Air integrated computer and tec diving

[tbone1004]

if I was diving backmount manifolded doubles or singles regularly, and the Sub-Gear XP, Mares Puck, Suunto Cobra etc were around $300 instead of where they are, then I would use one as my primary SPG and backup bottom timer. Cost of a cheap dive computer is $200-$250, and an SPG is about $70-80, so the money factor works out for the convenience of having it all in one unit. Since I dive independent doubles, sidemount, etc etc, then it doesn't work for me at this point in time.

 

[Colliam7]

My next tech diving question. I have a Suunto Cobra air integrated console computer. I was considering using it as a back up to my Mares Nemo wide for tec 40 and 45. . . . 1. Is this configuration okay? . . .
2. If not, why?

Interesting question. And, it appears that it is subject to interpretation from other posters. So, my answer may not address what you are asking, but I will try to answer - as I understand the question.

My understanding of the question is that you are asking about using a console computer as a back-up to your primary BOTTOM TIMER and DEPTH GAUGE- the Mares Nemo Wide computer - and not as a primary gas supply information source. Honestly, I don't see a real issue. After all, you are essentially taking a back-up bottom timer, so you are doing a 'good thing' And, you are getting the advantage of a digital back-up to your SPG. As a caveat - I don't think you are suggesting that you would be diving without a SPG as you primary source of gas supply data. If you are, I see some problems with that - I trust analog gauges more than digital / electronic gauges.

The only issue I see is placement. Which first stage are you going to connect it to? I would imagine that you would hook it up to the right post, with a traditional brass and glass SPG on the left post. Is that correct? if so, good on you in that you are using available equipment.

Personally, I do not particularly like consoles - they are bulky / cumbersome from my perspective - and I really don't like consoles used in a technical rig. But, that is a personal preference, and you are not in any way bound by my individual idiosyncracies. I actually use a Suunto transmitter on my right post, and a HeLO2 on my left wrist, as a back-up bottom timer / computer / wireless air-integrated gas gauge (I like the convenience of rotating my wrist and looking at my pressure, but I still check my SPG regularly). My primary gas supply information comes from a B&G SPG running off the left post. My primary depth / time information comes from my primary computer, on my right wrist.

If my right wrist bottom timer / depth gauge fails, I go to my left wrist bottom timer / depth gauge, call the dive (if we are still on the bottom) and use my back-up computer for depths and deco times. If both fail, I use my buddies depth and run time. If my SPG fails, I use my airless AI pressure data from my HeLO2, and call the dive.

 

[tbone1004]

Bill, the Cobra assuming it is stand alone, without the compass, is about the same size as a 2.5" SPG, so it's not that bad. I was thinking of it being used as a large SPG that happens to have depth and time built into it

 

[Veritably337]

I have an analog SPG on my left post. My plan was to put the Cobra AI computer in the right post and route under right arm. Concerned it may interfere with long hose. The idea is to use it as a back up BT depth gauge not as a deco computer. Also has a compass mounted on it- convenient


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[tbone1004]

if your instructor is OK with it, I'd mount the console on the left post, remove the compass, and use that as your primary SPG and bottom timer if you have a second deco computer. Unfortunately console mount compasses just kind of suck overall imho so I would get rid of it completely and use a wrist compass or preferably a slate mounted compass.

Route it per normal, or if you really want to keep the compass, mount it on the left post, and put a clip on the end of the compass. This will cross over and clip to your right d-ring. This will be under the long hose and basically be treated like your drysuit hose.

 

[doctormike]

I have an analog SPG on my left post. My plan was to put the Cobra AI computer in the right post and route under right arm. Concerned it may interfere with long hose. The idea is to use it as a back up BT depth gauge not as a deco computer. Also has a compass mounted on it- convenient

I think that your concern is valid, and if you use a canister light (your "voice" in tech diving) that cable may interfere with your extra hose as well. I'm no tech instructor but I wouldn't do it. It goes against one of the main principals that I took from my training, the importance of a clean, streamlined rig without unnecessary complications.


Think about what is important to backup in your original question:


1) Time/depth: You need this to do your deco, so you need it backed up. I use a bottom timer for this on my left wrist, with my computer on my right wrist. I have a dedicated bottom timer, but any cheap/old/used wrist mounted computer that can be put into gauge mode can serve this purpose.


2) Ascent profile: You need this for deco also, so you have your computer backed up by a slate (my preference), or a second computer.


3) Tank pressure: Assuming that you are diving manifolded doubles, you would have one SPG monitoring this. Although a new diver would probably think that tank pressure is the MOST important thing to back up, that's not really the case in tech diving, especially compared to 1 and 2. The reason is that since you have done your gas planning ahead of time, you know that (barring catastrophic gas loss) you have enough back gas to finish the dive with all required deco, even in a lost gas scenario where you don't have your deco bottle. If your SPG quits, you would turn the dive early, so you would actually have more gas than you had anticipated, and you should have no problem doing your deco. SPG failure and catastrophic gas loss? Two failures, we don't usually plan for that. Also, another thing that you learn in tech training is to have a pretty good idea of your tank pressure without looking at the SPG...


The only advantage that I see of repurposing your old AI computer would be saving a relatively small amount of money (in a sport where you can easily spend $1400 on a flashlight). A tech instructors probably wouldn't accept an AI computer in place of an analog SPG, but maybe I'm wrong. If you really get into tech diving, the actual expenditure isn't much. Put your Cobra on eBay, buy an SPG and a bottom timer (or old computer for gauge mode), and call it a day.

 

[Colliam7]

Bill, the Cobra assuming it is stand alone, without the compass, is about the same size as a 2.5" SPG, so it's not that bad. I was thinking of it being used as a large SPG that happens to have depth and time built into it

In that context, it is very much like what you describe - a slightly large SPG. You make a good point - he would have the Cobra 'hard-hosed' and should just take it out of any console cover, and use it that way. I like the idea!

 

[DevonDiver]

I have a Petrel, but when I teach courses it is relegated to backup as all my training dives are managed from custom tables and the student has to demonstrate capacity to follow a precise, preplanned runtime.

My technical diving is nearly all on deep wrecks, so the dive profiles are very square and predictable at the bottom. That means there's very little difference between what precut tables anticipate and my dive computer subsequently delivers. Most dives have less than a couple of minutes difference between tables and computer (unless, for some reason, I ascend early).

Personally, I wouldn't recommend using an integrated computer (in gauge mode). It brings potential failures that you wouldn't have with a standalone bottom-timer and analogue SPG. Also, one failure deprives you of 2 sources of critical data.

I'd hazard a guess that there's more chance of a cobra failing unexpectedly than a simple bottom timer or analogue SPG.

Utilising old computers as bottom timers in gauge mode is fine. But just because it's been flawless for xx years doesn't mean it's trustworthy. Everything fails eventually. Battery and/or software powered devices tend to fail without warning.... analogue stuff tends to fade over time, giving ample warning for you to replace it.

I wouldn't permit a backup analogue SPG to support a digital one. That simply adds unacceptable failure points. If you don't trust the digital SPG, don't use it.

The crux of this thread is about understanding the difference between what you COULD do.... and what you SHOULD do.

Technical diving doesn't reward compromises.

 

[JohnnyC]

I wouldn't do it, but in this case I wouldn't necessarily begrudge someone using it. It's not like I'd refuse to dive with you because you had it. I don't think it would be any more of a hose charlie-foxtrox than say a dual-bladder wing. In that case you've got a whole other inflator on the right side too, coming from the left post.

My biggest issue is that a failure not only turns into a lost gas scenario (to which you've multiplied the additional point of failure b/c of the analog spg PLUS this), but you've also lost all redundant depth/time monitoring.

I don't dive independent doubles because manifold failures are so uncommon as to be statistically nil, but theoretically full independent redundancy is the absolute best way to go. In this case, you're not independently being redundant, you're actually adding an additional point of failure without the benefit of independence. Now realistically the worst that will happen is either a leak that you catch early during your bubble check, or a dead battery, in which case it's just doing nothing for you.

Like I said, it wouldn't stop me from diving with you, but it's not a configuration I would use.

 

[abscuba]

If you are starting into tech simple is the way to go and reusing an old AI will just add complication and increase possibility of a failure to only gain a bottom timer. When you start adding tanks, rebreathers, redundant computers, and all the other stuff that starts showing up in your kit as you go farther into tech simplicity becomes very important. To top this your kit is going to change as you find what you like and what fits the kind of diving you do. If I am diving OC tech I generally dive side mount which gives me independent doubles, but no room for an AI computer. Tech diving is expensive it sux but its a reality, its not the time to go on the cheap end. Talk with your instructor, talk with tech divers in your area, look at their kits and find out why they are set up that way and invest in your kit it is what is keeping you alive. If it fails you do not have direct access to the surface which is why tech divers get very particular about their set up. You would be better served with analog SPGs and a computer intended for tech diving.