Gradient Factor

Simon Ciantar · 18th January 2006, 07:51

Decowenie,

I understand perfectly what you are saying , did nt even know i had a profile which i could edit !

----------------------------------

Thanks guys a great deal for all info I will be engrossed in some reading for some time to come and than probably come with more questions.

What im interested mostly at the moment is how I can make my decompression profiles safer whilst using Trimix as diluent in the 60 - to 80 mtrs range.

One problem im seeing is that since i use a VR3 , this will be giving me very different profile then your modified table using GF's , presumably your VR3 will be giving you a more aggressive profile than your table , so what do you do, ignore the VR3 and use the tables ... and then what would such an expensive piece of equipment be doing on my wrtist for ? !

I like to work the other way round , cut tables for max possible depth for a given dive and use my VR3 and keep the tables as backup.

Again thks to all

Simon

decoweenie · 18th January 2006, 08:13

The VR-3 profile is basically the Buhlmann algorithm with 2-min Pyle stops, but called "microbubbles stop". It means less deep and intermediate stops in exchange for longer shallow stops.

The general GF profiles should start deeper and have shorter shallow stops.

The overall runtime should be fairly similar with the VR-3 profiles a little bit more conservative (i.e. longer).

You have a few options:

Spend 195 quid and upgrade the VR-3 to include VPM mode. Based on Delta-P past history, I would tend to think they will include some build-in conservatism into the algorithm so it will not be as aggressive as PC-computed VPM tables. Therefore, it will be more in-line with the GF profiles.
Sell the VR-3 off and dive GF tables exclusively if your bottom profiles are squarish.
Sell the VR-3 off, buy the HS Explorer and start diving RBGM profiles. They will resemble more to the GF profiles.
Sell the VR-3 off, buy the Cochran EMC-20C. Supposedly, their profiles start deeper similar to GF profile, but I can't tell you that based on personal experience yet. Mine is coming, so soon...
Or as you have mentioned, use tables as primary and VR-3 as back-up.

Tom F. · 18th January 2006, 09:56

Quote: (Originally Posted by decoweenie)

Spend 195 quid and upgrade the VR-3 to include VPM mode. Based on Delta-P past history, I would tend to think they will include some build-in conservatism into the algorithm so it will not be as aggressive as PC-computed VPM tables. Therefore, it will be more in-line with the GF profiles.

Are the VR3 the only way to get an VPM-B computer?

I used to dive V-planner tables and a bottomtimer, but after I got my Vision I have to use Bühlmann GF profiles, but I would also like to have a VPM-B back-up computer.

Tom F.

decoweenie · 18th January 2006, 10:03

Quote: (Originally Posted by Tom F.)

Are the VR3 the only way to get an VPM-B computer?

As far as I know, yes.

Simon Ciantar · 19th January 2006, 07:16

Quote: (Originally Posted by 01RMB)

APD recommend in the Vision manual.

It is essential to apply Gradient factors to modify the ascent depending on gas mix used, bottom time and diving depth.
The following table represents gradient factors in common use for a variety of dives.

Attachment 847

It is clear that Bühlmann models work in the air diving range and result in a low DCS incidence. (Note: the word “low” is used as opposed to “zero”!) Between 40m and 100m there are no validated decompression tables for Trimix and the % of dives that result in DCS is unknown.

Just a thought :

Is nt it strange that APD recommend the use of GF's in their manual and then dont include it in their own software ?![ As least as I understand it the new vision computer works on Bulhman just like VR3 and proplanner or am I mistaken ?]

Simon

Tom F. · 19th January 2006, 07:55

Quote: (Originally Posted by Simon Ciantar)

Just a thought :

Is nt it strange that APD recommend the use of GF's in their manual and then dont include it in their own software ?![ As least as I understand it the new vision computer works on Bulhman just like VR3 and proplanner or am I mistaken ?]

Simon

The Trimix version of the Vision software allow you to set the high and low GF. in the Nitrox version you can choose between 5 or 6 different levels of conservatime.Tom F.

Ali · 19th January 2006, 09:39

[quote=decoweenie]Simon,

Your profile doesn't state what level of diving you do, so I hope it is understandable for what I said earlier...

You would be surprised, but I personally know one trimix instructor who has no idea about decompression. He can't explain the difference between VPM, RGBM and GF for example.

So having a card says nothing to me, but the least we could do is we shouldn't be giving deco information for someone who doesn't have the "training". Right ?

Such are the discussions on our boat at times

......but Phi , you missed the famous mixing course when all the formulas were taught wrong...someone made a complete ass of himself.

decoweenie · 19th January 2006, 09:57

Quote: (Originally Posted by Simon Ciantar)

...Is nt it strange that APD recommend the use of GF's in their manual and then dont include it in their own software ?

As Tom F explained, you could directly control the GF hi/lo values with the trimix version of Vision. On the Nitrox version, there are pre-determined sets of GF as different levels of conservatism.

Mark Chase · 19th January 2006, 16:52

Quote: (Originally Posted by decoweenie)

The VR-3 profile is basically the Buhlmann algorithm with 2-min Pyle stops, but called "microbubbles stop". It means less deep and intermediate stops in exchange for longer shallow stops.

The general GF profiles should start deeper and have shorter shallow stops.

The overall runtime should be fairly similar with the VR-3 profiles a little bit more conservative (i.e. longer).

You have a few options:

Spend 195 quid and upgrade the VR-3 to include VPM mode. Based on Delta-P past history, I would tend to think they will include some build-in conservatism into the algorithm so it will not be as aggressive as PC-computed VPM tables. Therefore, it will be more in-line with the GF profiles.
Sell the VR-3 off and dive GF tables exclusively if your bottom profiles are squarish.
Sell the VR-3 off, buy the HS Explorer and start diving RBGM profiles. They will resemble more to the GF profiles.
Sell the VR-3 off, buy the Cochran EMC-20C. Supposedly, their profiles start deeper similar to GF profile, but I can't tell you that based on personal experience yet. Mine is coming, so soon...
Or as you have mentioned, use tables as primary and VR-3 as back-up.

Or 6 Do what I do

Rough estimate of 2atms from max depth for my first stop then 3m/min ascent folowing the VR3 and adding either a pause or a stop every 3m inbetween the stops offered by the VR3 depending on how deep and how long the dive was.

Its sort of VPMB-ChasE

ATB

Mark Chase

decoweenie · 19th January 2006, 17:00

Quote: (Originally Posted by Mark Chase)

Or 6 Do what I do

Mark,

Are you recommend people to follow what you pull out from your

without any explanations ?

18th January 2006, 07:51	#11 (permalink)
Simon Ciantar New Member Current Rebreather/s: Inspiration Classic Other Rebreather/s: Join Date: May 2005 Location: Malta Posts: 38	Re: Gradient Factor Decowenie, I understand perfectly what you are saying , did nt even know i had a profile which i could edit ! ---------------------------------- Thanks guys a great deal for all info I will be engrossed in some reading for some time to come and than probably come with more questions. What im interested mostly at the moment is how I can make my decompression profiles safer whilst using Trimix as diluent in the 60 - to 80 mtrs range. One problem im seeing is that since i use a VR3 , this will be giving me very different profile then your modified table using GF's , presumably your VR3 will be giving you a more aggressive profile than your table , so what do you do, ignore the VR3 and use the tables ... and then what would such an expensive piece of equipment be doing on my wrtist for ? ! I like to work the other way round , cut tables for max possible depth for a given dive and use my VR3 and keep the tables as backup. Again thks to all Simon
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18th January 2006, 08:13	#12 (permalink)
decoweenie Crash Test Dummy Current Rebreather/s: Other CCR Other Rebreather/s: Other CCR Join Date: Feb 2005 Location: Cairo Posts: 5,510	Re: Gradient Factor The VR-3 profile is basically the Buhlmann algorithm with 2-min Pyle stops, but called "microbubbles stop". It means less deep and intermediate stops in exchange for longer shallow stops. The general GF profiles should start deeper and have shorter shallow stops. The overall runtime should be fairly similar with the VR-3 profiles a little bit more conservative (i.e. longer). You have a few options: Spend 195 quid and upgrade the VR-3 to include VPM mode. Based on Delta-P past history, I would tend to think they will include some build-in conservatism into the algorithm so it will not be as aggressive as PC-computed VPM tables. Therefore, it will be more in-line with the GF profiles. Sell the VR-3 off and dive GF tables exclusively if your bottom profiles are squarish. Sell the VR-3 off, buy the HS Explorer and start diving RBGM profiles. They will resemble more to the GF profiles. Sell the VR-3 off, buy the Cochran EMC-20C. Supposedly, their profiles start deeper similar to GF profile, but I can't tell you that based on personal experience yet. Mine is coming, so soon... Or as you have mentioned, use tables as primary and VR-3 as back-up. __________________ "...after a while you get bored offering advice to a bull that like to keep butting the fence with its head rather than walking through the open gate..." - Rebreather World PM
(Offline)

18th January 2006, 09:56	#13 (permalink)
Tom F. New Member Current Rebreather/s: Inspiration Vision Other Rebreather/s: Inspiration Classic Join Date: Sep 2005 Location: Herlev, Denmark Posts: 41	Re: Gradient Factor Quote: (Originally Posted by decoweenie) Spend 195 quid and upgrade the VR-3 to include VPM mode. Based on Delta-P past history, I would tend to think they will include some build-in conservatism into the algorithm so it will not be as aggressive as PC-computed VPM tables. Therefore, it will be more in-line with the GF profiles. Are the VR3 the only way to get an VPM-B computer? I used to dive V-planner tables and a bottomtimer, but after I got my Vision I have to use Bühlmann GF profiles, but I would also like to have a VPM-B back-up computer. Tom F.
(Offline)

18th January 2006, 10:03	#14 (permalink)
decoweenie Crash Test Dummy Current Rebreather/s: Other CCR Other Rebreather/s: Other CCR Join Date: Feb 2005 Location: Cairo Posts: 5,510	Re: Gradient Factor Quote: (Originally Posted by Tom F.) Are the VR3 the only way to get an VPM-B computer? As far as I know, yes. __________________ "...after a while you get bored offering advice to a bull that like to keep butting the fence with its head rather than walking through the open gate..." - Rebreather World PM
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19th January 2006, 07:16	#15 (permalink)
Simon Ciantar New Member Current Rebreather/s: Inspiration Classic Other Rebreather/s: Join Date: May 2005 Location: Malta Posts: 38	Re: Gradient Factor Quote: (Originally Posted by 01RMB) APD recommend in the Vision manual. It is essential to apply Gradient factors to modify the ascent depending on gas mix used, bottom time and diving depth. The following table represents gradient factors in common use for a variety of dives. Attachment 847 It is clear that Bühlmann models work in the air diving range and result in a low DCS incidence. (Note: the word “low” is used as opposed to “zero”!) Between 40m and 100m there are no validated decompression tables for Trimix and the % of dives that result in DCS is unknown. Just a thought : Is nt it strange that APD recommend the use of GF's in their manual and then dont include it in their own software ?![ As least as I understand it the new vision computer works on Bulhman just like VR3 and proplanner or am I mistaken ?] Simon
(Offline)

19th January 2006, 07:55	#16 (permalink)
Tom F. New Member Current Rebreather/s: Inspiration Vision Other Rebreather/s: Inspiration Classic Join Date: Sep 2005 Location: Herlev, Denmark Posts: 41	Re: Gradient Factor Quote: (Originally Posted by Simon Ciantar) Just a thought : Is nt it strange that APD recommend the use of GF's in their manual and then dont include it in their own software ?![ As least as I understand it the new vision computer works on Bulhman just like VR3 and proplanner or am I mistaken ?] Simon The Trimix version of the Vision software allow you to set the high and low GF. in the Nitrox version you can choose between 5 or 6 different levels of conservatime.Tom F.
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19th January 2006, 09:39	#17 (permalink)
Ali New Member Current Rebreather/s: Other Rebreather/s: Join Date: Jun 2005 Location: UAE, Dubai Posts: 3	Re: Gradient Factor [quote=decoweenie]Simon, Your profile doesn't state what level of diving you do, so I hope it is understandable for what I said earlier... You would be surprised, but I personally know one trimix instructor who has no idea about decompression. He can't explain the difference between VPM, RGBM and GF for example. So having a card says nothing to me, but the least we could do is we shouldn't be giving deco information for someone who doesn't have the "training". Right ? Such are the discussions on our boat at times ......but Phi , you missed the famous mixing course when all the formulas were taught wrong...someone made a complete ass of himself.
(Offline)

19th January 2006, 09:57	#18 (permalink)
decoweenie Crash Test Dummy Current Rebreather/s: Other CCR Other Rebreather/s: Other CCR Join Date: Feb 2005 Location: Cairo Posts: 5,510	Re: Gradient Factor Quote: (Originally Posted by Simon Ciantar) ...Is nt it strange that APD recommend the use of GF's in their manual and then dont include it in their own software ? As Tom F explained, you could directly control the GF hi/lo values with the trimix version of Vision. On the Nitrox version, there are pre-determined sets of GF as different levels of conservatism. __________________ "...after a while you get bored offering advice to a bull that like to keep butting the fence with its head rather than walking through the open gate..." - Rebreather World PM
(Offline)

19th January 2006, 16:52	#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: 2,692	Re: Gradient Factor Quote: (Originally Posted by decoweenie) The VR-3 profile is basically the Buhlmann algorithm with 2-min Pyle stops, but called "microbubbles stop". It means less deep and intermediate stops in exchange for longer shallow stops. The general GF profiles should start deeper and have shorter shallow stops. The overall runtime should be fairly similar with the VR-3 profiles a little bit more conservative (i.e. longer). You have a few options: Spend 195 quid and upgrade the VR-3 to include VPM mode. Based on Delta-P past history, I would tend to think they will include some build-in conservatism into the algorithm so it will not be as aggressive as PC-computed VPM tables. Therefore, it will be more in-line with the GF profiles. Sell the VR-3 off and dive GF tables exclusively if your bottom profiles are squarish. Sell the VR-3 off, buy the HS Explorer and start diving RBGM profiles. They will resemble more to the GF profiles. Sell the VR-3 off, buy the Cochran EMC-20C. Supposedly, their profiles start deeper similar to GF profile, but I can't tell you that based on personal experience yet. Mine is coming, so soon... Or as you have mentioned, use tables as primary and VR-3 as back-up. Or 6 Do what I do Rough estimate of 2atms from max depth for my first stop then 3m/min ascent folowing the VR3 and adding either a pause or a stop every 3m inbetween the stops offered by the VR3 depending on how deep and how long the dive was. Its sort of VPMB-ChasE 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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19th January 2006, 17:00	#20 (permalink)
decoweenie Crash Test Dummy Current Rebreather/s: Other CCR Other Rebreather/s: Other CCR Join Date: Feb 2005 Location: Cairo Posts: 5,510	Re: Gradient Factor Quote: (Originally Posted by Mark Chase) Or 6 Do what I do Mark, Are you recommend people to follow what you pull out from your without any explanations ? __________________ "...after a while you get bored offering advice to a bull that like to keep butting the fence with its head rather than walking through the open gate..." - Rebreather World PM
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