Trimix Versus HeliOx and Deco time

Lancer4545 · 2nd May 2008, 10:12

Quote: (Originally Posted by Beanie)

same as you would nitrox, there's only two gases so measure on of them (Oxygen)

Doesn't that mean you have to ANALYZE it!!!!

Lance

Lancer4545 · 2nd May 2008, 10:17

Quote: (Originally Posted by solocavediver)

Let's note that Heliox takes longer on VPM, so it clearly isn't just Dr. Buhlmann who reckons longer deco on 10/90.

The mathematical reason (for VPM) is that VPM works by (as far as possible) holding the supersaturation pressure constant in your tissues (NB it's NOT exactly possible to do this for all compartments at once, but VPM gets as close as it can to this). Helium comes out early, Nitrogen comes out late; so you can spread the decompression process more evenly throughout your ascent by using a mixture of N2 and He as diluent, and that results in shorter deco.

Cheers,

Charles.

Charles,

Isn't that the point I am making......

So how are these guys diving HeliOx and slashing their deco times compared to Trimix??

Is it calculated or is it tempting fate........

Lance

rossh · 2nd May 2008, 10:39

Hi Lance,

Just checking your plan there. Try that Heliox dive again with a set point of say 1.3 (vs the 1.0 shown) - it changes the run time by 100 mins. That may explain your friends faster plans.

Regards

Lancer4545 · 2nd May 2008, 10:47

Quote: (Originally Posted by rossh)

Hi Lance,

Just checking your plan there. Try that Heliox dive again with a set point of say 1.3 (vs the 1.0 shown) - it changes the run time by 100 mins. That may explain your friends faster plans.

Regards

Hi Ross,

I did and this is what I came up with.......Not a lot of difference in the run time with the more conservative set points but the CNS and OTUs are a bit on the scarey side for me....... and still 42 mins longer than the same dive on 16/45

Lance

***Beanie*** · 2nd May 2008, 10:50

Quote: (Originally Posted by Lancer4545)

Doesn't that mean you have to ANALYZE it!!!!

Lance

yeah point, not quite sure what Nigel meant then.
could be that anyold heliox will do as dil cause the mix you breathe will always be th same on CCR, of course no use to bail onto or flush with and not particularly good practice.

Brad_Horn · 2nd May 2008, 11:32

Lance,

It isn't an answer to your issue, however you may find some of the following interesting reading, inparticular with the use of Heliox as a Dil.
http://cradpdf.drdc.gc.ca/PDFS/zbb67/p509694.pdf HeO2 CUMA Repetative Dive Table Trials

Regards
Brad

Lancer4545 · 2nd May 2008, 12:21

I have been advised to remove the plans from the posts.........so they're now gone

Ross, I ran the plans with the last deco stop at 3m instead of 6m as in my plans and they then aligned with yours.......Not that it really made any difference...only a couple of minutes which is neither here nor there.

In the real world who does 2 hours of deco at 3m???? Ever tried it!!!

Still no plausable explaination for the reduced run times yet......Anyone??

Regards,

Lance

**nigelh** · 2nd May 2008, 12:27

Quote: (Originally Posted by Lancer4545)

Doesn't that mean you have to ANALYZE it!!!

No that was just me being stupid.
It's not needing a full bloded helium analyser that I meant.
Brain not in gear.

I never was very good at Fridays...

Quote: (Originally Posted by Lancer4545)

Isn't that the point I am making......
So how are these guys diving HeliOx and slashing their deco times compared to Trimix??
Is it calculated or is it tempting fate.......

I'd go for tempting fate but all deco is tempting fate. I tend to stick with ol' Professor Bühlmann but only because his stuff still seems to be OK after a good many years. I'm always suspicious at things that promise to get me out of the water faster. I know that if I don't pad the basic Bühlmann profile I feel like rubbish and, in my ignorance, I put this down as sub-clinical bent. Whether the deep stops and extra time I do contribute anything other than leaving me feeling better after a dive I don't know. I might just be kidding myself.

solocavediver · 3rd May 2008, 17:44

We wonders, yes we wonders. I have known cavedivers who would accelerate their deco by using questionable PPO2 (>1.6) to keep the oxygen window wide. That would do the trick I suspect, especially on VPM, though it's more dangerous on rebreathers because O2 and CO2 combine to damage you. Or, VPM deco with 0 conservatism can be scarily fast on ascent. Or, if they actually have dive computers which know their exact profile, and are running VPM or similar, a small change in the profile can make a big difference to the predictions. Or maybe they are just cheating; or maybe they are intelligently cheating because they have done this sort of dive before and know that they can get away with VPM conservatism of -3 or whatever.....

I wonder.

Quote: (Originally Posted by Lancer4545)

Charles,

Isn't that the point I am making......

So how are these guys diving HeliOx and slashing their deco times compared to Trimix??

Is it calculated or is it tempting fate........

Lance

Mark Chase · 3rd May 2008, 18:31

Quote: (Originally Posted by Lancer4545)

Doesn't that mean you have to ANALYZE it!!!!

Lance

Not realy

X amount of 02 then just add helium and you can be 100% cirtain what you have in the tin without analising it.

Mind you i still would

ATB

Mark

2nd May 2008, 10:12	#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: Trimix Versus HeliOx and Deco time Quote: (Originally Posted by Beanie) same as you would nitrox, there's only two gases so measure on of them (Oxygen) Doesn't that mean you have to ANALYZE it!!!! 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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2nd May 2008, 10:17	#12 (permalink)
Lancer4545 Closed Circuit Divers Aus Current Rebreather/s: Megalodon Other Rebreather/s: Join Date: Jun 2007 Location: Cairns QLD Australia Posts: 574	Re: Trimix Versus HeliOx and Deco time Quote: (Originally Posted by solocavediver) Let's note that Heliox takes longer on VPM, so it clearly isn't just Dr. Buhlmann who reckons longer deco on 10/90. The mathematical reason (for VPM) is that VPM works by (as far as possible) holding the supersaturation pressure constant in your tissues (NB it's NOT exactly possible to do this for all compartments at once, but VPM gets as close as it can to this). Helium comes out early, Nitrogen comes out late; so you can spread the decompression process more evenly throughout your ascent by using a mixture of N2 and He as diluent, and that results in shorter deco. Cheers, Charles. Charles, Isn't that the point I am making...... So how are these guys diving HeliOx and slashing their deco times compared to Trimix?? Is it calculated or is it tempting fate........ 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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2nd May 2008, 10:39	#13 (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: Trimix Versus HeliOx and Deco time Hi Lance, Just checking your plan there. Try that Heliox dive again with a set point of say 1.3 (vs the 1.0 shown) - it changes the run time by 100 mins. That may explain your friends faster plans. Regards __________________ Regards, Ross Hemingway V-Planner VPM-B Nitrox Trimix CCR Deco planning for Technical Divers www.v-planner.com
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2nd May 2008, 10:47	#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: Trimix Versus HeliOx and Deco time Quote: (Originally Posted by rossh) Hi Lance, Just checking your plan there. Try that Heliox dive again with a set point of say 1.3 (vs the 1.0 shown) - it changes the run time by 100 mins. That may explain your friends faster plans. Regards Hi Ross, I did and this is what I came up with.......Not a lot of difference in the run time with the more conservative set points but the CNS and OTUs are a bit on the scarey side for me....... and still 42 mins longer than the same dive on 16/45 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 Last edited by Lancer4545 : 2nd May 2008 at 12:14.
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2nd May 2008, 10:50	#15 (permalink)
*Beanie* Politeness officer Current Rebreather/s: Inspiration Classic Other Rebreather/s: Inspiration Vision Join Date: Jan 2005 Location: In da house! yeah baby! Posts: 3,163	Re: Trimix Versus HeliOx and Deco time Quote: (Originally Posted by Lancer4545) Doesn't that mean you have to ANALYZE it!!!! Lance yeah point, not quite sure what Nigel meant then. could be that anyold heliox will do as dil cause the mix you breathe will always be th same on CCR, of course no use to bail onto or flush with and not particularly good practice. __________________ Beanie Gallery Admin & Library Assistant. www.outlawdivers.org.uk www.beandiving.co.uk www.beanengineering.co.uk www.divelife.co.uk
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2nd May 2008, 11:32	#16 (permalink)
Brad_Horn Checklist, tick! Current Rebreather/s: Home Build Other Rebreather/s: Not Bought Yet Inspiration Classic MK 15.X Home Build Join Date: Mar 2005 Location: Australia Posts: 57	Re: Trimix Versus HeliOx and Deco time Lance, It isn't an answer to your issue, however you may find some of the following interesting reading, inparticular with the use of Heliox as a Dil. http://cradpdf.drdc.gc.ca/PDFS/zbb67/p509694.pdf HeO2 CUMA Repetative Dive Table Trials Regards Brad
(Online)

2nd May 2008, 12:21	#17 (permalink)
Lancer4545 Closed Circuit Divers Aus Current Rebreather/s: Megalodon Other Rebreather/s: Join Date: Jun 2007 Location: Cairns QLD Australia Posts: 574	Re: Trimix Versus HeliOx and Deco time I have been advised to remove the plans from the posts.........so they're now gone Ross, I ran the plans with the last deco stop at 3m instead of 6m as in my plans and they then aligned with yours.......Not that it really made any difference...only a couple of minutes which is neither here nor there. In the real world who does 2 hours of deco at 3m???? Ever tried it!!! Still no plausable explaination for the reduced run times yet......Anyone?? Regards, 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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2nd May 2008, 12:27	#18 (permalink)
nigelh New Member Current Rebreather/s: Inspiration Vision Other CCR Other Rebreather/s: Inspiration Classic Other CCR Join Date: Mar 2005 Location: Brighton, Sussex, UK Posts: 792	Re: Trimix Versus HeliOx and Deco time Quote: (Originally Posted by Lancer4545) Doesn't that mean you have to ANALYZE it!!! No that was just me being stupid. It's not needing a full bloded helium analyser that I meant. Brain not in gear. I never was very good at Fridays... Quote: (Originally Posted by Lancer4545) Isn't that the point I am making...... So how are these guys diving HeliOx and slashing their deco times compared to Trimix?? Is it calculated or is it tempting fate....... I'd go for tempting fate but all deco is tempting fate. I tend to stick with ol' Professor Bühlmann but only because his stuff still seems to be OK after a good many years. I'm always suspicious at things that promise to get me out of the water faster. I know that if I don't pad the basic Bühlmann profile I feel like rubbish and, in my ignorance, I put this down as sub-clinical bent. Whether the deep stops and extra time I do contribute anything other than leaving me feeling better after a dive I don't know. I might just be kidding myself. __________________ nigelh Last edited by nigelh : 2nd May 2008 at 12:31.
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3rd May 2008, 17:44	#19 (permalink)
solocavediver New Member Current Rebreather/s: Other CCR Home Build Other Rebreather/s: Other CCR Home Build Join Date: Apr 2006 Location: Leeds UK Posts: 98	Re: Trimix Versus HeliOx and Deco time We wonders, yes we wonders. I have known cavedivers who would accelerate their deco by using questionable PPO2 (>1.6) to keep the oxygen window wide. That would do the trick I suspect, especially on VPM, though it's more dangerous on rebreathers because O2 and CO2 combine to damage you. Or, VPM deco with 0 conservatism can be scarily fast on ascent. Or, if they actually have dive computers which know their exact profile, and are running VPM or similar, a small change in the profile can make a big difference to the predictions. Or maybe they are just cheating; or maybe they are intelligently cheating because they have done this sort of dive before and know that they can get away with VPM conservatism of -3 or whatever..... I wonder. Quote: (Originally Posted by Lancer4545) Charles, Isn't that the point I am making...... So how are these guys diving HeliOx and slashing their deco times compared to Trimix?? Is it calculated or is it tempting fate........ Lance
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3rd May 2008, 18:31	#20 (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: 2,470	Re: Trimix Versus HeliOx and Deco time Quote: (Originally Posted by Lancer4545) Doesn't that mean you have to ANALYZE it!!!! Lance Not realy X amount of 02 then just add helium and you can be 100% cirtain what you have in the tin without analising it. Mind you i still would ATB Mark __________________ 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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