Ratio Deco - Deco On The Fly - Anyone???

Janos · 5th December 2006, 08:19

I don't like GUE Ratio deco as comparing the profiles I find it scarily aggressive. It's generally a few more minutes less than VPM-B set to nominal conservatism.

Ratio deco is just pattern matching. I was asked by Woz to knock up some "rules" for OC air/Nitrox diving with 50% as a decompression gas. I called it "deco on the pie" because of my love of pork products. It produces results that are similar to 20/80 Bulhman

Link: Deco on the Pie (DOTP) - YD Dive Forums & Scuba Community

I'm sure it's easy enough to do something similar for deep CCR dives, but what do you standardise on? What setpoint, diluent do you use? Is the setpoint steady or falling? What deco algorithmn do you use? what conservatism?

Janos

Woz · 5th December 2006, 09:04

AFAIK Ratio deco is pretty straight forward for standard gases. I think it works like this (but don't go and use it and get bent them come wheelchairing to me to complain as I might and probably am wrong):

Set point is at 45m. For every minute of bottom time you do a minute of deco. Gases are 21/35 and deco on 50%.
Half of the deco is at 6m. Valid for up to 50 mins total deco only.
For the other half, spread it out from 21m up as follows:

Deco time 21m 18m 15m 12m 9m
5min........ 1 ....1 ....1 ....1 ....1
10 min .... 2 ....2 ....2 ....2 ....2
15 min .... 3 ....3 ....3 ....3 ....3
20 min .... 4 ....4 ....4 ....4 ....4
25 min .... 5 ....5 ....5 ....5 ....5

Also add time at the 21m stop to make a min of 3 min to take advantage of the oxygen window.
For each added 3m depth, add 5 mins deco. For each 3m taken off, remove 5 mins deco.
If you lose your fiddy then double the stop times.

For example:
25 min dive to 48m.

Total deco 30 mins.
Half deco at 6m=15 mins
Rest of deco is 3 mins at 3m intervals from 21m.

Buhlmann 20/80 gives:
v 045 02:15 002 21/35
- 045 22:45 025 21/35
^ 024 02:06 027 21/35
~ 024 00:53 028 21/35
~ 021 01:00 029 50
~ 018 01:00 030 50
~ 015 01:00 031 50
~ 012 02:00 033 50
~ 009 03:00 036 50
~ 006 17:00 053 50

And interestingly for air Buhlmann gives almost identical results:
v 045 02:15 002 21
- 045 21:45 024 21
^ 024 02:06 026 21
~ 024 00:53 027 21
~ 021 01:00 028 50
~ 018 01:00 029 50
~ 015 01:00 030 50
~ 012 02:00 032 50
~ 009 04:00 036 50
~ 006 16:00 052 50

Janos · 5th December 2006, 10:27

Quote: (Originally Posted by Woz)

AFAIK Ratio deco is pretty straight forward for standard gases. I think it works like this (but don't go and use it and get bent them come wheelchairing to me to complain as I might and probably am wrong):

You are wrong. Or you are not complete. "Deco" in a DIR context means that when you're breathing your stage. So the stops below 21m aren't "deco" in DIR-speak.

You also need to slow your ascent rather than rushing up to 21m. For shallow dives this is at 2/3 max depth (roughly). For deeper dives you add in a second stop at 80% of pressure. What rate you go up at depends on your bottom time, but it's typically 3m/min. (ie 1min every 3m) from the shallower deep stop. For longer bottom times, this will increase up to 5mins every 3m.

However i'm not DIR trained so I've prolly got it wrong too. Anyone else not DIR trained want to chip in?

Janos

mstroeck · 5th December 2006, 10:40

Quote: (Originally Posted by Janos)

I don't like GUE Ratio deco as comparing the profiles I find it scarily aggressive. It's generally a few more minutes less than VPM-B set to nominal conservatism.

Ratio deco is just pattern matching. I was asked by Woz to knock up some "rules" for OC air/Nitrox diving with 50% as a decompression gas. I called it "deco on the pie" because of my love of pork products. It produces results that are similar to 20/80 Bulhman

Link: Deco on the Pie (DOTP) - YD Dive Forums & Scuba Community

I'm sure it's easy enough to do something similar for deep CCR dives, but what do you standardise on? What setpoint, diluent do you use? Is the setpoint steady or falling? What deco algorithmn do you use? what conservatism?

Janos

GUE type ratio deco is not very aggressive, as far as I'm aware. Perhaps you are talking about AG's ratio deco article? The deco described there can be a bit agressive in fringe cases, but in the vast majority of cases you'd still be in water about as long as with standard VPM/RGBM deco calculation, especially since you are well advised to round absolutely everything up by a healthy margin.

The whole point of DOTF, though, is that you don't need to do it exactly as the doctor prescribes. Nobody says you have to go out of the water when the calculated time is up, or that you can't bring O2 but deco out on a 50% schedule. The DIR-police also won't lynch you for doing another 10 minutes on 50/25% or 15 minutes on oxygen :-)

Mark Chase · 5th December 2006, 11:41

The 5thD link explains ratio deco across al the ratios and it does it in fairley simple terms.

For me Ratio Deco is for when every other opportunity to calculate deco has failed. So that meens no HH no Sherewater and no buddy with VR3 Vision what ever. I looked at the 5th D system and decided in a high presure situation i couldent be figuring all that crap out so i use the Chasey Simplified system.

In this event I work on the folowing set points (18/45 used for prety much everything down to 60m

45m 1:1 ratio
50 1:1.5
60 1:2
70 1:2.5
80 1:3
80+ screw that take back up tables

So 50mins at 48m Round it up to 50 ratio 2:1 i have 75min of ascent

1.5 X 50mins = 75min + 50 = 125min run time

Running Vplanner on my prefered VPMBE level 2 I get first stop at 26 and 114 min run time. so 125 is close enough

Id work on the folowing

10m/min till 2ATMs above max depth then 3m/min up to first stop depth (to be decided bassed on depth) then spilt half the remaining time for the 6m stop and half for the remaining ascent.

so 50 @ 48m id do my first stop at 32m then a 3m/min ascent to 21

Time so far 7min apx

68 to go so 34min @ 6

Then Id do half of 34 at 9 and work backwards in halves rounded up. So

1 @ 21
3 @ 18
5 @ 15
9 @ 12
17 @ 9
34@6

I dont think for one min that this is an ideal or even a good profile but it will no doubt get me out of the water in one piece and its simple to work out.

As with all DOTF systems it tends to shift from conservitive to agresive across the range but I just like the math better then the GUE one.

ATB

Mark Chase

decoweenie · 5th December 2006, 12:07

Quote: (Originally Posted by cedricverdier)

I didn't read Phi's article and I regret it (Phi, please!) but it's not rocket science to figure out how it works. But remember that everything is empirical. In this case you're maybe the only guinea pig...

Cedric,

Here it is...

Remember that I am not as good of a writer as you, so if someone wants to polish it into a more easily understanding format, you are more than welcome to it.

As Cedric said, this is just an attempt to fit MY standard deco practice. It might not be suitable for you since I tend to be more aggressive. However, it is easy enough to increase the variables to lenghten the stops.

Janos · 5th December 2006, 13:17

Quote: (Originally Posted by mstroeck)

GUE type ratio deco is not very aggressive, as far as I'm aware. Perhaps you are talking about AG's ratio deco article? The deco described there can be a bit agressive in fringe cases, but in the vast majority of cases you'd still be in water about as long as with standard VPM/RGBM deco calculation, especially since you are well advised to round absolutely everything up by a healthy margin.

I don't think the above is true. Everytime I have looked at a profile in the 60m range it has come out as more aggressive than VPM-B+0.

Quote: (Originally Posted by mstroeck)

The whole point of DOTF, though, is that you don't need to do it exactly as the doctor prescribes. Nobody says you have to go out of the water when the calculated time is up, or that you can't bring O2 but deco out on a 50% schedule. The DIR-police also won't lynch you for doing another 10 minutes on 50/25% or 15 minutes on oxygen :-)

This is true of any deco algorithmn. However the useful thing about a deco algorithmn (whether it's DOTF, VPM, Buhlman etc) is the minimum time it lets you to get out of the water.

Janos

chunter · 5th December 2006, 22:25

Thanks everyone for all of the useful informaiton. I have read all of it as well as the websites and articles referred to in posts. For me...and let me say that again...FOR ME, it seems foolhardy to trust a mathmatical calculation done on the fly. There also seem to be a lot of rules dealing with limitations on each profile (ie "this only applies to decompressions shorter than 50 minutes"). For my own education, I will learn the system, however, it will only be for the worst case scenario. Even then, what happens if I don't have standardized gasses for my bailouts? I typically dive 10/50tx for my deep dives with 50% for additional bailout. How would that look on a DOTF schedule? Isn't it easier to cut tables with scenarios ranging from 5 to 90 minutes bottom time and all depths within the range of the gasses you plan to dive? I can get a huge number of deco scenarios (both OC bailout and CCR) on a single sheet of 8.5"x11" wet paper (NeverTear).

I guess any ECCR diver is relying on electronics to a certain extent anyway. Most DIR and GUE divers also use computers set to "freedive mode" or bottom timers with average depth etc. Perhaps the most hard-core only use analog clocks for timers (or count in thier heads) and vertical lines to the surface with depth markers on them.

I'll take my chances with two VR3s, another backup timer, and tables. If I'm not smart enough to figure out which is failing, I guess Darwin's law has prevailed. DOTF seems to be a useful tool, but I'm not going to use it in place of a computer and tables anytime soon (unless there are no other options). The human error factor seems to be greater than the likelyhood of all other electronics failing simultaneously. In that situation, I'd stay down as long as I could using whatever gasses/CO2 scrubber I had available at the time.

Anyway, I really appreciate everyone's feedback and will continue to read following posts.

Aloha,
Charlie

Mark Chase · 5th December 2006, 22:49

I used to spend many hours planning and re planning each dive. Then I ended up with a VR3. I decided i would cut bailout tables and because i knew roughly enough about deco to pad it out on my own I cut tables at 100/100GF to give me a base line out of the water. From that base line, I'd do deco bassed on available gas.

At some point i got two VR3s and ditched the tables. However all those dives planned on a baseline taught me that there was a massive margin between what i was doing and 100/100GF (close to straight Buhlman)

Possibly as a result of this i have become a lot more relaxed about deco. I have been known to scrap the last 10-15mins of a 90min deco hang because I felt conditions made that the safer choice.

Having spent now many many hours comparing proper ratio deco with Chasey ratio deco and numbers generated on VPMBE level 2 I have decided its close enough for jazz.

I feel confident that if one computer went wrong and the other totally disagreed with it that I could work out ratio deco and decide which one to follow with a fair degree of confidence.

On deco hangs i have nothing better to do so i work out the ratio deco and see how it compares with what the Hammer Head tels me to do. This exercise under relaxed conditions has made me much more confident with ratio deco.

However I wont be giving up the computers. I love glancing down and having all the relevant info to hand. I have better things to do on the bottom phase than worry about deco calks.

ATB

Mark Chase

5th December 2006, 08:19	#11 (permalink)
Janos "Two Sheds" Current Rebreather/s: Classic Kiss Other Rebreather/s: Classic Kiss Join Date: Feb 2005 Location: East Surrey Posts: 600	Re: Ratio Deco - Deco On The Fly - Anyone??? I don't like GUE Ratio deco as comparing the profiles I find it scarily aggressive. It's generally a few more minutes less than VPM-B set to nominal conservatism. Ratio deco is just pattern matching. I was asked by Woz to knock up some "rules" for OC air/Nitrox diving with 50% as a decompression gas. I called it "deco on the pie" because of my love of pork products. It produces results that are similar to 20/80 Bulhman Link: Deco on the Pie (DOTP) - YD Dive Forums & Scuba Community I'm sure it's easy enough to do something similar for deep CCR dives, but what do you standardise on? What setpoint, diluent do you use? Is the setpoint steady or falling? What deco algorithmn do you use? what conservatism? Janos __________________ You can lead a horse to water but you can't climb a ladder with a large bell in both hands - Vic Reeves www.hellfins.com/shed
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5th December 2006, 09:04	#12 (permalink)
Woz Custom Title Allowed! Current Rebreather/s: Home Build Other Rebreather/s: Home Build Join Date: Jun 2005 Location: Nottingham Posts: 185	Re: Ratio Deco - Deco On The Fly - Anyone??? AFAIK Ratio deco is pretty straight forward for standard gases. I think it works like this (but don't go and use it and get bent them come wheelchairing to me to complain as I might and probably am wrong): Set point is at 45m. For every minute of bottom time you do a minute of deco. Gases are 21/35 and deco on 50%. Half of the deco is at 6m. Valid for up to 50 mins total deco only. For the other half, spread it out from 21m up as follows: Deco time 21m 18m 15m 12m 9m 5min........ 1 ....1 ....1 ....1 ....1 10 min .... 2 ....2 ....2 ....2 ....2 15 min .... 3 ....3 ....3 ....3 ....3 20 min .... 4 ....4 ....4 ....4 ....4 25 min .... 5 ....5 ....5 ....5 ....5 Also add time at the 21m stop to make a min of 3 min to take advantage of the oxygen window. For each added 3m depth, add 5 mins deco. For each 3m taken off, remove 5 mins deco. If you lose your fiddy then double the stop times. For example: 25 min dive to 48m. Total deco 30 mins. Half deco at 6m=15 mins Rest of deco is 3 mins at 3m intervals from 21m. Buhlmann 20/80 gives: v 045 02:15 002 21/35 - 045 22:45 025 21/35 ^ 024 02:06 027 21/35 ~ 024 00:53 028 21/35 ~ 021 01:00 029 50 ~ 018 01:00 030 50 ~ 015 01:00 031 50 ~ 012 02:00 033 50 ~ 009 03:00 036 50 ~ 006 17:00 053 50 And interestingly for air Buhlmann gives almost identical results: v 045 02:15 002 21 - 045 21:45 024 21 ^ 024 02:06 026 21 ~ 024 00:53 027 21 ~ 021 01:00 028 50 ~ 018 01:00 029 50 ~ 015 01:00 030 50 ~ 012 02:00 032 50 ~ 009 04:00 036 50 ~ 006 16:00 052 50 __________________ Still punting shiny diving tatt to gullible divers www.kitfondle.co.uk Last edited by Woz : 5th December 2006 at 09:07.
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5th December 2006, 10:27	#13 (permalink)
Janos "Two Sheds" Current Rebreather/s: Classic Kiss Other Rebreather/s: Classic Kiss Join Date: Feb 2005 Location: East Surrey Posts: 600	Re: Ratio Deco - Deco On The Fly - Anyone??? Quote: (Originally Posted by Woz) AFAIK Ratio deco is pretty straight forward for standard gases. I think it works like this (but don't go and use it and get bent them come wheelchairing to me to complain as I might and probably am wrong): You are wrong. Or you are not complete. "Deco" in a DIR context means that when you're breathing your stage. So the stops below 21m aren't "deco" in DIR-speak. You also need to slow your ascent rather than rushing up to 21m. For shallow dives this is at 2/3 max depth (roughly). For deeper dives you add in a second stop at 80% of pressure. What rate you go up at depends on your bottom time, but it's typically 3m/min. (ie 1min every 3m) from the shallower deep stop. For longer bottom times, this will increase up to 5mins every 3m. However i'm not DIR trained so I've prolly got it wrong too. Anyone else not DIR trained want to chip in? Janos __________________ You can lead a horse to water but you can't climb a ladder with a large bell in both hands - Vic Reeves www.hellfins.com/shed
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5th December 2006, 10:40	#14 (permalink)
mstroeck New Member Current Rebreather/s: Dolphin Other Rebreather/s: Dolphin Join Date: Nov 2005 Location: Vienna, Austria Posts: 32	Re: Ratio Deco - Deco On The Fly - Anyone??? Quote: (Originally Posted by Janos) I don't like GUE Ratio deco as comparing the profiles I find it scarily aggressive. It's generally a few more minutes less than VPM-B set to nominal conservatism. Ratio deco is just pattern matching. I was asked by Woz to knock up some "rules" for OC air/Nitrox diving with 50% as a decompression gas. I called it "deco on the pie" because of my love of pork products. It produces results that are similar to 20/80 Bulhman Link: Deco on the Pie (DOTP) - YD Dive Forums & Scuba Community I'm sure it's easy enough to do something similar for deep CCR dives, but what do you standardise on? What setpoint, diluent do you use? Is the setpoint steady or falling? What deco algorithmn do you use? what conservatism? Janos GUE type ratio deco is not very aggressive, as far as I'm aware. Perhaps you are talking about AG's ratio deco article? The deco described there can be a bit agressive in fringe cases, but in the vast majority of cases you'd still be in water about as long as with standard VPM/RGBM deco calculation, especially since you are well advised to round absolutely everything up by a healthy margin. The whole point of DOTF, though, is that you don't need to do it exactly as the doctor prescribes. Nobody says you have to go out of the water when the calculated time is up, or that you can't bring O2 but deco out on a 50% schedule. The DIR-police also won't lynch you for doing another 10 minutes on 50/25% or 15 minutes on oxygen :-) __________________ Michael Ströck
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5th December 2006, 11:41	#15 (permalink)
Mark Chase I go down for ages Current Rebreather/s: Classic Kiss Other Rebreather/s: Inspiration Classic Join Date: Jan 2005 Location: Kent Posts: 2,694	Re: Ratio Deco - Deco On The Fly - Anyone??? The 5thD link explains ratio deco across al the ratios and it does it in fairley simple terms. For me Ratio Deco is for when every other opportunity to calculate deco has failed. So that meens no HH no Sherewater and no buddy with VR3 Vision what ever. I looked at the 5th D system and decided in a high presure situation i couldent be figuring all that crap out so i use the Chasey Simplified system. In this event I work on the folowing set points (18/45 used for prety much everything down to 60m 45m 1:1 ratio 50 1:1.5 60 1:2 70 1:2.5 80 1:3 80+ screw that take back up tables So 50mins at 48m Round it up to 50 ratio 2:1 i have 75min of ascent 1.5 X 50mins = 75min + 50 = 125min run time Running Vplanner on my prefered VPMBE level 2 I get first stop at 26 and 114 min run time. so 125 is close enough Id work on the folowing 10m/min till 2ATMs above max depth then 3m/min up to first stop depth (to be decided bassed on depth) then spilt half the remaining time for the 6m stop and half for the remaining ascent. so 50 @ 48m id do my first stop at 32m then a 3m/min ascent to 21 Time so far 7min apx 68 to go so 34min @ 6 Then Id do half of 34 at 9 and work backwards in halves rounded up. So 1 @ 21 3 @ 18 5 @ 15 9 @ 12 17 @ 9 34@6 I dont think for one min that this is an ideal or even a good profile but it will no doubt get me out of the water in one piece and its simple to work out. As with all DOTF systems it tends to shift from conservitive to agresive across the range but I just like the math better then the GUE one. ATB Mark Chase __________________ Is it supposed to make that noise ? I took my unit to the dive shop and demanded they bolt on every thing that would fit. Join my elite diving teem and get a Tshirt "Doing It Chasey"Hammerhead Eccr Advanced Diving System
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5th December 2006, 13:17	#17 (permalink)
Janos "Two Sheds" Current Rebreather/s: Classic Kiss Other Rebreather/s: Classic Kiss Join Date: Feb 2005 Location: East Surrey Posts: 600	Re: Ratio Deco - Deco On The Fly - Anyone??? Quote: (Originally Posted by mstroeck) GUE type ratio deco is not very aggressive, as far as I'm aware. Perhaps you are talking about AG's ratio deco article? The deco described there can be a bit agressive in fringe cases, but in the vast majority of cases you'd still be in water about as long as with standard VPM/RGBM deco calculation, especially since you are well advised to round absolutely everything up by a healthy margin. I don't think the above is true. Everytime I have looked at a profile in the 60m range it has come out as more aggressive than VPM-B+0. Quote: (Originally Posted by mstroeck) The whole point of DOTF, though, is that you don't need to do it exactly as the doctor prescribes. Nobody says you have to go out of the water when the calculated time is up, or that you can't bring O2 but deco out on a 50% schedule. The DIR-police also won't lynch you for doing another 10 minutes on 50/25% or 15 minutes on oxygen :-) This is true of any deco algorithmn. However the useful thing about a deco algorithmn (whether it's DOTF, VPM, Buhlman etc) is the minimum time it lets you to get out of the water. Janos __________________ You can lead a horse to water but you can't climb a ladder with a large bell in both hands - Vic Reeves www.hellfins.com/shed
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5th December 2006, 22:25	#18 (permalink)
chunter I like diving Current Rebreather/s: Sport Kiss MK 15.X Other Rebreather/s: Inspiration Classic Inspiration Vision Evolution Classic Kiss Join Date: Jul 2006 Location: Honolulu Posts: 481	Re: Ratio Deco - Deco On The Fly - Anyone??? Thanks everyone for all of the useful informaiton. I have read all of it as well as the websites and articles referred to in posts. For me...and let me say that again...FOR ME, it seems foolhardy to trust a mathmatical calculation done on the fly. There also seem to be a lot of rules dealing with limitations on each profile (ie "this only applies to decompressions shorter than 50 minutes"). For my own education, I will learn the system, however, it will only be for the worst case scenario. Even then, what happens if I don't have standardized gasses for my bailouts? I typically dive 10/50tx for my deep dives with 50% for additional bailout. How would that look on a DOTF schedule? Isn't it easier to cut tables with scenarios ranging from 5 to 90 minutes bottom time and all depths within the range of the gasses you plan to dive? I can get a huge number of deco scenarios (both OC bailout and CCR) on a single sheet of 8.5"x11" wet paper (NeverTear). I guess any ECCR diver is relying on electronics to a certain extent anyway. Most DIR and GUE divers also use computers set to "freedive mode" or bottom timers with average depth etc. Perhaps the most hard-core only use analog clocks for timers (or count in thier heads) and vertical lines to the surface with depth markers on them. I'll take my chances with two VR3s, another backup timer, and tables. If I'm not smart enough to figure out which is failing, I guess Darwin's law has prevailed. DOTF seems to be a useful tool, but I'm not going to use it in place of a computer and tables anytime soon (unless there are no other options). The human error factor seems to be greater than the likelyhood of all other electronics failing simultaneously. In that situation, I'd stay down as long as I could using whatever gasses/CO2 scrubber I had available at the time. Anyway, I really appreciate everyone's feedback and will continue to read following posts. Aloha, Charlie
(Offline)

5th December 2006, 22:49	#19 (permalink)
Mark Chase I go down for ages Current Rebreather/s: Classic Kiss Other Rebreather/s: Inspiration Classic Join Date: Jan 2005 Location: Kent Posts: 2,694	Re: Ratio Deco - Deco On The Fly - Anyone??? I used to spend many hours planning and re planning each dive. Then I ended up with a VR3. I decided i would cut bailout tables and because i knew roughly enough about deco to pad it out on my own I cut tables at 100/100GF to give me a base line out of the water. From that base line, I'd do deco bassed on available gas. At some point i got two VR3s and ditched the tables. However all those dives planned on a baseline taught me that there was a massive margin between what i was doing and 100/100GF (close to straight Buhlman) Possibly as a result of this i have become a lot more relaxed about deco. I have been known to scrap the last 10-15mins of a 90min deco hang because I felt conditions made that the safer choice. Having spent now many many hours comparing proper ratio deco with Chasey ratio deco and numbers generated on VPMBE level 2 I have decided its close enough for jazz. I feel confident that if one computer went wrong and the other totally disagreed with it that I could work out ratio deco and decide which one to follow with a fair degree of confidence. On deco hangs i have nothing better to do so i work out the ratio deco and see how it compares with what the Hammer Head tels me to do. This exercise under relaxed conditions has made me much more confident with ratio deco. However I wont be giving up the computers. I love glancing down and having all the relevant info to hand. I have better things to do on the bottom phase than worry about deco calks. ATB Mark Chase __________________ Is it supposed to make that noise ? I took my unit to the dive shop and demanded they bolt on every thing that would fit. Join my elite diving teem and get a Tshirt "Doing It Chasey"Hammerhead Eccr Advanced Diving System
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