What was your "experimental" deco for a given profile?

Mozi · February 5th, 2006, 04:16 PM

I did not really know how to phrase my question in the title. So I'll explain.

Whether it is because you had to or whether because you were using your self as guinea pig or whether you started to cut more and more for a profile that you got used to, or cut out one deco gas, what is the least or an "experimental" deco you did? However you need to have "gotten away" with profile and felt good after. I guess I could have been less PC and asked what was the craziest deco you ever did for a certain profile

I was experimenting in the Red Sea with Faisal: no O2 and only large 80 AL of 50%. Bottom times were 15 minutes at an average of 75-80 meters but we had hit a 100 meters for like 2-3minutes. Deco "method" was not ratio, it was following Irvine 's "loose" but clear recommendations on the wkpp. So we literally curved it out from 80% of ATAs, then at the intersection with the 50%, we focused on O2 window and curved upwards. We did the profile I believe 3 times and it worked. On one of them though, my left shoulder was sore, kind of like a bruise which started 5 minutes after surfacing and went away after 20 minutes.

I enjoy doing deco that way more than ratio by the way. Makes you think of each step...

I am quite curious about how this thread will evolve.

Mozi

decowarrior · February 5th, 2006, 05:10 PM

not strictly dir but when v planner came out we did some pretty short stops where a twenty min bottom time at 90m was longer than your longest stop, the theory made sense in much the way ratio does deep stops offload gas earlier but i hink the profiles were just too short as in 86 mins for 16 mins on the bottom, some of us werent pottable bent however i think too much strain and it would have been a pot job, and many times after these dives yuo defintley felt fizzy the new hybrid tables feel much better and are considerabley longer

Mark Chase · February 5th, 2006, 08:44 PM

Sorry totally not DIR but after 40mins bottom time avg depth 55m max 60m I developed a migraine. We scraped the planned bottom time and bailed out. I was virtually blind and spinning like a top. We followed a VR3 out on 0 safety and shaved the 6m stop we were out of the water in 50mins but if I tell you I spent the 6m hang clipped off to a lift bag you get the idea.

Neither of us were bent which amazed me.

Normally we would have done the deco in our heads using a 3m/min ascent from 2atms and forming a curve from 21 to the 6 and spending 6 getting from 6 to the surface. Our profile this dive looked more like classic Bhulman with a pyle stop or two thrown in.

I think we got away with it because the water was 17c. In the winter (6 -10c) I think we would have been in the helicopter.

ATB

Mark Chase

lizardland · February 6th, 2006, 01:44 AM

Quote: (Originally Posted by decowarrior)

not strictly dir but when v planner came out we did some pretty short stops where a twenty min bottom time at 90m was longer than your longest stop, the theory made sense in much the way ratio does deep stops offload gas earlier but i hink the profiles were just too short as in 86 mins for 16 mins on the bottom, some of us werent pottable bent however i think too much strain and it would have been a pot job, and many times after these dives yuo defintley felt fizzy the new hybrid tables feel much better and are considerabley longer

Erik Baker gave me an early copy of VPM which I used in much the same way, such as 90m dive, 15min bottom time, out the water in less than an hour. Bent twice, potted once. One thing that myself and a few other VPM bendees said was that a VPM bend seems to resolve a lot easier than a Buhlmann table bend. My first hit went completely after driving for 2hrs on O2 and a long hose, with the second I dived a week later without any problem (I had to get some bottles that I'd left out a cave, stupid I know)

I use Hamilton's M11F6 algorithm now. I'm sure VPM is much improved but being bent twice within 12 months despite 10yrs of gas diving without a problem was too much for me.

JS1scuba · February 6th, 2006, 03:08 AM

Quote: (Originally Posted by Mozi)

I am quite curious about how this thread will evolve.

Mozi

Hi there- you did not specify your bottom gas so i assume you used 14/60 with 50/50 EAN.

Here is the profile run using Hamilton-Kenyon Bubble Model through NAUTILUS. The shape is clean and runs about 87 minutes. A little oxygen would have been better, and a little 35 or 36 would have been better too. The drop in PO2 on the 14% shallower than 30 msw extends this a bit more than it needs to be. This is eveident by the very low cns % at the back end.

But even adding O2 would have only cut this back about 10 minutes or so, but it's good to know that you could.

cheers

JDS

ahar · February 6th, 2006, 11:38 AM

Quote: (Originally Posted by JS1scuba)

Hi there- you did not specify your bottom gas so i assume you used 14/60 with 50/50 EAN.

Here is the profile run using Hamilton-Kenyon Bubble Model through NAUTILUS. The shape is clean and runs about 87 minutes. A little oxygen would have been better, and a little 35 or 36 would have been better too. The drop in PO2 on the 14% shallower than 30 msw extends this a bit more than it needs to be. This is eveident by the very low cns % at the back end.

But even adding O2 would have only cut this back about 10 minutes or so, but it's good to know that you could.

cheers

JDS

Interesting that V-Planner (set at +2 conservatism) kicks out a very similar profile all they way up to 9m, then it sticks a 35 min stop at 6m. Also interesting that changing the conservatism to 0 only shortens the shallow and mid range stops a bit so overall run time is 91 mins rather than 98 mins

I take it the HKBM is the DIR 'standard' ?

jluttichau · February 6th, 2006, 12:04 PM

Quote: (Originally Posted by Mozi)

Deco "method" was not ratio, it was following Irvine 's "loose" but clear recommendations on the wkpp.

I would like to see what the differences are, could you post a RD and a WKPP profile for the same dive?

Cheers
Jonas

Mozi · February 6th, 2006, 12:25 PM

Hi Joel, bottom gas was 10/70. Total RT was close to what you have on that program, but i shape and distribution are different. Jonas, on ratio, total deco would be close to the amount we did, but we were a more aggressive, distribution logic is the same. Here is the profile we did, after the last stop at 6 meters, we did a 6-8 to surface:

80 15
60 30 sec
57 30 sec
54 30 sec
51 30 sec
48 1
45 1
42 1
39 1
36 1
33 1
30 2
27 2
24 2
21 7 50% O2
18 7
15 5
12 5
9 8
6 10

rossh · February 7th, 2006, 07:30 AM

Hello Stuart,

I was just looking at your original report on this from 2001 on the deco list. Perhaps we could revisit this? Your report says the code used was your own implementation in the XS program? You are correct that this is now superseded by current VPM-B.

In the few years since then, one thing that stands out in todays perspective of your plan - the switch from a 12/56 onto a EAN 34 mix. That's a huge spike in ppN2 inert pressure between mixes - from a 1.4 ppN2 at 39m up to 2.8 ppN2 on the next stop. And this does not start to diminish until 15 mins later at 18m. This one thing would likely have played a big part of troubles on the day.

It's certainly true that the times in your plan were fast, but gas choices are are an equally important part of this. I'm sure many here would agree that a big shot of nitrogen in your deco mix down deep is not very satisfactory.

Regards

Quote: (Originally Posted by lizardland)

Erik Baker gave me an early copy of VPM which I used in much the same way, such as 90m dive, 15min bottom time, out the water in less than an hour. Bent twice, potted once. One thing that myself and a few other VPM bendees said was that a VPM bend seems to resolve a lot easier than a Buhlmann table bend. My first hit went completely after driving for 2hrs on O2 and a long hose, with the second I dived a week later without any problem (I had to get some bottles that I'd left out a cave, stupid I know)

lizardland · February 7th, 2006, 10:34 AM

Quote: (Originally Posted by rossh)

Hello Stuart,

I was just looking at your original report on this from 2001 on the deco list. Perhaps we could revisit this? Your report says the code used was your own implementation in the XS program? You are correct that this is now superseded by current VPM-B.

In the few years since then, one thing that stands out in todays perspective of your plan - the switch from a 12/56 onto a EAN 34 mix. That's a huge spike in ppN2 inert pressure between mixes - from a 1.4 ppN2 at 39m up to 2.8 ppN2 on the next stop. And this does not start to diminish until 15 mins later at 18m. This one thing would likely have played a big part of troubles on the day.

It's certainly true that the times in your plan were fast, but gas choices are are an equally important part of this. I'm sure many here would agree that a big shot of nitrogen in your deco mix down deep is not very satisfactory.

Regards

It's interesting how things change in just a few years isn't it? At the time this would have been a fairly normal profile. The code was indeed the original VPM incorporated into XS. As I recall there had been a few similar incidents around the same time that prompted the VPM-B re-write? I have an historic bend... cool!!!

Anyway, you are totally right. Everyone's thinking on gas switches has changed considerably in such a short time. One of the reasons I went CC is deco is much kinder, the changes in inerts are much more gradual.

Using Hamilton tables isn't a criticism of VPM, the results aren't that far different but I know the model and I understand it. From working with VPM on an algorithm level I'm not going to pretend I know what is going on

February 5th, 2006, 04:16 PM	#1 (permalink)
Mozi(Offline) New Member Join Date: Jan 2006 Location: Beirut, Lebanon Posts: 80	What was your "experimental" deco for a given profile? I did not really know how to phrase my question in the title. So I'll explain. Whether it is because you had to or whether because you were using your self as guinea pig or whether you started to cut more and more for a profile that you got used to, or cut out one deco gas, what is the least or an "experimental" deco you did? However you need to have "gotten away" with profile and felt good after. I guess I could have been less PC and asked what was the craziest deco you ever did for a certain profile I was experimenting in the Red Sea with Faisal: no O2 and only large 80 AL of 50%. Bottom times were 15 minutes at an average of 75-80 meters but we had hit a 100 meters for like 2-3minutes. Deco "method" was not ratio, it was following Irvine 's "loose" but clear recommendations on the wkpp. So we literally curved it out from 80% of ATAs, then at the intersection with the 50%, we focused on O2 window and curved upwards. We did the profile I believe 3 times and it worked. On one of them though, my left shoulder was sore, kind of like a bruise which started 5 minutes after surfacing and went away after 20 minutes. I enjoy doing deco that way more than ratio by the way. Makes you think of each step... I am quite curious about how this thread will evolve. Mozi Last edited by Mozi; February 5th, 2006 at 06:03 PM.

February 5th, 2006, 08:44 PM	#3 (permalink)
Mark Chase(Offline) New Member Join Date: Nov 2005 Location: Kent England Posts: 905	Sorry totally not DIR but after 40mins bottom time avg depth 55m max 60m I developed a migraine. We scraped the planned bottom time and bailed out. I was virtually blind and spinning like a top. We followed a VR3 out on 0 safety and shaved the 6m stop we were out of the water in 50mins but if I tell you I spent the 6m hang clipped off to a lift bag you get the idea. Neither of us were bent which amazed me. Normally we would have done the deco in our heads using a 3m/min ascent from 2atms and forming a curve from 21 to the 6 and spending 6 getting from 6 to the surface. Our profile this dive looked more like classic Bhulman with a pyle stop or two thrown in. I think we got away with it because the water was 17c. In the winter (6 -10c) I think we would have been in the helicopter. ATB Mark Chase __________________ The only DIR Inspiration diver in the village

February 6th, 2006, 11:38 AM	#6 (permalink)
ahar(Offline) New Member Join Date: Nov 2005 Location: Harrow - NW London Posts: 42	Quote: (Originally Posted by JS1scuba) Hi there- you did not specify your bottom gas so i assume you used 14/60 with 50/50 EAN. Here is the profile run using Hamilton-Kenyon Bubble Model through NAUTILUS. The shape is clean and runs about 87 minutes. A little oxygen would have been better, and a little 35 or 36 would have been better too. The drop in PO2 on the 14% shallower than 30 msw extends this a bit more than it needs to be. This is eveident by the very low cns % at the back end. But even adding O2 would have only cut this back about 10 minutes or so, but it's good to know that you could. cheers JDS Interesting that V-Planner (set at +2 conservatism) kicks out a very similar profile all they way up to 9m, then it sticks a 35 min stop at 6m. Also interesting that changing the conservatism to 0 only shortens the shallow and mid range stops a bit so overall run time is 91 mins rather than 98 mins I take it the HKBM is the DIR 'standard' ? __________________ There are 10 types of people in this world - those that understand binary and those that don't. Last edited by ahar; February 6th, 2006 at 11:50 AM.

February 6th, 2006, 12:25 PM	#8 (permalink)
Mozi(Offline) New Member Join Date: Jan 2006 Location: Beirut, Lebanon Posts: 80	Profiles Hi Joel, bottom gas was 10/70. Total RT was close to what you have on that program, but i shape and distribution are different. Jonas, on ratio, total deco would be close to the amount we did, but we were a more aggressive, distribution logic is the same. Here is the profile we did, after the last stop at 6 meters, we did a 6-8 to surface: 80 15 60 30 sec 57 30 sec 54 30 sec 51 30 sec 48 1 45 1 42 1 39 1 36 1 33 1 30 2 27 2 24 2 21 7 50% O2 18 7 15 5 12 5 9 8 6 10 Last edited by Mozi; February 6th, 2006 at 12:40 PM.

February 7th, 2006, 07:30 AM	#9 (permalink)
rossh(Offline) New Member Join Date: Nov 2005 Location: . Posts: 11	Hello Stuart, I was just looking at your original report on this from 2001 on the deco list. Perhaps we could revisit this? Your report says the code used was your own implementation in the XS program? You are correct that this is now superseded by current VPM-B. In the few years since then, one thing that stands out in todays perspective of your plan - the switch from a 12/56 onto a EAN 34 mix. That's a huge spike in ppN2 inert pressure between mixes - from a 1.4 ppN2 at 39m up to 2.8 ppN2 on the next stop. And this does not start to diminish until 15 mins later at 18m. This one thing would likely have played a big part of troubles on the day. It's certainly true that the times in your plan were fast, but gas choices are are an equally important part of this. I'm sure many here would agree that a big shot of nitrogen in your deco mix down deep is not very satisfactory. Regards Quote: (Originally Posted by lizardland) Erik Baker gave me an early copy of VPM which I used in much the same way, such as 90m dive, 15min bottom time, out the water in less than an hour. Bent twice, potted once. One thing that myself and a few other VPM bendees said was that a VPM bend seems to resolve a lot easier than a Buhlmann table bend. My first hit went completely after driving for 2hrs on O2 and a long hose, with the second I dived a week later without any problem (I had to get some bottles that I'd left out a cave, stupid I know) __________________ Ross Hemingway V-Planner http://www.v-planner.com

February 5th, 2006, 05:10 PM	#2 (permalink)
decowarrior(Offline) New Member Join Date: Jan 2006 Location: stoke on trent Posts: 31	not strictly dir but when v planner came out we did some pretty short stops where a twenty min bottom time at 90m was longer than your longest stop, the theory made sense in much the way ratio does deep stops offload gas earlier but i hink the profiles were just too short as in 86 mins for 16 mins on the bottom, some of us werent pottable bent however i think too much strain and it would have been a pot job, and many times after these dives yuo defintley felt fizzy the new hybrid tables feel much better and are considerabley longer

February 6th, 2006, 01:44 AM	#4 (permalink)
lizardland(Offline) LCS Join Date: Nov 2005 Location: Evidently Chickentown Posts: 591	Quote: (Originally Posted by decowarrior) not strictly dir but when v planner came out we did some pretty short stops where a twenty min bottom time at 90m was longer than your longest stop, the theory made sense in much the way ratio does deep stops offload gas earlier but i hink the profiles were just too short as in 86 mins for 16 mins on the bottom, some of us werent pottable bent however i think too much strain and it would have been a pot job, and many times after these dives yuo defintley felt fizzy the new hybrid tables feel much better and are considerabley longer Erik Baker gave me an early copy of VPM which I used in much the same way, such as 90m dive, 15min bottom time, out the water in less than an hour. Bent twice, potted once. One thing that myself and a few other VPM bendees said was that a VPM bend seems to resolve a lot easier than a Buhlmann table bend. My first hit went completely after driving for 2hrs on O2 and a long hose, with the second I dived a week later without any problem (I had to get some bottles that I'd left out a cave, stupid I know) I use Hamilton's M11F6 algorithm now. I'm sure VPM is much improved but being bent twice within 12 months despite 10yrs of gas diving without a problem was too much for me.

February 6th, 2006, 12:04 PM	#7 (permalink)
jluttichau(Offline) Custom User Title Join Date: Nov 2005 Location: Denmark Posts: 437	Quote: (Originally Posted by Mozi) Deco "method" was not ratio, it was following Irvine 's "loose" but clear recommendations on the wkpp. I would like to see what the differences are, could you post a RD and a WKPP profile for the same dive? Cheers Jonas

February 7th, 2006, 10:34 AM	#10 (permalink)
lizardland(Offline) LCS Join Date: Nov 2005 Location: Evidently Chickentown Posts: 591	Quote: (Originally Posted by rossh) Hello Stuart, I was just looking at your original report on this from 2001 on the deco list. Perhaps we could revisit this? Your report says the code used was your own implementation in the XS program? You are correct that this is now superseded by current VPM-B. In the few years since then, one thing that stands out in todays perspective of your plan - the switch from a 12/56 onto a EAN 34 mix. That's a huge spike in ppN2 inert pressure between mixes - from a 1.4 ppN2 at 39m up to 2.8 ppN2 on the next stop. And this does not start to diminish until 15 mins later at 18m. This one thing would likely have played a big part of troubles on the day. It's certainly true that the times in your plan were fast, but gas choices are are an equally important part of this. I'm sure many here would agree that a big shot of nitrogen in your deco mix down deep is not very satisfactory. Regards It's interesting how things change in just a few years isn't it? At the time this would have been a fairly normal profile. The code was indeed the original VPM incorporated into XS. As I recall there had been a few similar incidents around the same time that prompted the VPM-B re-write? I have an historic bend... cool!!! Anyway, you are totally right. Everyone's thinking on gas switches has changed considerably in such a short time. One of the reasons I went CC is deco is much kinder, the changes in inerts are much more gradual. Using Hamilton tables isn't a criticism of VPM, the results aren't that far different but I know the model and I understand it. From working with VPM on an algorithm level I'm not going to pretend I know what is going on