Stressed out about Dive Tables

[CPTOZZY]

Last Christmas I paid for my son and his girlfriend to get Certified. The Day before the Written Test He was stressing out about how much information there was and how it was impossible to expect him to learn it in such a short time.
Now my kid is smart (I'm not just saying that either), so it kind of took me buy surprise. I was thinking maybe he doesn't want to get certified, Maybe he is scared of the open water, maybe.....

Then he blurted out, "The Gas laws and physics are easy, but I've only got the dive table memorized to 70 feet - Theres no way I'll have it all memorized, much less be able to calculate multiple dives by tomorrow".

........crickets.......crickets

ahhh - uuhmm...I replied.. "You don't have to MEMORIZE the Dive tables son, they let you look at them for the test"

[Vercingetorix]

Heck, our test was a take-home test. Open book, too.

But, ya gotta admire the lad's determination.

[BouzoukiJoe A.K.A. wrecker130 AKA Chuck Norris AKA joeforbroke (banned)]

Originally Posted by CPTOZZY

Last Christmas I paid for my son and his girlfriend to get Certified. The Day before the Written Test He was stressing out about how much information there was and how it was impossible to expect him to learn it in such a short time.
Now my kid is smart (I'm not just saying that either), so it kind of took me buy surprise. I was thinking maybe he doesn't want to get certified, Maybe he is scared of the open water, maybe.....

Then he blurted out, "The Gas laws and physics are easy, but I've only got the dive table memorized to 70 feet - Theres no way I'll have it all memorized, much less be able to calculate multiple dives by tomorrow".

........crickets.......crickets

ahhh - uuhmm...I replied.. "You don't have to MEMORIZE the Dive tables son, they let you look at them for the test"

Too funny.

[Rainer]

Funny story.

Serious question, though: Do you guys not have the dive tables memorized at this point? At least max NDLs for a given recreational depth? Having that stuff committed to memory (or even just the 120 rule) makes dive planning a lot easier. I wish my OW instructor had emphasized this.

[BouzoukiJoe A.K.A. wrecker130 AKA Chuck Norris AKA joeforbroke (banned)]

I know the 120 rule and some, but not all of the NDLs. I definitely don't know pressure grouops and RNTs by heart.

I always know before I dive at what point I need to be back at the anchor line - I have a table in my pocket and some stuff written on my slate to help me get out of a jamb if I have a computer failure.

I'm sure I will learn a lot more avout dive planning in my deco class.

[Rainer]

Originally Posted by BouzoukiJoe

I know the 120 rule and some, but not all of the NDLs. I definitely don't know pressure grouops and RNTs by heart.

I always know before I dive at what point I need to be back at the anchor line - I have a table in my pocket and some stuff written on my slate to help me get out of a jamb if I have a computer failure.

I'm sure I will learn a lot more avout dive planning in my deco class.

Yeah, having the pressure group / RNT stuff memorized would be a bit much. For the diving we do, however, knowing max allowable NDLs is all we make use of (plus standard gases and proscribed ascent rates).

[reactive]

I'm gonna bite... What's the 120 rule?

[navyhmc]

It took me a while to re-memorize the NDL's because I learned on the older charts where 60' was NDL of 60 minutes. Like Bouzouki, I have my charts on me.
NDL's:
50'=80 min
60'=55 min
70'=40 min
80=30 min
90=25 min
100'=20 min
110'=16 min
120'=13 min
130'=10 min
140'=8 min

[CompuDude]

Originally Posted by reactive

I'm gonna bite... What's the 120 rule?

Old trick from Navy tables.

Depth + time = 120. (so 40' + 80 min = 120, there's your limit. 80' + 40 min = 120, etc.)

Lop off some time to be more conservative, especially at 60/60 (bad combo).

Good rule of thumb for recreational NDLs using air, within a certain range, obviously. Can be adapted for Nitrox, too, with minimal math.

Compare it the tables you're trained on, and you'll see how it lines up. Use it as a guideline, not a rule.

[nrembis]

Originally Posted by navyhmc

It took me a while to re-memorize the NDL's because I learned on the older charts where 60' was NDL of 60 minutes. Like Bouzouki, I have my charts on me.
NDL's:
50'=80 min
60'=55 min
70'=40 min
80=30 min
90=25 min
100'=20 min
110'=16 min
120'=13 min
130'=10 min
140'=8 min

and that is conservative compared to mine, so memorization of charts is not that important. I have been diving my tables for 20 years and am still alive so they cant be too far off

for example my table gives 200min@ 40' and 100min@ 50'