Recreational RGBM vs. Technical RGBM

[kcprofessor]

I am using a Suunto Helo2 as my basic dive computer with a Vyper Air as the back-up. On recent dives, the two computers were giving widely different results for the depth and duration of the deco stops, with the Vyper giving a much longer time. I changed the RGBM mode on the Vyper to attenuated, and that got the results closer to the Helo2, but still as much as six minutes difference on the final deco stop. Obviously, I followed the more conservative computer as I didn't want a lock-out, but the main question is : "is there any way to get the two computers to sync reasonably closely, or do I just need to buy another Helo2? Compared to other computers, the Helo2 appears to be very conservative anyway, so I don't want to make the Helo2 more conservative to match the Vyper. Does anybody have any experience with this set-up?

 

[MB NZ]

Depending on how the computers are setup, you may be able to get the information to match on the first dive of the day UNTIL the point you start your ascent because the HelO2 'off gasses" very differently. Not much use really.

I went through this and ended up buying a second HelO2. I've been diving with them for two years and like them, but I've no doubt there are better technical computers out there.

I don't think the HelO2 is that conservative, compare P-1 and P-2 with generic dive planning software. Whether you trust the algorithm or not is another question.

 

[Scott]

Oh how I feel your pain! I have the same setup.
At first I used Suunto's software to plan the dive, download it into the Helo2 and run the Vyper in gauge mode.
I still have the setup and will use it depending on the buddies I'm diving with.
Most of my dive buddies are using other brands and V-planner or I-deco software to plan their dives, so I started using the same software and running both in gauge mode for OW tec dives. Yeah, I could have saved a ton of $$ by just purchasing bottom timers. Hindsight.
I recently completed a full cave course and after having to wake my instructor up from his nap waiting for my Suunto to clear, those two will be for sale and a Shearwater or Liquivision will be on my wrist.

 

[Hendrik@Suunto]

kcprofessor,

The HelO2 and Vyper Air run off of different algorithms. The Vyper Air operates from the Suunto RGBM, and HelO2 from the Suunto technical RGBM. The RGBM is intended for recreational use, as the technical RGBM is for deeper technical dives. I have included links for some additional information.
Suunto RGBM Dive Algorithms - Suunto

http://ns.suunto.com/pdf/Suunto_RGBM.pdf

Also, please refer to the link below to the HelO2 user guide to section 10.2 & 10.2.1 http://ns.suunto.com/Manuals/HelO2/Userguides/Suunto_HelO2_UserGuide_EN.pdf

Best Regards,
Chris from Suunto

 

[kcprofessor]

kcprofessor,

The HelO2 and Vyper Air run off of different algorithms. The Vyper Air operates from the Suunto RGBM, and HelO2 from the Suunto technical RGBM. The RGBM is intended for recreational use, as the technical RGBM is for deeper technical dives. I have included links for some additional information.
Chris from Suunto

Chris,
Thanks for your reply, but I am still not understanding what the difference is in the algorithm. Are you saying that the Vyper Air should not be used for "deeper" dives? If so, what is the practical depth limit? Also, the explanation of the attenuated RGBM is causing concern since it just says that "experienced" divers may want to use it. All I know is that this reduces the conservatism.

 

[tkdgodess]

I have a vyper 2 as a back up to an x1 (vpm-b +3)

the vyper does not calculate deeper stops (say a 70 foot) it want me shallower at 20 feet. It keeps adding deco time until i am the depth it wants me to be, which is not in sync with my actual dive plan or x1.

I have stopped using my vyper in computer modes, it stays in gauge mode. It just keeps adding deco until you are at the shallow depth it wants you to be, lots of deco. Better have enough gas to clear it. I suspect the helo gives you credit for deeper stops instead of racking up deco.


once i forgot to change it to gauge mode and i had 30 mins more of deco on it, I gave it to one of my buddies who insists on diving recreational computers for technical dives (dives a written plan) have fun off gassing your computer and mine brrrrr im going for a hot chocolate.

 

[MB NZ]

I suspect the helo gives you credit for deeper stops instead of racking up deco.

It does and you get "credit" for any depth shallower than an on-gassing depth and that's the difference.

The recreational Suunto computers want you at 3.0 - 5.9 metres to off-gas, so if you're not in this range, you will get no credit and may even incur further decompression penalties. That's why you can get to your stop depth with more decompression commitment than when you left the sea bed (or deepest point on the dive) with Suunto recreational computers.

 

[kcprofessor]

Interesting discussion so far. I have been using Suunto computers for a long time, and the earlier models didn't give you any credit for deco below the ceiling. The four-button models (Vyper Air) have a deep stop program that can be turned on or off. I left it on. Compared to the Helo2, the deep stops are pretty close, but when you get to the shallow stop at 4 to 5 meters, there is a large difference in deco obligation. So far I have learned that the algorithms are different, although I don't know why the differences. I guess one reason is that the Vyper Air will reluctantly let you do a deco dive, while the Helo2 is made for those of us who make a habit of what I tell my open water students never to do. The real issue is that the various algorithms are going to give different results and I am trying to figure which one works best for me.

 

[KenGordon]

It does and you get "credit" for any depth shallower than an on-gassing depth and that's the difference.

The recreational Suunto computers want you at 3.0 - 5.9 metres to off-gas, so if you're not in this range, you will get no credit and may even incur further decompression penalties. That's why you can get to your stop depth with more decompression commitment than when you left the sea bed (or deepest point on the dive) with Suunto recreational computers.

So what is happening when my Zoop shows a ceiling of 7m?

I use a helo2 as a main computer and a Zoop as a backup/timer. On a simple single gas dive when they are both set to the same conservatism and mix then they seem to line up unless I ignore the helo2 deep stops and it punishes me with an extra minute. I wouldn't bet my life on this, it is just how it seems to me.

 

[Searcaigh]

I use a helo2 as a main computer and a Zoop as a backup/timer. On a simple single gas dive when they are both set to the same conservatism and mix then they seem to line up unless I ignore the helo2 deep stops and it punishes me with an extra minute. I wouldn't bet my life on this, it is just how it seems to me.

I have been using deep stops for a couple of years now, and this article sort of reinforced it for me, even on NDL dives and with gas switching to provide some conservatism to my recreational dives on a wreck that I was frequently diving on at 30M with EAN32 (gas switch to EAN50 at 21M) normally adding a 2 minute stop at 15M, then ascending slowly to 6M for my normal 3 minute safety stop.

After using the HelO2 I reduced the deep stop to 1 minute as per the computer, and did not notice any significant increase at 6M, it still displays 3 minutes

So I guess since you ignore the deep stop it is just adding it to your 6M stop as compensation, to be honest calling it a punishment might not be the correct term, although I understand what you are saying.

This year I "accidentally" moved into Tech diving, as I was not theoretically allowed to use EAN50 with a PADI Nitrox certification, and perhaps good salesmanship by the instructor, I am now recreationally trimix certified, no regrets it was a great course (IANTD) but has opened up a new can of worms regarding decompression diving (risks/benefits) using computers and working from tables (VPN-B+3)

As I get older though I realise my limitations and have no intention to get bent, so perhaps the assumed conservatism of Suunto's RGBM is not a bad thing, an extra minute in the water is better than a day in a chamber.