Shadow Divers: John Chatterton's Interview with ScubaBoard

[Rick Inman]

Rick
If I'm not mistaken, the computer is not "running" the dive. It's just merely reading off your pre-cut dive plan.

I thought it could do both, but I could be wrong. Maybe someone who has one will chime in.

 

[Rick Inman]

Rick
If I'm not mistaken, the computer is not "running" the dive. It's just merely reading off your pre-cut dive plan.

I thought it could do both, but I could be wrong. Maybe someone who has one will chime in.

I just confirmed it with a dealer. Yes, the Liquidvision X1 DOES calculate deco on the fly. It's not just electronic cut tables.

 

[RiverRat]

I just confirmed it with a dealer. Yes, the Liquidvision X1 DOES calculate deco on the fly. It's not just electronic cut tables.

Interesting. But does that mean, if you input your table, it "overrides" your plan? Or does it just give you the option to run the plan, like a "guage" mode and have a second option to run "computer" mode?

 

[Chatterton]

Rick,

I am not sure I understand what is meant by Ratio Deco? Can you elaborate on the finer points?


Cheers

JC

And of course, now we have "proven" software like V-Planner, which makes it as easy as downloading and punching in the plan to cut tables, with almost unlimited parameters, including mixing formulas, lost gas scenarios, etc. Makes you wonder if it isn't almost too easy (ie, letting the software run your dive without knowledge as to the "why" and "how").

But the value of learning about deco profiles by sitting in your living room running a countless verity of simulated dives hasn't changed.

I've also seen divers with V-Planner loaded on their Liquid Vision computers jump in the water and let their computers run their dives.
I think the balance may be in knowing the how and why, being able to plan the dive using the math (gas planning, tables, etc), have the experience to know in your head roughly what a good deco would be on the fly, and then using good software like VP to cut the tables.

John, I would be interested to know your take on Ratio (on the fly) Deco??

 

[Rick Inman]

Rick,

I am not sure I understand what is meant by Ratio Deco? Can you elaborate on the finer points?


Cheers

JC

John,

I will do my best to explain what I know. I have not taken the class, so, take it for what it's worth. Others who have taken the class may expound or correct my errors.

Ratio Deco is GUE's on-the-fly method of calculating a deco profile in your head without the use of cut tables or a computer. Basically, by tracking your average depth in your head during the dive (something these divers do on a regular basis) and following some standard rules of thumb, you determine your deco based on the dive as it unfolds.

Divers use predetermined standard gases for both backgas and deco. Deco depths are broken up into "segments". Here is the DIR-X version of stop segments and standard gases:

Deco Gas Depth Range Number of Stops
12/60 300’/90m – 250’/75m 6 stops
15/55 240’/72m – 200’/60m 5 stops
21/35 190’/57m – 130’/39m 7 stops
35/30 120’/36m – 80’/24m 5 stops
50% Nitrox 70’/21m – 30’/9m 5 stops
Oxygen 20’/6m – 0’/0m “2.5” stops 20’/6m stop + slow ascent

So for example, the 70' to 30' segment has 5 stops, meaning 70', 60', 50', 40' and 30'. Time at stops is determined by rules-of-thumb based on bottom time at average depth.

Of course, there is a lot more to it than I am saying here (see pdf attachment at bottom of post). And this method of on-the-fly deco does not negate dong a proper dive plan. Many divers also run pre-dive profiles on programs like V-Planner or DecoPlanner.

Here is a dive my buddy and I are doing Saturday, planned on V-planner, and how it might be using DIR-X Ratio Deco (times do not reflect S curve):

Ratio Deco:

200' 30 minutes 18/45
70 5 minutes ean50
60 5 minutes
50 5 minutes
40 5 minutes
30 5 minutes
20 22 minutes (with 12 minutes on O2 and 6 minutes on backgas)
20-0 3 minutes

*200' dive for 30 minutes (using 220 as the setpoint and a 1:2 ratio for bottom time to deco time)
We would subtract 10 minutes from 60 minutes (2X bottom time) because we are 20 feet less than 220.
So we would spread out deco 1/2 over 70-30 and 1/2 from 20' to surface or 25 minutes between 70 and 30 and 25 minutes at 20' with backgas breaks.

VPM:
DIVE PLAN
Surface interval = 2 day 0 hr 0 min.
Elevation = 2,100ft (c)
Conservatism = + 2
200 26 (30) 18/45
130 0 (33) 18/45
120 1 (34) 18/45
110 1 (35) 18/45
100 2 (37) 18/45
90 2 (39) 18/45
80 3 (42) 18/45
70 2 (44) 50
60 3 (47) 50
50 3 (50) 50
40 5 (55) 50
30 8 (63) 50
20 25 (88) 100

Attached is the 5th D-X (now UTD) ratio deco PDF file.

 

[Chatterton]

Rick,

You did a pretty good job of explaining it, as near as I can tell? As a mental exercise, I can see how some divers might like to apply this as some sort of tool to better understand deco. A lot of divers can roughly figure dives based on experience. As a practical method of calculating deco, I am not too interested?

I take deco seriously, and I realize that small errors can cause big problems. I have never been treated for the bends. I plan my dive, I plan for contingencies. I use a computer, or two computers, a depth gauge, and carry a table or two as well. If all that turns to crap, I follow my buddy and then do a little more hang than he/she does.

Before I would be forced into making on the fly calculations in my head, I would have to have a computer (or two) go down, lost my tables, lost my buddy, but somehow kept my depth gauge so I can do my mental stops? By that time, I would expect my head to have blown up and to be too task loaded to calculate all that much anyway?

I am not a GUE diver, and do not subscribe to their philosophy, however there is plenty of room in diving for people ot express themselves as divers in a variety of ways. If someone wants to train with Ratio Deco, more power to them.

Personally, I do not necessarily believe in all of the science we use to calculate our on and off gassing, especially as it pertains to helium. That is to say that I think some of the math is wrong. Then again we are trying to use time and depth to roughly calculate something that is really molecular in nature. As time goes on we will better understand what it really happening, maybe?

Just my opinion.


CHeers

JC

 

[RiverRat]

You make some valid points John. As a beginning tech diver (TDI Adv Nitrox/Deco) I'm starting to see that there is lot we just don't know yet. I do admit I like GUE's approach to standard gasses etc. and their overall strategy to keep things simple and organized where possible. But I think at my level I would not want to get bogged down with ratio deco. I've got more important things to think about while training for more challenging dives. For me I like v-planner and backup tables and contingency plans. I see some divers are cross checking RD with vplanner anyway? So why not just stick with vplanner? Like you said, you'd have to have multiple failures or screw up real bad to lose all of your redundant systems. If it was that bad I'd just pad my deco as much as possible with what gas reserves I've got? Anyway thanks to all for the valuable info here.

 

[SkipperJohn]

WOW...
Only a few months ago I discovered this forum. I was looking for info on a camera I just bought for my annual trips & snorkel dives in Aruba. After 3 or 4 days of reading I decided to get certified. 3 weeks later all that was left was my OW. Another 2 weeks later I finished (at the age of 54) and thought I would now be diving Aruba once a year... A week later and I spent all sorts of $ on equipment, suits and plan on diving here (the south coast of Long Island New York) every chance I get.
I lived here all my life and been fishing here since I was 5. Every once in a while while on head boats someone would mention a wreck we were fishing on was sunk by German U-boats. I was intrigued. Once I got my own boat and masters licence I would seek out these wrecks and not only fish them but do all I could to learn about them. Living in Lynbrook LI, where I believe Aqua Explorers was based out of, I soon began to buy their books.
Fast forward to last week. Someone I work with suggest I read SD. After 3 days I just reached the pictures in the middle. The book is everything you all said. Even for non-divers. The characters as well. Not unlike many of the old salts I know in the fishing arena, each with a color all his own. Anyway, thanks to my previous awareness of these wrecks and this book, I am making all sorts of plans to get the proper certification & equipment and hope to soon be diving many of the wrecks that dot these shores (I am jonesing for the San diego, which when I first started fishing her I knew it simply as the Gun Boat).
Thanks for the eye opening. Again, great book, great story, very very well written and congratulations on your success!

As for the u-boat, I have a few fishing charts form quite a few years back (unsure of the actual date as I am in my office now) that refer to the area as the "Triple Wrecks". There are 3 wrecks in the area of which one is the u-boat and it has always been known as a fishing hot spot. Often times the fish and birds help us find these spots as we navigate to other destinations and see life. It's not always electronics and detective work. usually just dumb luck (as my fishing log and numbers book can attest to). I have no clue if any of this predates the dives.

 

[Chatterton]

SJ,

As you are probably aware, anyone can submit information with regards to wrecks and obstructions to NOAA. This information goes into AWOIS (Automated Wreck & Obstruction Information System), and the locations gets included in both paper and electronic charts. Once something is entered into the AWOIS system, it like never leaves, even if it is proven to not exist.

The SS Carolina, for example, was recorded on the NOAA charts at the location given by the vessel's Captain, after the sinking. The Captain was not in the wheelhouse when the attack occured and his estimated location was way off. When we found the wreck, it was far from that location, but the charts still carry the wreck symbol at the Captain's erroneous co-ordinates. If I submitted the new location, and someone else might have already done this, it would be included as well.

Essentially, the Triple Wrecks is only three wreck symbols, not really three wrecks. It is an area of ocean roughly 60 miles from the Jersey coast where there are three charted wreck symbols. As you state, they are known to most of the offshore fishermen. However, there are no known wrecks to exist within miles of those three locations. The Uboat is in that general area of ocean, but not attributed to the sources of any of the Triple Wreck sites.

If you go to AWOIS, you can get whatever information that NOAA has with regards to their inclusion of the sites, which often includes the source of the information with dates and so on.


CHeers

JC

WOW...
Only a few months ago I discovered this forum. I was looking for info on a camera I just bought for my annual trips & snorkel dives in Aruba. After 3 or 4 days of reading I decided to get certified. 3 weeks later all that was left was my OW. Another 2 weeks later I finished (at the age of 54) and thought I would now be diving Aruba once a year... A week later and I spent all sorts of $ on equipment, suits and plan on diving here (the south coast of Long Island New York) every chance I get.
I lived here all my life and been fishing here since I was 5. Every once in a while while on head boats someone would mention a wreck we were fishing on was sunk by German U-boats. I was intrigued. Once I got my own boat and masters licence I would seek out these wrecks and not only fish them but do all I could to learn about them. Living in Lynbrook LI, where I believe Aqua Explorers was based out of, I soon began to buy their books.
Fast forward to last week. Someone I work with suggest I read SD. After 3 days I just reached the pictures in the middle. The book is everything you all said. Even for non-divers. The characters as well. Not unlike many of the old salts I know in the fishing arena, each with a color all his own. Anyway, thanks to my previous awareness of these wrecks and this book, I am making all sorts of plans to get the proper certification & equipment and hope to soon be diving many of the wrecks that dot these shores (I am jonesing for the San diego, which when I first started fishing her I knew it simply as the Gun Boat).
Thanks for the eye opening. Again, great book, great story, very very well written and congratulations on your success!

As for the u-boat, I have a few fishing charts form quite a few years back (unsure of the actual date as I am in my office now) that refer to the area as the "Triple Wrecks". There are 3 wrecks in the area of which one is the u-boat and it has always been known as a fishing hot spot. Often times the fish and birds help us find these spots as we navigate to other destinations and see life. It's not always electronics and detective work. usually just dumb luck (as my fishing log and numbers book can attest to). I have no clue if any of this predates the dives.

 

[vyvial]

I just went and got both books after reading this topic