How does the table math work?

[orange_diver]

He's right that it can be a problem, but it's usually only noticeable with deeper dives that get you into decompression, and usually involve helium. For example, you do a trimix dive to 180 feet for 20 minutes and you plan on switching gases at 70 feet to a nitrox mixture (note that these numbers are made up and don't represent an actual dive profile). If it takes you a minute longer than you planned to ascend from 180 feet to 70 feet, not counting stops (equivalent to a 23 feet per minute ascent as opposed to 30), that's an extra minute you've spent breathing helium that must now be offgassed.

true in theory, but in practice if you are over 1 min at depth in a runtime like you are talking about i wouldn't sweat it if i absolutely could not make it up during my deco from 70' for some reason.

what i'm saying is, the models are fuzzy themselves, made for the masses, which is why some people get bent following them and other people do not get bent ignoring them. and that could change from day to day.

one of the most important things i've been taught as i do these longer tech dives is to listen to my body as i run these profiles and add deco time here and there if i need to depending on how i'm feeling both in and out of the water.

that's something no table or computer is going to be able to do for you.

 

[Reg Braithwaite]

There is simply no need to do any calculations yourself in the 21st Century.

Maybe, maybe not. There's a whole 'nother religion with a TLA (three letter acronym) that prefers to calculate deco on the fly, although they do have an associated business that sells a program for cutting tables.

Not that they are right and you are wrong, or you are right and they are wrong, but I take a middle road and believe there are different approaches.

Getting back to the core of this thread, I believe that for all recreational and most light technical diving, it is important to know how to do the calculations well enough to cut a dive plan for yourself if you choose. I can't really speak to hard-core technical diving, I'm talking about stuff like diving with one bottom mix and one deco gas.

I believe it's cool to use a computer on your wrist or to cut tables with a program or even to follow pre-printed standard tables if that's your choice, but I would be--umm, suprised--if someone was completely incapable of doing that kind of dive without computer assistance.

 

[orange_diver]

two "TLA" divers in the red sea did a wreck dive called the Yolanda at 590'. on OC. using ratio deco. no computers needed to plan or execute (except a bottom timer if that counts).

btw ratio deco or "deco-on-the-fly" doesn't mean we just jump in and figure it out along the way. we have a very good idea of exactly what our avg depth is going to be and how long we will be there, how much gas we need and how long our deep and deco stops will be before we hit the water.

we just don't use a computer or tables in the usual sense of the word to get there or to figure out contingencies once under water.

 

[cfenton]

btw ratio deco or "deco-on-the-fly" doesn't mean we just jump in and figure it out along the way. we have a very good idea of exactly what our avg depth is going to be and how long we will be there, how much gas we need and how long our deep and deco stops will be before we hit the water.

we just don't use a computer or tables in the usual sense of the word to get there or to figure out contingencies once under water.

Exactly.

All decompression tables/computers are based on mathematical models that can't possibly account for all the variables of human physiology. They're extremely imperfect at best and simply represent the "best" schedule for decompression at the time they were made. Ratio deco is just a much simpler mathematical model.

 

[nereas]

Maybe, maybe not. There's a whole 'nother religion with a TLA (three letter acronym) that prefers to calculate deco on the fly, although they do have an associated business that sells a program for cutting tables.

Not that they are right and you are wrong, or you are right and they are wrong, but I take a middle road and believe there are different approaches.

Getting back to the core of this thread, I believe that for all recreational and most light technical diving, it is important to know how to do the calculations well enough to cut a dive plan for yourself if you choose. I can't really speak to hard-core technical diving, I'm talking about stuff like diving with one bottom mix and one deco gas.

I believe it's cool to use a computer on your wrist or to cut tables with a program or even to follow pre-printed standard tables if that's your choice, but I would be--umm, suprised--if someone was completely incapable of doing that kind of dive without computer assistance.

One deco mix is really just basic tech training, not really serious tech diving.

I have no doubt that the quickie in-your-head methods work fine for such lite stuff.

And by the same token, I seriously doubt that anyone would be alive after using an in-your-head method for a 100 m dive of 20 mins or more. Contrary to orangeman's post.

But the whole tech topic is off point in this thread. The point in this thread is that table methods are not taught well enough nor understood by novice NDL divers. Thus any basic retail dive computer is superior to the current method of teaching tables in the quickie retail cert courses. My opinion, only, of course, based on my observations, as further evidenced by the OP's question.

 

[cfenton]

I have no doubt that the quickie in-your-head methods work fine for such lite stuff.

And by the same token, I seriously doubt that anyone would be alive after using an in-your-head method for a 100 m dive of 20 mins or more. Contrary to orangeman's post.

Red Sea Explorers - 180 meter Dive on Yolanda

I implore you to email AG and tell him about your convictions.

 

[DwayneJ]

A good read...

Team foxturd: Tech1 Ratio Deco - Explained

 

[orange_diver]

One deco mix is really just basic tech training, not really serious tech diving.

it's serious to myself and my team. we've worked two hard years to comfortably do those dives. are there much more bad ass divers doing more demanding dives out there? for sure, but these "basic" tech dives can still kill/cripple you.

And by the same token, I seriously doubt that anyone would be alive after using an in-your-head method for a 100 m dive of 20 mins or more. Contrary to orangeman's post.

see cfenton's posted link above to the Yolanda. The diver's name is Faisal and he was certainly alive and kicking when i dove with him a couple months ago (well after the Yolanda dive).

your posts lead me to believe that you only dive on the internet.

nereas, your avatar looks like it has more tech dives than you do.

 

[4sak3n]

Is someone SERIOUSLY advocating using and abusing a computer by following its recommendations to the letter without understanding how it works or, more importantly, what its limitations are? And is he advocating doing this for tech dives?!?

 

[Reg Braithwaite]

Is someone SERIOUSLY advocating using and abusing a computer by following its recommendations to the letter without understanding how it works or, more importantly, what its limitations are? And is he advocating doing this for tech dives?!?

In all fairness, I haven't read a single post on this thread suggesting that, although in the heat of the moment you could take something that way. Let's have a little reset, shall we?

The whole thing started with a question about the reliability of tables as measured by observing divers who have been trained to use tables. I get the impression that most of the folks on this thread agree that there is something wrong in the training process, quite possibly the training on the use of tables and not the tables themselves.

From there we had an assertion that training on the use of dive computers would be superior to training on the use of tables for basic OW diving given the real-world limitations of OW training. IOW, we are not talking about GUE Recreation 1 training, we are talking about cut-rate PADI/NAUI OW delivered to people who are on their cell phones making travel plans while they watch a washed-out VCR tape in the basement of their LDS.

And from there we had an entertaining digression about "light" tech, wherein I think we all agree that a diver ought to know the principles behind dive planning. There is certainly room for multiple opinions about whether one should actually dive with a gas-switching computer or not and so forth, but I didn't read anything suggesting that such a dive should be done by someone who has zero other clue about how deco works

These are just my observations...