Solo and Redundant Computer(or how is most solo diving done?)

[iamjblevine]

In a different thread,

Redundant computer also needed.

Is this a realistic requirement for solo diving? I see a redundant computer a necessity on a dive vacation. Where you want to maximize time in the water. A loss of data means you sit out a day or more to clear the tables and start table diving. Is much solo diving done on vacations or is it mainly shore diving done on your own and if the computer dies, you thumb the dive.
That said, if you have a spare I can't see a reason not to carry it. I think for me where and how is most solo diving done?
Off a boat with an operator?
or
Shore independently of operators?


Thanks,

 

[chrpai]

That's the one thing I haven't brought myself around to buying yet. I was told to, but I just can't see the point for the solo dives I do.

I'm very aware of my depth, time and remaining NDL during a dive. I also have a mechanical SPG. I've tied knots into my reel at 5, 10, 15 and 20'. I figure if my computer craps out I'll just shoot a bag and ascend to twenty feet and turn the dive. The ABC song can be used to appx 30 seconds so I should be able to get pretty close to my exit point.

Maybe one of these days I'll get another computer.... or maybe someone will explain a reason I haven't thought of.

 

[GillScales]

Almost all of my solo dives are non-repetitive, single tank dives, usually above 60ft, so computers are not generally needed. If I'm on vacation and doing other dives within 24hrs, I'll bring my comp along to track RNTs etc.

 

[bbarnett51]

I don't need one for my dives but mine are fairly shallow. 60ft or less.

 

[BUDMANOK]

I get some strange looks but since I have them (3) computers I always wear two. Why not if you have them? The algorithms are similar so I get basically the same NDL from both.

 

[drrich2]

I use a backup (my old VT3, which I replaced with a Cobalt).

I'm thinking the recommendation might be rooted in the idea that many people rely on their computer for depth gauge functionality, and if a sensor malfunctioned and you were alone, with no one to notice you wandering down way deep, occasionally glancing at the backup might tip you off.

There are dive sites where one cold wander much deeper than intended without realizing it.

Another argument for it is human nature. Often people travel to dive, even if only a long car trip. Yes, if your main computer craps out, you should in theory call the dive immediately, and stop diving till you get it fixed or replaced. But some people might not do that - idiotic or not, it is what it is. If they've got a backup computer, that might help hold Darwin at bay for those who choose to keep diving anyway.

Richard.

 

[Dr. Lecter]

Computers die, sometimes unexpectedly. Ask yourself what you'd do if, at the worst possible moment in the dive (including whatever you think is a reasonable allowance for happens) your computer flooded. If you're not sure, or the answer involves a plan without any basis in deco theory, you should consider some form(s) of redundancy.

Personally, it depends on how close I'm cutting things. 120' dive with no more than 15 minutes of ascent time and a full set of double 100s/AL80 of 50% or 80%, I'm comfortable bringing one computer, my Seamaster, and a SMB with marked line. If the computer dies, I won't have any trouble figuring out a plan based on how long I've been down, the max and estimated average depths, and depth on the way back up . . . plus I have plenty of gas to fudge to the conservative side. 200' dive with over an hour of ascent time, or the same 120' dive on just a single tank, and I'll have at least two computers and a pre-cut set of tables on top of the watch, marked line, and brain.

 

[GrumpyOldGuy]

I do often dive with a backup computer for 2 of the reasons mentioned above
1) Save dive day if the battery dies suddenly (not needed to safely end the dive, just the next dives)
2) I don't trust the depth sensors, having 2 insures a flaky one won't endanger me and I will realize something is off even without a buddy.

 

[davidbaraff]

My computer is also my source for how much air I have (it is wireless and air-integrated). I pondered long and hard over whether or not I should buy an SPG as a source of redundancy should my computer fail during a dive, depriving me of knowing how much air I had left. I got some very good advice about this, which I will repeat here:

"At any point in your dive, you should always have enough air to surface. So if at some point you have a malfunction and you don't know how much air you have, if you're doing stuff right you know one thing for sure --- you have enough air to safely get back to the surface. So up you go, and your dive is over."

So if I ever look down and my computer has packed it in, no problem. I know I have enough air left for my safety stop, even, and certainly enough to get to the surface. So up I go.

That being said: I always bring my SPG along in my bag, so I can hook it up *on the boat* if for some reason my computer won't sync (i.e. a wireless transmission failure). That failure has never happened (er, since I started bringing the SPG along --- it failed on the boat and I hadn't brought the SPG along. Annoying. Not dangerous). The SPG has never moved from my bag, since I started bringing it along, on many many dives. (Many solo, many not.)

---------- Post added May 30th, 2013 at 08:54 PM ----------

I should perhaps mention that when I dive, I am far, far, far from the NDL limits, so there's never a chance I'm going to stray into decoland.

 

[gekodivebali]

Consider these 2 real life incidents that have happened to me with dive computers:
1) middle of a dive while guiding. Computer totally craps out. Tells me I'm at 200m then back to the surface then down to 60m. Temperature and air reading wrong as well. Luckily I'm not on my own and get assisted back to the surface. Should not have been the last dive of the day. Incident prompted me to dive with a second computer even on non-solo non-deco dives.
2) beginning of the dive. Computer does not turn into dive mode at the beginning of descent. I force it into dive mode at 5m. The reading is off by 5m / 15ft for the entire dive. Very glad I had my backup computer to hint at the fact that something was wrong.

The first example is the same thing that would happen with no more battery: the computer is completely out of the game. It's ok if you have a way of knowing how deep you are and how much time you spend. If not, you could guess where 5m deep is and pre-emptively decompress as good as you can for as long as you can... Having a backup computer is easier and safer IMO

The second incident is caused by an overused computer (3000+ dives) and a faulty depth sensor. Here the computer is feeding you false info. You could realise quickly if you know the dive site very well. If not, This one could quickly become a biggy. Spending 50 minutes at 23m when your computer believes, you've been at 18m is very likely to result in you missing a fair bit of deco obligation. You will/should notice the issue on the safety stop at latest when you're at 10m and the computer says 5. If you do realise you can decompress as good as you can for as long as you... Or just follow your back up computer!

At the end of the day, diving with fully redundant life support is the only safish way to dive solo... That or stayin in an environment where there is no risk of exceeding MOD and NDL!