Why do some agencies recommend using a bottom timer instead of a computer

[LiteHedded]

I think all this talk of nebulous 'ratio deco' isn't helpful. Because one is perfectly reasonable when implemented the way it's taught and has been proven over 20 years or so. The other (UTD) is completely dumb and is probably what most of you are talking about, but it's hard to tell in all this back and forth

 

[Dan_P]

Start by answering these questions.

If only it were indeed the start.

I've already explained what my take would be on further litigations, so my response to the following should come as no surprise:

Why the f@#$ does Ratio Deco account for such an inordinate number of DCS incidents?

Source, please.
You'll need to support such a claim to have it addressed and accepted as though it's assumed or known to be valid.

You might choose to first demonstrate a significant difference in statistical occurence and then isolate the factor of using RD, but I'd be the first to agree that some leeway in personal choice of methodology would be cricket.

In either case, only then can we talk about assuming correctness of your narrative.

 

[Jack Hammer]

...yawn

 

[PfcAJ]

There may be any number of different sets of simple rules for calculating a "good enough" decompression schedule on the fly. One argument seems to be that it's a useful skill to have, the other argument is that the one set of rules is better than a dive computer. I do agree with one of those.

I’ve never argued that (gue) RD is better than a dive computer. My argument is, has, and will continue to be that it’s a useful method for generating a deco schedule that closely mimickes a buhlmann style ascent, within a fairly narrow set of parameters.

That it.

I think it’s silly to want *less* knowledge about decompression trends, which seems to be what some are advocating for in these threads.

 

[tbone1004]

@Dan_P I don't have an MD or PhD in a related field, hence why, unlike you, I choose to listen to those that are actively studying decompression research instead of claiming you know better than they do on how to most effectively decompression. Saying that you are going to go against the state of the art recommendations from those people implies that you feel like you know better than they do. As you are not qualified to do so, one can only assume you are blindly following your leader, in this case AG, who does in fact claim he knows better than they do, hence your current decompression strategy that goes against the learnings of the research and recommendations of those who are actually qualified to make those recommendations.

sorry if any of this is way out of order, I have been teaching for the last 2 weeks and days are quite long, so haven't actually read this thread in its entirety

 

[dmaziuk]

I think it’s silly to want *less* knowledge about decompression trends, which seems to be what some are advocating for in these threads.

One could say they're in good company: "because in much wisdom there is much grief, and increasing knowledge results in increasing pain".

 

[Dan_P]

@tbone1004 no.
If for nothing but good order - those "recommendations" have been repeatedly pointed out not to be recommendations.

But, to address your post, I think most of what needs to be said, has been.
If you'll address what I'm saying rather than what you're imagining me say, I imagine we'll have more trot with things all.
Quickly browsing through the thread:

If I were claiming that RD was "optimal" in terms of the physiological decompression process, I could understand objections or calls for substantiation.

If I were saying that using a PDC left you more at risk of DCS, I could understand objections.

But what I'm saying is, it can't be said to be dangerous, I find it highly practical and it is explicitly presented to me in a manner that encourages personal adaptation as one develops.
Which I personally choose to do - adapt it, that is.

These wild objections to that, I find to be clearly motivated by sentiment.

Let me say this:
I hold the Bonus Pater Familias-principle to be entirely pivotal.
But if I were the sort that would stuff my dog in the microwave to dry after bathing it, probably I'd be more prone to litigate, say, microwave manufacturers and the like.

 

[Germie]

You're not asking the right questions. He's an ethical researcher. He doesn't deal in absolutes in regard to "is this safe for you?". I'm not a researcher and have no issues being blunt about how problematic I find Ratio Deco to be. Here, let me ask the right questions for you... @Dr Simon Mitchell:

• Would you use Ratio Deco?
• Would you let your wife/daughter/son use Ratio Deco?
• Would you teach other divers to use Ratio Deco?
• Do you encourage others to use Ratio Deco?

Feel free to explain your answers, but please don't feel obliged.

1) NO
2) NO
3) Not that way, but I tell people how it works and go further with Pragmatic deco. If you are forgotten to write a runtimetable in wetnotes, and your computer stops working, and you remember your TTS last time, you can use this to get to surface safe (with a bottomtimer). Or if you remember your total divetime, and you have a bottomtimer, you can calculate your decostops by head. I use pragmatic deco to make stops more easy to remember, a 1-3-4-6-4-5 list is too hard to remember, so a 4-4-4-4-4 list is easy (just an example, not thinking about eventually S-curves if you want to use). Or if 3 minutes more bottomtime gives your 8 minutes more decotime you can say: that will be 4 minutes at last stop at 6m and on 4 other stops 1 minute extra. Then you don't need to make another runtimetable. Even with a best mix plan and a total divetime (by a planner) you can make the decostops by head if you don't write them on a slate.
3) NO, just as backup/bailout option

 

[The Chairman]

Source, please.

Friends I know. FRIENDS I KNOW. You want me to list names? Most are pretty embarrassed about what happened (simple math problem), a few are in denial about it and all would feel that I've betrayed them were I to divulge their names. Two are posting in this thread, one on either side of the discussion.

Ratio Deco is not the Holy Grail of diving. It does not grant the user a penultimate understanding of deco and full control of their DCS destiny. Again: WHAT'S THE BENEFIT? I have gone diving, many times into deco for almost 49 years without it. Unless you can prove it's significantly safer (good luck with that) or that it will bring me a cold beer after I finish diving, I don't see a need to waste cognitive resources learning it or using it on a dive.

Friends don't let friends dive Ratio Deco.

Now, someone brings up that there's a difference between two types of Ratio Deco. Again, what's the benefit? Where's the study that shows me it's safer than my Shearwaters or my Garmin Descent? Show me how it's safer than my first PDC: my Orca Skinny Dipper. I never got bent off of that either.

 

[PfcAJ]

Friends I know. FRIENDS I KNOW. You want me to list names? Most are pretty embarrassed about what happened (simple math problem), a few are in denial about it and all would feel that I've betrayed them were I to divulge their names. Two are posting in this thread, one on either side of the discussion.

Ratio Deco is not the Holy Grail of diving. It does not grant the user a penultimate understanding of deco and full control of their DCS destiny. Again: WHAT'S THE BENEFIT? I have gone diving, many times into deco for almost 49 years without it. Unless you can prove it's significantly safer (good luck with that) or that it will bring me a cold beer after I finish diving, I don't see a need to waste cognitive resources learning it or using it on a dive.

Friends don't let friends dive Ratio Deco.

Now, someone brings up that there's a difference between two types of Ratio Deco. Again, what's the benefit? Where's the study that shows me it's safer than my Shearwaters or my Garmin Descent? Show me how it's safer than my first PDC: my Orca Skinny Dipper. I never got bent off of that either.

Gues version spits out the same ascent schedule as buhlmann. It’s nothing crazy dude.

As I said before, I don’t know ANYONE who has got bent using gue ratio deco. I know a solid handful who have been bent using tables and computers.