Can Suunto Cobra 2 be used for deco diving?

[Blackwood]

So are the people with actual decompression diving experience lining up to say that it is reasonable to use a Cobra 2 to plan and execute decompression dives? Or are you lining up to say that it is risky to plan and execute decompression dives with a Cobra 2, and that its management of decompression stops is best used as a safety feature for when a planned no-decompression dive ends up being deeper or longer than intended?

Just looking for some consensus here.

I find the terminology rstofer used to be apt.

The Cobra (et. all) as it relates to >NDL is for those 'oops' dives.

I haven't used the model(s) in question, but I doubt you can plan a >NDL dive with it. Rather, if you exceed NDL, it kicks into some hyper conservative mode that holds you in the shallows and then keeps you out of the water.

If planning >NDL dives, use models like the VR3 and the X1. "Recreational" computers simply aren't designed for it.

ratio deco ... as I understand [is] an aggressive approach to calculating deco obligations

At the risk of inviting another 30 pager...

Ratio Deco is actually fairly conservative (from an obligation standpoint. You can argue the application of oxygen vacancy to the profile if you like). It scales well with GF buhlmann models (upon which it's essentially based), and is conservative compared with bubble models (like VPM).

 

[Hatul]

I'd love to see any evidence that supports this statement.

I agree with your sentiment. There is a lot of anti-computer opinion here offering no evidence. There appears no reason that a dive computer cannot provide proper decompression stops.

Adam

 

[Slonda828]

I have an original cobra, and it was the first computer I purchased when I started diving, I have over 30 dives on it, and I got it from my old First Sergeant, who had about 100 on it. It's a great computer.

Here's what the MANUAL for it says (which I copied this below statement from 2 minutes ago):

"Dives with required decompression stops are not recommended. You should ascend and begin decompression immediately when the dive computers shows you that a decompression stop is required."

Simply put, the manufacturer has stated implicitly that this is a recreational computer with deco times for accidental forays into deco, NOT intentional ones. This is a lot like the NAUI air tables, which have deco times, but are NOT deco tables.

Now, do I personally care what you do with your gear? Nope. I'm just telling you what the people who made your equipment are telling you. However, I don't care if you run with scissors, or drive with a football helmet on either.

 

[cvigue]

No, the cobra & cobra 2 are not deco computers. Their algorithm is designed for NDL diving. If you inadvertently go over your non stop limit they will get you out of trouble by giving you an overload of deco time. This is the case for almost all of the NDL computers on the market.

The Sunnto & Mares computers are supposed to use RGBM. This turns out not to be the case. They are a neo Haldanian model that has been beaten till it performs something like an RGBM. The deep stops of the current versions have nothing to do with the deeper stops inherent in bubble models. The reality is that there are very few dive computers out there that have the processing power to crunch enough numbers fast enough to cope with any of the bubble models.

The cobra can be used for deco diving if you would like to cut tables & put it in gauge mode. I did this with mine for a few years prior to upgrading to a computer capable of dealing with multi mix, multi gas, decompression diving.

What I'm most concerned with is throwing out $700 on a bit of gear that I won't want to use for at least 3+ years. I dove a little with a borrowed Cobra and I really liked it; it gave me the information I wanted in a simple and easy to read display unlike the VT-Pro I'd been using which was prone to losing data signal from the tank pressure transducer and even when it was working I found the display to be poorly organized and non-intuitive.

The loss of signal issues are making me hesitate to consider a hoseless wrist computer.

Instead of the Cobra 2, if you can get either the cobra or the new cobra 3. the 3 allows the compass to be tilted more and appears to work better.

Ah OK. When is the 3 out?

It is perfectly functional for virtually all recreational diving.

Well that's all I'm doing now but for this sort of money I'd like to have room to grow unless the room to grow comes at the cost of losing the rec-easy mode.

 

[NudeDiver]

What I'm most concerned with is throwing out $700 on a bit of gear that I won't want to use for at least 3+ years

Unless you are planning to get into technical diving in those three years, then this is not a problem. Even if you are, you can still use the Cobra in gauge mode as a timer. So, overall, I don't think you'd need to throw it out. However, if you're paying $700 for that thing, you're overpaying. By a lot.

The loss of signal issues are making me hesitate to consider a hoseless wrist computer.

I've never had a signal loss issue with my hoseless wrist computer (Vytec).

 

[NudeDiver]

What I'm most concerned with is throwing out $700 on a bit of gear that I won't want to use for at least 3+ years

Unless you are planning to get into technical diving in those three years, then this is not a problem. Even if you are, you can still use the Cobra in gauge mode as a timer. So, overall, I don't think you'd need to throw it out. However, if you're paying $700 for that thing, you're overpaying. By a lot. You can get a regular Cobra for under $550 and are unlikely to see any difference other than saving money. You can also go used and save even more, or get a Vytec with transmitter. A Vytec DS with trans just sold on here for something like $525.

The loss of signal issues are making me hesitate to consider a hoseless wrist computer.

I've never had a signal loss issue with my hoseless wrist computer (Vytec).

 

[rstofer]

In my opinion (and one that is not universally shared), I would skip air integration altogether. A simple SPG on my left hip D ring is just fine.

First, the HP sensor in the computer is sometimes a failure point for hose integration. Second, I don't trust the tranmitter/receiver setup for wireless integration. In either case, if I am going to rely on air integration, I want it to be 100% reliable. Not 99.99%

Then too, air integration doesn't always work well with the gas switches used for deco diving.

So, skip that whole experience and see what you can get for the same kind of money but without air integration.

I'm not suggesting that the Nitek Duo actually qualifies as a deco capable computer but it will compute deco stops as deep as 90' and it does handle 2 gases. That should probably cover dives to around 200'. According to the old Navy tables, you could dive 300' 40 minutes and not need a 90' stop. Not that I'll ever find out!

But the Nitek Duo doesn't handle trimix or any of the exotic blends most often used in deco diving. Air and Nitrox, that's it.

If you really want to go nuts with deco diving, there are very few choices in computers. In fact, I would guess that almost everybody who has been trained for this type of diving has a written plan and just uses 2 computers in gauge mode.

Richard

 

[MXGratefulDiver]

I agree with your sentiment. There is a lot of anti-computer opinion here offering no evidence. There appears no reason that a dive computer cannot provide proper decompression stops.

Adam

The evidence in this case comes directly from your computer manufacturer.

Somewhere near the front of the manual it will have a statement to the effect that the computer was designed for no-decompression dives only, with a disclaimer that you should not use it for planned decompression diving.

Choose the appropriate tools for the job. Recreational dive computers aren't the appropriate tool for decompression diving.

... Bob (Grateful Diver)

 

[NudeDiver]

I guess we have to ask the poster outright:

a). Is your question, whether one of the Cobra computers CAN do/handle/accomodate a deco dive, in the event that you violate an NDL and incur a deco obligation?

b). Is your question, whether one of the Cobra computers is the right tool for the job, with respect to planned deco dives?

Both questions are answered by the manual that comes with the device (which may be downloaded). The answers are "yes" and "no" respectively. There is some caveat to B, in that if you put it in gauge mode, you can use it like any other bottom timer with tables, so in this configuration, the answer to "B" could be "yes" as well.

 

[Scott]

Somewhere near the front of the manual it will have a statement to the effect that the computer was designed for no-decompression dives only, with a disclaimer that you should not use it for planned decompression diving.

Only a few disclaimers inside the manual. I guess that answer would be ...not advised

WARNING NOT FOR PROFESSIONAL USE! Suunto dive computers are intended for recreational use only. The demands of commercial or professional diving may expose the diver to depths and conditions that tend to increase the risk of decompression illness (DCI). Therefore, Suunto strongly recommends that the device is not used for any commercial or professional diving activities.

DIVES THAT REQUIRE DECOMPRESSION STOPS ARE NOT RECOMMENDED. YOU SHOULD ASCEND AND BEGIN DECOMPRESSION IMMEDIATELY WHEN THE DIVE COMPUTER SHOWS YOU THAT A DECOMPRESSION STOP IS REQUIRED!
Note the blinking ASC TIME symbol and the upward pointing arrow.

When used properly, Suunto Cobra2 is an outstanding tool for assisting properly trained, certified divers in planning and executing sport dives. It is NOT A SUBSTITUTE FOR CERTIFIED SCUBA INSTRUCTION, including training in the principles of decompression.