Info Why are tables not taught in OW classes anymore?

[boulderjohn]

My point is that there is nothing fundamentally different between an NDL dive and a "deco dive" as such.

Here are three NDL profiles..

1. Diver A goes to 100 feet for 17 minutes and begins an ascent at 30 FPM. He ascends to 15 feet, does a 3 minute safety stop, and goes to the surface.
2. Diver B goes to 100 feet for 17 minutes and begins an ascent at 30 FPM. That ascent takes him to 50 feet, where he does a 2.5 minute deep stop. She then ascends to 15 feet, does a 3 minute safety stop, and goes to the surface.
3. Diver B goes to 100 feet for 17 minutes and begins an ascent at 30 FPM. That ascent takes him to 50 feet, where he explores the reef for 20 minutes. He then ascends to 30 feet and explores the reef for another 20 minutes. He then ascends to 15 feet, does a 3 minute safety stop, and goes to the surface.

All 3 dives end with the diver doing a 3 minute safety stop and going to the surface. The safety stop is an insurance measure. The diver should be OK going directly to the surface without it.

So in an NDL dive, there is no clear evidence in research that delays upon ascent make any difference in surfacing. A couple weak studies, in fact, suggest that some delays are helpful, which is why DAN Europe advocates deep stops on NDL dives (dive #2 above). In contrast, once you are in a decompression dive, any delay in ascent, whether it be a slower ascent rate or stops along the way, results in longer required decompression before surfacing and even deeper required stops before surfacing.

You don't see a difference there?

 

[scubadada]

Say I dive with two computers, one set to GF 35/75 and one that is set to 45/85...

...and you are still basically wrong with your carefully chosen example. The GF high of 85 allows you to make a direct ascent to the surface while, with the GF high of 75, you would violate the ceiling and deco stop with a direct ascent.

It seems like you and I simply think differently.

Again, the Basic Forum. Regardless of what computer, decompression algorithm, and settings you choose, stay above the NDL for your no stop dive and so a safety stop with your ascent. If you exceed the NDL and go into decompression, follow the recommendations of your computer to make a safe ascent.

From a thread, Why are tables not taught in OW classes anymore?
You may ask yourself, "Well, how did we get here?"

 

[inquis]

The fundamental difference between dives is how much compression and decompression happened, along with many other factors like rest, hydration, health, exertion level, etc.

If you're putting health in that "fundamental difference" list (which I agree is correct), surely risk tolerance would belong as well. I mean, I definitely take that into consideration when planning a dive.

Your argument hinges on you diving two computers with differing safety margins. However, one of them violates your risk tolerance, so you would ignore it anyway. (If they both satisfied your risk tolerance, they would both show no-stop or both show deco.)

 

[L13]

...and you are still basically wrong with your carefully chosen example. The GF high of 85 allows you to make a direct ascent to the surface while, with the GF high of 75, you would violate the ceiling and deco stop with a direct ascent.

It seems like you and I simply think differently.

Again, the Basic Forum. Regardless of what computer, decompression algorithm, and settings you choose, stay above the NDL for your no stop dive and so a safety stop with your ascent. If you exceed the NDL and go into decompression, follow the recommendations of your computer to make a safe ascent.

From a thread, Why are tables not taught in OW classes anymore?
You may ask yourself, "Well, how did we get here?"

I agree with every thing you said except "wrong" should be replaced with "right" in the first sentence, . (and it doesn't "feel" like it addresses my point)

I guess, for me, the fundamental nature of a dive is its physiological effects,and we use procedural methods to deal with them. And for you, the fundamental nature of a dive is the procedure methods we use to deal with those physiological effects. I think you are right that we simply think differently. (it also appears that I am in a minority).

We both seem to agree on the procedural methods. I'm not sure if we agree on the physiology (though I suspect we are at least not far apart).

The same applies to almost everyone else I am debating with in this thread. I mostly agree with them procedurally, I mostly agree with them physiologically. I keep presenting physiological arguments. They keep presenting procedural arguments. Both them and I feel the other isn't listening. I get pissy and rude. Not a good outcome.

So, lets just let it go.

 

[L13]

From a thread, Why are tables not taught in OW classes anymore?
You may ask yourself, "Well, how did we get here?"

Someone suggested that NDL/deco dives were fundamentally different. And I argued that they are fundamentally the same, particularly at the border between NDL/deco which is the most relevant region for basic scuba.

They are very different procedurally, even though they are almost the same physiologically. But, which is "fundamental" ?

 

[dmaziuk]

So in an NDL dive, there is no clear evidence in research that delays upon ascent make any difference in surfacing. A couple weak studies, in fact, suggest that some delays are helpful, which is why DAN Europe advocates deep stops on NDL dives (dive #2 above).

If you ascend slowly enough to on-gas your "other compartment" into a ceiling, you will by definition no longer be on a no-stop dive. Conversely if you are within NDL at every point in the dive, then you can proceed directly to the surface at any point. It's a catch-22, nothing to study here.

 

[dmaziuk]

But, which is "fundamental" ?

It starts with an M and ends with a zero, usually pronounced M-naught.

HTH

 

[L13]

So in an NDL dive, there is no clear evidence in research that delays upon ascent make any difference in surfacing. A couple weak studies, in fact, suggest that some delays are helpful, which is why DAN Europe advocates deep stops on NDL dives (dive #2 above). In contrast, once you are in a decompression dive, any delay in ascent, whether it be a slower ascent rate or stops along the way, results in longer required decompression before surfacing and even deeper required stops before surfacing.

And yet, the analysis of any Haldane model for decompression would predict both of these results. If faster tissues are the dominant limits on a dive, slow down a bit early in the ascent. If the slower tissues are the dominant limits on the dive, speed up a bit early in the ascent. In eithmidr case, don't overdo it, or you will switch which is dominant.

Short dives (tend to be NDL) will be more dominated by faster tissues.
Long dives (tend towards deco) will be more dominated by slower tissues.

You don't see a difference there?

Difference in procedure? Yes.
Difference in fundamental nature of the dives? No. The common fundamental nature of the dives is the reason the differences in procedure exist.(but if I though procedure was fundamental, I would say Yes)

 

[L13]

Dammit!

I said I would let it go and then kept commenting. I need an intervention!

 

[inquis]

If the slower tissues are the dominant limits on the dive, speed up a bit early in the ascent. In eithmidr case, don't overdo it, or you will switch which is dominant.

That is simply not how the physiological models work. Speeding up the ascent will not cause the controlling tissue to switch to a faster one. By definition, all the faster ones already have shallower ceilings.

I'm happy to explain further in DM, but I agree, we've strayed well off the topic of teaching tables in OW classes.