Info Why are tables not taught in OW classes anymore?

[chillyinCanada]

I hope an explanation will be offered. The purpose of using a table is to avoid going into deco. Using a table in a way that is not intended can put you into deco. So are you saying that if we write about why such procedures should not be used when using a table, we are too advanced?

No

 

[John C. Ratliff]

I thought I'd add some perspective to this discussion. Here's the way we conducted a dive in the 1970s, before dive computers (I don't like using a lot of acronyms).

Blue Lake Log001 by John Ratliff, on Flickr

Blue Lake Log002 by John Ratliff, on Flickr

Now, you can see that we used not only dive tables, but had to use the altitude dive tables. Obviously, today with dive computers this would have been an easier dive. BUT, I think the dive computer would need to be set up for diving at an altitude of 3500 feet.

Now, a challenge to you guys and gals; can you now come up with a dive log in this kind of detail that shows exactly what you did on your dive almost fifty years later (48 years, actually)?

SeaRat

 

[tursiops]

My major objection here was the extensive discussion of using tables for multilevel dives, I think that discussion belonged elsewhere.

Is the contention that basic diving does not include multilevel dives?

The whole point of the OP was to say that today's OW divers mostly do multilevel dives, and tables are not designed to do that, while computers do it automatically.

 

[steinbil]

I do not think that is the case. My major objection here was the extensive discussion of using tables for multilevel dives, I think that discussion belonged elsewhere.

I was taught using tables for multilevel dives in my OW class in 2021. I dived this way until a few months after I got my Perdix, when I decided to try the Tech mode. It's a valid alternative to computers for completely novice divers right out of OW.

How is this not basic?

 

[Blackcrusader]

The whole point of the OP was to say that today's OW divers mostly do multilevel dives, and tables are not designed to do that, while computers do it automatically.

Or you could say " my thoughts are that today's OW divers mostly do multilevel dives, and tables are not designed to do that, while computers do it automatically" as you are the OP lol

This is how it is with multilevel recreational dives, I just rely on my Perdix to do real time dive NDL calculations and let me just relax and enjoy my dives.

 

[EFX]

I thought I'd add some perspective to this discussion. Here's the way we conducted a dive in the 1970s, before dive computers (I don't like using a lot of acronyms).

Blue Lake Log001 by John Ratliff, on Flickr

Blue Lake Log002 by John Ratliff, on Flickr

Now, you can see that we used not only dive tables, but had to use the altitude dive tables. Obviously, today with dive computers this would have been an easier dive. BUT, I think the dive computer would need to be set up for diving at an altitude of 3500 feet.

Now, a challenge to you guys and gals; can you now come up with a dive log in this kind of detail that shows exactly what you did on your dive almost fifty years later (48 years, actually)?

SeaRat

Curiously, nothing about exposure protection and nothing on weight. So, not detailed enough for me. Unless those details are in your write up which I had a hard time reading.

 

[John C. Ratliff]

Curiously, nothing about exposure protection and nothing on weight. So, not detailed enough for me. Unless those details are in your write up which I had a hard time reading.

The water temperature was listed as 45 degrees F, and two of us were in full wetsuits, with Bruce in a Unisuit (one of the first successful neoprene dry suits). I had both a hood and a full-face mask with neoprene around the edges, which kept the cold water off my face totally. Each of us also had either gloves or mitts (3-finger mitts were used early-on, mostly home-made). Bruce’s Unisuit leaked, and he only had a space blanket on under it and so he got pretty cold. I remarked in the write-up that the space blanket only restricted radiant heat, and not conductive or connective heat loss. So the Unisuit, once it was compromised by the leak, was not as good as our wetsuits.

I also mentioned that I did a weight check, and needed to take some weight off my weight belt to be neurally buoyant.

I understand that now cursive writing is not even taught in schools, so my handwritten log would be doubly hard to read (cursive, plus poorly written cursive with abbreviations).

SeaRat

 

[Eric Sedletzky]

Alright @boulderjohn and @tursiops, tell me what you think about this dive on tables.
First dive of the day, no residual nitrogen.
Descend to 90’, spend 13 mins at 90’ including descent time and then moving up to 60’.
90’ max NDL- 25 mins. 13 spent = 50% BT used.
60’ original NDL - 55 mins, new allowable NDL 27 mins. Time spent at 60’ - 13 mins, move up to 40’ (13 mins includes time to get up to 40’)
Original full NDL at 40 = 140 mins. New time
Allowed = 35 (.75 of NDL has been used up at 90’ and 60’) spend 30 mins at 40’. Go to 15’ for 4 mins then end dive.
Total dive including descent, bottom time(s), ascent, and stop, total dive time 1 hour.
Is this dive doable and reasonably safe in your opinions even though it violates the rules if the PADI tables?

 

[scubadada]

Alright @boulderjohn and @tursiops, tell me what you think about this dive on tables.
First dive of the day, no residual nitrogen.
Descend to 90’, spend 13 mins at 90’ including descent time and then moving up to 60’.
90’ max NDL- 25 mins. 13 spent = 50% BT used.
60’ original NDL - 55 mins, new allowable NDL 27 mins. Time spent at 60’ - 13 mins, move up to 40’ (13 mins includes time to get up to 40’)
Original full NDL at 40 = 140 mins. New time
Allowed = 35 (.75 of NDL has been used up at 90’ and 60’) spend 30 mins at 40’. Go to 15’ for 4 mins then end dive.
Total dive including descent, bottom time(s), ascent, and stop, total dive time 1 hour.
Is this dive doable and reasonably safe in your opinions even though it violates the rules if the PADI tables?

I don't know about your table calculations, MultiDeco thinks the dive is OK. A GF high of 95 is pretty close to PADI RDP NDLs, probably a little less.

 

[boulderjohn]

Alright @boulderjohn and @tursiops, tell me what you think about this dive on tables.
First dive of the day, no residual nitrogen.
Descend to 90’, spend 13 mins at 90’ including descent time and then moving up to 60’.
90’ max NDL- 25 mins. 13 spent = 50% BT used.
60’ original NDL - 55 mins, new allowable NDL 27 mins. Time spent at 60’ - 13 mins, move up to 40’ (13 mins includes time to get up to 40’)
Original full NDL at 40 = 140 mins. New time
Allowed = 35 (.75 of NDL has been used up at 90’ and 60’) spend 30 mins at 40’. Go to 15’ for 4 mins then end dive.
Total dive including descent, bottom time(s), ascent, and stop, total dive time 1 hour.
Is this dive doable and reasonably safe in your opinions even though it violates the rules if the PADI tables?

As someone with a whole lot of experience doing multilevel dives with a computer, I will answer off the top of my head. If I left 90 feet after 13 minutes and went to 60 feet, my computer would be showing me a lot of NDL time remaining. If I left 60 feet after 13 minutes and ascended to 40 feet, I'm sure my computer would show me that I had a lot more than 30 minutes. With a computer and enough gas, this could easily become a 90 minute dive.

So your suggested dive profile would result in a safe dive.

The problem is that your system is untested and unverified by any research. It might produce a safe dive, as it did in this case. It might not. Right now the only way to confirm it is to compare it with a computer, as scubadada did. The only thing we know based on research is that the table guidance was over one minute before you left the 60 foot level. After that, you were diving without any established guidance.