How do you back up your computer?

[NudeDiver]

NudeDiver, I'll bet that if you really did have a computer failure that you'd apply some common sense

Gee - I do believe I advocated using common sense several posts back....

I'll take my backup computer out of the dive bag, pop it into my console and bring it along for the next dive.

I fail to see the advantage of this approach vs simply diving with two computers in the first place, and several disadvantages. For example, if you're at 30m on your second of 4 planned dives for the day and your computer goes **** up - well, dive over. You also have just ended your buddy's dive. Thanks. Now you can make it back up to the surface, unaware of your depth (except for your buddy's computer), and possibly unaware of your air pressure (no help from the buddy there). Overall, you have heavily increased your dependence on your buddy. Once back to the surface, you can sit around on your extended surface interval, fooling around with your bag and your second computer, getting it set up, etc. Your buddy can spend his bitching about why you didn't have your backup computer with you ON THE DIVER. It's great that you HAVE a second computer - but had you had it with you at depth, you could have continued the dive, your buddy could have continued the dive, and neither of you would miss a beat.

Now - if BOTH of my computers crap out while out diving - then I am done. I can take the hint

 

[String]

If my computer dives on a dive i dig out the backup tables from my pocket to get out of that dive then assume code G (bsac tables) to start the SI calculations for the next dive. Its not hard. Certainly no reason to sit out the next dive or anything longer.

 

[Charlie99]

I fail to see the advantage of this approach <backup computer on the boat> vs simply diving with two computers in the first place, and several disadvantages. For example, if you're at 30m on your second of 4 planned dives for the day and your computer goes **** up - well, dive over. You also have just ended your buddy's dive. Thanks. Now you can make it back up to the surface, unaware of your depth (except for your buddy's computer), and possibly unaware of your air pressure (no help from the buddy there). Overall, you have heavily increased your dependence on your buddy. Once back to the surface, you can sit around on your extended surface interval, fooling around with your bag and your second computer, getting it set up, etc. Your buddy can spend his bitching about why you didn't have your backup computer with you ON THE DIVER. It's great that you HAVE a second computer - but had you had it with you at depth, you could have continued the dive, your buddy could have continued the dive, and neither of you would miss a beat.

Now - if BOTH of my computers crap out while out diving - then I am done. I can take the hint

I could bring spares of everything, including a spare BCD and an extra pair or two of fins, but somewhere you have to draw the line. I take with me on the dive what I need to safely abort the dive.

I have never been on a dive where I couldn't safely abort the dive if my computer failed. My non-AI computer has never failed on 600+ dives. If it does, I might end my dive early. Or I might simply go shallower than normal. For my diving, the risk-reward of a potential failure of the dive computer leads me to leave extra junk behind on the boat, while accepting a miniscule risk of having to abort a dive. Were I diving in conditions where I didn't have complete faith in my ability to safely abort without a computer, then I'd bring a backup.

My comment about you "applying common sense" wasn't meant as a personal dig at you. What I'm really trying to say is that a lot of experienced divers actually know a lot more about their profile and loading than they might think at first. If you are like a lot divers, many of your dives have similar profiles. You know what to expect on your computer on one of these familiar profiles. You may not be keeping track of your profile in any sort of formal way, but you know from experience what your computer should be saying.

You would also most likely know if you have been pushing NDL limits or not, and this would help you make a rational decision. An obvious example is a shore dive that I often do --- 70 to 90 minutes with a max depth of 40' or so, with typical average depth of 25 or 30'. Were my computer to fail between a pair of such dives (or even if it fails during such a dive) it would be a total non-issue. I would just complete my dive as usual.

 

[gcbryan]

I actually dive more like Nudediver but think more like Charlie. I have two wrist computers and usually wear them on every dive. I don't need to. If I only wore one and it failed on a dive it would be no problem but since I have two there is no reason not to strap both on. I've also done dives with no computer when mine failed on shore.

If they weren't wrist units I wouldn't use two. I keep one in guage mode (although on vacation I'd probably keep both in computer mode). If I decide to go into a little deco my computer quits giving me runtime info so I get that from the other unit in guage mode. I have had a computer's battery fail while underwater, I had one leak and fail, and another simply gave wildly inaccurate information.

Computers are just a backup to what you should already know however. I do believe that one shouldn't be using two computers because the failure of a computer is such a big deal...it's not.

As was pointed out, if you are aware of your surroundings and your computer goes out you know how deep you were when it went out. Just get substantially shallower and continue on with your dive. You will run out of air before anything else is a problem.

Keep your next dive shorter and shallower if you want to. Once you understand the parameters of your usual dives you will see that in many cases whether you have a computer or not it's hard to get into trouble (in many cases you could get into trouble of course!).

 

[NudeDiver]

If I only wore one and it failed on a dive it would be no problem but since I have two there is no reason not to strap both on.

Well, that's exactly it. Charlie's comment about the possibility of bringing spares of everything is completely non sequitur. If you don't HAVE two computers - OK, fine. But if you DO have two of them, given the complete triviality of bringing them both on the dive, I just don't see any reason not to. Clip the extra on the BC and forget about it - no worries. But if you actually need it, it seems like you (and your buddy) will be glad it's there. That's all

 

[DaleC]

I think the talk of redundant computers is interesting (and carry on by all means) but it doesn't really apply to the OP's question. He wants to know of a different method of calculating his dive profile that doesn't depend on a computer. The only option I can see is to begin learning tech techniques as Blackwood and the others suggest.

I don't see the need to wear two computers myself for simple rec diving (not the same as having two computers). As stated, any failure just calls for a common sense recollection of the max depth and rough time of the dive and then referral to the tables with enough padding to be safe. In my case I dive locally and can afford to take the time to do that.

Like Richard I use my computer for tracking depth and time but refer to the tables for my PG and SI's. I know that this isn't really representative of most dives but I prefer the conservative nature of a square profile at this point. From this prospective the only failure the computer offers is in the tracking of time/depth which can just be checked against a Buddy's numbers. I also use my common sense and adjust the tables somewhat depending on what the actual dive profile was.

Of course, that's just my opinion and doesn't necessarily apply to anyone else.

 

[gcbryan]

I think the talk of redundant computers is interesting (and carry on by all means) but it doesn't really apply to the OP's question. He wants to know of a different method of calculating his dive profile that doesn't depend on a computer. The only option I can see is to begin learning tech techniques as Blackwood and the others suggest.
...

The OP is the one who originally brought up the use of two computers I believe.
edit: actually I may be confusing "Sailnaked" and "Nudediver"
Regarding your comments above you don't even need to use "tech" techniques or depth averaging really. If you are diving within recreational limits your options are limited...no deeper than 130 fsw and depending on the site and your own preferences perhaps less. So all you really need to do is consider how deep you could possible go and how long you are allowed to stay there.

Just learn the NDL's for example for 60-100 fsw if that's your deepest range. The shallower stuff is not an issue. You can stay there until you run out of air so all you really need to know is how long you can stay at 60,70,80,90, and 100 fsw for example. That's not hard to remember.

In other words you back up your brain with a computer.

 

[Blackwood]

Just learn the NDL's for example for 60-100 fsw if that's your deepest range. The shallower stuff is not an issue. You can stay there until you run out of air so all you really need to know is how long you can stay at 60,70,80,90, and 100 fsw for example. That's not hard to remember.

Let's not forget that the OP specifically asked about multilevel diving, not how to default back to a square table.

Is there any system people have when diving multilevel to keep up with all the depths and times?

The answer being: yes.

 

[SailNaked]

Ok as the OP I can say what it is that I am looking for and basicly blackwood is right on thank you for your thoughtful and helpful posts. I have no desire to get 2 computers for my wife and I. yes she has one, and common conservatism says her dive computer is not mine and can not be used as mine, as in why she has one in the first place.

the answer to my question is there is not a "system" short of tracking it on a slate. to be able to recover exactly and transfer over to tables square or circular in the event of a computer failure, and I understand that you can ballpark it with keeping mental notes. I did not know that you could use average depth but that is another whole other discussion.

In my very limited experience, that would not have been sufficient, I dove a long time with some assumptions that were wrong. so it is a good thing I never got bent.

first I assumed that with one tank and less that 60Ft I was pretty much safe because I would run out of air before I hit the NDL. and that a 2 hour SI would put me back on that same curve.

My computer logged the two dives at the beginining of this post and when I went to log them and looked up the PG's I was shocked and that blew up my assumption.

Thank you all for your answers, I have a system in mind to do what I want and I will test it out next time I dive and let you all know if it is too distracting or simple enough to be used to back up the computer in a manual way.

 

[Charlie99]

I did not know that you could use average depth but that is another whole other discussion.

The super-condensed version of that discussion is that if you are going from deep to shallow, then you can safely use a square profile table using your average depth and total divetime.

For example, after first 10 minutes at 100' and then 10 minutes at 60' you will have N2 loadings a bit less than than if you had been 20 minutes at 80'. That is not true if you first did 10 minutes at 60' and then 10 minutes at 100'.