VR3 BUH or VPM

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

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MrClive

hi mate,

i too have c4 vr3 ( 2007 ), with BUH,
i will be very intrested in any feed back you get from this thread.


regards,
clive

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Lancer4545

Hi Clive,

My thoughts and that's why I put up the post.

Obviously 2 different lines of thought with the 2 different algorythms but I would have never thought there would be as much as 60 mins extra deco on one to the other.

Unfortunately my dive planning software only has VPM so I cannot compare dive profiles as can be done with some other software systems.

The main thing was I didn't get bent but I sure could have done with one of those underwater MP3 players and a couple of good waterproof magazines to pass the long hours hanging there!!!

Lance

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duc996bp

This is indeed an interesting thread, I too would be very interested in other divers thoughts on this subject.

I could be wrong but I am sure DrMike uses a VR3 with VPM. Why? and not BUH.

John

kiwi_diver

I have to admit that I have next to no experience with deco. But my understanding is that at deep stops below a certain depth you are still on-gassing. Those deeper "deep stops" may be providing some other physiological benefit that improves your chances of a successful deco (gentle organ expansion and recovery perhaps?) but you may not be off-gassing until some of the shallower "deep stops".

Hopefully, you'll get a definative answer from one of the hyperbaric medicine types.

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Serge

For all it's worth, Marvin Gozum did a presentation on the latest developments in decompression modeling and hyperbaric medicine at the Beneath the Sea last weekend. He was corresponding with Dave Shaw before his unfortunate attempt at repeating his record rebreather dive to 800 ft in South Africa. Marvin asked Dave what he was using to calculate his decompression schedule; it was VPM.

Dave & Sandy

Hiya,

I would suggest talking to a specialist. Gasman on this site is a hyperbaric doc in Melbourne. PM him for some info so you can make an educated choice between the two. He has been conducting Doppler tests on divers using various deco algorithims and collating data.

We have recently moved away from VPM and to Bulhman with GF. VPM was giving us problems in certain situations.

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Dave & Sandy

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Dsix36

Can you tell us more about these "certain situations"?

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tecdivertraining

Hi Lance

I remember discussing this with you while you were here, and since my new computer arrived a week ago I have had chance to make some deeper dives with them,

Its clear the Bulhman vr3 is not the same as the 16 compartment table implementation its a modified version with a deep stop implementation to help control those fast tissues and would seem on the 60m dives I made to produce very similar profiles with similar run-times to my VPM, Vr3. You are probably on the money that its penalizing you for staying deeper - longer on the VPM computer as these stops were all a little longer and deeper and my bottom time was short.

The older Vr3 I have does not have VPM in and was a micro bubble stop algorithm that only produced mid point stops rather than ever 3m like this new one.

Cheers

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tecdivertraining

I believe thats the VPMB/E On V-planner. That was the modification for Dave's dive.

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