Computers & DIR

[Soggy]

What formula do you use to extrapolate heluim mixtures (EAD) ?

For 21/35, I dive it just like the air tables say, but add deep stops at 80% and 65% ATAs based on my maximum depth.

30/30 (if I ever used it) would be dived just like 32% (a 20% EAD advantage over air)....again, with a proper ascent and deep stops, although not as deep. I usually do my first stop on 32% or 30/30 at around 50% of my maximum depth.

 

[maximdim]

As soon as you start doing gas switches during the same dive you'd find your computer almost useless (unless it has support for multi gases, but then we're really talking expensive). What's the point ot see NDL which computer calculated based on 32% O2 if you already switched to 50%?

 

[Goose75]

...if reliability is a consideration, wouldn't a digit BT suffer some of the same fates as a computer?

I have to agree with you there.

 

[Randy43068]

I have to agree with you there.

your watch is also your backup timer of sorts.

 

[lamont]

Dive computers have been getting better. For recreational diving and less aggressive technical dives the major objection to them are going to be:

- not diving with your brain fully engaged
- setting the gas mixtures and such wrong and other UI issues
- stupid ways they may punish you because the manufacturer doesn't want to get sued

And for aggressive technical dives, you won't find a computer out there that will replicate WKPP schedules, e.g.:

http://www.wkpp.org/articles/Decompression/max_deco.htm

If you can find a computer that doesn't have fits over the CNS% and the O2 at 30 fsw in that profile and gives correct deep stops, it'll still probably give at least 2x the deco in that schedule. I also have a hard time picturing what a good UI would be that would allow you to run that dive without making any mistakes (particularly if you're task loaded because something went into the crapper and pushing buttons on the bend-o-matic is the last thing on your mind...)

 

[Rick Inman]

Dive computers have been getting better. For recreational diving and less aggressive technical dives the major objection to them are going to be:

- not diving with your brain fully engaged
- setting the gas mixtures and such wrong and other UI issues
- stupid ways they may punish you because the manufacturer doesn't want to get sued

And for aggressive technical dives, you won't find a computer out there that will replicate WKPP schedules, e.g.:

http://www.wkpp.org/articles/Decompression/max_deco.htm

If you can find a computer that doesn't have fits over the CNS% and the O2 at 30 fsw in that profile and gives correct deep stops, it'll still probably give at least 2x the deco in that schedule. I also have a hard time picturing what a good UI would be that would allow you to run that dive without making any mistakes (particularly if you're task loaded because something went into the crapper and pushing buttons on the bend-o-matic is the last thing on your mind...)

My computer told me I was just fine on the dives before I got bent a few weeks ago.

Last week, when I hit 85', my computer started flashing at me and beeping at me with arrows flashing to go up and basically shouting to me that I was going to die.

I ignored it and followed our plan.

Turns out (discovered after the dive), that when I was changing the EAN%, I had also somehow changed the PPO2 to 1.0.

 

[Goose75]

Dive computers have been getting better. For recreational diving and less aggressive technical dives the major objection to them are going to be:

- not diving with your brain fully engaged
- setting the gas mixtures and such wrong and other UI issues
- stupid ways they may punish you because the manufacturer doesn't want to get sued

...)

I'm not a tec diver but I'm working in that direction. With that in mind, here's my thoughts on your points:

-Diving has no monopoly on this very real problem. Plenty of threads along these lines.
-I can see this as an increased concern that needs due diligence but not rejection.
-Yup. It's pretty much guaranteed they will and they will be sued anyway.

 

[HarryH97]

So I'm reading the DIR Fundamentals book, and I have a few questions/comments regarding the dis-approval of computers when "Doing It Right. My class is still 4 months away, but I like to be prepared. For those of you at home, please follow along in your book (page 107).

I was going to go over each of the Baker's Dozen, but after re-reading this a dozen times, all the points seem to direct to the same argument that computers are too inflexable.

My 10 years of diving has always told me the opposite. Granted, I have not used computer generated tables very often, but in my experience, the implied conservatism of a computer is alway much more flexible than tables.

I whole-heartedly agree that there is a relience on computers, expecially among long time computer divers, but how would diving a digital bottom timer be any different than diving a wrist mounted, non-air integrated computer?

What you find out is that all you need is Depth and Time to figure out your ascent strategy. It's actually quite simple. With MDL, Deep Stops, and slow ascents, you're going to be cleaner than what your computer says. In fact, if you aren't clean, you can readjust your ascent curve to get cleaner. The reference/set points and learning how to shape your curve will carry you thru trimix and multi-level diving. You'll find tremendous freedom in readjusting your dive "on the fly" as situations dictate and have a higher level of situational awareness without a computer. And best of all, you don't even need to carry any deco tables.

As for gauges failing, you can always ask your teammates for regular depth sampling if you're multi-leveling. Otherwise, with deep square profiles, max depth is all you need along with your time. That's why the back-up timer is so important.

After the class, you can sell your computer.

Sincerely,
H2

 

[boomx5]

What kind of software do you use, and what about multi-level diving?

I don't normally use software. As far as multilevel dives go, we use a form of depth averaging and ratio deco adjusted on the fly to get our profiles. It's actually quite simple to do if one is given the tools on how to accomplish the task. For the record, I'm not against software generated tables as I have used them before, I just don't use them for 99% of my diving.

 

[lamont]

There's an episode of Deep Sea Detectives where Chatterton gets out of the water and says something like "Both my dive computers went out on my that dive -- that's why you've got a buddy" which pretty much sums up why I think dive computers in technical diving are a bad idea. Given the number of times I've forgotten to set my computer to 32% on the surface before a dive, I'm pretty sure that I'd forget to punch in gas switches underwater and render the computer information useless for the rest of the dive.

I now manage (obviously not alone) something like 23,000 Linux boxes, and I'm far from technophobic, but I also have a deep appreciation of the limitations of technology. One of those worst limitations is the UI and the possibility of making mistakes with the UI. Having a readout of depth and time, relying on your brain and with redundant information from 2 other teammates is the simplest UI possible.

Incidentally, I also dive recreationally now with a Suunto Vyper that is still in computer mode. Personally I think that stating a rule like "no computers" is short-sighted. However, my experience with my Vyper in computer mode is that its kind of annoying. If I jump into the water after having forgot to set it to 32%, then the computer functionality becomes largely useless. I can't fix that problem in the water because Suunto's lawyers are probably worried about people people pushing past their NDLs by adjusting their gas mixture in the water. After I get out, I'll have done a "deco dive" and the Vyper will be displaying a little "!" mark and will have given me too much gas loading and will arbitrarily punish my NDLs on the next dive because I went into deco (and not due to anything with the actual deco model, but just an arbitrary factor). And there's no way to fix it after I get out, again because the lawyers are probably "concerned for my safety". If that's an example of a good computer for recreational use, I'll really doubt anyone makes a good computer for technical diving where the UI issues are much worse...