Place of dive tables in modern diving

[boulderjohn]

Sit it out topside.

Ah--and so that is an advantage because.....?

BTW, here is the dive I actually did: 125' for 30 minutes. It was a great dive.

 

[stuartv]

Calm down, sparky.

EAN32, knock 10' off your max depth.
EAN36, knock 20' off your max depth. (don't bring that onto a boat, you limit the cap's options)

EAN28 is sweet. Use air tables and enjoy the added safety margin.

Are you an OW or Nitrox instructor? Is that what you would teach your students?

My point, really, is that when someone cites A reason to learn tables as being able to figure out their dive plan in their head, I think that is a somewhat outdated approach, because of the ubiquity of Nitrox these days. Thus, that particular reason for learning tables is not a good one, to me.

 

[stuartv]

Sit it out topside.

And thus why, to address an earlier post, tables, including Navy tables, might be seen as conservative.

EDIT: Not just conservative, but needlessly conservative.

 

[lowviz]

...//... My point, really, is that when someone cites A reason to learn tables as being able to figure out their dive plan in their head, I think that is a somewhat outdated approach, because of the ubiquity of Nitrox these days. Thus, that particular reason for learning tables is not a good one, to me.

Muddled thinking.

Start with basic, albeit imperfect, concepts. Build on that.


As to your 'overly conservative' post: yes, it is. If you don't have a backup computer, then pass on the second dive. Don't confuse "everything I can squeeze out of a dive day" with '"This doesn't feel right because I can't check this against a computer"

 

[The Chairman]

The dive operator gave me the computer without resetting it and I ended up wearing a computer that believed that the dive I was about to do would be my THIRD DIVE of the day.

How is this the computer's fault?

Today there are agencies that train you to dive on computers from day one and they are proud of it. It is seen as a sign of embracing tomorrow and being progressive.

This is simplistic. I have yet to see a set of dive tables on a boat outside of class. The goal is to teach a diver to use the equipment they're most likely to use. They are far, far, far more likely to use a PDC than any tables, so why teach the latter? I do teach the rule of 120 as a backup and we do exercises that validate what their PDC is telling them. They learn the rule of 140 for EAN32. No, they don't use these rules to govern their diving... just as a backup to see if things are reasonable.

But the big point here... is diving a PDC that's been used within the last 24 hours is a bad idea. Better to use a tissue someone else has already sneezed in than to do that.

 

[lowviz]

Ah--and so that is an advantage because.....?

BTW, here is the dive I actually did: 125' for 30 minutes. It was a great dive.

Glad for you.

And you did that dive why??? What gave you the confidence to do it?

 

[boulderjohn]

Glad for you.

And you did that dive why??? What gave you the confidence to do it?

Why did I do the dive? Why do I do any dive? I like diving.

What gave me the confidence to do that dive? I am confident every time I begin a NDL dive--aren't you? Why would I not feel confident?

 

[tursiops]

I just finished logging the dives I did this morning. I did two recreational, NDL dives on a wreck called the Lady Luck. As I did, I wondered what my second dive would have looked like if my computer had gone bad after the first dive and I was one of those people who say that if that were to happen, they would just switch to the tables for the second dive. So I am going to post the data below and hope someone will advise me on what I would have done under that scenario. How would the tables have guided me for that second dive?

Gas: EANx 29
Maximum depth: 132 feet
Total dive time: 26 minutes, including a 30 FPM ascent and a 3 minute safety stop.
Surface interval: 1:03
Gas for second dive: EANx 30
Planned maximum depth: 130 feet.

Let's see: EANx 29 at 132 ft is 116 ft EAD, call it 120. I'll assume salt water.
EANx30 at 130 ft is 111 ft EAD, call it 120 again.
26 mins - 3 min SS - 132/30=5 min ascent time (call it 4 to be safe) means 19 minutes Bottom Time.
But the NDL for 120 ft is 15 minutes, so you've just done a deco dive.
On (new Navy) tables, you screwed up.
However -- here's the Good News -- on the older Navy tables, and TDI's version of Bulmann, that deco dive would require a 2min deco stop at 10 ft, so your safety stop saved you from being crippled. Good job!
The Bad News is your second dive was probably not a good idea. Perhaps a minute of BT, then into serious deco.
Did you have enough gas in your dive plan?

 

[boulderjohn]

Let's see: EANx 29 at 132 ft is 116 ft EAD, call it 120. I'll assume salt water.
EANx30 at 130 ft is 111 ft EAD, call it 120 again.
26 mins - 3 min SS - 132/30=5 min ascent time (call it 4 to be safe) means 19 minutes Bottom Time.
But the NDL for 120 ft is 15 minutes, so you've just done a deco dive.
On (new Navy) tables, you screwed up.
However -- here's the Good News -- on the older Navy tables, and TDI's version of Bulmann, that deco dive would require a 2min deco stop at 10 ft, so your safety stop saved you from being crippled. Good job!
The Bad News is your second dive was probably not a good idea. Perhaps a minute of BT, then into serious deco.
Did you have enough gas in your dive plan?

Funny. My computer did not have any problem with my doing that second dive.

As for gas, I finished the first dive with about 50 cubic feet left in the tank, and I finished the second with about 32 cubic feet left (had to do some real work in a ripping current for a while on that dive).

 

[KeithG]

Funny. My computer did not have any problem with my doing that second dive.

As for gas, I finished the first dive with about 50 cubic feet left in the tank, and I finished the second with about 32 cubic feet left.

Or the first dive.

One of my favourite recreational dive profiles is a max of 90 feet and a duration of 90 minutes. Obviously a multilevel dive. Something that can easily be done safely with a computer. And is way off the charts with tables...