Info Why are tables not taught in OW classes anymore?

[scubadada]

Do really want to get into this AGAIN?

Just because you call it "misstatement" doesn't make it so and doesn't make your argument valid at all.

I am not going to get into this AGAIN just because I don't think it is proper to hijack this thread like what happened in previous threads

Everyone has to choose their own nomenclature, see SAC and RMV. For me, there are 2 types of dives, no stop, allowing a direct ascent to the surface, and deco, requiring one or more mandatory stops prior to surfacing.

The most important thing in communication is that others know what you are talking about

 

[boulderjohn]

Just to be clear, are you saying that riding the NDL from depth is as safe/risky as a square profile to the same depth at NDL?

I am saying that doing a multi-level dive with a computer warning you that you are approaching NDL is safer than doing a multi-level dive based on a table's max time and just guessing how long you have at different depths as you ascend, a process some have argued for without using the word "guessing."

The line between NDL and deco in reality depends upon the individual diver on the individual day. Computer and table algorithms use their research base to identify the most likely numbers.

 

[BoltSnap]

For me, there are 2 types of dives, no stop, allowing a direct ascent to the surface, and deco, requiring one or more mandatory stops prior to surfacing.

Only two types:

1. "No-Required Stop" Dive.

2. "Required Stop" Dive.

 

[boulderjohn]

He said "if you begin an ascent within NDLs, it does not seem to matter how slowly you ascend, as long as you don't go into deco". I interpret that as meaning it does not affect the risk.

If I had meant that, I would have said it. Please read carefully.

If two divers dive to within NDLs and begin the ascent, the one who does a direct ascent to the surface will certainly be at less risk than one who lingers at various depths for a multi-level dive. That is not the comparison I was making.

Many people in this post have said that table divers can do multi-level dives after leaving the bottom on such a dive, just as computer divers do, even though those tables provide no research-validated way of doing such an ascent. I am simply comparing doing a multi-level dive using a computer algorithm designed to support multilevel diving to doing a multilevel dive using a tale followed by guessing.

 

[steinbil]

If I had meant that, I would have said it. Please read carefully.

You literally wrote "if you begin an ascent within NDLs, it does not seem to matter how slowly you ascend, as long as you don't go into deco". I simply objected to that. There is nothing wrong with my reading comprehension in this case. If you don't stand by that statement, maybe you shouldn't repeat it.

I am saying that doing a multi-level dive with a computer warning you that you are approaching NDL is safer than doing a multi-level dive based on a table's max time and just guessing how long you have at different depths as you ascend, a process some have argued for without using the word "guessing."

Many people in this post have said that table divers can do multi-level dives after leaving the bottom on such a dive, just as computer divers do, even though those tables provide no research-validated way of doing such an ascent. I am simply comparing doing a multi-level dive using a computer algorithm designed to support multilevel diving to doing a multilevel dive using a tale followed by guessing.

Here we go again. Maybe you want to take this argument to the proper thread in the proper forum, where I can actually respond to this? And maybe you would like to respond to any of my previous posts that you seem to ignore any time you don't have any real arguments? Or are you just interested in mudslinging?

 

[L13]

A common misstatement on ScubaBoard is that all dives are decompression dives. In reality, there is a big difference between a dive with no required decompression stops and what is commonly called a decompression dive (one with required decompression stops). In an NDL dive, a slow ascent does not matter. Take your sweet time, do a safety stop, and head for the surface. Once required decompression is reached, it matters very much. The longer you tarry at depth, the longer and deeper the required decompression stops.

Is a 14min dive to 30m a deco dive or an NDL dive?

Using SubSurface with arbitrary settings and GF high = 95% : 2 min NDL remaining
using GF low = 50%, GF high = 60% : 7min of DECO REQUIRED (ceiling begins 8min into the dive)

so which is it? Deco or NDL?

 

[inquis]

so which is it? Deco or NDL?

Diver's choice of conservatism will dictate.

 

[boulderjohn]

Is a 14min dive to 30m a deco dive or an NDL dive?

Using SubSurface with arbitrary settings and GF high = 95% : 2 min NDL remaining
using GF low = 50%, GF high = 60% : 7min of DECO REQUIRED (ceiling begins 8min into the dive)

so which is it? Deco or NDL?

As I said earlier (and it was likely missed), what is important is the reality of what is happening to the diver on the dive. Unfortunately, we don't know that reality for certain, so we use algorithms that have been slowly developed over more than a century to tell us what is most likely happening. How close that comes to reality depends upon the algorithm, and today it also depends upon the amount of conservatism we impose on that algorithm.

In the case described, I would say with 99.9% certainty that the dive is an NDL dive but it is possible to manipulate an algorithm far enough to treat it as a deco dive.

 

[L13]

As I said earlier (and it was likely missed), what is important is the reality of what is happening to the diver on the dive. Unfortunately, we don't know that reality for certain, so we use algorithms that have been slowly developed over more than a century to tell us what is most likely happening. How close that comes to reality depends upon the algorithm, and today it also depends upon the amount of conservatism we impose on that algorithm.

In the case described, I would say with 99.9% certainty that the dive is an NDL dive but it is possible to manipulate an algorithm far enough to treat it as a deco dive.

I could be wrong, but I seem to remember that there have been documented incidences of DCS with GF's at or below 50%/60%.

All dives involve inert gas compressing into tissues, and the decompressing out. Using algorithms, etc., we set thresholds where we treat some dive differently than others, but in reality they all are fundamentally the same, except for the level of risk. When the risk is trivial we take no precautions, when they are significant, we do deco stops (or safety stops, which are just deco stops with a different name).

 

[L13]

Is a "deco dive" a dive where decompression occurs? Then all dives are deco dives.

Is a "deco dive" a dive where a stop is done to decompress? Then all dives with a safety stop are deco dives.

Are only dives that have a stop called a deco stop "deco dives"? Planed stops, or executed stops?

What about dives that were not planed to require a "deco stop" that accidentally have a "deco obligation" according to the divers computer settings but the diver didn't notice it, and ascended without a stop and without DCS? No deco stop was planed or executed, is that a "deco dive." What if her buddy that did the identical dive did get DCS, does that make it a "deco dive" for one but not the other?

The term is somewhat fuzzy, and policing the ways it is used is counter productive to communication. Those that say "all dives are deco dives" are communicating a valuable concept to understand about what is actually happening on a dive. Those that say "dives with deco stops are deco dives" are communication valuable ideas about the practical execution of dives.

Like most words and phrases, it has multiple definitions depending on the usage. Take a look in any dictionary, very few words have only one definition listed.

This is is what I object to:

A common misstatement on ScubaBoard is that all dives are decompression dives.

It is not a "misstatement" it is a different "what is commonly called a decompression dive" than the one you use below, but as you note, it is a common statement. It is not a "misstatement". It is completely correct given the definition being use, which is a common (as you state above) definition.

Here you are a little more reasoned, note what I have put in bold:

In reality, there is a big difference between a dive with no required decompression stops and what is commonly called a decompression dive (one with required decompression stops).