VR3 BUH or VPM

rossh · 25th April 2008, 04:02

Hi Stuart, I happen to have your post to the DecoList from 2001. I have included it below, as it explains matters in greater detail.

**

This whole matter is 6 or 7 years old. The deco plan below has been superseded by VPM-B back in 2003.

The post says the plan used the absolute minimum of settings (no conservatism), giving a very fast plan, and this was from your own XS test program. It says you further skipped over some deco stops, and cut the final deco short by 5 minutes. Also it says you were exerting lots of energy before and after the dive. Other problems noted were numb extremities and prior DCS issues, and a scooter that was jammed on. It also says the divers suit was flooding and the dry suit was deliberately over-inflated to fight off the cold, leading to the diver needing to "hang on" to the line throughout the deco.

The report says the injury was in the elbows, and it cleared up with just surface breathing of O2.

I would offer that the real damage was done by:

1/ The EAN34 mix. This spiked the ppN2 up by 1.25 to 3ATA, and introduced issues of IBCD into the ascent. Divers today would probably use a selection of mixes that avoided these issues.

2/ The heavy lifting before and after the dive, gave cause for the elbows to become injury sites, along with the cold and effort used to hold the line throughout he deco to combat the bouyancy problems experienced.

3/ A dive plan that had no margin for errors, but many were encountered.

May I suggest, that this particular dive, and the divers procedures used here, as described in the report, are not typical or representative of the general diving population. Many of the procedures and experiences mentioned in the report, are now known to be detrimental to a good deco outcome.

Regards rossh

************

<< cross post removed >>

graham_hk · 25th April 2008, 07:08

Quote: (Originally Posted by rossh)

Hi Stuart, I happen to have your post to the DecoList from 2001. I have included it below, as it explains matters in greater detail.

**

The post says the plan used the absolute minimum of settings (no conservatism), giving a very fast plan, and this was from your own XS test program. It says you further skipped over some deco stops, and cut the final deco short by 5 minutes. Also it says you were exerting lots of energy before and after the dive. Other problems noted were numb extremities and prior DCS issues, and a scooter that was jammed on. It also says the divers suit was flooding and the dry suit was deliberately over-inflated to fight off the cold, leading to the diver needing to "hang on" to the line throughout the deco.

The report says the injury was in the elbows, and it cleared up with just surface breathing of O2.

I would offer that the real damage was done by:

1/ The EAN34 mix. This spiked the ppN2 up by 1.25 to 3ATA, and introduced issues of IBCD into the ascent. Divers today would probably use a selection of mixes that avoided these issues.

2/ The heavy lifting before and after the dive, gave cause for the elbows to become injury sites, along with the cold and effort used to hold the line throughout he deco to combat the bouyancy problems experienced.

3/ A dive plan that had no margin for errors, but many were encountered.

May I suggest, that this particular dive, and the divers procedures used here, as described in the report, are not typical or representative of the general diving population. Many of the procedures and experiences mentioned in the report, are now known to be detrimental to a good deco outcome.

Regards rossh

Ross your arguments and discussion style are somewhat puzzling and I suspect are not doing Vplanner sales any good. The more you say unfortunately the more convincing the other points of view becomes.

Please can you show me proof that IBCD caused the bend and also comment on the impact of the >20% reduction in exposure (which incidentally you forgot, maybe conveniently, to comment on when making your somewhat spurious conclusions about said dive).

Graham

**DeepBlueInnovation** · 25th April 2008, 07:59

Quote: (Originally Posted by graham_hk)

Please can you show me proof that IBCD caused the bend
Graham

I think you have mis-interpreted his last post Graham; he didn't claim that Stuart suffered an IBCD type bend, merely that he was risking it by jumping from a 12/56 mix to EANX34. I believe that this is generally accepted as a high risk switch to make, particularly in light of the provided profile, although please elucidate if you have reason to believe otherwise.

Cheers,

Ben.

rossh · 25th April 2008, 08:23

Quote: (Originally Posted by graham_hk)

Ross your arguments and discussion style are somewhat puzzling ......

Hi Graham,

I'm trying to make the point here, that many DCS problems are a result of the procedures used in a dive, and conditions of the site. The above dive example is one of those. But some here instead "blame the model" or say "the model did it too me", which I find to be an invalid argument.

No deco model will make up for errors in procedure and dive practices, conditions that warrant additional time, diver physiology, and a hundred other well known things that can ruin a deco. A great deal has been written about these matters already.

Consider that most DCS incidents occur with actual dives times well inside any models time limitations, and when cross compared to other models, are within those times too. This would suggest that the particular incident was coming, regardless of the model used on the day. That leaves the cause to procedures, mixes, and dive practice problems and the divers own physiology, both on the dive day and overall, and so on.

tecdivertraining · 25th April 2008, 08:54

[quote=graham_hk;183365]Ross your arguments and discussion style are somewhat puzzling and I suspect are not doing Vplanner sales any good. The more you say unfortunately the more convincing the other points of view becomes.

Hi Graham

I could not agree more to your above statement, I actually wrote a similar post early and decided not to post it.

I respect all the opinions in this thread and only agree with a handfull, but remember this what works works, and when training new students in deeper diving techniques its essential to build confidence in procedures, threads like this with overloaded post from the software author create lots of confusion, already this week the chap taking his class with me is unsure he wants to dive using V-planner having read all this, totaly his call, as an educated diver.

I not suggesting they should not be informed but its all a bit unprofessional in my opinion.

I have personally conducted several 100's of dives using V-planner without event Like I say what works works. But lets leave the education on such advanced topics were it should be, in a classroom with a instructor to provide all the info and options.

Just my 2 cents..

Drmike · 25th April 2008, 09:13

Quote: (Originally Posted by rossh)

many DCS problems are a result of the procedures used in a dive, and conditions of the site. The above dive example is one of those. .

Really? Its amazing how you can be so very certain of that fact.

I would have thought it was practically impossible to be sure one way or another.

lizardland · 25th April 2008, 09:18

Ross,

I'm a bit confused by your point. As I said in my original post, I was not disputing the fact that by today's standards it probably wasn't the best plan. And as I also said I was not pointing the finger at anyone but myself. The VPM list post was feedback to EB & EM. Yes, it was generated by XS which was a straight translation of the FORTRAN code into Visual Basic and it had been verified against the compiled version which Erik had sent me. I know why I got bent, that is not the issue and I've no interest in autopsying an event that must be at least 5yrs old.

I did not post my incident to say that VPM is unsafe, by my own admission things went wrong. The contention is that VPM was never rewritten in response to DCI incidents. That is completely wrong. Posting my report with your critique does not address that contention, it just strikes me as diversion. The re-write of VPM was because incidents happened which made EB & EM revisit the code and create VPM/B. There were a good number of incidents reported which made them take another look at the code. One man's "maths & physics" is someone else's "bend".

Cheers,

Stuart

Drmike · 25th April 2008, 09:25

Quote: (Originally Posted by lizardland)

The re-write of VPM was because incidents happened which made EB & EM revisit the code and create VPM/B.

so that would be the changes due to 'maths and physics reasons' then

spin-spin-spin

Mark Chase · 25th April 2008, 09:40

Quote: (Originally Posted by solocavediver)

Concerning how well tested VPM is, the GUE/wkpp guys use VPM based deco in their long dives around the 200'-300' region (60-90m). Of course they're also trying to sell you deco software so their statements should be taken with an automatic pinch of salt, but they do have a good record of not bending people too often. If you're a wkpp diver I suspect the difference between VPM and Buhlmann adds up over time to many days in the decompression habitat that you don't have to spend, so they definitely reckon it a good thing. For their kind of diving - 200-300', warm water, divers required to be fit, often several hours bottom time - I think you can regard VPM as pretty well tested. And I think it is really well established that deeper stops are a good thing (even in my limited experience, I know this to be true), so someone has to come up with some sort of a mathematical model for the process. In a few years' time, VPM will be uncontroversial I reckon - in the meanwhile, use best judgement....

Cheers,

Charles.

I don't quite get this.

GE were using Decoplanner GF deco profiles heavily modified with their own ratio deco planning. They have now Incorporated a VPMB in to the deco planner program and i have read many comments about GUE profiles being closer to Vplanner than to Buhlman but nothing on Vplaner and cut tables being used for dives. The "several hour" dives i understood were ran at GI3s/Bill Hamilton's famous saturation deco profile, which doesn't look much like VPM to me.

All the information I got from GUE divers running deep dives was based around a modification of a 30/90GF plan.

So whilst GUE may now be working with VPM Its fair to say 90% of their dives seem to use straight ratio deco and the small 10% of deep cave and deep OW dives may or may not be using VPM but I bet its modified?

Putting GUE or WKPP forward as long term testers of VPM doesn't seem to fit with the available information.

ATB

Mark

rossh · 25th April 2008, 09:51

Hi Stuart,

I appreciate what your saying there. However, I don't think your dive is a much of a proper example or test. I'm just trying to balance things up. And all this is 6 or 7 years old now.

*************

This thread has been a long stream of attacks and miss informations by a handful of regular trouble makers.

*************

Why VPM-B, and what is the math reasons?
The practical problem of the initial release was that it was range bound - both deep and shallow plans (though no-one noticed the shallow end). Hence once this became apparent, the authors carried out a review and a revision was made to VPM-B. All this happened in 2002 and VPM-B has been the standard ever since. Here are explanation notes by the Author Erik Baker.

Quote: (Originally Posted by VPM-B explanation note of Erik Baker (from 2002))

This post explains the changes to the original VPM code for implementing the Boyle's Law compensation algorithm (VPM-B).
....
The main difference between the original VPM algorithm and this new one is that during the decompression calculation, the allowable gradients for each compartment are modified (reduced) at each stop by the Boyle's Law compensation subroutine. In the original VPM, the allowable gradients remained fixed throughout each deco schedule iteration and were only modified by the Critical Volume subroutine for the next deco schedule iteration.
.....
A completely new subroutine BOYLES_LAW_COMPENSATION is in the program. This new subroutine uses many of the common variable and arrays and the subroutine RADIUS_ROOT_FINDER which are already in the program. The new subroutine solves the cubic equation to determine the expansion of a gas bubble due to reduction in pressure between each deco stop. With a Boyle expansion of a gas bubble, the gradient for bubble formation changes (gets reduced) because the Laplace condition, Deco_Gradient = 2*gamma/radius, changes (gets smaller) as the bubble gets larger.

25th April 2008, 04:02	#171 (permalink)
rossh RBW Member Current Rebreather/s: Not Bought Yet Other Rebreather/s: Not Bought Yet Join Date: Jul 2005 Location: Canada Posts: 118	Re: VR3 BUH or VPM Hi Stuart, I happen to have your post to the DecoList from 2001. I have included it below, as it explains matters in greater detail. This whole matter is 6 or 7 years old. The deco plan below has been superseded by VPM-B back in 2003. The post says the plan used the absolute minimum of settings (no conservatism), giving a very fast plan, and this was from your own XS test program. It says you further skipped over some deco stops, and cut the final deco short by 5 minutes. Also it says you were exerting lots of energy before and after the dive. Other problems noted were numb extremities and prior DCS issues, and a scooter that was jammed on. It also says the divers suit was flooding and the dry suit was deliberately over-inflated to fight off the cold, leading to the diver needing to "hang on" to the line throughout the deco. The report says the injury was in the elbows, and it cleared up with just surface breathing of O2. I would offer that the real damage was done by: 1/ The EAN34 mix. This spiked the ppN2 up by 1.25 to 3ATA, and introduced issues of IBCD into the ascent. Divers today would probably use a selection of mixes that avoided these issues. 2/ The heavy lifting before and after the dive, gave cause for the elbows to become injury sites, along with the cold and effort used to hold the line throughout he deco to combat the bouyancy problems experienced. 3/ A dive plan that had no margin for errors, but many were encountered. May I suggest, that this particular dive, and the divers procedures used here, as described in the report, are not typical or representative of the general diving population. Many of the procedures and experiences mentioned in the report, are now known to be detrimental to a good deco outcome. Regards rossh ********** << cross post removed >> Last edited by rossh : 25th April 2008 at 23:10. Reason: Added date information
(Offline)

25th April 2008, 07:08	#172 (permalink)
graham_hk Custom Title Allowed! Current Rebreather/s: RB80 / Clone Other Rebreather/s: Inspiration Classic Classic Kiss MK 15.X RB80 / Clone Join Date: Nov 2005 Location: Philippines Posts: 107	Re: VR3 BUH or VPM Quote: (Originally Posted by rossh) Hi Stuart, I happen to have your post to the DecoList from 2001. I have included it below, as it explains matters in greater detail. ** The post says the plan used the absolute minimum of settings (no conservatism), giving a very fast plan, and this was from your own XS test program. It says you further skipped over some deco stops, and cut the final deco short by 5 minutes. Also it says you were exerting lots of energy before and after the dive. Other problems noted were numb extremities and prior DCS issues, and a scooter that was jammed on. It also says the divers suit was flooding and the dry suit was deliberately over-inflated to fight off the cold, leading to the diver needing to "hang on" to the line throughout the deco. The report says the injury was in the elbows, and it cleared up with just surface breathing of O2. I would offer that the real damage was done by: 1/ The EAN34 mix. This spiked the ppN2 up by 1.25 to 3ATA, and introduced issues of IBCD into the ascent. Divers today would probably use a selection of mixes that avoided these issues. 2/ The heavy lifting before and after the dive, gave cause for the elbows to become injury sites, along with the cold and effort used to hold the line throughout he deco to combat the bouyancy problems experienced. 3/ A dive plan that had no margin for errors, but many were encountered. May I suggest, that this particular dive, and the divers procedures used here, as described in the report, are not typical or representative of the general diving population. Many of the procedures and experiences mentioned in the report, are now known to be detrimental to a good deco outcome. Regards rossh Ross your arguments and discussion style are somewhat puzzling and I suspect are not doing Vplanner sales any good. The more you say unfortunately the more convincing the other points of view becomes. Please can you show me proof that IBCD caused the bend and also comment on the impact of the >20% reduction in exposure (which incidentally you forgot, maybe conveniently, to comment on when making your somewhat spurious conclusions about said dive). Graham
(Offline)

25th April 2008, 07:59	#173 (permalink)
DeepBlueInnovation Learning to Kiss Current Rebreather/s: Not Bought Yet Other Rebreather/s: Prism Topaz Not Bought Yet Join Date: Sep 2005 Location: Perth, Western Australia Posts: 368	Re: VR3 BUH or VPM Quote: (Originally Posted by graham_hk) Please can you show me proof that IBCD caused the bend Graham I think you have mis-interpreted his last post Graham; he didn't claim that Stuart suffered an IBCD type bend, merely that he was risking it by jumping from a 12/56 mix to EANX34. I believe that this is generally accepted as a high risk switch to make, particularly in light of the provided profile, although please elucidate if you have reason to believe otherwise. Cheers, Ben.
(Offline)

25th April 2008, 08:23	#174 (permalink)
rossh RBW Member Current Rebreather/s: Not Bought Yet Other Rebreather/s: Not Bought Yet Join Date: Jul 2005 Location: Canada Posts: 118	Re: VR3 BUH or VPM Quote: (Originally Posted by graham_hk) Ross your arguments and discussion style are somewhat puzzling ...... Hi Graham, I'm trying to make the point here, that many DCS problems are a result of the procedures used in a dive, and conditions of the site. The above dive example is one of those. But some here instead "blame the model" or say "the model did it too me", which I find to be an invalid argument. No deco model will make up for errors in procedure and dive practices, conditions that warrant additional time, diver physiology, and a hundred other well known things that can ruin a deco. A great deal has been written about these matters already. Consider that most DCS incidents occur with actual dives times well inside any models time limitations, and when cross compared to other models, are within those times too. This would suggest that the particular incident was coming, regardless of the model used on the day. That leaves the cause to procedures, mixes, and dive practice problems and the divers own physiology, both on the dive day and overall, and so on. __________________ Regards, Ross Hemingway V-Planner Live for the X1 V-Planner VPM-B Nitrox Trimix CCR Deco planning for Technical Divers www.v-planner.com
(Offline)

25th April 2008, 08:54	#175 (permalink)
tecdivertraining EXPLORER Current Rebreather/s: Inspiration Classic Inspiration Vision Evolution Megalodon Ouroboros Dolphin Other Rebreather/s: Not Bought Yet Dolphin Join Date: May 2005 Location: Phuket, Thailand Posts: 532	Re: VR3 BUH or VPM [quote=graham_hk;183365]Ross your arguments and discussion style are somewhat puzzling and I suspect are not doing Vplanner sales any good. The more you say unfortunately the more convincing the other points of view becomes. Hi Graham I could not agree more to your above statement, I actually wrote a similar post early and decided not to post it. I respect all the opinions in this thread and only agree with a handfull, but remember this what works works, and when training new students in deeper diving techniques its essential to build confidence in procedures, threads like this with overloaded post from the software author create lots of confusion, already this week the chap taking his class with me is unsure he wants to dive using V-planner having read all this, totaly his call, as an educated diver. I not suggesting they should not be informed but its all a bit unprofessional in my opinion. I have personally conducted several 100's of dives using V-planner without event Like I say what works works. But lets leave the education on such advanced topics were it should be, in a classroom with a instructor to provide all the info and options. Just my 2 cents.. __________________ Mathew Partridge Technical Director Pro-Tech Dive College www.protechdivers.com www.tech-ccr.com
(Offline)

25th April 2008, 09:13	#176 (permalink)
Drmike RBW Member 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: 3,378	Re: VR3 BUH or VPM Quote: (Originally Posted by rossh) many DCS problems are a result of the procedures used in a dive, and conditions of the site. The above dive example is one of those. . Really? Its amazing how you can be so very certain of that fact. I would have thought it was practically impossible to be sure one way or another. __________________ Cave diving is a sport Wreck diving is a sport Diving in general is a sport 'Rebreather diving' is not a sport its the delusional obsession with a highly dangerous and often inappropriate piece of equipment Last edited by Drmike : 25th April 2008 at 09:16.
(Offline)

25th April 2008, 09:18	#177 (permalink)
lizardland Yak Current Rebreather/s: MK 15.X Home Build Other Rebreather/s: Classic Kiss Home Build Join Date: Mar 2005 Location: North... Posts: 1,387	Re: VR3 BUH or VPM Ross, I'm a bit confused by your point. As I said in my original post, I was not disputing the fact that by today's standards it probably wasn't the best plan. And as I also said I was not pointing the finger at anyone but myself. The VPM list post was feedback to EB & EM. Yes, it was generated by XS which was a straight translation of the FORTRAN code into Visual Basic and it had been verified against the compiled version which Erik had sent me. I know why I got bent, that is not the issue and I've no interest in autopsying an event that must be at least 5yrs old. I did not post my incident to say that VPM is unsafe, by my own admission things went wrong. The contention is that VPM was never rewritten in response to DCI incidents. That is completely wrong. Posting my report with your critique does not address that contention, it just strikes me as diversion. The re-write of VPM was because incidents happened which made EB & EM revisit the code and create VPM/B. There were a good number of incidents reported which made them take another look at the code. One man's "maths & physics" is someone else's "bend". Cheers, Stuart __________________ Can you imagine drifting along in the sea with your mouth open and a load of f***ing plankton going in? You'd like it, would you? www.westons-cider.co.uk Azerbaijani Association of Technical Divers Publicity Officer and Goat Wrangler
(Offline)

25th April 2008, 09:25	#178 (permalink)
Drmike RBW Member 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: 3,378	Re: VR3 BUH or VPM Quote: (Originally Posted by lizardland) The re-write of VPM was because incidents happened which made EB & EM revisit the code and create VPM/B. so that would be the changes due to 'maths and physics reasons' then spin-spin-spin __________________ Cave diving is a sport Wreck diving is a sport Diving in general is a sport 'Rebreather diving' is not a sport its the delusional obsession with a highly dangerous and often inappropriate piece of equipment
(Offline)

25th April 2008, 09:40	#179 (permalink)
Mark Chase RBW Member Current Rebreather/s: Classic Kiss Other Rebreather/s: Inspiration Classic Join Date: Jan 2005 Location: Kent Posts: 2,863	Re: VR3 BUH or VPM Quote: (Originally Posted by solocavediver) Concerning how well tested VPM is, the GUE/wkpp guys use VPM based deco in their long dives around the 200'-300' region (60-90m). Of course they're also trying to sell you deco software so their statements should be taken with an automatic pinch of salt, but they do have a good record of not bending people too often. If you're a wkpp diver I suspect the difference between VPM and Buhlmann adds up over time to many days in the decompression habitat that you don't have to spend, so they definitely reckon it a good thing. For their kind of diving - 200-300', warm water, divers required to be fit, often several hours bottom time - I think you can regard VPM as pretty well tested. And I think it is really well established that deeper stops are a good thing (even in my limited experience, I know this to be true), so someone has to come up with some sort of a mathematical model for the process. In a few years' time, VPM will be uncontroversial I reckon - in the meanwhile, use best judgement.... Cheers, Charles. I don't quite get this. GE were using Decoplanner GF deco profiles heavily modified with their own ratio deco planning. They have now Incorporated a VPMB in to the deco planner program and i have read many comments about GUE profiles being closer to Vplanner than to Buhlman but nothing on Vplaner and cut tables being used for dives. The "several hour" dives i understood were ran at GI3s/Bill Hamilton's famous saturation deco profile, which doesn't look much like VPM to me. All the information I got from GUE divers running deep dives was based around a modification of a 30/90GF plan. So whilst GUE may now be working with VPM Its fair to say 90% of their dives seem to use straight ratio deco and the small 10% of deep cave and deep OW dives may or may not be using VPM but I bet its modified? Putting GUE or WKPP forward as long term testers of VPM doesn't seem to fit with the available information. ATB Mark __________________ See my "Doing It Chasey" video where I'm locked into a padded room, naked, with two ball bearings and within an Hour, I manage to lose one and break the other!!! Kevin Juergensen 16/11/08 [/quote]
(Offline)

25th April 2008, 09:51	#180 (permalink)
rossh RBW Member Current Rebreather/s: Not Bought Yet Other Rebreather/s: Not Bought Yet Join Date: Jul 2005 Location: Canada Posts: 118	Re: VR3 BUH or VPM Hi Stuart, I appreciate what your saying there. However, I don't think your dive is a much of a proper example or test. I'm just trying to balance things up. And all this is 6 or 7 years old now. *********** This thread has been a long stream of attacks and miss informations by a handful of regular trouble makers. ********* Why VPM-B, and what is the math reasons? The practical problem of the initial release was that it was range bound - both deep and shallow plans (though no-one noticed the shallow end). Hence once this became apparent, the authors carried out a review and a revision was made to VPM-B. All this happened in 2002 and VPM-B has been the standard ever since. Here are explanation notes by the Author Erik Baker. Quote: (Originally Posted by VPM-B explanation note of Erik Baker (from 2002)*) This post explains the changes to the original VPM code for implementing the Boyle's Law compensation algorithm (VPM-B). .... The main difference between the original VPM algorithm and this new one is that during the decompression calculation, the allowable gradients for each compartment are modified (reduced) at each stop by the Boyle's Law compensation subroutine. In the original VPM, the allowable gradients remained fixed throughout each deco schedule iteration and were only modified by the Critical Volume subroutine for the next deco schedule iteration. ..... A completely new subroutine BOYLES_LAW_COMPENSATION is in the program. This new subroutine uses many of the common variable and arrays and the subroutine RADIUS_ROOT_FINDER which are already in the program. The new subroutine solves the cubic equation to determine the expansion of a gas bubble due to reduction in pressure between each deco stop. With a Boyle expansion of a gas bubble, the gradient for bubble formation changes (gets reduced) because the Laplace condition, Deco_Gradient = 2gamma/radius, changes (gets smaller) as the bubble gets larger. Last edited by rossh : 25th April 2008 at 11:49.
(Offline)

Thread Tools
Show Printable Version Email this Page
Display Modes
Linear Mode Switch to Hybrid Mode Switch to Threaded Mode