Another Tables vs. Computers Thread

[Kevrumbo]

This is the definitive method right here Folks, what all OW divers should be learning the rudiments of, right after AOW, during Basic Nitrox and continuing on with a full understanding in Adv. Nitrox/Deco & Trimix (and finally putting that computer in Gauge Mode):
http://www.breakthrudiving.com/xducation/pdf/ratiodeco.pdf
Qualified, quantified & codified, brought to you by a certain famous Instructor/Explorer (infamous to some Detractors from the GUE Collective ):
http://www.naui.org/trainer_locator_more.php?ID=272

 

[JeffG]

This is the definitive method right here Folks, what all OW divers should be learning the rudiments of, right after AOW, during Basic Nitrox and continuing on with a full understanding in Adv. Nitrox/Deco & Trimix (and finally putting that computer in Gauge Mode):
http://www.breakthrudiving.com/xducation/pdf/ratiodeco.pdf
Qualified, quantified & codified, brought to you by a certain famous Instructor/Explorer (infamous to some Detractors from the GUE Collective ):
http://www.naui.org/trainer_locator_more.php?ID=272

The Heretic.

 

[Kevrumbo]

The Heretic.

Hey Jeff, one more game and you may be carrying all our Tanks & Gear down here !

 

[JeffG]

Hey Jeff, one more game and you may be carrying all our Tanks & Gear down here !

yea yea yea. Everyones a comedian

 

[Web Monkey]

I just dive until I feel the nitrogen pressure gradient get too high, then I ascend a bit.

I dive until I feel my aura turns gray, then I ascend until it's deep blue again.

Either that, or when I've reached my NDL or turn pressure. I know it's one of those.

Terry

 

[Charlie99]

This is the definitive method right here Folks, what all OW divers should be learning the rudiments of, right after AOW, during Basic Nitrox and continuing on with a full understanding in Adv. Nitrox/Deco & Trimix (and finally putting that computer in Gauge Mode):
http://www.breakthrudiving.com/xducation/pdf/ratiodeco.pdf

OK. How about explaining to this slow learner how ratio deco applies to the sort of dives we have been discussing. Or perhaps you might prefer the question "How does ratio deco apply to minimum deco dives?"

 

[Kevrumbo]

OK. How about explaining to this slow learner how ratio deco applies to the sort of dives we have been discussing. Or perhaps you might prefer the question "How does ratio deco apply to minimum deco dives?"

For starters, look at page 10 (Minimum Deco paragraph) and p.14 (Min Air Deco Table) of the pdf file link.

 

[Charlie99]

For starters, look at page 10 (Minimum Deco paragraph) and p.14 (Min Air Deco Table) of the pdf file link.

You mean that the secret on how to calculate multilevel NDL profiles is in the following paragraph?

Minimum Deco.
The concept of N.D.L. derives from the idea that one does not “require” deco and therefore it is a No Deco Limit dive and the diver can return directly to the surface without any decompression stops. This concept makes some sense in the context of a dissolved gas theory. If the Buhlmann curve (maximum M-Value) is not reached before getting to the surface, then the diver is not required to make a deco stop at 10’/3m or deeper and is allowed to surface directly from depth. This type of model does not take into consideration the fact that a diver always experiences some bubbles in their system and that these need to be addressed, even after a short bottom time (for which the Buhlmann model would allow a direct ascent to the surface). The diver should make some decompression stops to address these bubbles and/or micro bubbles. These stops are termed Minimum Deco and should be conducted starting at 50% of max depth of the dive. The diver will start their ascent at the normal rate of 30’/10m per min until they reach this 50% mark, where they will slow their ascent rate to 10’/3m per min. A good way to practice this is to make a stop for 30 seconds at the stop depth and then spend 30 seconds ascending to the next stop. The diver should continue this slowed ascent rate (10’/3m per min) until they finish the 20’/6m stop. From 20’/6m you do a gradual 3min ascent to the surface to release the pressure slowly where it is changing the most. We use this concept both when conducting what is thought of as an traditional N.D.L. dive (See N.D.L. table below) and if we do a bailout (less than 5min bottom time) when we are deeper than 130’/39m.

It is indeed a very nice and useful discussion on a good ascent profile. But it doesn't help much in planning multilevel dives.

As far as I can tell, the air ndl table in that article is about as useful as the PADI RDP or the USN table in terms of calculating multilevel profiles.

Maybe I'm missing something here.

 

[limeyx]

OK. How about explaining to this slow learner how ratio deco applies to the sort of dives we have been discussing. Or perhaps you might prefer the question "How does ratio deco apply to minimum deco dives?"

min deco is a subset of ratio deco. (which was kind of my point way earlier in the thread)

min deco is just ration deco were:
- the "gas switch" occurs above the surface (so you dont do one)
- you do "pauses" from 0.8 ATA to 0.65 ATA (0.7 depth to 0.5 depth approx)
- you do 1 min stops from 0.65 ATA to "next rule" (which since no gas switch, is the surface)

 

[limeyx]

You mean that the secret on how to calculate multilevel NDL profiles is in the following paragraph?



It is indeed a very nice and useful discussion on a good ascent profile. But it doesn't help much in planning multilevel dives.

As far as I can tell, the air ndl table in that article is about as useful as the PADI RDP or the USN table in terms of calculating multilevel profiles.

Maybe I'm missing something here.

Kinda, kinda not the NDL table is essentially a (slightly conservative) air table.
However, I think you should not confuse the planning of the "bottom" portion of a dive with the ascent.

Ratio deco helps you plan the ascent from a given dive, not necessarily the dive itself.

You plan the dive based on some kind of time at some kind of avg depth (within some fairly narrow window of depths, BT's) then you can use ratio deco to plan the ascent (or indeed massaged versions of tables which is another technique).

Deco is based on the average depth, so if I was doing a dive with some time at 100 and some at 40, I would actually (since there is a big variance in the depths) do the deco for 100 feet. If I was diving between 80 and 100 for an average of 90, then do the 90 deco.