The old tables vs computer argument

[Blackwood]

but they used up time going to this new site, so you want the maximum bottom time, and they want to get back for the afternoon run...which leaves a problem.. you can take longer, but your surface interval will be shorter.. or you can dive shorter and have that one hour (but no longer) surface interval. I choose to have the longer dive, with a shorter surface interval...your system does not allow that.

There are adjustments (doubling the shallow stops, etc.).

The computer actually knows that you have been working and greatly reduced your NDL, so you don't add a chamber ride to being tired.

Which computer knows that?

Your system hopes that it so conservative that you cover this event.. computers can actually adjust for it.

So can this system. The schedule I posted was the minimum decompression. Feel free to add more to taste.

You plan a dive for say 80 degree water, but when you actually do the dive, the temperature at the bottom is 74 (that actually happen last July in the northern gulf)..suddenly, your three mil is not so warm...

The computers can be made to adjust for sudden, unexpected changes in a way that doing math in your head cannot. However, if you have lots of time, are on no schedule, it still works well. Trouble is, that is not the majority of the diving being done..

Same answer, and same question confused: )

And diving very conservatively ends up meaning a lot of missed bottom time and lost dives.

FWIW, throughout a day, I can probably get more BT with this system than with say the PADI RDP using its published methodology or many computers.

Try an example: I have a task at 100FSW that will take me 2 hours to complete. I'm diving 32%, so NDL is 30 minutes. Assuming I don't exceed NDL, using MDL/Ratio, how long will it take? Using the RDP, how long will it take? Using your computer, how long will it take?

I have neither tables nor a computer handy, but one decisive advantage of this system is that I don't need one to answer the first question. I can do it in my head. With no adjustments assuming perfect conditions:

Dive 1: Descent takes about 1.5 min, 30 min on the bottom, about 7 minutes to ascend
Dive 2: Sit for 90 minutes, descent takes about 1.5 min, 30 min on the bottom, about 7 minutes to ascend
Dive 3: Sit for 90 minutes, descent takes about 1.5 min, 30 min on the bottom, about 7 minutes to ascend
Dive 4: Sit for 90 minutes, descent takes about 1.5 min, 30 min on the bottom, about 7 minutes to ascend

Total time spent, 424 minutes (of which 120 is at 100 feet). Of course, that doesn't have any margin for delays. Also, in real life I'd probably pad the repet ascents to 12 minutes. With surface swims, gearing up delays, padded deco, etc., you could probably do it in 8-9 hours in the real world.

I'm not certain, but I imagine your standard buhlmann table will keep you out of the water for quite some time after dive 2, and a computer will probably call you bent at some point throughout the day.

Which agency(ies) offer "ratio decompression" training? Are there any training requirements?

GUE (as part of full courses) and UTD (as a 'workshop') offer if formally.

You can do it online here: http://www.unifiedteamdiving.com/page/ratio-deco

 

[Mr Carcharodon]

An other vote for ratio deco.

Do realize however that using RD assumes that you will be aware enough of your dive that you know your average depth to 10 fsw or so, and that you can do a controlled ascent with stops on the way up. Not all beginners can.

Ratio is rather simpler than using tables. Complexity seems to be a major objection yet this is a concern that does not seem to have much substance at least at a min deco level. And there is no problem using a computer and calculating your own NDLs at the same time. So you have both sets of information available.

 

[DiveNav]

UWATEC or OMS digital depth gauge/bottom timer along with a Casio G-shock watch or other such device in stop watch mode.....

..... So, yes, there is computer technology involved in the devices, but they do not track or interfere with my dive profiles......

Hi,
I am familiar with Ratio Deco (taking a class with Andrew Georgitsis 's UTD .... just for fun).

I was just pointing out that we are daily surrounded by technology (do you know how many micro-controllers are there in your car? And in your house?) but when it comes to diving, some of us (I believe a small minority) almost refuses to adopt it (in this case dive computers) claiming they are not safe enough :shocked2:
Of course this is not your case.

Alberto

 

[b1gcountry]

when it comes to diving, some of us (I believe a small minority) almost refuse to adopt [technology] (in this case dive computers) claiming they are not safe enough :shocked2:
Of course this is not your case.

I hear more people argue from a logistical point of view, or that it just works better for that person based on the diving they do.

We are, none of us, aquatic creatures, and have no way of judging pressure, depth, or time without the use of some sort of mechanical device. So we are all screwed without the use of some form of technology.

Tom

 

[Thalassamania]

A note about ratio deco:

Ratio deco is basically a curve fitting exercise. There is NO underlying or unifying theory. Ratio deco is rather untested, when compared to "accepted" tables that were derived from a theoretical construct.

But ... ratio deco appears to work and the profiles that are derived from it usually fit on the "safe" side of those that are derived from more conventional models ... but the science has yet to be done.

 

[Blackwood]

A note about ratio deco:

Ratio deco is basically a curve fitting exercise. There is NO underlying or unifying theory.

It's based on decoplanner.

 

[Rainer]

If it's a curve fitting exercise (and it is, plus some ideas about O2-window, etc), and you're fitting a curve that HAS been accepted, what's the issue? What needs to be verified? At best, the curve fitting (which is what you do in an RD class; you sit there and see how RD curves match against those generated by Buhlmann, VPM, etc).

A note about ratio deco:

Ratio deco is basically a curve fitting exercise. There is NO underlying or unifying theory. Ratio deco is rather untested, when compared to "accepted" tables that were derived from a theoretical construct.

But ... ratio deco appears to work and the profiles that are derived from it usually fit on the "safe" side of those that are derived from more conventional models ... but the science has yet to be done.

 

[Puffer Fish]

If it's a curve fitting exercise (and it is, plus some ideas about O2-window, etc), and you're fitting a curve that HAS been accepted, what's the issue? What needs to be verified? At best, the curve fitting (which is what you do in an RD class; you sit there and see how RD curves match against those generated by Buhlmann, VPM, etc).

Yes and no.. as it is using very simple calculations.. some of the profiles do not fit, some are almost perfect duplicates.

As they are so simple, that if that was the best method, everyone would be using it, and having a computer do it would be easy.

We have the technology today to test any profile and measure the microbubbles it generates...the fact that there there is no published data means either some don't want to know, or it failed and they don't want to know that.

A good example of this is one of the first examples of a profile involving 32% nitrox...that profile does not fit any of the known and tested math. But the other one in that post does... rather hit and miss. Not surprising considering how complex the real math is.

 

[b1gcountry]

We have the technology today to test any profile and measure the microbubbles it generates...the fact that there there is no published data means either some don't want to know, or it failed and they don't want to know that.

I'm not sure what you are saying here. I don't think there have been any real comprehensive studies involving doppler imaging of divers after a dive since the RDP was created. Not that I've heard of anyway. And while it is pretty easy to test ANY profile, it's pretty hard to test EVERY given profile and series of profiles.

Tom

 

[Rainer]

And if you think doppler studies alone can "confirm" any decompression theories, well...