Necessity of a back up computer/watch for NDL diving

[Clayton122]

I am currently trying to decide whether I should wear a back up in the form of a second dive computer (full redundancy as I need an AI feature) or watch (limited redundancy as I don't have an SPG) for rec diving strictly within NDL and am wondering what other SB members are doing and what their rationale is.

At the moment, I lean towards the conclusion that a backup device being unnecessary because in the event of a total dive computer failure or prolonged loss of AI signal, I would generally be aware of my air and NDL remaining, with the ability to shoot my DSMB up as an ascend line even in the event of buddy separation, with a little knot tied into the line at safety stop depth that would allow me to count 3 minutes in my head whilst remaining at the target depth. Should I lose my DSMB, the old slow conservative bubble guided direct ascend to the surface, with an optionally guessed safety stop in the shallows is still a backup-backup solution. The other point is that my dive computer would have to fail many times over for a second device and the hassle that comes with it to be practically and financially justified versus missing one or two dives of the day, which is fairly unlikely.

I'd like to know how you feel about the issue, whether your backup device has proven useful in the past (remember, let's assume no deco/overhead/solo diving for this scenario), whether you wear a dive watch out of old habit, or whether you put up with a second computer, just in case?

I had a back up save a dive for me recently.

I was doing some diving down in Tulum Mexico over New Years. I had set all my computers to 32% Nitrox the night before because that is what I had ordered from the Dive shop for the mornings dive.

What I had forgotten about, is my main computer ( Oceanic Pro Glide Plus 3 integrated air ) will reset its self back to 21% air after 12 hours of non use. My secondary computer ( wrist style Mares Puck Pro ) stays set to whatever you set it to forever until you put in a different setting.

About halfway through an 80 foot dive, my Oceanic was screaming at me to get to the surface, where as my wrist still gave me like 15 more minutes until I hit NDL. Without that wrist computer, I would have had to abort because I had not consulted a dive table to know what time I could spend at depth on 32%.

 

[AdivingBel]

 

[scrane]

I don't think a backup is a necessity for rec diving, and I wouldn't go out and buy a second computer as a backup, but if you happen to own two (or more) why not?

 

[seeker242]

Local NDL diving, no backup. An expensive trip with multiple dives over multiple days, where I don't want to miss a single dive, yes backup.

 

[BlueTrin]

Local NDL diving, no backup. An expensive trip with multiple dives over multiple days, where I don't want to miss a single dive, yes backup.

Makes sense, if you invested 5-10 business days of holidays + 1/2 day of packing and close to a thousand or more on flight and accommodation/food. It makes sense to protect the cost of your holiday

Plus you can get cheap computers on the second hand market which would be totally ok for a backup (or even as a main)

 

[scubadada]

I had a back up save a dive for me recently.

I was doing some diving down in Tulum Mexico over New Years. I had set all my computers to 32% Nitrox the night before because that is what I had ordered from the Dive shop for the mornings dive.

What I had forgotten about, is my main computer ( Oceanic Pro Glide Plus 3 integrated air ) will reset its self back to 21% air after 12 hours of non use. My secondary computer ( wrist style Mares Puck Pro ) stays set to whatever you set it to forever until you put in a different setting.

About halfway through an 80 foot dive, my Oceanic was screaming at me to get to the surface, where as my wrist still gave me like 15 more minutes until I hit NDL. Without that wrist computer, I would have had to abort because I had not consulted a dive table to know what time I could spend at depth on 32%.

So you still had your gas pressure on your PP3 and NDL on your backup computer. Unless you satisfied the deco obligation on your PP3 it would have gone into violation gauge mode and would not have cleared until a >24 hour SI. Did you continue to use your PP3 in gauge mode for subsequent dives or was that your last dive? You didn't mention anything about having a backup SPG

 

[Clayton122]

So you still had your gas pressure on your PP3 and NDL on your backup computer. Unless you satisfied the deco obligation on your PP3 it would have gone into violation gauge mode and would not have cleared until a >24 hour SI. Did you continue to use your PP3 in gauge mode for subsequent dives or was that your last dive? You didn't mention anything about having a backup SPG

I turned off all the audible alarms at that point, and just used the PP3 as my SPG for the next dive, and used my back up for NDL. NDL wasnt an issue on the next dive anyways as it was a very shallow dive.

First dive was @ 80 feet, second dive was @ 30 feet.

 

[NorCalDM]

As others have said if I'm on a trip I always have two computers but local shore diving not so much. Also when I'm diving recreational nitrox I usually run an air profile but I always analyze my cylinder and check my MOD.

 

[Chavodel8en]

I'm a cheapskate. For years, my primary device was a (cheap ironman) watch & the depth gauge that came w my used regulator. I was mainly doing local shallow shore dives, so it was fine. There are a few local shore dives where I could get deep - I just avoided going deep. So that was me for like 6 years, 75 dives.

I only bought a computer when I had a vacation coming w/ deeper recreational wreck diving. I used the watch + depth gauge as backup. Didn't feel the need to account for the small chance of my computer dying, especially since I have a non-diving spouse, so I don't dive every day on vacation - or at home.

But recently, the Puck Pros were soooo cheap on LeisurePro ($150 I think) that I just bought one.

So my next dive, after ~150 dives, I will finally have 2 computers with me. My cheap earlier self is ashamed of me. I still voted "watch", as that has been my general gear.

 

[Clayton122]

I'm a cheapskate. For years, my primary device was a (cheap ironman) watch & the depth gauge that came w my used regulator. I was mainly doing local shallow shore dives, so it was fine. There are a few local shore dives where I could get deep - I just avoided going deep. So that was me for like 6 years, 75 dives.

I only bought a computer when I had a vacation coming w/ deeper recreational wreck diving. I used the watch + depth gauge as backup. Didn't feel the need to account for the small chance of my computer dying, especially since I have a non-diving spouse, so I don't dive every day on vacation - or at home.

But recently, the Puck Pros were soooo cheap on LeisurePro ($150 I think) that I just bought one.

So my next dive, after ~150 dives, I will finally have 2 computers with me. My cheap earlier self is ashamed of me. I still voted "watch", as that has been my general gear.

My Puck Pro was my first computer, and I still love it. I often refer to that over my primary air integrated computer.