor to Fused RGBM
...
We appreciate your understanding and patience in this matter."



I'll probably have to switch to something else...

 

[Joffrey]

Thank you for the inputs! I'll indeed read in more detail about the difference between the RGBM and Buhlmann models. I understand that using different models will result in different dive plan.
What is extremely surprising for me is the great difference between Suunto's old Tech RGBM and new Fused RGBM - I expected some differences, but not more than twice longer dive time!
Please take a look at two absolutely identical simulations - descent to 62m with 12m/s, one additional minute at the same depth and then ascending according to the algorithm. Both plans are made with the same settings with deepstops turned off! Surface time is not taken into consideration.
The results are: 15 minutes for Tech RGBM and 34 minutes for Fused RGBM.
If that is the case I'd better post this computer on eBay... Is someone able to check the same profile on another model?

Hello, and new to the forum here. I own a DX computer, and was looking for information regarding this Fuse tech marketing algorithm, as I have experienced much longer ascent times than expected when diving between 40 and 60m.

The computer is fine and gives good bottom times for consecutive dives with depth <= 40m.
When diving at deeper depth, somewhere between 40 and 45m, the new "Fuse" algorythm kicks in, and it basically adds 1+mn ascent time for each 20s you stay at the bottom.

While doing a quick (5mn) dive at 55M on air, the computer gave me 35mn ascent time, while other computers from the team gave only 15mn.

I have contacted customer support for explanation (and sent the profiles for the problematic dives), and after 5 months, the answer is: You should not dive on air under 40m, you should use trimix, and the DX Computer is very conservative as Air is not the optimal gas for such depths. This is very discussable, and I am aware of the increased risks, but still, by adding so much ascent time, the computer becomes dangerous and can lead to out of air situations if you follow it blindly.

There is no way to disable this "Suunto Fused™ RGBM" on the computer, and no firmware upgrade scheduled to fix the issue.

My dilemma is that I now have to leave it on the boat if we plan to go < 40m. Really unacceptable for a EUR1000+ computer. Thank you Suunto...