Ongoing discussion of Ratio Deco

[limeyx]

What dive would not require deepstops?

Tobin

I guess a short dive to 30 or 40 feet on 32%

 

[limeyx]

err... I guess rec. dives in the 50ft or shallower range.
...

Deco dives in the 100 ft or shallower ranges since the bottle switch is at first deep stop range.(no deep stop is required.)

All this will be covered when you take tech1.

Milo

For deco dives in the 100 foot range, Gideon suggested it is much better to use 100% rather than 50%, so you'd definitely need deep stops for those kinds of dives to get to 20 feet for the switch.

 

[cool_hardware52]

err... I guess rec. dives in the 50ft or shallower range.

Since min. deco stops would be 30, 20, 10 don't really see a need for deep stops on these dives.

Or

Deco dives in the 100 ft or shallower ranges since the bottle switch is at first deep stop range.(no deep stop is required.)

All this will be covered when you take tech1.

Milo

What theoretical tissues are "treated" by deepstops and which are treated by Min deco?

Tobin

 

[limeyx]

Deep stops aren't unique to Ratio Deco, every GUE trained diver applies deep stops when required.


We also apply deepstops, oxygen window, S-curves and dissolved gas theory during our deco.

We use the software to generate a total time on a particular gas, and then apply the various theories to optimise a decompression strategy.
How exactly does DOTF work better?

Sincerly,
Chris

Right, so you aren't "using DecoPlanner" either -- seriously, I dont see how you can claim that this technique (which is one of the two we had presented in our class), any more scientific than ratio deco ?

DecoPlanner spits out a deco plan (times, depths etc.) for a given profile. If you deviate from that then you are really no longer using decoplanner and I would say that you cannot strongly make the statement that your modified profile is "using decoplanner" or any more scientific.

Ratio Deco works better because:

1) YOU get to choose how many minutes, not some application that might have bugs, inconsistencies in it, or even give different results over different "upgrades"
2) DOTF is different (but related) to Ratio Deco -- DOTF gives you the ability (to me) to modify the deco as the dive plan changes underwater. Ratio Deco does a good job here because once you see the patterns, you can generate a deco plan for a wide range of profiles. Sure, you can also do this with tables, but that does not seem as easy to me.

It seems either you dive the exact DecoPlanner plan (and then can claim the "science" behind it), or you modify the plan, and you are in the same level of confidence as ratio deco.

This is also something that somewhat bothers me when computer divers start adding arbitrary "Deep Stops" (which I think are a good idea obviously) that their computer doesn't know about. How do you then know when/where to do those stops? For how long? Most seem to be something like "seat of the pants" stops and then hope the computer can somehow cope (although this is getting off topic by now)

 

[cool_hardware52]

Are deep stops required when monkey diving?
Just curious...

Chris

Yes

Tobin

 

[limeyx]

If you read George Irvine's Gavin scooter list you would find several examples of GI arguing with AG over Ratio Deco. Irvine showed some examples of dives in the 250-300 feet range where ratio deco didn't come close to his minimum deco that he and J.J. came up with after years of diving Wakulla. J.J. said he told Andrew about minimum deco during a plane ride back from Europe but Andrew dumbed it down in such a way that GI says it should not be considered DIR.

Was that the same argument where Andrew responded with actual RD profiles, and every single one was at least or more conservative than George's profiles ? I do remember a conversation that went that way, but am maybe not aware of what you are referring to.

 

[ScubaMilo]

For deco dives in the 100 foot range, Gideon suggested it is much better to use 100% rather than 50%, so you'd definitely need deep stops for those kinds of dives to get to 20 feet for the switch.

Good point!
I was just pointing out dives which would not require deep stops.
Not saying it is the optimal way to execute this dive.

but point taken,

Milo

 

[limeyx]

What theoretical tissues are "treated" by deepstops and which are treated by Min deco?

Tobin

The two are kind of different concepts.

"Deep Stops" attempts to reduce bubble growth by slowing the ascent at a deeper depth than traditional deco algorithms suggest. In theory since the bubbles are really small at these depths, they are easier to crush/eliminate than when they get big (as they would on a straight DecoPlanner profile).

The theory is, that the reasoning against deep stops that goes like "let the bubbles grow a bit bigger and do more time shallower" doesn't really work well because by that point the bubbles are much much harder to get rid of, and this leads to fatigue.

Also, the theory (I think) is that allowing those bubbles to grow, could lead to a higher chance of a typeII hit.

Min deco is simply the least amount of deco you can do for a given dive profile and exit the water safely (more deco is always allowed

Min deco is a bit confusing because we usually use it to refer to MDL/NDL type diving, but really we do calculate a "minimum deco" for every dive we do, which we can then pad if we see the reason (cold water, stiff current etc.)

 

[limeyx]

Good point!
I was just pointing out dives which would not require deep stops.
Not saying it is the optimal way to execute this dive.

but point taken,

Milo

Agreed.

I am however, somewhat surprised at your take on RD, given who I think your instructor for tech was ???

 

[FishTaco]

No one has really answered the criticism that DOTF is inconsistent in its "conservatism-settings" thru-out the same range ie T1 or T2 (or maybe I missed it). Do you agree but don´t care (perhaps because you modify the "output" in the less conservative parts of the range) or disagree?

Law of primacy in effect...I guess they just don't care.

Chris