The old tables vs computer argument

tridacna · Aug 12, 2009

I just came back from diving in Bermuda. There was a couple on the boat that "seemed" pretty competent. I had a brief chat with the wife on the ride out to the dive site. She saw that I used two computers and told me that she did not trust them and preferred tables. My dive was to max 60 ft for about an hour. She surfaced with her husband before us. No issues. Second dive was shallower; BT about 70 mins. But the bottom terrain was very "up and down" and in order to remain below the enormous surges, one had to navigate up and down a lot. My profile looked like a very ragged sawtooth Both my computers showed NDLs were not even close. She surfaced after me and my buddy. Apparently she had become "confused" about her tables/planning. End result: Mild DCS and six rides (so far) to the local chamber for her.

I suspect that it's just much easier to constantly monitor your NDLs with a computer than tables. It was almost impossible to stay at a constant or "planned" depth on this dive. How do table divers accomplish this?

RJP · Aug 12, 2009

tridacna:
End result: Mild DCS and six rides (so far) to the local chamber for her.

Mild DCS...and SIX chamber rides? Something ain't right there.

gsk3 · Aug 12, 2009

tridacna:
I suspect that it's just much easier to constantly monitor your NDLs with a computer than tables. It was almost impossible to stay at a constant or "planned" depth on this dive. How do table divers accomplish this?

You use the max depth as the input to the table and it works out just fine. You get less bottom time this way, but that's better than a DCS hit and winds up being more conservative than a computer (which gives you credit for the higher depths when you are at them, possibly inappropriately if you are "bubble pumping").

Personally I use a computer because I'm still not entirely comfortable with contingencies on tables, but I like knowing the table values as well in case all goes to ****.

Karloss · Aug 12, 2009

Personally if I were diving tables and ran into a situation to where I had to go deeper than my planned dive because of surge or whatnot, I would call the dive off.

Blackwood · Aug 12, 2009

tridacna:
It was almost impossible to stay at a constant or "planned" depth on this dive. How do table divers accomplish this?

Diligence.

Personally, when I dive N/MDL tables, I use the average depth of my profile, not the maximum. I also know my table without looking at it (it simply consists of the limit at each 10' rather than a huge array of information that is useless to me, and is thus very easy to memorize). If a site put my average depth a little deeper or shallower than I expected, I would adjust either my bottom time or my ascent profile accordingly.

tridacna · Aug 12, 2009

RJP:
Mild DCS...and SIX chamber rides? Something ain't right there.

Six USN 5 rides is not that unusual when you don't have to pay for them.

tridacna · Aug 12, 2009

squarepeg:
Personally if I were diving tables and ran into a situation to where I had to go deeper than my planned dive because of surge or whatnot, I would call the dive off.

Agreed. Which is why computers make more sense to me.

Garrobo · Aug 12, 2009

Many people of every generation have a problem acception new things. Like a home computer for instance. When the desktop PC was becoming popular I just didn't see the importance or the value of them. Changed my mind though when Windows 98 came out. Another instance is the electric starter on a Harley. I thought that only sissies would use a button to start one. After about twenty years of cranking, hurting my ankle and cussing because I didn't get the gas/air mixture right I gave up and got one. Never be without either one now. I've only dived with a computer and never learned the tables. It's going to stay that way.

rstofer · Aug 12, 2009

tridacna:
I suspect that it's just much easier to constantly monitor your NDLs with a computer than tables. It was almost impossible to stay at a constant or "planned" depth on this dive. How do table divers accomplish this?

It very easy. Just after the SIT, you precalculate the NDLs for all possible dives and write them on your slate. During the dive you look at your max depth needle and your timer. Simple as that. You don't mess with multi-level, all profiles are square and to your max depth.

There was a time before computers and when chambers were simply not available. At all...

Richard

rstofer · Aug 12, 2009

Blackwood:
Diligence.

Personally, when I dive N/MDL tables, I use the average depth of my profile, not the maximum. I also know my table without looking at it (it simply consists of the limit at each 10' rather than a huge array of information that is useless to me, and is thus very easy to memorize). If a site put my average depth a little deeper or shallower than I expected, I would adjust either my bottom time or my ascent profile accordingly.

It's pretty easy to memorize the first dive NDLs. Knowing the adjusted NDLs versus depth is a little more difficult. That's why I would write them on a slate.

I have never bothered to memorize the tables. They were always in my BC pocket and, in the old days, I could read them underwater.

Alas, today I use a computer. Not so much for the air calculations as for the Nitrox calcs. Particularly total OTL. I just don't want to do that calculation after every dive. In fact, were it not for Nitrox, I would have never bothered with a computer. I was quite happy with square profiles and NAUI tables.

Richard

The old tables vs computer argument

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