Diving two computers ?

[Stoo]

For those types of dives,, it's hard to justify. The main advantage of a PDC is on mutilevel dives. A bottom timer and some tables in you pocket would do the job.

I used to use an Apeks Quantum as backup to my Petral. I found that on 40/85, the end result was about the same as the Quantum on medium conservancy. How I got there varied, but they both cleared about the same time. Most of my dives are in the 110' to 160' range, air back-gas and O2 for deco. Typically deco is around 3 or 4 minutes to 20 minutes, plus a little more for safety.

When Mrs Stoo got a Perdix, I sold the pucks. The Shearwaters are crazy reliable. If I am doing a "bigger" dive, she won't be there, so I borrow her Perdix for my backup.

 

[northernone]

Square profile recreational dive... I have been happy with a backup timer and tables in my pocket.

Realistically, it's NDL diving and I don't see need for the added cost and complexity of strapping on another computer.

What's the minimum doomsday planning scenario where it would be necessary to have a second computer?

Scenario that comes to mind for a OW diver in a buddy team as per their training:
1. Lost buddy
2. Lost/dead computer
3. Did not call the dive and ascend
4. Exceeded NDL

Seems like if I expect an equipment based solution to save me when all three of those seem likely the dive computer is the least of my worries.

Which situation are you thinking seems likely where you'd need it?

Cameron

 

[RyanT]

Are you saying having tables for 1,2,3, minutes passed NDL scenarios on top of the NDL profile we are diving?

Pretty much. If you make a short dive within the NDL limits, then obviously you can just make an ascent with safety stop. If something happens to your plan and you stay a couple of minutes longer, then you'd have a bottom timer and tables to tell you how long your obligation is at 15 or 20'. In all actuality, if you are planning NDL dives, then this is probably overkill. Personally though, when I drop much below 100', I like to have an alternative plan.

 

[RyanT]

@Landlocked123, does the viz in Juturna open up again near the bottom?

 

[caruso]

I dive 2 identical computers, if you're looking for votes.

 

[Chilly_Diver]

Given that I am now doing dives mostly in the 110-130 range I am considering purchasing another dive computer as a backup. These are bounce dives on air with very little bottom time - 2-6 minutes (I have very conservative gradient factors set on my petrel) as I am working on a charting project at the local quarry with a handful of dive buddies. I am trying to weigh if it makes sense to invest in another petrel as a backup given we will be pushing NDL limits. These are no deco dives but given the dive profiles I feel this may be a wise investment. Do most people that dive 2 computers dive the same one?

I would recommend a cheap bottom timer/gauge and AN/DP training.

 

[Magnus Lundstedt]

I dive 2 computers, not identical but simular.

I would say that what you can gain with a backup computer, in the kind of diving you do, is the ability to dive within 24 hours from a computer failiure.

If the computer fails you do not need any tables or extra computer, if the computer fails, just end the dive. I am sure you can surface and do a safety stop together with your buddy even if your computer have failed.

The advantage of having a backup computer is that you do not need to wait until complete reset of yout nitrogen levels before diving with a new computer.

 

[Landlocked123]

So while I understand that training and tables is the most fail proof fallback I still feel a secondary reliable computer would be a reliable solution as well. The scenario I wanted a backup reliable computer for is to account for any reason we may end up in deco. As I mentioned earlier we are taking as many precautions to avoid this. We carry multiple redundant lift options. Build in 3-4 minutes to work things out in case of any issues, use reels and strobes to venture off the shotline etc. Each dive is aimed at accomplishing a specific task and each time we dive the plan but in case Murphy shows up I just wanted redundancy in my computer as well. I have ran the different scenarios of foreseable dealys that would put us past NDL and the deco ogligations are minimal in the worst case scenario I could come up with (short of medical etc) a handful of minutes of deco. We carry an abundant amount of gas.

 

[Landlocked123]

Ryan - near zero viz 70 all the day down to 115. At 115 it opened up a bit and I would say 2-3 foot viz at 130. Cant say below that. Here is the profile from the dive.

 

[RyanT]

So while I understand that training and tables is the most fail proof fallback I still feel a secondary reliable computer would be a reliable solution as well.

Yes. If I could afford a second shearwater, so I was running identical algorithms, then two computers would be my choice.