Necessity of a back up computer/watch for NDL diving

[dmaziuk]

This is incorrect. The multi-level calculations also take into account time not spent in ascent...which for a non-multilevel calculation is time to get to the surface.

Could you re-state it without the double-negative so I may actually understand what it means?

 

[Neilwood]

Being that this is a true multi-level dive of course I would use the computer only. Personally, I wouldn't bother to learn The Wheel or other ways to figure it out manually. On my very first post OW dive (no DC) I was down to 54' for maybe 3 minutes and the rest of the time about 20'. My tables said I should already be in the chamber....

My point exactly. Using a DC this is a do-able dive within NDL (at no point was I riding the NDL) however to try to cut this with tables will very likely have you in deco.

 

[dmaziuk]

My point exactly. Using a DC this is a do-able dive within NDL (at no point was I riding the NDL) however to try to cut this with tables will very likely have you in deco.

My understanding of the thread is that it's not whether you try to do this with tables -- who in their right mind would want to anyway, it's what you do if your computer dies just before this dive. There is no DC, that's the pre-condition. Pop quiz is

1. you wore the 2nd DC all along,
2. you miss the dive, or
3. what do you do hotshot?

 

[tursiops]

You wouldn't be thinking about this article, would you?

Why, yes, in fact, I would. Thanks for saving me the trouble of finding it!

 

[Joneill]

My understanding of the thread is that it's not whether you try to do this with tables -- who in their right mind would want to anyway, it's what you do if your computer dies just before this dive. There is no DC, that's the pre-condition. Pop quiz is

1. you wore the 2nd DC all along,
2. you miss the dive, or
3. what do you do hotshot?

I go with #1. I don't dive locally - therefore, I don't want to risk being sidelined by a nonfunctioning dive computer after spending money on a dive trip! For me, a backup DC is a no brainer!

 

[caruso]

I go with #1. I don't dive locally - therefore, I don't want to risk being sidelined by a nonfunctioning dive computer after spending money on a dive trip! For me, a backup DC is a no brainer!

^^^^This^^^^

 

[scubadada]

Sorry, who's going to use tables or the dive wheel for dives these days? Maybe in training, after that, why would you not use a computer?

 

[broncobowsher]

Sorry, who's going to use tables or the dive wheel for dives these days? Maybe in training, after that, why would you not use a computer?

A computer, or 2 computers? That is the question. A computer is given. But is the second a necessity or just a luxury? There is no edge where that happens. It is a transition. For a standard NDL dive you should have no issue ending a dive safely without a computer. Now starting another dive, that is the luxury part. If you need a computer to end your dive, you either are not diving NDL or got really crappy training.

 

[CT-Rich]

I haven’t read the full thread, but here are my thoughts;
Losing the AI will make subsequent dives much harder, because knowing how much gas you have is pretty much mission critical.

Not knowing depth and time are things that would bother me because I like to know things like that. However, they are not essential for every dive. If you are going to have a hard bottom at 40 fsw, none of that really matters. As long as you know approximately what what your first was and whether you have any chance going into deco on the second dive, you can decide what is reasonable.

Err on the side of caution,

Should you have a back up DC? Are you okay sitting out the next dive because your computer failure beached you? If the answer is “no” then buy a backup, keep a battery in it and stick it in your BCD pocket. It doesn’t need to be identical to the one that died, it just needs to be on all the dives and you know how to use it. A decent used DC can be had on eBay for $50. If you are using AI, you will want to have and SPG somewhere at hand.

Some people go on their Sunday dive expeditions without so much as a spare o-ring. How much extra crap you bring along is entirely up to you.

How much you are willing to adjust your dive plan or spend on backup gear is also upto the individual. I know people who could outfit another entire diver from the trunk of their car.

 

[TMHeimer]

I haven’t read the full thread, but here are my thoughts;
Losing the AI will make subsequent dives much harder, because knowing how much gas you have is pretty much mission critical.

Not knowing depth and time are things that would bother me because I like to know things like that. However, they are not essential for every dive. If you are going to have a hard bottom at 40 fsw, none of that really matters. As long as you know approximately what what your first was and whether you have any chance going into deco on the second dive, you can decide what is reasonable.

Err on the side of caution,

Should you have a back up DC? Are you okay sitting out the next dive because your computer failure beached you? If the answer is “no” then buy a backup, keep a battery in it and stick it in your BCD pocket. It doesn’t need to be identical to the one that died, it. Considering my just needs to be on all the dives and you know how to use it. A decent used DC can be had on eBay for $50. If you are using AI, you will want to have and SPG somewhere at hand.

Some people go their Sunday dive expeditions without so much as a spare o-ring. How much extra crap you bring along is entirely up to you.