learn from tables or dive computer?

[Matthew]

That's what it seems like.

Using tables to continue after a computer failure is do-able so long as you know what's going on.

Can you cite concrete examples?

 

[bradshsi]

AFAIK tables are neither designed nor tested for that, youll be better off with one of the many deco software for that purpose. But for my easy, relatively shallow, warm water single tank rec dives, its much much simpler and more sensible to use a computer in a conservative, intelligent manner.

What kind of profiles do you do and what do you use?

A typical cold* water profile (for me) would be something like 80 ft for 15 minutes then ascend to 50 ft for 20 minutes and then up to about 30 ft for the remainder (10 to 15 minutes)

This profile is off the regular PADI table, but can be done with the PADI Wheel or with the Flat Table (see also this link for an Excel version ).



However I'd agree it's easier with a computer. I'm just pointing out that multi level can be planned/done with a table and it makes for a good reality check against what your computer is telling you.


*Note that the PADI table requires you to count dives as 10 ft deeper for cold water.

Disclaimer: Don't use the flat table, my example profile, or any of my other suggestions as they are the spawn of all evil and will cause you to die a painful and horrible DCS death followed by a visit to hell where all the demons have really bad buoyancy control...

 

[jbd]

http://www.scubaboard.com/showthread.php?t=26859&highlight=deco+on+the+fly

Impressive, but that's UP's personal method which he perfected for himself. He wouldnt even recommend it to others, so I wouldnt be confident experimenting on my own.

And its not within the tables, see posts 2 and 3.

Thats not the method I'm thinking of. There is another one that involves the the kind of profiles found on the tables.

Now that I have come to the end of the thread the method is quite similar to that given in the link noted by bradshsi above.

 

[Matthew]

Thats not the method I'm thinking of. There is another one that involves the the kind of profiles found on the tables.

Could it be something similar to the post Bradshsi linked to? Flat Table

 

[jbd]

2. Those who are arguing against the value of ascent rate indicators in buoyancy training, saying "that should happen in initial training" are not seeing this from the student's point of view. Regardless of initial training, when students venture into the ocean for the first time and are in blue water with no reference for depth, it will be MUCH easier for them to control their buoyancy if they have a sensitive ascent rate indicator. This could just as well be on a bottom timer as on a computer, but the point is, when you can look at an instrument that tells you precisely when you're going up and how fast, you're going to learn quicker and better how to control your depth. What could possibly be wrong with that? This is especially true because I would be willing to bet that the vast majority of DCS cases in single tank rec diving, particularly among new divers, are due to factors like rapid ascents, poor buoyancy control, maybe some dehydration and ancillary factors like obesity, exercise, etc... and NOT by blowing NDL. The simple fact that among most new divers air consumption is pretty high and the capacity of an AL80 (by far the most common size tank) makes it less likely that new divers will exceed NDls by a large margin.

Regarding this in general--what Mike said in post #64.

 

[jbd]

Could it be something similar to the post Bradshsi linked to? Flat Table

Yes it was something similar. But it has been a few years ago since it was discussed.

 

[jbd]

This could just as well be on a bottom timer as on a computer, but the point is, when you can look at an instrument that tells you precisely when you're going up and how fast, you're going to learn quicker and better how to control your depth. What could possibly be wrong with that?

Whats wrong with that is, that the only information the instrument is giving the diver is that he or she is ascending too fast, nothing more.

Whats really important is that the diver is ascending too fast in the first place, because they have not learned how to control ascent and descent rates through proper bouyancy control. That is something that needs to be taught in their OW course before they ever get certified.

 

[MikeFerrara]

Mike, those are the sort of experiences I'm looking for, thanks. In each case you described, using tables to finish a dive started with a computer did not happen; the one deco dive you described was planned and executed with planning software, not the computer. The others were shallow enough so that you had no decompression concerns. Right?

That's about right. I don't recall every having a computer fail when I was relying on it for decompression information, though my conputer diving career was fairly short. Now days I just use a bottom timer. I use software when I need it and do the rest in my head.

 

[Fotoz4FX]

I'm going to be taking my open water cert class in the next month and am still deciding on a dive shop. There are some that advertise that they don't utilize dive tables and work exclusively from dive computers and I'm not necessarily sure this is a good thing. Any opinions?

I'm sure I'll be using a computer but it seems as if one would benefit greatly from at least learning to use the tables first, in order to understand what the dive computer is doing for you and in case you lose your computer, it's malfunctioning, in an emergency, etc.

Any thoughts appreciated.

Ask them if they can change a battery underwater.

 

[jbichsel]

Originally Posted by jbichsel
True, but tables don't have...algorithims that can be flawed

They don't?

Oops, you caught me. What I should have said was tables don't have software code that can be flawed.

My whole point on this is that I don't want to rely solely on a computer, nor do I want to dive with someone who does.

When I jump in the water, I want to have a mental check list of where we should be in the profile. I want to have an idea of how long at what depth, total allowable BT and have a safety margin built in.

Should my computer fail, I want to have some idea as to where in my plan I am, and have a warm fuzzy by being able to know that I will return to the surface as something other than a statistic.

Look, we all gree, I hope, that redundancy in diving is a good thing. So what is wrong with providing knowledge of tables as redundancy for a computer?

2. Those who are arguing against the value of ascent rate indicators in buoyancy training, saying "that should happen in initial training" are not seeing this from the student's point of view. Regardless of initial training, when students venture into the ocean for the first time and are in blue water with no reference for depth, it will be MUCH easier for them to control their buoyancy if they have a sensitive ascent rate indicator. This could just as well be on a bottom timer as on a computer, but the point is, when you can look at an instrument that tells you precisely when you're going up and how fast, you're going to learn quicker and better how to control your depth. What could possibly be wrong with that? This is especially true because I would be willing to bet that the vast majority of DCS cases in single tank rec diving, particularly among new divers, are due to factors like rapid ascents, poor buoyancy control, maybe some dehydration and ancillary factors like obesity, exercise, etc... and NOT by blowing NDL. The simple fact that among most new divers air consumption is pretty high and the capacity of an AL80 (by far the most common size tank) makes it less likely that new divers will exceed NDls by a large margin.

In my opinion, we're back to the inadequacy of initial training. There is not enough emphasis placed on proper training of new divers in buoyancy control or ascent control. There are too few dives required for certification and the controls are not rigid enough. Too little time is spent covering the possible contributing factors of DCS to have new divers understand how behavior affects diving.

I have refused to dive with people that were hung over from a night of drinking before diving. Nothing happened to them, but I think it's only a matter of time before Murphy get his hands on them.

But hey, we live in a society governed by "I want it now", and a market that says "Ok".