Info Why are tables not taught in OW classes anymore?

[tridacna]

I have over 2200 dives on DSAT, I've never been bent either

In 1978 I did over 140 dives in coldish ocean water (52-62F) with no tables. Every one over an hour. Never bent or even close. (I think). TBH…none were below 40 feet!

 

[scubadada]

In 1978 I did over 140 dives in coldish ocean water (52-62F) with no tables. Every one over an hour. Never bent or even close. (I think). TBH…none were below 40 feet!

I did a couple hundred dives between 1970 and 1980 on Navy tables, often up to the limts. Most of those were just a dive a day and I was much more like a Navy diver then

 

[dmaziuk]

1) DCS risk of ZHL-16C GFhigh 85% < X%.
2) DCS risk of "method" < DCS risk of ZHL-16C GFhigh 85% ("method" always produces shorter NDLs)
==>
3) DCS risk of "method" < X%

No further testing and validation is necessary to assert 3) if 1) and 2) are true.

Yes. Exactly. Herr Doktor Buhlmann has tested and verified ZH-L16 at GF High 85% and found the risk to be below X percent. Of something. Therefore no further anything is necessary.

 

[scubadada]

Yes. Exactly. Herr Doktor Buhlmann has tested and verified ZH-L16 at GF High 85% and found the risk to be below X percent. Of something. Therefore no further anything is necessary.

Take a look at the Saul Recreational Planner to get an idea of your risk of DCS at the NDL for your computer on air or 32%. The planner uses an ascent rate of 60 ft/min and includes a 3 min safety stop SAUL Recreational Dive Planner | Modern Decompression

 

[tridacna]

I did a couple hundred dives between 1970 and 1980 on Navy tables, often up to the limts. Most of those were just a dive a day and I was much more like a Navy diver then

You weren’t fighting lobsters. I still have the battle scars on my hands. We had tables but the 60/60 rule was what we followed. As a teenager I didn’t give a fig anyway because we were invincible.

 

[scubadada]

You weren’t fighting lobsters. I still have the battle scars on my hands. We had tables but the 60/60 rule was what we followed. As a teenager I didn’t give a fig anyway because we were invincible.

Ha, we just did difficult beach entries and exits in very cold water with poor visibility and entangling kelp everywhere. Yes, I was invincible. Of course, we did not have Great Whites going for our livers like you did

PS, you grab them by the tail so that they don't pinch you

 

[tursiops]

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?

Your dive can be done on the eRDPml. It does not violate any rules or put you into deco. Where the eRDPml results differ from yours is -- as a multilevel dive -- you get less NDL than you think by using the square tables. So, you actually end up closer to your nitrogen limits than you thought. This is the problem: using the square-profile tables does not tell you when your dive plan would have been flawed. You were fortunate.

 

[Eric Sedletzky]

Your dive can be done on the eRDPml. It does not violate any rules or put you into deco. Where the eRDPml results differ from yours is -- as a multilevel dive -- you get less NDL than you think by using the square tables. So, you actually end up closer to your nitrogen limits than you thought. This is the problem: using the square-profile tables does not tell you when your dive plan would have been flawed. You were fortunate.

I don’t have a wheel handy to check it, but I’ll ask around, maybe there’s one in a drawer somewhere at the dive shop. It would be interesting to see where the wheel would have stood on that dive.
I don’t know if I even remember how to use it.

 

[tursiops]

I don’t have a wheel handy to check it, but I’ll ask around, maybe there’s one in a drawer somewhere at the dive shop. It would be interesting to see where the wheel would have stood on that dive.
I don’t know if I even remember how to use it.

The Wheel is just a circular slide rule version of the eRDPml, so you should get the same answer as I did.

 

[boulderjohn]

As I remember the rules for tables are the dive starts from the time you drop under the waves and begin your descent to the time you are done at your deepest depth and begin your ascent. There is no hard rule on how long it takes you to get to the surface as long as you do not stop or exceed the speed of your smallest bubbles or 60’ per minute (now 30’ per minute).

This is the problem: using the square-profile tables does not tell you when your dive plan would have been flawed.

As I have said many, many times over the years, once you begin an ascent within NDLs, you can generally take your sweet time on that ascent, as long as you don't dilly dally long enough to go into deco. In many and perhaps most cases you will be just fine. The problem is you are winging it the whole time, and you won't know when you have crossed the line.