Onboard vs. Offboard Deco

Mark Chase · 4th November 2006, 10:27

Quote: (Originally Posted by denzel)

Offboard.
KISS.

Q's?

Denz.

PS Mark, is there any piece of equipment that doesn't break in your hands?

My dick still works OK

ATB

Mark Chase

**trob09** · 4th November 2006, 11:30

Quote: (Originally Posted by diverklondike)

My onboard is provided via my Hammerhead... One of the benifits of this is that if I were to go SCR for some reason the onboard computer is always calculating deco based on what's in the loop.

Hey Mark,

Just a quick question that I don't understand...what event would cause you to go SCR but would still leave you with functioning PO2 monitors in the loop?

Tim

decoweenie · 4th November 2006, 12:15

Quote: (Originally Posted by trob09)

...what event would cause you to go SCR but would still leave you with functioning PO2 monitors in the loop?

Compromises on the scrubber.

**trob09** · 4th November 2006, 13:13

Quote: (Originally Posted by decoweenie)

Compromises on the scrubber.

Perhaps I'm overly cautious, but if I had a compromised scrubber, I'm off the unit and onto OC bail-out. But hey, I do things that others think are inappropriate....

viscya · 4th November 2006, 14:09

Quote: (Originally Posted by trob09)

...what event would cause you to go SCR but would still leave you with functioning PO2 monitors in the loop?

Out of O2.

**trob09** · 4th November 2006, 14:17

Quote: (Originally Posted by viscya)

Out of O2.

but would you go SCR or would you just add a richer off-board gas (50% or so bail-out deco gas) and stay on CCR?

Mark Chase · 4th November 2006, 16:47

Quote: (Originally Posted by trob09)

but would you go SCR or would you just add a richer off-board gas (50% or so bail-out deco gas) and stay on CCR?

Total loss of 02 and a C02 hit. Plugging in the 50 and running off that is a possibility but the build up of nitrogen on a deep dive might be an issue. What would be the effect on the loop gas of running a 50% nitrogen mix at say 70m for 30mins with an origional dill of 14/65? I have never worked this out. It would be a great mathematical exercise for someone more clever than me.

Bearing in mind if i had the option between semi closed and OC Id go OC every time. If I am SC there has to inadequate bailout gas to get me home, so at a guess I am stuck at depth or lost at depth and my scrubber is compromised.

Its right up there with getting castrated on my wish list

Even running SCR as a drill makes me nervous Id hate to do it for real.

ATB

Mark Chase

viscya · 4th November 2006, 20:05

Quote: (Originally Posted by Mark Chase)

Total loss of 02 and a C02 hit. Plugging in the 50 and running off that is a possibility

Excuse me???? If you have a CO2 hit your OC! I don't believe there is ANYONE that advises staying on the loop SC after CO2 hit. If you over breathed, then you may consider going back on and flushing, but that's no reason for SC. If the scrubber is compromised SC is OUT.

If you are out of O2 deep, then SC on Dil. As you ascent, you can plug in richer gas if you have that option. Your still going to have to work it SC.

silent running · 4th November 2006, 21:11

Quote: (Originally Posted by Mark Chase)

In line VR3 always ran shorter than the stand alone unit. Usually between 5 -15mins. Both VR3s were capable of PP02 monitoring and i would swap their duties around occasionally jut to make sure they both worked OK and the discrepancy remained. It didn't bother me over the period of 80mins+ deco. Id usually sit out the extra time and surface as soon as it cleared where as before i had an integrated I would clear the VR3 then add on a bit just in case so i was probably doing 10mins extra on top of that again.

Clearing deco a few min quicker using it in line is very low down on my list of priorities. I am much more interested in its role as an independent back up PP02 monitor and for calculation of deco following a problem. I have never been in a hurry to get out of the water unless staying in has been bad for my health.

ATB

Mark CHase

So I guess your controller is running a bit hot. Which means that a stand alone comp would still give you a safety margin. As for getting out of the water sooner rather than later, I don't have a problem with a long hang either and always stay in the water with my VR3 buddies who have 20+minutes more deco than my HE as a safety margin and because that's what buddies do. But it sure is nice to know that I could get out of the water if I needed to.

I understand the value of an inline sensor for an SCR situation, but again this is something that can be delt with by putting in a conservative OC average mix in your comp.

Also, scrubber duration becomes very important in crisis. If your scrubber is only rated for 3 hrs in cold water, that's not much of a safety margin for the trapped at 65M scenerio you had in the previous post. I would change the lime everytime I did a long deco dive in cold water. I know it's not always practical, but the alternative is to get another unit that has a longer scrubber duration. Better scrubber duration=less likelyhood of having to go SCR...

viscya · 4th November 2006, 23:11

Quote: (Originally Posted by silent running)

... Better scrubber duration=less likelyhood of having to go SCR...

????? Where is DrMike when you need him!

4th November 2006, 10:27	#21 (permalink)
Mark Chase RBW Member Current Rebreather/s: Classic Kiss Other Rebreather/s: Inspiration Classic Join Date: Jan 2005 Location: Kent Posts: 2,858	Re: Onboard vs. Offboard Deco Quote: (Originally Posted by denzel) Offboard. KISS. Q's? Denz. PS Mark, is there any piece of equipment that doesn't break in your hands? My dick still works OK ATB Mark Chase __________________ 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)

4th November 2006, 11:30	#22 (permalink)
trob09 . Current Rebreather/s: Megalodon Other Rebreather/s: Join Date: Feb 2005 Posts: 701	Re: Onboard vs. Offboard Deco Quote: (Originally Posted by diverklondike) My onboard is provided via my Hammerhead... One of the benifits of this is that if I were to go SCR for some reason the onboard computer is always calculating deco based on what's in the loop. Hey Mark, Just a quick question that I don't understand...what event would cause you to go SCR but would still leave you with functioning PO2 monitors in the loop? Tim
(Offline)

4th November 2006, 12:15	#23 (permalink)
decoweenie Crash Test Dummy Current Rebreather/s: Other CCR Other Rebreather/s: Other CCR Join Date: Feb 2005 Location: Cairo Posts: 5,487	Re: Onboard vs. Offboard Deco Quote: (Originally Posted by trob09) ...what event would cause you to go SCR but would still leave you with functioning PO2 monitors in the loop? Compromises on the scrubber. __________________ "...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)

4th November 2006, 13:13	#24 (permalink)
trob09 . Current Rebreather/s: Megalodon Other Rebreather/s: Join Date: Feb 2005 Posts: 701	Re: Onboard vs. Offboard Deco Quote: (Originally Posted by decoweenie) Compromises on the scrubber. Perhaps I'm overly cautious, but if I had a compromised scrubber, I'm off the unit and onto OC bail-out. But hey, I do things that others think are inappropriate....
(Offline)

4th November 2006, 14:09	#25 (permalink)
viscya Wrecking Crew Current Rebreather/s: Classic Kiss Other Rebreather/s: Join Date: Oct 2005 Location: Marlton New Jersey Posts: 138	Re: Onboard vs. Offboard Deco Quote: (Originally Posted by trob09) ...what event would cause you to go SCR but would still leave you with functioning PO2 monitors in the loop? Out of O2. __________________ "There is nothing majestic or dignified about being left to silently rot and collapse under heaps of old fishing net forgotten and unappreciated in dark and unvisited waters." DrMike
(Offline)

4th November 2006, 14:17	#26 (permalink)
trob09 . Current Rebreather/s: Megalodon Other Rebreather/s: Join Date: Feb 2005 Posts: 701	Re: Onboard vs. Offboard Deco Quote: (Originally Posted by viscya) Out of O2. but would you go SCR or would you just add a richer off-board gas (50% or so bail-out deco gas) and stay on CCR?
(Offline)

4th November 2006, 16:47	#27 (permalink)
Mark Chase RBW Member Current Rebreather/s: Classic Kiss Other Rebreather/s: Inspiration Classic Join Date: Jan 2005 Location: Kent Posts: 2,858	Re: Onboard vs. Offboard Deco Quote: (Originally Posted by trob09) but would you go SCR or would you just add a richer off-board gas (50% or so bail-out deco gas) and stay on CCR? Total loss of 02 and a C02 hit. Plugging in the 50 and running off that is a possibility but the build up of nitrogen on a deep dive might be an issue. What would be the effect on the loop gas of running a 50% nitrogen mix at say 70m for 30mins with an origional dill of 14/65? I have never worked this out. It would be a great mathematical exercise for someone more clever than me. Bearing in mind if i had the option between semi closed and OC Id go OC every time. If I am SC there has to inadequate bailout gas to get me home, so at a guess I am stuck at depth or lost at depth and my scrubber is compromised. Its right up there with getting castrated on my wish list Even running SCR as a drill makes me nervous Id hate to do it for real. ATB Mark Chase __________________ 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)

4th November 2006, 20:05	#28 (permalink)
viscya Wrecking Crew Current Rebreather/s: Classic Kiss Other Rebreather/s: Join Date: Oct 2005 Location: Marlton New Jersey Posts: 138	Re: Onboard vs. Offboard Deco Quote: (Originally Posted by Mark Chase) Total loss of 02 and a C02 hit. Plugging in the 50 and running off that is a possibility Excuse me???? If you have a CO2 hit your OC! I don't believe there is ANYONE that advises staying on the loop SC after CO2 hit. If you over breathed, then you may consider going back on and flushing, but that's no reason for SC. If the scrubber is compromised SC is OUT. If you are out of O2 deep, then SC on Dil. As you ascent, you can plug in richer gas if you have that option. Your still going to have to work it SC. __________________ "There is nothing majestic or dignified about being left to silently rot and collapse under heaps of old fishing net forgotten and unappreciated in dark and unvisited waters." DrMike
(Offline)

4th November 2006, 21:11	#29 (permalink)
silent running Mature mouth breather Current Rebreather/s: Prism Topaz Other Rebreather/s: Join Date: Jun 2005 Location: U.S.A. Brooklyn, New York Posts: 1,873	Re: Onboard vs. Offboard Deco Quote: (Originally Posted by Mark Chase) In line VR3 always ran shorter than the stand alone unit. Usually between 5 -15mins. Both VR3s were capable of PP02 monitoring and i would swap their duties around occasionally jut to make sure they both worked OK and the discrepancy remained. It didn't bother me over the period of 80mins+ deco. Id usually sit out the extra time and surface as soon as it cleared where as before i had an integrated I would clear the VR3 then add on a bit just in case so i was probably doing 10mins extra on top of that again. Clearing deco a few min quicker using it in line is very low down on my list of priorities. I am much more interested in its role as an independent back up PP02 monitor and for calculation of deco following a problem. I have never been in a hurry to get out of the water unless staying in has been bad for my health. ATB Mark CHase So I guess your controller is running a bit hot. Which means that a stand alone comp would still give you a safety margin. As for getting out of the water sooner rather than later, I don't have a problem with a long hang either and always stay in the water with my VR3 buddies who have 20+minutes more deco than my HE as a safety margin and because that's what buddies do. But it sure is nice to know that I could get out of the water if I needed to. I understand the value of an inline sensor for an SCR situation, but again this is something that can be delt with by putting in a conservative OC average mix in your comp. Also, scrubber duration becomes very important in crisis. If your scrubber is only rated for 3 hrs in cold water, that's not much of a safety margin for the trapped at 65M scenerio you had in the previous post. I would change the lime everytime I did a long deco dive in cold water. I know it's not always practical, but the alternative is to get another unit that has a longer scrubber duration. Better scrubber duration=less likelyhood of having to go SCR...
(Offline)

4th November 2006, 23:11	#30 (permalink)
viscya Wrecking Crew Current Rebreather/s: Classic Kiss Other Rebreather/s: Join Date: Oct 2005 Location: Marlton New Jersey Posts: 138	Re: Onboard vs. Offboard Deco Quote: (Originally Posted by silent running) ... Better scrubber duration=less likelyhood of having to go SCR... ????? Where is DrMike when you need him! __________________ "There is nothing majestic or dignified about being left to silently rot and collapse under heaps of old fishing net forgotten and unappreciated in dark and unvisited waters." DrMike
(Offline)

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