Another Tables vs. Computers Thread

[Thalassamania]

I believe this is the model SSI uses and the tables I used in OW and for many of my early dives. Of course, people do take SIs so there is another table to use to calculate your new pressure group going into the 2nd dive. How does this affect your argument?

I have no idea. I was not arguing anything, just presenting some data.

Note: this refers to MULTILEVEL diving, not REPETITIVE diving.

 

[Thalassamania]

If you learn decompression theory first it is irrelevant if computers or tables come next, they are the same thing, ways to interpret a model.

 

[TheRedHead]

I have no idea. I was not arguing anything, just presenting some data.

Note: this refers to MULTILEVEL diving, not REPETITIVE diving.

I'm not understanding why there would be an SI accounted for in multilevel diving?

 

[TheRedHead]

If you learn decompression theory first it is irrelevant if computers or tables come next, they are the same thing, ways to interpret a model.

True, but is every diver capable of understanding deco theory? If you really delve into it, you run into calculus.

 

[Thalassamania]

Me neither. By definition a Surface Interval only goes with repetitive diving, not multi-level diving.

 

[Charlie99]

I'm not understanding why there would be an SI accounted for in multilevel diving?

One way to calculate a multilevel dive is to treat it as a series of repetitive dives with zero SI in between. For example the dive profile I posted back a ways .... 10 minutes@ 100', 10@70', 20@50', 20@ 40' would be treated as 4 repetitive dives, with zero SI between each dive.

That is essentially what the "Graver" method is, and that's essentially how the PADI Wheel works.

It becomes obvious if you just grab your preferred set of tables and crank through it as 4 back to back dives. How this works is more obvious on the PADI RDP, where the Repetitive Dive Time table has the same entries as the Dive Time wiht End-Of-Dive Group Letter table. On the NOAA/SSI/USN tables, they don't match up exactly because most of the entries in Dive Time table have been rounded to even 5 minute increments.

It can result in some dive profiles slightly beyond model limits, which PADI eliminates by using some reduced NDLs on the wheel.

 

[TheRedHead]

Me neither. By definition a Surface Interval only goes with repetitive diving, not multi-level diving.

Then what does the following paragraph taken form your post mean?

While more conservative than the Graver method, there is still the same basic problem. Since there is no 10 minute surface interval, nitrogen pressures in the 40 minute compartment can build up to unacceptable level which is undetected by the 120 minute compartment that governs the repetitive group designation.

Do the group designations have a built-in 10 minute surface interval?

Multi-level diving without a computer using tables is very confusing AND when you are multi-level diving on a wall and working your way up, computers allow more fluidity to the dive plan. When I dived tables, I planned all my dives as square profiles. I think the only way you can wrap your mind around it would be understanding the shape of the curve rather than trying to use tables. A very valuable tool available with most dive computers is the downloaded graph where you can look at the shape of the curve and by looking at enough dives and curves, you can get a better handle on the profiles.

 

[TheRedHead]

One way to calculate a multilevel dive is to treat it as a series of repetitive dives with zero SI in between. For example the dive profile I posted back a ways .... 10 minutes@ 100', 10@70', 20@50', 20@ 40' would be treated as 4 repetitive dives, with zero SI between each dive.

Ugh. Just run it through a deco planner instead and cut your own tables.

 

[Thalassamania]

Then what does the following paragraph taken form your post mean? Do the group designations have a built-in 10 minute surface interval?

Repetitive dive calculations have a built in 10 minute surface interval

Multi-level diving without a computer using tables is very confusing AND when you are multi-level diving on a wall and working your way up, computers allow more fluidity to the dive plan.

I'd use a computer for those dives.

 

[TheRedHead]

Repetitive dive calculations have a built in 10 minute surface interval

That wasn't in my OW manual. I've learned something new today.

I'd use a computer for those dives.

Me too.