printable copy of dive tables?

[tursiops]

I understand. What it comes down to is tht I was more right with my original belief than with my change of mind. Unless you do a pretty much direct ascent on your computer dive, you cannot use a table for a follow-up dive because you won't know your pressure group.

However, you could say you are in Pressure Group "Z" when you surface from that multilevel dive (you can't be any worse than that if you stayed within your NDL) and plan your next dive based on that.

The problem is, how do you know you are still within your NDL on the first dive? Sure, you can do a multi-level dive, but that does not tell you when you are approaching NDL. Not all multilevel dives will stay within NDL.

Here's an example: you are using your computer and drop down to 130 ft for just a few minutes; you computer says you are within your NDL (all is good) and you start up to do your multi-level dive. Your computer stops working. You do not know how long you can spend at 80 ft, or 60 ft, or 40 ft, and still stay within your NDL. All you can do is ascend at the moment your computer fails and go to the surface, ending your dive. Any other strategy risks going into deco and not knowing.

Now, if you want to do a repetitive dive, you can assume you are in PG "Z" and use the tables.

 

[boulderjohn]

The problem is, how do you know you are still within your NDL on the first dive?

You can only be sure if your computer works fine and then fails after the dive.

 

[Eric Sedletzky]

I understand. What it comes down to is that I was more right with my original belief than with my change of mind. Unless you do a pretty much direct ascent on your computer dive, you cannot use a table for a follow-up dive because you won't know your pressure group.

It’s still not going to be right.
The computer logs and takes into account every depth and time spent underwater from start to finish. A table begins as soon as you submerge, but the time you spend to get down to your bottom depth all goes towards that bottom depth time. Then when your bottom time is up you begin your ascent at which time the dive is over. But you have to make a direct ascent without dilly dallying at your 30’ per minute (used to be 60 or smallest bubbles) and make your stop.
The computer will continue to log all the time spent going down and coming up at each depth every few seconds. So no they are not the same.
There is no way to make a computer match the same profile as a table. If you run a table then way it’s supposed to be, most of the time they are more conservative than computers.

 

[boulderjohn]

It’s still not going to be right.
The computer logs and takes into account every depth and time spent underwater from start to finish. A table begins as soon as you submerge, but the time you spend to get down to your bottom depth all goes towards that bottom depth time. Then when your bottom time is up you begin your ascent at which time the dive is over. But you have to make a direct ascent without dilly dallying at your 30’ per minute (used to be 60 or smallest bubbles) and make your stop.
The computer will continue to log all the time spent going down and coming up at each depth every few seconds. So no they are not the same.
There is no way to make a computer match the same profile as a table. If you run a table then way it’s supposed to be, most of the time they are more conservative than computers.

I think I am being misinterpreted, but the idea that you have to go directly to the surface at a defined rate with tables is not correct. I did a study of ascent practices a few years ago with the intent of writing on article on best practices, and I got it from the top with PADI that there is no clear definition of how slowly you have to ascend when using tables--hence the "no faster than" language. DSAT's studies leading to the RDP did not show any problems with slower ascents, but it was not carefully studied. If you read the DAN articles, you will see the same vague "ascend slowly" language.

I never wrote that article because (as Simon Mitchell warned me when I started out) there is no good, clear information on delaying strategies for an NDL ascent. It really is the difference between a NDL dive and a decompression dive. If a diver has reached the level of required decompression stops, any delay adds to the need for decompression. With an NDL dive, you have a lot of range in ascent strategies before you go into deco and need more than a simple safety stop. As you point out, and as I have said countless times in the past, a table cannot calculate that.

 

[Stoo]

Tables can complicate the training process.

This is a unique spin on tables and training. It's been many years since I stopped teaching, so honestly I have no clue if tables are still taught or not. What I can tell you with absolute certainty is that computers fail. All. The. Time. Understanding tables should have given you a better idea of how your computer works. In an ideal world, all divers would carry some tables in their pocket for those days when the inevitable happens. As a minimum, if you're relying entirely on computers. you really should be wearing two of them.

As for having a set, any good shop should have some... There are many flavours of them.

 

[rongoodman]

Understanding tables should have given you a better idea of how your computer works.

People keep saying this but never explain why. The tables are just the output from some decompression model printed on a piece of paper or plastic. They say nothing about how the numbers were arrived at, or how your computer does what it does either.

 

[Stoo]

People keep saying this but never explain why. The tables are just the output from some decompression model printed on a piece of paper or plastic. They say nothing about how the numbers were arrived at, or how your computer does what it does either.

Well, the tables are generally the result of experimentation and calculations. I suppose for most people, the "how they were developed" isn't really important. What's important is that they have decades of use behind them, so as a backup to a computer, they're a cheap and simple option. FWIW, I just carry two computers... that's the simplest thing.

 

[OMyMyOHellYes]

computers fail. All. The. Time. Understanding tables should have given you a better idea of how your computer works. In an ideal world, all divers would carry some tables in their pocket for those days when the inevitable happens. As a minimum, if you're relying entirely on computers. you really should be wearing two of them.

Yup. computers fail. Papers do too: I lost them or left them in the hotel room or the clip holding them failed and they're sunk in 1,200 feet of sea water or my dog ate them or I dropped my cigar on them and they burned up.

I wanted to understand how they used to do it, so I did the research and figured tables out. Intelelctually, it was worth it to me but I am perversely old fashioned. I still use wet ink fountain pens and single-blade safety razors.

But I also did all my flight training using an old E6-B or Jeppesen CR. Whiz-wheels when electronic computers were available. But nobody uses whiz-wheels anymore. Except for a few that like the nostalgia. (My father was an AA pilot and they had to carry volumes of approach plates for every airport, enroute charts, and a Jeppesen CR computer (a very specialized circular slide rule a wind geometry disk on the back for figuring wind components and course correction). They don't do that any more. You will typically find none of those on a Part 121 carrier in the flight deck in the US now. They use iPads. Though most folk found it tedious, I actually enjoyed updating my binders with plate and chart revisions that arrived in the mail every couple of weeks.) Even more old-fashioned, once upon a time, jet airliners had a bubble window in the roof so crew could drag out a sextant and determine their position. They figured out better ways. That's how it is.

Those anachronistic ways gave way to better evolution of technology. That's how it goes.

I am completely a dive computer person in the water. But yes, redundancy is the rule.

 

[Stoo]

Papers do too: I lost them or left them in the hotel room or the clip holding them failed and they're sunk in 1,200 feet of sea water or my dog ate them or I dropped my cigar on them and they burned up.

LOL none of those are "failures". They're all operator error, without exception. A plastic table in a pocket, secured with a boltsnap is about as bombproof as you cant get. Of course for it to be of much use, you also need a watch and a depth gauge but most of us wear a watch, and if you've been paying any attention to your computer you likely know how deep you've been...

But I agree, dual 'pooters is definitely the simpler solution.

 

[Eric Sedletzky]

LOL none of those are "failures". They're all operator error, without exception. A plastic table in a pocket, secured with a boltsnap is about as bombproof as you cant get. Of course for it to be of much use, you also need a watch and a depth gauge but most of us wear a watch, and if you've been paying any attention to your computer you likely know how deep you've been...

But I agree, dual 'pooters is definitely the simpler solution.

We used to use those curved forearm slates that had flip up panels so we had alternate dive plans jotted down.
When I dive locally I don’t bother with a computer because I never het close to NDL. All my dives are dictated by gas supply.
If I don’t need it I don’t take it.