VR3 BUH or VPM

Lancer4545 · 7th April 2008, 10:18

It would seem there are more than a few of us wanting to know the actual benefit of paying the extra dollars and using the VPM algorythm over the BUH.

I under stand the basic theory that the VPM prevents the formation of microbubbles by starting the stops deeper as compared to the BUH treating the microbubbles but is this really what it's all about?

I'd hope someoone with a better understanding of the mechanics of the 2 different algorythms would have replied and tried to explain it and any advantages of one over the other.

Or am I just missing something.......

Thanks for the replies so far.

Lance

tecdivertraining · 7th April 2008, 11:10

Quote: (Originally Posted by Lancer4545)

It would seem there are more than a few of us wanting to know the actual benefit of paying the extra dollars and using the VPM algorythm over the BUH.

I under stand the basic theory that the VPM prevents the formation of microbubbles by starting the stops deeper as compared to the BUH treating the microbubbles but is this really what it's all about?

I'd hope someoone with a better understanding of the mechanics of the 2 different algorythms would have replied and tried to explain it and any advantages of one over the other.

Or am I just missing something.......

Thanks for the replies so far.

Lance

Hi Lance

The only people who know exactly whats in the VR3 is delta P so best give them a call I doubt they will tell you though, They have modified both versions of VPM & BUH to suit .

If you would like papers on the history of VPM let me know and I will send you over the document.

Cheers

Mike · 7th April 2008, 11:23

Quote: (Originally Posted by Lancer4545)

It would seem there are more than a few of us wanting to know the actual benefit of paying the extra dollars and using the VPM algorythm over the BUH.

If you want the benefits of VPM, then Gasman is probably not the first person I'd be asking

A lot of the discussion comes back to Buhlman being a model based on a bunch of testing. VPM and RGBM both have theoretical bases and are being tested on divers now, and 'tweeked'.

Mike

Lancer4545 · 7th April 2008, 11:23

Quote: (Originally Posted by tecdivertraining)

Hi Lance

The only people who know exactly whats in the VR3 is delta P so best give them a call I doubt they will tell you though, They have modified both versions of VPM & BUH to suit .

If you would like papers on the history of VPM let me know and I will send you over the document.

Cheers

Thanks Matt,

I already have seen it somewhere before.....I think it was in your Mod 2 handout.

I did get a reply from Al Wright and he just said the BUH computer probably penalised me for the deeper stops on the VPM comp but that was all and I had pretty much already worked that out for myself.

I wasn't aware they had modified the algorythm..........and they probably aren't going to elaborate on it either...

Hope you're having fun with the Meg cross-over guys

Lance

Drmike · 8th April 2008, 13:04

Quote: (Originally Posted by Lancer4545)

Hey Guys,

I recently returned from a dive trip where I took both my VR3 computers and dived them both. They are both running Ver 2007, one has BUH and the other has been upgraded to VPM.

My thinking was that I would dive the most conservative of the 2 which I did but with interesting results.

All the dives were around 75m with the longest bottom time being 50mins. As expected the VPM computer started the stops deeper than the BUH and was constant throughout all the dives. by the time I had cleared the stop the BUH comp had cleared also and was indicating a stop at the next higher level.

This was the case right the way up to the 9m stop where the BUH computer sometimes still had a little time left to run at the stop also but when I got to the final 6m stop and cleared the VPM computer the BUH had, on this particular dive, another 60mins to run.

It would appear the BUH computer had been penalising me for the time I was stopped at the deeper stops whilst following the VPM.

I follow the thinking behind the VPM modelling as compared to the BUH but is the VPM really any better in the real world or is it just as hit and miss as BUH?

Any thoughts on the subject or experiences, bad experiences on one over the other?

Thanks,

Lance

Hi Lance I normally dive with 3 'VR3s'

an old VR3 buh a newer VR3 Buh and VR3 VPM (boris)

my observations are same as yours.

I usually clear all 3 comps but 'bend' the buh vr3s by following vpm vr3 deep stops

Drmike · 8th April 2008, 13:18

Quote: (Originally Posted by Mike)

Buhlman being a model based on a bunch of testing. VPM and RGBM both have theoretical bases and are being tested on divers now, and 'tweeked'.

Mike

well said

Buh is well tested and verified model - VPM (in comparison) simply is not. Its being constantly tweaked so as it doesnt bend divers and in doing so is becoming increasingly - perhaps unsurprisingly, more and more like Buh

rossh · 9th April 2008, 01:55

Quote: (Originally Posted by Drmike)

well said

Buh is well tested and verified model - VPM (in comparison) simply is not. Its being constantly tweaked so as it doesnt bend divers and in doing so is becoming increasingly - perhaps unsurprisingly, more and more like Buh

NO... that's wrong Mike.

VPM-B is the only revision, and this was released in Jan 2003. VPM-B has remained unchanged in this configuration since, and VPM-B is the most widely used bubble model today.

The VPM-B/E design is one of convenience. Some divers wanted a "best of both worlds" approach, that is: all the deep stops from a bubble model, combined with all the shallow stops of a Bulhmann style plan. VPM-B/E satisfies this request. Not all divers want or need to use this much deco.

The history of VPM and some of its accomplishments are listed here.

********

Added for OP. The VPM in your VR3, is not real VPM. It would appear to be some kind of approximation or emulation. Some report its output can be OK at times, but often its way off from your tablet plan.

The only computer available with real VPM-B and VPM-B/E installed, is the Liquivision X1 with V-Planner Live installed.

Drmike · 9th April 2008, 02:37

Quote: (Originally Posted by rossh)

NO... that's wrong Mike.

NO....it is right Ross

lets examine what I said :

Quote: (Originally Posted by Drmike)

Buh is well tested and verified model - VPM (in comparison) simply is not.

Are you suggesting VPMB/x has had anywhere near the scientific validation and testing that Buh has?? - No of course not so my point is correct.

Quote: (Originally Posted by Drmike)

Its being constantly tweaked so as it doesnt bend divers

and in doing so is becoming increasingly - perhaps unsurprisingly, more and more like Buh

First we had the suicidal VPM A, (that nobody in their right mind still uses as everyione that did got bent) then that was 'tweaked' to the less dangerous VPMB (that still resulted in too many bends) so that was 'tweaked to give VPMBE (which does apear to work better. possibly because model has been adjusted the closest so far to Buh

) You yourself acknowledge that VPMBE is 'best of both world' ie is basically Buh over VPM - so again Im correct in that each sucessive 'tweak' has resulted in the model becoming more and more like Buh and in the process become more and more useful

Quote:

The VPM-B/E design is one of convenience. Some divers wanted a "best of both worlds" approach, that is: all the deep stops from a bubble model, combined with all the shallow stops of a Bulhmann style plan.

Exactly, deep/freq divers found the model not to work well so it was 'tweaked' to closer to Buh.....which was my point yes?

Quote:

The history of VPM and some of its accomplishments are listed here.

Your list has always been dubious. Do you still have CV dive down as a 245m VPM dive? (edited: no I see its down as a 226m dive now

) You also have Ben down as using VPM/BE for Sra Keow III when he didnt!

Quote: (Originally Posted by Ben)

I used z-planner and open circuit for this dive with 60% safety factor.

[source:- The Deco Stop]
A list of dives done or supposedly done on VPM is NOT validation (YOU made that point VERY clear to me a while back, see decostop thread)

So I put it to you your list is neither accurate nor in any way validation.

The problem with quoting dives done as validation or a 'data point' is that unless you were there alongside each of the divers its impossible to actually verify if they strictly followed VPM plan including descent/ascent speeds mixes etc. Seeing as I know and dive with half the people on your list I can easily show you which ones 'tweaked' what they were doing so their actual deco wasnt really VPM (for eg one dive you have down the diver setpoint was higher than VPM tables assumed. On another dive you have listed diver 'winged it' as ascent rates from depth and times were all wrong (so his actual deco bore no relationship to the quoted VPM used). I know myself dives Ive done I tend to tweak here and there depending on my mood yet still I tell people I did VPMBE or VR3buh. My point is theres too much inherant variation in non control group dives to be usefull. Propper model validation is done by scientific studies with control. Where is that/when has that been done with VPM/X?
Im diving with Matt Read this weekend (latest name on your list) Ill ask him if he truly followed VPM - it wouldnt surprise me if he (like many) tweaked it. If he/people do its difficult to really draw definite conclusions re:model validation - thats my only point.

Quote:

Added for OP. The VPM in your VR3, is not real VPM. .

Neither is VPMB or VPM BE, none of them bare any resemblance to the original VPM!

Now Im not saying VPMBE isnt any good - I use it for dive planning (the most useful application) and cutting back up tables- but as far as following it for deco is concerned I preffer to follow real time deco off vr3vpm mostly because a computer will always be more accurate that tables when it comes to descent speeds/ascent speeds and times as well as dive profiles (which can have a huge effect on deco on very deep dives) and cave dives

Drmike · 9th April 2008, 04:09

Quote: (Originally Posted by Mike)

If you want the benefits of VPM, then Gasman is probably not the first person I'd be asking

For those that dont know, Gasman is a respected hyperbaric Doc

rossh · 9th April 2008, 04:12

Quote: (Originally Posted by Drmike)

...
Neither is VPMB or VPM BE, none of them bare any resemblance to the original VPM!

Wrong again Mike....

VPM-B is just one single change to a single function, and this gives an ascent that has more curve to it. All the same science and gas properties are within VPM-B as VPM. The VPM-B revision was done by Eric Baker and Erik Maiken - two of the same group that gave us the original implementation. All models evolve and are revised. VPM was revised just once in 2003 to the current VPM-B in use today.

Quote: (Originally Posted by Drmike)

Quote:

The VPM-B/E design is one of convenience. Some divers wanted a "best of both worlds" approach, that is: all the deep stops from a bubble model, combined with all the shallow stops of a Bulhmann style plan.

Exactly, deep/freq divers found the model not to work well so it was 'tweaked' to closer to Buh.....which was my point yes?

Is there anyone left who really dives a pure Bulhmann plan? And I mean real raw Bulhmann.... not the padded up versions in computers and software. Answer... NO. Those who use a Bulhman based plan will pad it with GF or Pyle stops, or both. So kindly Mike, stop trying to make us all feel guilty about VPM-B/E. Many divers are using a hybrid plan now, they do it for extra safety and comfort, and any time additional prudence is required. And that is good practice.

7th April 2008, 10:18	#11 (permalink)
Lancer4545 Closed Circuit Divers Aus Current Rebreather/s: Megalodon Other Rebreather/s: Join Date: Jun 2007 Location: Cairns QLD Australia Posts: 574	Re: VR3 BUH or VPM It would seem there are more than a few of us wanting to know the actual benefit of paying the extra dollars and using the VPM algorythm over the BUH. I under stand the basic theory that the VPM prevents the formation of microbubbles by starting the stops deeper as compared to the BUH treating the microbubbles but is this really what it's all about? I'd hope someoone with a better understanding of the mechanics of the 2 different algorythms would have replied and tried to explain it and any advantages of one over the other. Or am I just missing something....... Thanks for the replies so far. Lance __________________ You can run but you can't hide! ISC Appointed Megalodon Dealer for East Australia http://www.closedcircuitdivers.com.au info@closedcircuitdivers.com.au
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7th April 2008, 11:10	#12 (permalink)
tecdivertraining RebreatherWorld Sponsor Current Rebreather/s: Inspiration Classic Inspiration Vision Evolution Megalodon Dolphin Other Rebreather/s: Not Bought Yet Dolphin Join Date: May 2005 Location: Phuket, Thailand Posts: 401	Re: VR3 BUH or VPM Quote: (Originally Posted by Lancer4545) It would seem there are more than a few of us wanting to know the actual benefit of paying the extra dollars and using the VPM algorythm over the BUH. I under stand the basic theory that the VPM prevents the formation of microbubbles by starting the stops deeper as compared to the BUH treating the microbubbles but is this really what it's all about? I'd hope someoone with a better understanding of the mechanics of the 2 different algorythms would have replied and tried to explain it and any advantages of one over the other. Or am I just missing something....... Thanks for the replies so far. Lance Hi Lance The only people who know exactly whats in the VR3 is delta P so best give them a call I doubt they will tell you though, They have modified both versions of VPM & BUH to suit . If you would like papers on the history of VPM let me know and I will send you over the document. Cheers __________________ Mathew Partridge Technical Director Pro-Tech Dive College www.protechdivers.com www.tech-ccr.com
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7th April 2008, 11:23	#13 (permalink)
Mike Prism 'prentice Current Rebreather/s: Prism Topaz Other Rebreather/s: Inspiration Classic Evolution Join Date: Feb 2005 Location: Melbourne Posts: 322	Re: VR3 BUH or VPM Quote: (Originally Posted by Lancer4545) It would seem there are more than a few of us wanting to know the actual benefit of paying the extra dollars and using the VPM algorythm over the BUH. If you want the benefits of VPM, then Gasman is probably not the first person I'd be asking A lot of the discussion comes back to Buhlman being a model based on a bunch of testing. VPM and RGBM both have theoretical bases and are being tested on divers now, and 'tweeked'. Mike __________________ Open ....... Closed Mind ........ Loop
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7th April 2008, 11:23	#14 (permalink)
Lancer4545 Closed Circuit Divers Aus Current Rebreather/s: Megalodon Other Rebreather/s: Join Date: Jun 2007 Location: Cairns QLD Australia Posts: 574	Re: VR3 BUH or VPM Quote: (Originally Posted by tecdivertraining) Hi Lance The only people who know exactly whats in the VR3 is delta P so best give them a call I doubt they will tell you though, They have modified both versions of VPM & BUH to suit . If you would like papers on the history of VPM let me know and I will send you over the document. Cheers Thanks Matt, I already have seen it somewhere before.....I think it was in your Mod 2 handout. I did get a reply from Al Wright and he just said the BUH computer probably penalised me for the deeper stops on the VPM comp but that was all and I had pretty much already worked that out for myself. I wasn't aware they had modified the algorythm..........and they probably aren't going to elaborate on it either... Hope you're having fun with the Meg cross-over guys Lance __________________ You can run but you can't hide! ISC Appointed Megalodon Dealer for East Australia http://www.closedcircuitdivers.com.au info@closedcircuitdivers.com.au
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8th April 2008, 13:04	#15 (permalink)
Drmike Custom Title Allowed! Current Rebreather/s: MK 15.X Ouroboros Other CCR Home Build Other Rebreather/s: Inspiration Classic Other CCR Home Build Join Date: Feb 2005 Posts: 3,128	Re: VR3 BUH or VPM Quote: (Originally Posted by Lancer4545) Hey Guys, I recently returned from a dive trip where I took both my VR3 computers and dived them both. They are both running Ver 2007, one has BUH and the other has been upgraded to VPM. My thinking was that I would dive the most conservative of the 2 which I did but with interesting results. All the dives were around 75m with the longest bottom time being 50mins. As expected the VPM computer started the stops deeper than the BUH and was constant throughout all the dives. by the time I had cleared the stop the BUH comp had cleared also and was indicating a stop at the next higher level. This was the case right the way up to the 9m stop where the BUH computer sometimes still had a little time left to run at the stop also but when I got to the final 6m stop and cleared the VPM computer the BUH had, on this particular dive, another 60mins to run. It would appear the BUH computer had been penalising me for the time I was stopped at the deeper stops whilst following the VPM. I follow the thinking behind the VPM modelling as compared to the BUH but is the VPM really any better in the real world or is it just as hit and miss as BUH? Any thoughts on the subject or experiences, bad experiences on one over the other? Thanks, Lance Hi Lance I normally dive with 3 'VR3s' an old VR3 buh a newer VR3 Buh and VR3 VPM (boris) my observations are same as yours. I usually clear all 3 comps but 'bend' the buh vr3s by following vpm vr3 deep stops __________________ Get a girlfriend you sad twat - a Rebreather is an unfaithful mistress - dont blind yourself to her faults just because she goes down on you
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8th April 2008, 13:18	#16 (permalink)
Drmike Custom Title Allowed! Current Rebreather/s: MK 15.X Ouroboros Other CCR Home Build Other Rebreather/s: Inspiration Classic Other CCR Home Build Join Date: Feb 2005 Posts: 3,128	Re: VR3 BUH or VPM Quote: (Originally Posted by Mike) Buhlman being a model based on a bunch of testing. VPM and RGBM both have theoretical bases and are being tested on divers now, and 'tweeked'. Mike well said Buh is well tested and verified model - VPM (in comparison) simply is not. Its being constantly tweaked so as it doesnt bend divers and in doing so is becoming increasingly - perhaps unsurprisingly, more and more like Buh __________________ Get a girlfriend you sad twat - a Rebreather is an unfaithful mistress - dont blind yourself to her faults just because she goes down on you Last edited by Drmike : 8th April 2008 at 13:21.
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9th April 2008, 01:55	#17 (permalink)
rossh New Member Current Rebreather/s: Not Bought Yet Other Rebreather/s: Not Bought Yet Join Date: Jul 2005 Location: Canada Posts: 99	Re: VR3 BUH or VPM Quote: (Originally Posted by Drmike) well said Buh is well tested and verified model - VPM (in comparison) simply is not. Its being constantly tweaked so as it doesnt bend divers and in doing so is becoming increasingly - perhaps unsurprisingly, more and more like Buh NO... that's wrong Mike. VPM-B is the only revision, and this was released in Jan 2003. VPM-B has remained unchanged in this configuration since, and VPM-B is the most widely used bubble model today. The VPM-B/E design is one of convenience. Some divers wanted a "best of both worlds" approach, that is: all the deep stops from a bubble model, combined with all the shallow stops of a Bulhmann style plan. VPM-B/E satisfies this request. Not all divers want or need to use this much deco. The history of VPM and some of its accomplishments are listed here. ****** Added for OP. The VPM in your VR3, is not real VPM. It would appear to be some kind of approximation or emulation. Some report its output can be OK at times, but often its way off from your tablet plan. The only computer available with real VPM-B and VPM-B/E installed, is the Liquivision X1 with V-Planner Live installed. __________________ Regards, Ross Hemingway V-Planner VPM-B Nitrox Trimix CCR Deco planning for Technical Divers** www.v-planner.com Last edited by rossh : 9th April 2008 at 02:12. Reason: added exta details.
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9th April 2008, 02:37	#18 (permalink)
Drmike Custom Title Allowed! Current Rebreather/s: MK 15.X Ouroboros Other CCR Home Build Other Rebreather/s: Inspiration Classic Other CCR Home Build Join Date: Feb 2005 Posts: 3,128	Re: VR3 BUH or VPM Quote: (Originally Posted by rossh) NO... that's wrong Mike. NO....it is right Ross lets examine what I said : Quote: (Originally Posted by Drmike) Buh is well tested and verified model - VPM (in comparison) simply is not. Are you suggesting VPMB/x has had anywhere near the scientific validation and testing that Buh has?? - No of course not so my point is correct. Quote: (Originally Posted by Drmike) Its being constantly tweaked so as it doesnt bend divers and in doing so is becoming increasingly - perhaps unsurprisingly, more and more like Buh First we had the suicidal VPM A, (that nobody in their right mind still uses as everyione that did got bent) then that was 'tweaked' to the less dangerous VPMB (that still resulted in too many bends) so that was 'tweaked to give VPMBE (which does apear to work better. possibly because model has been adjusted the closest so far to Buh ) You yourself acknowledge that VPMBE is 'best of both world' ie is basically Buh over VPM - so again Im correct in that each sucessive 'tweak' has resulted in the model becoming more and more like Buh and in the process become more and more useful Quote: The VPM-B/E design is one of convenience. Some divers wanted a "best of both worlds" approach, that is: all the deep stops from a bubble model, combined with all the shallow stops of a Bulhmann style plan. Exactly, deep/freq divers found the model not to work well so it was 'tweaked' to closer to Buh.....which was my point yes? Quote: The history of VPM and some of its accomplishments are listed here. Your list has always been dubious. Do you still have CV dive down as a 245m VPM dive? (edited: no I see its down as a 226m dive now ) You also have Ben down as using VPM/BE for Sra Keow III when he didnt! Quote: (Originally Posted by Ben) I used z-planner and open circuit for this dive with 60% safety factor. [source:- The Deco Stop] A list of dives done or supposedly done on VPM is NOT validation (YOU made that point VERY clear to me a while back, see decostop thread) So I put it to you your list is neither accurate nor in any way validation. The problem with quoting dives done as validation or a 'data point' is that unless you were there alongside each of the divers its impossible to actually verify if they strictly followed VPM plan including descent/ascent speeds mixes etc. Seeing as I know and dive with half the people on your list I can easily show you which ones 'tweaked' what they were doing so their actual deco wasnt really VPM (for eg one dive you have down the diver setpoint was higher than VPM tables assumed. On another dive you have listed diver 'winged it' as ascent rates from depth and times were all wrong (so his actual deco bore no relationship to the quoted VPM used). I know myself dives Ive done I tend to tweak here and there depending on my mood yet still I tell people I did VPMBE or VR3buh. My point is theres too much inherant variation in non control group dives to be usefull. Propper model validation is done by scientific studies with control. Where is that/when has that been done with VPM/X? Im diving with Matt Read this weekend (latest name on your list) Ill ask him if he truly followed VPM - it wouldnt surprise me if he (like many) tweaked it. If he/people do its difficult to really draw definite conclusions re:model validation - thats my only point. Quote: Added for OP. The VPM in your VR3, is not real VPM. . Neither is VPMB or VPM BE, none of them bare any resemblance to the original VPM! Now Im not saying VPMBE isnt any good - I use it for dive planning (the most useful application) and cutting back up tables- but as far as following it for deco is concerned I preffer to follow real time deco off vr3vpm mostly because a computer will always be more accurate that tables when it comes to descent speeds/ascent speeds and times as well as dive profiles (which can have a huge effect on deco on very deep dives) and cave dives __________________ Get a girlfriend you sad twat - a Rebreather is an unfaithful mistress - dont blind yourself to her faults just because she goes down on you Last edited by Drmike : 9th April 2008 at 03:38.
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9th April 2008, 04:09	#19 (permalink)
Drmike Custom Title Allowed! Current Rebreather/s: MK 15.X Ouroboros Other CCR Home Build Other Rebreather/s: Inspiration Classic Other CCR Home Build Join Date: Feb 2005 Posts: 3,128	Re: VR3 BUH or VPM Quote: (Originally Posted by Mike) If you want the benefits of VPM, then Gasman is probably not the first person I'd be asking For those that dont know, Gasman is a respected hyperbaric Doc __________________ Get a girlfriend you sad twat - a Rebreather is an unfaithful mistress - dont blind yourself to her faults just because she goes down on you
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9th April 2008, 04:12	#20 (permalink)
rossh New Member Current Rebreather/s: Not Bought Yet Other Rebreather/s: Not Bought Yet Join Date: Jul 2005 Location: Canada Posts: 99	Re: VR3 BUH or VPM Quote: (Originally Posted by Drmike) ... Neither is VPMB or VPM BE, none of them bare any resemblance to the original VPM! Wrong again Mike.... VPM-B is just one single change to a single function, and this gives an ascent that has more curve to it. All the same science and gas properties are within VPM-B as VPM. The VPM-B revision was done by Eric Baker and Erik Maiken - two of the same group that gave us the original implementation. All models evolve and are revised. VPM was revised just once in 2003 to the current VPM-B in use today. Quote: (Originally Posted by Drmike) Quote: The VPM-B/E design is one of convenience. Some divers wanted a "best of both worlds" approach, that is: all the deep stops from a bubble model, combined with all the shallow stops of a Bulhmann style plan. Exactly, deep/freq divers found the model not to work well so it was 'tweaked' to closer to Buh.....which was my point yes? Is there anyone left who really dives a pure Bulhmann plan? And I mean real raw Bulhmann.... not the padded up versions in computers and software. Answer... NO. Those who use a Bulhman based plan will pad it with GF or Pyle stops, or both. So kindly Mike, stop trying to make us all feel guilty about VPM-B/E. Many divers are using a hybrid plan now, they do it for extra safety and comfort, and any time additional prudence is required. And that is good practice. __________________ Regards, Ross Hemingway V-Planner VPM-B Nitrox Trimix CCR Deco planning for Technical Divers www.v-planner.com Last edited by rossh : 9th April 2008 at 04:24.
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