I finally get it (or, gauges and why they make sense)

First, some background:
I took Fundies almost half a year ago now, and have done about 50 dives since then. I was reasonably system-compatible going in, but certainly the class changed my diving, even having read a lot and spent two days with Bob (Sherwood) previously. During the class, though, I made a conscious decision not to give up my computer immediately but rather keep diving it in computer mode while I dove tables in my head, for a few reasons:
-Fundies preaches gauge use, but doesn't teach much if anything about the practical aspects of how to go about doing so (there are tables...but they weren't in the printed materials when I took the course, and they weren't taught, and tables are a pain to remember, etc.; there is ratio deco...but it's not taught at this level; and there's the rule of 120(air) and 130(Nitrox32), which appears nowhere in the printed materials, and is a bit hush hush, perhaps for liability reasons). It's rather like Helium in that respect (ask ScubaFeend how he feels about that one!).
-While I'm about as conservative about pushing limits as it gets, my OW training was hardcore Jersey (that's a positive, despite what some may think), and I still have the mindset of, "What if I get trapped in monofilament and am detained an extra 5 minutes?" Barring total catastrophic loss of my buddy's gas, I'd have plenty of gas to do any required deco, but I wouldn't know how much time I needed to spend doing it. A computer solves that. So would Ratio Deco, but again, not taught at this level.
-I sat down with the PADI NDL tables and compared them to the rule of 120, and found them to correspond pretty nicely, but I still didn't quite trust the thing. How good can it be when it's not written down anywhere?

Fast forward a few months (about 3 months ago), and I'm diving in 90fsw. Still diving rule of 130 (since I'm on Nitrox), with several minutes of MDL time to go. Computer decides I need 3 minutes of deco at 10 feet, but clears it by the time I reach 10 feet. Minorly annoying, but not a problem. It's a DiveRite Duo at SF2 (maximum conservatism). If it really bothered me I'd turn the SF down so it would be less conservative, but still act as a check.

Fast forward to this month, and I'm diving in 60fsw on air (ouch. Can I say that in this forum? ). Rule of 120 gives me another 8 minutes of MDL time. The computer decides at this point that I need 13 minutes of decompression...at 10 feet. Note this accumulated quite rapidly, since I noticed it at 3 minutes of decompression about three minutes prior, and had decided to ignore the computer since I was diving the rule of 120 and there was a simulated OOA situation which seemed more pressing.

Anyway, I'm done diving the computer as a computer. It's not the amount of deco (although given the OOA it became even clearer to me why more deco is not always better and that it's a balancing of risks), but that it wanted the entire 13 minutes at 10 feet. When I did a nice ascent at 30, then 20 for a while, then 10, it gave almost no credit for the 20 foot stop and penalized for the 30. If I really had racked up nearly the Rec3 course limit's worth of decompression, I'm quite sure I wouldn't want to do it all at 10 feet!

So if I had to do it over again, would I still keep the computer in computer mode post-Fundies? Yes. I think I learned a lot by making the transition pretty slow, and at very least I needed the crutch for a little while. But I think I've reached the point where it's more of a net risk than a net benefit.

Comments/criticisms welcome, as always.
Ari

You're not alone.

I dove my computer as a computer for about a year after Fundies . . . then I bent the thing, forgetting to reset it for Nitrox AGAIN on the third or fourth day of our Cozumel trip. And I kept diving, because I knew it was wrong -- and then I realized that, if I wasn't going to pay attention to what it said to me, I really didn't need it any more.

Nowadays, I let VPM run on my X1 because it does so politely, off in a corner, and does nothing more than sigh and shrug its shoulders if I don't do as I'm told. Not surprisingly, what I do as a result of my training correlates extremely well with what it wants, anyway.

disclaimer - not gue or utd trained.

i'm glad you feel you're at a comfy point, ari. i've been reminded yet again why i just don't ever think i can do ratio deco or the rules - doing math in my head means i'm not really diving, i'm doing math in my head.

we were doing a dive last week in a cave we'd never been in. we went a ways downstream, then turned around & passed our entrance & kept going upstream. i spent a *long* time doing the recalculated thirds in my head, and that's easy math. i'm not math phobic, i understand math concepts, but doing math in my head means that's *all i'm doing*. i had no idea what we passed on that part of the dive until we turned around again. for me, there would be no bandwidth left.

Lynne- You were, as always and as you are for so many folks, one of the influences on my decision. I knew you'd kept on with the computer for a bit, and while I would have likely done it anyway it helped reinforce my decision.

The X1 sounds great. I think if I were to possess a computer with a more modern deco algorithm I might delay the permanent switch to gauge mode. But the ridiculousness of 13 minutes at 10 feet just got to me. I haven't taken any deco classes, but I have read Deco For Divers and Bove & Davis cover-to-cover, and so I have enough of a sense of things to be incensed ;-)

BabyDuck- I think keeping on diving with the computer as a backup is a perfectly viable option...indefinitely if that makes you more comfortable. I just know that when I can do the math in my head I can anticipate rather than react, and that makes me more comfortable, whether or not I've got the computer there confirming things.

Part of my point in posting this was that I wasn't totally comfortable with it on the get-go. And I do a *lot* of math every day at the moment. At some point it's not about comfort with math, it's about comfort with the specific calculation. Knowing about triple integrals and convex sets doesn't help much underwater ;-)

Ari

P.S. Comfort levels are a funny thing as well. Will you ever find me in a cave? Never say never, but...well...never!

I really don't believe that a computer is a bad thing at the recreational level. I think I've got a pretty open mind about it, but I just don't think newer divers need that task loading. I *DO* think that they need to do as you do, and try to execute the dive only using the computer as a safety check.

Once at the cave/trimix level however, I don't think a computer is needed.

ucfdiver:

I really don't believe that a computer is a bad thing at the recreational level. I think I've got a pretty open mind about it, but I just don't think newer divers need that task loading. I *DO* think that they need to do as you do, and try to execute the dive only using the computer as a safety check.

Once at the cave/trimix level however, I don't think a computer is needed.

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It does take a lot of discipline to not rely on the computer, though. I know because even post-Fundies there were dives where I relied on it a bit too much (which is to say, entirely). I'm rather glad to be swapping it into gauge mode, because then there's no complacency.

gsk3:

It does take a lot of discipline to not rely on the computer, though. I know because even post-Fundies there were dives where I relied on it a bit too much (which is to say, entirely). I'm rather glad to be swapping it into gauge mode, because then there's no complacency.

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I'll agree, it's easily used as a crutch. Your post in this thread is IMO an excellent example of a computer being used as a tool. Most computers I see are being used as a crutch.

Of course, I've also seen divers with bottom timers only ascend just because others are, which is even worse than a crutch

ucfdiver:

I'll agree, it's easily used as a crutch. Your post in this thread is IMO an excellent example of a computer being used as a tool. Most computers I see are being used as a crutch.

Of course, I've also seen divers with bottom timers only ascend just because others are, which is even worse than a crutch

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Haha nice. Yeah, that would be a bad idear.

Even being used as a tool, I found it darn hard to ignore the screen showing X more minutes of deco. Even though I *knew* I could just ascend. I eventually ignored the last 3 minutes of deco on it, because after over 20 minutes of trying to clear the deco "obligation" I was too frustrated to bother (took me a while to figure out it wasn't clearing as quickly as expected, in part because it got rid of my total time display once it went into deco mode unless I pressed a button, and in part because it was my first dive in my drysuit and I was slightly underweighted while following buddy and so a bit task-loaded). Darn thing was still angry at me a week later, although I imagine it would have been ok with my diving after 48 hours

So the combination of not being happy with its profile, it ceasing to display valuable information (total time underwater) right when that info was most needed, and it being a source of stress...meant it was time for it to go into gauge mode.

gsk3:

So the combination of not being happy with its profile, it ceasing to display valuable information (total time underwater) right when that info was most needed, and it being a source of stress...meant it was time for it to go into gauge mode.

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Those are some key points of why I switched from using a computer (Aeris Elite T3) in Gauge Mode, then to just buying a dedicated bottom timer (Aladin Tec2G) and now my Aeris is still sitting on my back porch with a dead battery . Occasionally I would forget to put my Aeris into Gauge Mode and it would display a bunch of information I didn't really need and/or trust (Air Time Remaining: 3 hours+ when using my HP100 doubles on a shallow training dive) and just get in my way. But one time I left it in computer mode, on air, for a Nitrox32 dive with around a 70-foot avg depth and it was just happy with me. I went way beyond the air tables on that one, but Aeris didn't mind.

Peace,
Greg

If you had that many issues with a computer having deco that far off on NDL dives, I would suggest that there's a situational awareness issue going on at the surface. IE if you can't remember to set a computer, did you do any other predive checks?

For repetitive diving, the nitek duo is pretty darn hard to "bend" doing ocean dives (not impossible, but not as easy as sloping cave dives). If it's showing deco I'd pay more attention or question my depth averaging.