Am I the only one that dives with 2 computers?

[Stoo]

Always carry two computers on a trip but only dive with one. I've never had a computer fail but if it did it would be no big deal. I'd just end the dive and grab my other computer for the next dive.

And get bent like a pretzel potentially... I fresh computer is useless for a repetitive dive, as far as deco goes...

---------- Post added September 8th, 2015 at 07:20 PM ----------

There are any number of things that can go wrong with dive gear, but next to a fin strap, a computer is probably the piece of gear that is most prone to failure. Anyone who has been diving any length of time has had a computer crap out on them, guaranteed. I find that the generic puck computers are the worst. I used to get two yers our them before they'd die. It didn't matter the brand... most of them are made by Seiko anyway, with a slightly different face on them.

I have been diving with two computers ever since they became common place. Initially I did this because I dive solo a lot, and most of those dives require some deco, so wearing two seemed like a good idea. My first computers were Aladdin Pros and then Aladdin Pro Nitrox. These were bombproof and the only time I wrecked one was when I drove over it with my Tahoe!

Eventually I moved over to changeable gas gizmos... Dive-Rite Duo, Apeks Quantums... None of them lasted more than a couple of seasons. I went over to Shearwater and by all accounts, it too is bombproof. But I still wear a backup puck. I'm likely going to pick up a Petral 2 soon "FOR MY WIFE" which I will borrow on real dives.

So ya, wear a backup. It's the only way you're going dive continuously on a vacation...

 

[redacted]

And get bent like a pretzel potentially... I fresh computer is useless for a repetitive dive, as far as deco goes...

---------- Post added September 8th, 2015 at 07:20 PM ----------

Useless!!! Have you forgotten how to do dive planning and management based on depth, time, and pressure group; or did you never learn?

 

[tstormdiver]

Useless!!! Have you forgotten how to do dive planning and management based on depth, time, and pressure group; or did you never learn?

Or beyond the square profile of tables..... J/S

 

[dmoore19]

I have 3 computers. They are Oceanic computers running the same algorithm.

I do it in case of a failure on a trip. I only get 1 or 2 trips per year and don't wish to have a problem. The Datamask is on my face, the OC-1 on my wrist and the BUD clipped to my BC. I have never had a computer failure, nor have I had a transmitter failure. I have only seen one persons computer fail during a trip, the battery died. It was because he did not change the battery before he went on the trip.

Why 3 you ask? Because I want to and I like computers.

 

[redacted]

Or beyond the square profile of tables..... J/S

There really is no such thing as beyond the square profile of tables for recreational divers. All dive can be reduced to the simple square profile of a table. It is not very efficient for building bottom time but it is better than sittin on shore for 24 hours. Or you can compute based on multi-level dive, or even work with average depth.

 

[KeithG]

i always carry 2 identical uwatec aladins. my backup is tucked in my bcd pocket. it cost $35 on ebay + $5 battery change. no reason not to have 2 or more.

and i am not sure which tables i should be using for backup purposes after completing two 90 foot dives for 90 minutes each before lunch. for the price of a second computer, why play guessing games?

as for sitting out a day on a liveaboard - it's their boat, they can make any rules they want. And this is a common rule. one which i can easily avoid.

 

[tr3a]

Hang the zoop on the line when you get out of the water. Or do an extra seven minutes on your safety stop... that's when the leprechaun riding a while shark is going to come by anyway.



But seriously... where are you getting the 35min vs 28min NDL example?

People love to beat up on how ultra conservative the Suunto algoritgm is. My buddy dives an Oceanic, I dive a Suunto. So effectively, he is diving a Suunto as his backup. We probably have somewhere on the order of 300 dives together.

My Suunto has never - NEVER EVER - limited our dive time on a recreational dive or caused us to need to leave the water earlier than his computer. On a recent dive in Bonaire to the Windjammer (+200ft) my Suunto gave me ONE extra minute of deco on a dive with 89 minutes of total run time. (And I hit 210ft while he only hit 198ft.) So if you want to consider that to be overly conservative... so be it. Personally I can't imagine a dive profile where my Suunto is going to give me 7 minutes less bottom time than my buddy's Oceanic.

Good post,
I have dove a gekko for 9 years. When we travel (multiple time per year) we normally dive 4-5 dives per day for 11-14 days at a stretch. My gekko has NEVER made me cut a dive short. My wife and I are usually first in the water and last out. Limit on dives is air supply, not computer!
Also on our many trips to Indo, ect the most common computer used by the guides are gekko/zoop and they dive even more

 

[mark01]

Two computers- Zoop / D6i, and a separate spg.

 

[stuartv]

So in the artificial world of this study at 36min into the dive assume my buddy and I are at 40ft. My computer says I have 21min of NDL and my buddy has a Lynx... which says he still has 72min of NDL remaining. But in the real world, neither of us have enough gas to spend 72 more minutes at 40ft... so what's the practical difference?

EDIT - I quickly ran their Dive #3 through V-Planner, and with a good SAC rate it would take 97cf of gas to run that dive to the end of the Suunto NDL at 40ft. Wanna max out the 72 extra min of NDL that the Lynx gives you? You'll need 160cf of gas. Wanna be conservative and assume you're planning appropriate reserves... that'd be 129cf and 212cf of gas respectively. (I'm hungry for dinner, so maybe my math is off. Feel free to check my work.)

You originally said this:

In the real world you might see a one minute difference on a recreational dive with a run time of 35min.

I ran that Dive 3 profile through Multi-Deco. I used a SAC of 0.6 cu-ft/min, which is just on the high side of normal for me for a mostly drift dive. I came out with a requirement for 95 cu-ft of air required, so very close to what you got.

I dive an HP120. That leaves me with 25 cu-ft of air left when the Suunto user has to get out. An AL80 has 13 cu-ft of air left at 500 psi. To have a similar, but slightly more conservative, amount of air left, I would target having 15 cu-ft left as worst case reserve. With that dive, that would give me 7 more minutes after the Suunto user had to get out. And, actually, that would give me several more minutes than at least 4 of the computers in the review.

Would I get to stay for as long as the Cobalt NDL allowed? No, not unless I was diving doubles. But, many of the more liberal computers would give way more time - and usable time with a pretty normal SAC and a 120 or 130 - than the "might see a ONE minute difference." I think a SAC of .6 or better and a 120 or bigger all seems pretty "real world".

So, again, I don't see how it is correct to say that:

In the real world you might see a one minute difference on a recreational dive with a run time of 35min.

In the real world, if you have a Cobalt (or a pretty good number of other, more liberal computers) and a Suunto (or several other more conservative computers), it seems very easy that you might see a MUCH bigger difference than 1 minute after 35 minutes of run time.

And, further, if you want to change the subject from what you'll see after 35 minutes to what you can actually DO from there, it also seems like a real world possibility that, besides just seeing that difference, you might actually be able to take advantage of it, to the tune of a number of minutes, if you have a SAC of .6 or better and a tank that is 120 or bigger.

Now, is the difference between a 43 minute dive and a 50 minute dive huge? No. It's actually 7 minutes. But, that is a WAY bigger difference than "might see a one minute difference". And it might be enough difference that it affects the choice some people make about what computer they choose to buy.

Or, what am I missing?

 

[kafkaland]

My standard rec configuration is a wireless air integrated Aeris 300 CS, and as a backup a Subgear XP-H, clipped of like a console, but as small as an SPG. Either one has failed, but not both at the same time. Should that ever happen, I have a table (with hand-written nitrox equivalent depths) and a spare SPG in my save-a-dive kit.