Backup computer for when your main fails while in diving trip ?

[scubadada]

What exactly would be the issue when diving according to the buddy's computer for the day?

Inexact gas loading for the dive and all subsequent dives. Could you get away with it, probably yes,

 

[berndo]

Inexact gas loading for the dive and all subsequent dives. Could you get away with it, probably yes,

Again, your computer isn't that exact. Why wouldn't you 'get away with it' when your buddy is getting away with it? You're basically diving the same profiles. What's the danger supposed to be here?

 

[MB NZ]

What exactly would be the issue when diving according to the buddy's computer for the day?

In a perfect world, no issue, but it's not a perfect world. I've just spent the last week diving with an extremely nice, but slightly crazed Dutchman. We had broadly similar profiles, but they would not have been identical. Probably good enough, but maybe not. On a liveaboard, you are doing 3-4 dives per day. What happens when buddy decides to skip the night dive or the early morning dive?

 

[FishWatcher747]

In a perfect world, no issue, but it's not a perfect world. I've just spent the last week diving with an extremely nice, but slightly crazed Dutchman. We had broadly similar profiles, but they would not have been identical. Probably good enough, but maybe not. On a liveaboard, you are doing 3-4 dives per day. What happens when buddy decides to skip the night dive or the early morning dive?

Right. So now you are changing the subject to avoid the original issue.

So for the horrible buddy teams where your buddy is diving a consistently shallower profile as you are and is also consistently riding the NDL there may be a problem.

 

[scubadada]

Again, your computer isn't that exact. Why wouldn't you 'get away with it' when your buddy is getting away with it? You're basically diving the same profiles. What's the danger supposed to be here?

This is a no-win argument. Even in a group, I do not dive with a buddy. I dive my own profile and would like my computer to reflect that. Do what you like (Blind Faith), we all have our tolerances.

 

[berndo]

What happens when buddy decides to skip the night dive or the early morning dive?

You're changing the story now. When you use the spare computer it doesn't have the gas loading for that day but will be pretty close on the next day. If you have a buddy that dives a different profile, it's not a buddy.
The OP is diving with his wife and asked if it's ok to have cheap computer as a spare and the answer to that is yes. They don't need a 500 Euro or 1000 Euro computer as a spare and carry it on every dive. A 150 or 200 Euro Suunto or whatever will be fine.

 

[berndo]

Even in a group, I do not dive with a buddy. I dive my own profile and would like my computer to reflect that. Do what you like, we all have our tolerances.

The question was not about solo diving and I think you're missunderstanding the deco models. They are not exact numbers. The reason why you're supposed to dive conservatively and do a safety stop is because the models aren't that exact. Again, we are talking about single tank NDL diving. If you're diving solo, you might wanna bring a 2nd computer, but that was not the question.

 

[RyanT]

So for the horrible buddy teams where your buddy is diving a consistently shallower profile as you are and is also consistently riding the NDL there may be a problem.

I've seen this...many times.

 

[MB NZ]

Right. So now you are changing the subject to avoid the original issue.

So for the horrible buddy teams where your buddy is diving a consistently shallower profile as you are and is also consistently riding the NDL there may be a problem.

Apologies, I thought the discussion had moved on.

 

[MB NZ]

You're changing the story now. When you use the spare computer it doesn't have the gas loading for that day but will be pretty close on the next day. If you have a buddy that dives a different profile, it's not a buddy.
The OP is diving with his wife and asked if it's ok to have cheap computer as a spare and the answer to that is yes. They don't need a 500 Euro or 1000 Euro computer as a spare and carry it on every dive. A 150 or 200 Euro Suunto or whatever will be fine.

Apologies, I thought the discussion had moved on. Regardless, multi-dive, multi-day diving, night dive finishes at 9pm, morning dive starts at 0700. I wouldn't that confident in switching computers. As for the buddy thing. I was there for him. The reverse wasn't true. I was carrying redundant gas and I'm a solo diver at heart, so no drama, but I wouldn't want to be relying on his computer. Yes, it's wrong, bad practice, against the book, but it is what it is. Lastly, a recreational Suunto computer is going to **** it's pants if you dive a Shearwater, even with a gradient factor of 30/70.