Computer + SPG? Or am I crazy?

[jhelmuth]

Personally I'd be hard pressed to scrub dives following a computer failure. I'd have a long surface interval to be sure, but I keep track of the dive as I'm going along.

I personally would have no trouble bailing out to tables after the computer failed.

Now folks, that's ME and how I would do it. You do it however you want to and keep the flames away. I feel comfortable enough with dive planning that I could figure my N2 loading pretty closely if the damn computer broke on a dive.

Could you sahre with us how you can figure your N2 loading pretty closely (under the prescribed failure0? Let's assume a 5 day dive trip and you're into day 3 on the 2nd dive... (total of 15 planned dives)



Thanks,


Jim

 

[The Kraken]

Nope, you're not crazy. If you are, then so am I.

With my dive watch, which also serves as a depth gauge, an SPG gives me complete redundancy in the case of computer failure.

the K

 

[Arizona_SVO]

OK... so what you are now revealing is that you are diving with a full set of gauges, and that you might be OK as long as you don't bust the tables (which IS table diving).

Note that is EXACTLY what I posted/said...


All the best,

Jim

Sorry, I musta missed that part where you said that.

Thought I made that clear that I dive with both based on my aviation experiences - so I can certainly see where the confusion sets in.

All the best right back to ya. Glad we got that cleared up.

 

[Randy43068]

Could you sahre with us how you can figure your N2 loading pretty closely (under the prescribed failure0? Let's assume a 5 day dive trip and you're into day 3 on the 2nd dive... (total of 15 planned dives)



Thanks,


Jim

Don't worry about it, it's what I'd do, not you.

 

[vladimir]

How will you properly plan your remaining dives and keep proper track of you inert gas loading under your proposed plan? please elabourate.

Stop and think through the problem, and you'll come to the same conclusion. Not doing the next dive (for 24 hours anyway) is not a tragedy - just a safe and proper practice underr the described circumstance.

UNLESS you had been diving tables (and then why have the computer), you MUST abandon all diving for a period of 24 hours (per table rules) to get back to a known saturation (for the puropse of table diving - or even to go to a new computer for that matter). Once you've established a new know basis, you can finish up diving.

Continuing a dive (under the portrayed AI computer failure) without a full set of gauges is a foolish thing to do. The proper and prudent procedure would be to abort the dive, get to a know state of saturation and pick up the diving from there.

You can do what you want - but the proper procedure (as I described it) is a well thought out plan for such a case. But you can obviously do whatever you want...

Here's another take on the question:

This question has been answered several times in the past, so here it is, one more time:

The AAUS Dive Computer workshop recommends 18 hours out of the water.

At the same workshop Emmerman and Sharkey presented ways of accurately getting onto tables if you'd kept good records, that they had independently worked out (references are to the Navy tables that were in use at the time, but the same approach will work with other tables:

Record the time of day, put the computer in dive planning mode, record all the Depth/Adjusted NOD limit pairs as they scrolled by on the computer (e.g., 60 ft would permit a 22 minute NOD dive, 50 feet would permit a 31 minute … etc). Each Adjusted NOD limit would be subtracted from the NOD limit for a new diver at that depth (e.g., for 60 ft: 60 min – 22 min = 38 min. For 50 ft: 100 min – 31 min = 69 min … etc.) that yields a number that represents how long you would have had to dive to that depth to have the amount of nitrogen you now have in you. Then you take each Depth/Time of Theoretical Dive back to the Repetitive Group Designation Table and grab a Group Designator (e.g., for 60 ft and 38 min: Group G. For 50 feet and 69 min: Group I … etc.) Then you take the “worst possible case” that is to say the highest letter (e.g., “I” in the example we are running).

So you'd call yourself a Group I diver at the time you originally recorded, and thus be able to use the tables. The only way to get back onto a computer, however, is to follow standard computer failure protocols (which was agreed at that workshop to be no diving for 18 hours).

Not simple, but potentially useful, the full write-ups can be found in the proceedings at the RUBICON site (free, but send them money anyway, it's for the best possible cause, the advancement of human knowledge).

Other thoughts if you can't sit out for 18 hours:

Two hours of surface breathing oxygen will take you from U.S. Navy Group N to Group A.

A couple of hours with a pure oxygen rebreather (or an oxygen stage) at 15 feet would set you up even better.

 

[Randy43068]

I don't dive with a computer, but with tables. Usually my limitation isn't N2 on a dive, but the air I'm carrying.

What I It would depend on where I was in the dive, depending on how many dives for the day, how many dives I've done over the last few days. I may not dive the rest of the day, but I'd probably not stay out for a full 24. But again, that would depend on where I was with how many days and such.

I agree, staying out for 24 is the best approach, but I may not do that. If the thing failed early on the first dive of the day, I'd just bail out to tables.

When I used to dive a computer I would check against tables for time and avg depth to see where I was. I never used a computer exclusively and probably never will.

 

[jhelmuth]

Don't worry about it, it's what I'd do, not you.

...I don't worry about it at all. Just thought you could share your wisdom with the rest of us. There is always the possibility that there is no good way to do what you say. Either way, it's informative....


All the best,

Jim

 

[Randy43068]

...I don't worry about it at all. Just thought you could share your wisdom with the rest of us. There is always the possibility that there is no good way to do what you say. Either way, it's informative....


All the best,

Jim

I'm not saying it's the best way, I'm not saying anyone else should do it. But to make the blanket statement that if the computer dies on a dive then I'm out for 24 may or may not be true. What I'd do would depend on a number of factors. That's all I'm trying to say.

But then again in the "real world" if it were to happen on a nice liveaboard I'd probably have no problem being out of the water for a day to enjoy the boat. Part of the fun of diving for me is the boat ride.

 

[jhelmuth]

I'm not saying it's the best way, I'm not saying anyone else should do it. But to make the blanket statement that if the computer dies on a dive then I'm out for 24 may or may not be true. What I'd do would depend on a number of factors. That's all I'm trying to say.

But then again in the "real world" if it were to happen on a nice liveaboard I'd probably have no problem being out of the water for a day to enjoy the boat. Part of the fun of diving for me is the boat ride.

It wasn't a blanket statement (go back and re-read what I posted... I think you and I are agreening that IF you are diving table with a computer as a back up, then it's not an issue - but that was NOT the premise of the discussion regarding the need for an SPG "backup" with an AI computer in case it fails).

However.... as an experienced (but un-certified) diver, do you feel that your training and knowledge is better in such matters than decades or professional research and data? BTW... that data was taken from "real world".

 

[Randy43068]

I'm not taking the bait..