Deco with too less air, options from the book

[Gilldiver]

I'v been away decompressing in Poland and only catching up now.

What I said was

"I don't dive Navy tables as a standard practice, but I have a copy on me for all deco dives. If things go real south - lost computer, lost buddy, lost anchor line, I still have a timer and depth gage and a set of tables.

Like I said, I don't dive them but I do carry a set for the event I get handed a ticket to hell and need to get off that bus."

This is where the bus ticket to hell came in. I keep a table in my tool bag and will check it every now and then on the hang - like there is much else to do sometimes?

But more important is this:


"I will also use them as a touch stone to check a computer generated or Ratio Deco schedule. If they are less then Navy Tables or close to them, I will check very closely to find out where the error is. Because there is an error if a modern table is getting me near Navy stops."

Face it, if a modern table or technique has you getting near to the old Navy tables for stops and/or run time, you most likely have made a mistake someplace. A quick check like this might have prevented the hit in Chuk of the diver who made the mistake in the mental math of RD. If he had checked a back up, he might have figured out his error and corrected his calculations.

 

[MXGratefulDiver]

But thats a two-way street.

How many of those who are critical of using computers as the only tool for decompression diving (f.e) have ever done a significant dive with f.e a VR3? People get bent on VR3s you say? They just dont "understand it" or it was "diver error"...using those arguments I can shut down any argument that VR3s arent the optimal aid for decompression diving...sometimes I think this is the tone of people advocating RD(and a lot of other stuff TBH)...

If you dont like people to criticize RD without "understanding it"(whatever that means) then you should demand the same of yourself before you criticize another method...if you havent taken a course with a VR3, and not any old course but the "right one", then you dont "understand it" and shouldnt criticize it...its certainly one way to go about promoting discussion...

I sometimes get the feel that the bar for "understanding it", for a lot of people, is that you agree with whatever it is that you are supposed to understand.

Uh ... you talkin' to me?

I dive a Liquivision X1 running V-Planner ... with a Tec2G in gauge mode as backup.

Hope that answers your question ... can we stop now with the stereotypes and personal slams?

... Bob (Grateful Diver)

 

[MXGratefulDiver]

I'v been away decompressing in Poland and only catching up now.

What I said was

"I don't dive Navy tables as a standard practice, but I have a copy on me for all deco dives. If things go real south - lost computer, lost buddy, lost anchor line, I still have a timer and depth gage and a set of tables.

Like I said, I don't dive them but I do carry a set for the event I get handed a ticket to hell and need to get off that bus."

This is where the bus ticket to hell came in. I keep a table in my tool bag and will check it every now and then on the hang - like there is much else to do sometimes?

But more important is this:


"I will also use them as a touch stone to check a computer generated or Ratio Deco schedule. If they are less then Navy Tables or close to them, I will check very closely to find out where the error is. Because there is an error if a modern table is getting me near Navy stops."

Face it, if a modern table or technique has you getting near to the old Navy tables for stops and/or run time, you most likely have made a mistake someplace. A quick check like this might have prevented the hit in Chuk of the diver who made the mistake in the mental math of RD. If he had checked a back up, he might have figured out his error and corrected his calculations.

At last ... thank you. Back to something useful.

I absolutely agree ... you should always "sanity check" whatever deco method you're using to make sure you've not committed brain flatulance somewhere along the way.

Electronics can fail ... but more often than not, human error can create false results. A sanity check will catch it, more often than not.

With most of my dives, the V-Planner software in my X1 is just slightly less conservative than the RD schedule I'd determined before the dive. It's a nice real-time sanity check. If they're off by more than a minute or two, I did something wrong.

... Bob (Grateful Diver)

 

[grazie42]

Uh ... you talkin' to me?

I dive a Liquivision X1 running V-Planner ... with a Tec2G in gauge mode as backup.

Hope that answers your question ... can we stop now with the stereotypes and personal slams?

... Bob (Grateful Diver)

Only in part, I was talking to the "general you" as well.

You said that someone who criticizes a method should "understand it". I said that it seems that to a lot of people that seems to mean that you should advocate it as well.

What I got from Chattertons post f.e is that he understands that some of the work of RD takes place inside the divers head, while in the water. For him, that is enough for him to decide its not for him. Afterwards quite a few posters argued that he doesent "understand" RD, but it seems (to me) that he knows enough to know its not for him (since he doesent want anything that requires the diver to think underwater). We may think he should have other criterias for that decision or that he overestimates the "work" that it takes to use RD underwater but since his requirement (seems) absolute, he knows enough to dismiss it(for himself) and enough to criticize it on the basis of his "prejudice"...

I didnt intend my post as stereotyping or a personal slam(Ive never dived a VR3 or made any dive solely by following a computer) so Im sorry you percieved it as one...

 

[Bismark]

What I got from Chattertons post f.e is that he understands that some of the work of RD takes place inside the divers head, while in the water. For him, that is enough for him to decide its not for him. Afterwards quite a few posters argued that he doesent "understand" RD, but it seems (to me) that he knows enough to know its not for him (since he doesent want anything that requires the diver to think underwater).

I don't know if you intended to say this, but this is one of the funniest things I have read in a while. I don't know JC but I am guessing that he is probably okay with at least something that "requires the diver to think underwater"..............

 

[Kevrumbo]

Gray ... since you quoted me in your previous reply and are now making statements referring to that quote, I'm going to ask you to consider what I said ...


Nowhere in there did I say anything about "so that people like KR wouldn't exist" ... nor was it implied. You are employing the very tactic you accused Bismark of using ... and to the same result.



So let me try again ... because there was nothing nefarious or judgmental in what I posted.

One should not attempt to learn decompression on the Internet ... regardless of method used. It's entirely too subjective and situational. Sure, you can learn the theory and history by reading a book ... or (if you trust the information) by what someone posts in a forum ... but all you're getting is the tools. It is the APPLICATION of those tools that matters. And in that respect, ALL decompression theories are more an art than a science ... and no matter which one you choose, what you're really doing is making a choice of which method you think is less likely to hurt you.

I used Kevrumbo as an example of someone who applied RD to a dive it was never intended for ... and as a result he got bent. That is NOT a judgment on KR as a diver. I don't know the guy, have never dived with him, and although I was involved in a discussion on another board where people were very hard on him, I was NOT one of those people. In fact, on more than one occasion he admitted I had made good points and asked reasonable questions about the reasons why he decided to do the dive as he did.

So no ... I don't wish that people like KR didn't exist ... I wish he would apply the tools he's attempting to use in his diving in the way they were intended, so that he doesn't hurt himself again.

Furthermore, on this and other boards I've seen people make broad comments about how using RD will cause you to get bent. I've dived with a couple divers who made the same comment ... when in fact it turns out they knew nothing about RD except what they'd been told by someone else who didn't understand it.

Misinformation CAN be dangerous ... and no matter HOW you attempt to explain RD on the Internet, the risk of misinformation is very high. That's why I think people shouldn't try learning it here. But that's also why I think it's important to correct someone who says something that you clearly know is mistaken or misleading ... because someone else reading the thread may decide to take it as factual. And that path leads to injury ...

... Bob (Grateful Diver)

Bob, that's a misinterpretation as well. . .

To reiterate: Ratio Deco was successfully used by myself on three previous deep air dives on the San Francisco Maru down to 54meters for 25min: the point is that on the incident dive, I erroneously conceded control & execution of the revised on-the-fly deco profile to my buddy which yielded a schedule that was nearly 30% less optimal than a Ratio Deco profile for that particular bottom time extension. Ironically, but thankfully --my buddy turned out okay. Nevertheless, I take full responsibility for what happened, I made things more complicated by my decisions during the dive, compounded by the narcosis of deep air. . .

I learned decompression theory and application of Ratio Deco in a formal class & recitation seminar with Andrew Georgitsis two years ago. Subsequently, I tried it out and posted some successful dives & profiles posted here and elsewhere, utilizing it on trimix as deep as 60meters here in SoCal and 69meters in the Philippines; and on deep air dives on previous Truk trips, up to the dives just prior to the incident three months ago. And nobody hardly said anything about it.

But since I reported the bends incident, the implication is now about an alleged misuse by myself of a Ratio Deco schedule causing it all, and how I picked-up to use the method off the Internet to begin with?

(C'mon Bob, be fair. After all that on the DMx Board --get it right !)

 

[Blackwood]

To reiterate: Ratio Deco was successfully used by myself on three previous deep air dives on the San Francisco Maru down to 54meters for 25min

By definition, it (Ratio Deco) was not (used).

You may have applied ratio deco rules to air, but you weren't doing ratio deco any more than my neighbor slapping an A badge on his Civic makes it an Acura.

But yes, I read your incident report, and what I took away from it was that you got hurt because you (knowingly) didn't do enough deco (as figured for a gas you hadn't been breathing), not exclusively because you happened to have been on air.

 

[Bismark]

Bob, that's a misinterpretation as well. . .

To reiterate: Ratio Deco was successfully used by myself on three previous deep air dives on the San Francisco Maru down to 54meters for 25min

I guess we have different definitions of successful. I would say you lucked out on the first three occasions and didn't on the dive where you got bent.

You were told by three different UTD instructors on the UTD forum that Ratio Deco does not apply to air diving. What part of that was unclear?

I don't know you and I don't wish bad to anyone. I think I understand what you are trying to do, but He does not ongas or offgas the same way N2 does. You may very well be able to come up with some math that lets you put a straight line over a curve for air much in the same way RD does for standard gases. You may even be able to bend that line a bit to make it more closely approximate the deco curve. That may be entirely possible. However, the numbers will not be the same, and the values for the RD rules will not be the same.

Think of RD as Ping Pong as opposed to table tennis: one is a trademarked name while the other is actually the sport itself. RD is a created name for something that works only with standard gases. When you apply these same rules to deep air diving you are no longer using RD. You may be using some kind of ratio but for the manner in which 99% of divers who use RD understand it, RD is a specific set of rules for a specific set of gases. They simply were never intended for use with air.

 

[Kevrumbo]

By definition, it (Ratio Deco) was not (used).

You may have applied ratio deco rules to air, but you weren't doing ratio deco any more than my neighbor slapping an A badge on his Civic makes it an Acura.

But yes, I read your incident report, and what I took away from it was that you got hurt because you (knowingly) didn't do enough deco (as figured for a gas you hadn't been breathing), not exclusively because you happened to have been on air.

Many of my Ratio Deco profiles used on previous Truk Trips are very close to decoplanner total times on an air bottom mix with certain GF's --of course the shape is different.

As Nick (Limeyx) wrote in TDS:

Part of the reason for basing the numbers on air bottom mix is that [earlier versions of] decoplanner (in some people's view) unfairly penalizes use of He, so the air "makes the numbers come reasonable" . . .so, no, I am not at all surprised the 21/35 and 18/45 numbers also "work" for an air mix . . .So in a sense it is a tautology that it "works" as it was kind of invented that way.

AG's monograph & Power Point presentation on Ratio Deco during the seminar two years ago implied that as well, IMO. . .

It is . . .what it is. And Ratio Deco was definitely used and practiced despite what you contend Blackwood. . .

 

[MXGratefulDiver]

(C'mon Bob, be fair. After all that on the DMx Board --get it right !)

I've always tried to be fair, Kevin ... but my understanding of RD is that it is intended to be used with standard gases, and air is not the standard gas for the dive you were doing. As such, RD was not applied as intended.

Do you believe that the deco profile for a 150-foot dive on air is equivalent to the same dive on 21/35? (Edit: Ah, never mind ... I see that in the ensuing responses you believe that it is ... can't help ya, then) ...

... Bob (Grateful Diver)