Info Why are tables not taught in OW classes anymore?

[cgblake]

Unfortunately, the tables do not have the information to let you do what you are talking about. Once you've been to (say) 63 ft, then you are committed to the 70 ft NDL (40 mins on an RDP), no matter what depth you dive at above 70 ft during the dive. Yes, if you went up to (say) 40 ft for most of your dive, you would be on-gassing less nitrogen, but the tables do not have the info to tell you anything other than NDL=40 mins, because you went to 63 ft. that's the problem with tables and their assumption of square profiles; if you ar actually diving a multiple levels, you are taking on less nitrogen than assumed by the table, but the table does not tell you how to manage that.

I will put this on the list of fool ideas not to try then. Thanks for the correction!
When I get better and into multi level dives i will revisit this, right now I need more dives to build good skills.

 

[lowwall]

EDIT: We cross-posted, and I agree the deco theory is drawing a thin line through a broad gray area. The fact remains, though, that cheap computers are widely available.

Like I said, this is from a theory perspective. I wouldn't do this, nor would I recommend anyone else do it. Even if you were to pad it, it's just not practical. I mean @cgblake was suggesting you could do this on the fly by taking the tables with you. The chances of screwing up the table fiddling at depth are not low.

Agreed, and you chose an example, that minimizes the issues.

The off-gassing/on-gassing does NOT depend on average depth. the process is not linear with depth.

I didn't choose the example. I was responding to someone else who chose the example.

I know that off and on gassing is not linear with depth, but it doesn't actually matter within the given precision for this example (nor for any other that's in this ballpark).

Read the references in my previous post; your suggested procedure is NOT correct, and appealing to the classic "well its all theory anyway" or the silly "because its just an approximation, another one won't hurt" is beneath you.

Why use the tables at all? Hey, they are just made up from some poorly tested model. [/sarcasm]

My "procedure" is a thought experiment, not a dive planning suggestion. That why I said it was theoretical. I find that understanding the theory is interesting, even though I leave the actual implementation up to my dive computer. I'm surprised that you don't feel the same way.

 

[tursiops]

Like I said, this is from a theory perspective. I wouldn't do this, nor would I recommend anyone else do it. Even if you were to pad it, it's just not practical. I mean @cgblake was suggesting you could do this on the fly by taking the tables with you. The chances of screwing up the table fiddling at depth are not low.



I didn't choose the example. I was responding to someone else who chose the example.

I know that off and on gassing is not linear with depth, but it doesn't actually matter within the given precision for this example (nor for any other that's in this ballpark).


My "procedure" is a thought experiment, not a dive planning suggestion. That why I said it was theoretical. I find that understanding the theory is interesting, even though I leave the actual implementation up to my dive computer. I'm surprised that you don't feel the same way.

We are not using "theory" in the same way.

 

[lowwall]

I will put this on the list of fool ideas not to try then. Thanks for the correction!
When I get better and into multi level dives i will revisit this, right now I need more dives to build good skills.

Get a computer. It's safer, simpler and you won't alienate potential dive buddies. Nobody wants their dive cut short because a buddy insists on using tables during a multi-level dive.

 

[Eric Sedletzky]

I will put this on the list of fool ideas not to try then. Thanks for the correction!
When I get better and into multi level dives i will revisit this, right now I need more dives to build good skills.

There’s nothing really to revisit if you mean trying to figure out a way to make a multi level tool out of a square profile table. It’s never going to work. Just use a computer like everyone else and forget about it.

 

[boulderjohn]

Maybe tables vs. DC is like stick shift vs. auto transmission?

Nope.

An automatic transmission does the same thing as a stick shift, only automatically. Use one or the other, and you shou;d get about the same results.

As in the example I gave, using a computer on a multilevel dive can give a dramatically different result compared to tables. In the example I gave, on a two tank dive, the computer user got nearly 2 more hours of total dive time than the table user.

 

[Eric Sedletzky]

The only time I might see tables being useful, and this would be rare, is if someone want’s to get into diving but has almost no money. Let’s say they get a bunch of hand me down gear, still good stuff just old, and it came with reg, octo, and a console with an analog depth gauge. If they had a wrist watch with a bezel that was usable as a timing device they could learn the tables and at least get in the water with some idea of how deep how long and go diving. Not ideal but better than nothing.
But I would never recommend that someone go out and buy new gear with tables in mind because by the time you spend money on an analog depth gauge and a half way decent timing device you’ve spent about the same money as a cheap entry level wrist computer. The computer can always be used in gauge mode if someone is still hell bent on using tables and as a bonus you have the convenience if having depth and time in one unit.

 

[Eric Sedletzky]

Nope.

An automatic transmission does the same thing as a stick shift, only automatically. Use one or the other, and you shou;d get about the same results.

As in the example I gave, using a computer on a multilevel dive can give a dramatically different result compared to tables. In the example I gave, on a two tank dive, the computer user got nearly 2 more hours of total dive time than the table user.

You can also use an automatic manually and down shift for hills, you just don’t have to push in the clutch.

 

[TMHeimer]

Nope.

An automatic transmission does the same thing as a stick shift, only automatically. Use one or the other, and you shou;d get about the same results.

As in the example I gave, using a computer on a multilevel dive can give a dramatically different result compared to tables. In the example I gave, on a two tank dive, the computer user got nearly 2 more hours of total dive time than the table user.

Gotcha. I was comparing the two based on you have to do something manually with both tables and stick shifts. Auto. transmissions and DCs are more like push a button or so and go. Less thinking and manual labour. But like with tables, all 4 of these things work well with regular practice.

 

[EFX]

If we extend the metaphor of manual ("a stick" shift) vs. automatic transmissions to diving with tables we can say that diving with tables is like using a manual transmission with a clutch. The advantage of a manual transmission is that you are in control of the rpm's. If you need maximum power you can stay in a lower gear with higher rpm's as long as you remain in the power band. Using a previous example of a multilevel dive to 63 ft. including shallower depths is like using a manual transmission in that you are always at a higher rpm than necessary. As has been already noted you have to analyze the dive as if it were a square profile at 70 ft. which is wasteful of NDL time.

As a side note, to add some humor, I saw a woman's t-shirt that displayed a witch with a pointed hat riding a broom stick. The caption above the picture in big capital letters read, "YES". Below the picture it read, "I can drive a stick." HaHaha.