New CCRB Sentinel Rebreather aka Baby Boris

silent running · 19th October 2007, 06:15

Quote: (Originally Posted by jhaaja)

How could that work? How would you stop the gas in the inhale CL from flowing to the exhale CL? Pressure difference between those CLs would make the gas flow to the exhale lung. Or is there something that I don´t get?

JH

Good question, maybe I wasn't clear or I'm being mush brained, but wouldn't the check/one way/flapper valves take care of that as it does in any dual CL design?

jhaaja · 19th October 2007, 06:20

But isn´t it so that the one way flapper valves are supposed to allow flow from inhale to exhale but not the other way?

JH

silent running · 19th October 2007, 07:01

Quote: (Originally Posted by jhaaja)

How could that work? How would you stop the gas in the inhale CL from flowing to the exhale CL? Pressure difference between those CLs would make the gas flow to the exhale lung. JH

OK, now I see what you're getting at. But, if the hydrostatic head is not so great as my BM CL buddies would have me believe, maybe it would not be enough on it's own to open the flappers? Or maybe it doesn't matter if the flapper valves are open a bit at all times as long as the gas is always moving in the right direction, maybe it would be effortless, hmm.

Or if the DSV had slightly stiffer flapper valves, then maybe the cracking pressure of those valves could be made the same as a loop with CLs on the same side of the body with nice, thin flappers.

I didn't mean to make things more complicated than they were already, maybe I should have left well enough alone, duho!

jhaaja · 19th October 2007, 07:05

I was thinking the same idea of stiffer valves, but that might be too bad for the WOB. Maybe the issue can be addressed with correct placement of the lungs so that they are in nearly the same pressure.

It is always nice to think

JH

dave t · 19th October 2007, 08:18

sorry this is confusing, my answers are in the white box with the quote text. its a bit early

)

Quote: (Originally Posted by silent running)

Hello Dave, thanks for all the info. I'd like to ask you some more about it:

I'm asuming by "mechanical" you mean the hydrostatic head created by whatever position the CLs are relative to the diver's lungs, yes? And is it also true that the drive pressure needed to move the gas around the loop is lower with 2 CLs than with one due to this mechanical assist and thus increases dwell time by slowing the gas flow?

By mechanical I mean as one lung expands (exhalation) the other colapses and creates a "servo assist" to the gas flow. This can be very evident if you watch twin lungs on a breathing machine at high rmv. Yes I think it slows gas down.

I'm gessing that the reason for this is that in a single CL loop, the volume of gas outside the scrubber will be greater at any given moment than with a dual CL loop and thus be more directly exposed to the water temp longer, yes?

Yes but after having a close look at Kevins design he has increased the size of the outer cannister, not the actual pack of sorb so he will use the outer can as a second lung volume and achieve extremely good insulation of the sorb thus giving long duration at depth. see I said he was smart

I'm not sure how this is possible. My understanding about back mounted CLs placement is that it should be high and as close to the diver's body as possible, yes? This would explain why I found the Atlantis/Dolphin to have better WOB than the CK. But I have always been concious of the hydrostatic head while diving a BM CL unit in any postion other than the optimal one while I have not noticed any big difference in the hydrostatic head while diving the Prism. If my perception is accurate, is there any way to offset this difference btw OTS and BM units? I ask because I dive in places where I am sometimes tossed into odd positions and always at a time of stress and high exertion, when high RMVs make the WOB shoot up and create potential for CO2 retention. I have had some bad experiences on Drager units in high RMV situations and am thus wary of BM CL units, but happy to stand corrected as it gives me more options

.

IF the bmcl's are place properly you will get no hydrostatic imbalance in any position except maybe laying on your back. Most of the bmcl's I see today are set to low, the important thing is to get the tee/top of the lung correctly placed at your shoulder.

And one last question if I may: Has anybody designed a dual CL unit with the inhale CL on the front and exhale CL on the back? I realize this design might be awkward, but it would seem to take maximum advantage of the hydrostatic head in all but the belly up position. And if we are maintaining mimimum loop volume as we should, the profile of any given CL placement other than one which wraps under the arm-ala Pelagian-should not be any more or less with BM or OTS CL units, volume is volume, yes?

volume is volume, no not always take OTS lungs, the top half is in fact only where the gas is hydrostatic pressure flattens the bottom half while the diver is swimming in normal position. I have tried laying one lung on top of another if thats what you mean but its quite restrictive and raises WOB and reduces mechanical access for buttons, dumps and such. But I think the closest to what you mean is the IDA series setups and breathing wise they work well.

best

Dave

Thanks, -Andy

silent running · 19th October 2007, 09:48

Dave, thanks for the clarifications and walking me through it.

I think I understand the servo assist idea, maybe a bit like a bellows works. And if 2 CLs do slow down gas velocity and incresase dwell time, wouldn't 3 lungs slow it down 1/3 more than 2 CLs?

As for the widening of the Sentinel scrubber helping with insulation, which in effect is functioning like a 2nd lung in a single lung design, would you take a guess at how much the gap is between the inside scrubbber stack and the outside housing? This design sounds a bit like the Prism radial-about .5 inch between the scrubber stack and the housing, thus providing insulation for the exhaled gas which travels in-out and up through the gap. Not sure of the gas flow direction in the Sentinel. The next question is: which is the best direction from an insulation scrubber efficiency standpoint-gas flowing in through that gap, or out through the gap?

By the hose t's being on the shoulder, do you mean resting them at the highest point, or on the front of the shoulder, or somewhere else?

dave t · 19th October 2007, 10:09

Yes well maybe three lungs would be better from a dwell time point but then WOB would be much higher, I guess its a compromise!

Its only a guess as I only got a quick look but I would say an inch to an inch and a half. The best direction is debatable, if you look at the test results of the classic kiss the exhale gas goes down a centre tube thus warming the sorb from the inside out (there is no outer gap on the kiss) and this appears to work very well. What one would think works very well is the exhale gas surrounding the sorb before being drawn into the actual pack. Kevin has proved this works on the sentinal but the inspiration is of the same design all be it a smaller gap and that didnt work quite so well. At the moment I am not decided on which way is best.

the tee's should sit almost on the top of your shoulder but just a little to the back, when you are in the swimming position or the upright position the tees will be almost level with your mouth and balance the hydrostatic effect. Any backmounted lung(s) should be adjustable to suit the individuals body shape and size

Dave

Scubascooby · 19th October 2007, 12:44

I have wondered if the Kiss Classic would benefit from extended lungs that have L-pieces where the hoses connect, instead of the current arrangement of connecting the hoses and the CL's to the head separately.

This would also produce a water trap in the exhale CL and would simplify the head design.

Ben Field · 19th October 2007, 13:20

Quote: (Originally Posted by Scubascooby)

I have wondered if the Kiss Classic would benefit from extended lungs that have L-pieces where the hoses connect, instead of the current arrangement of connecting the hoses and the CL's to the head separately.

This would also produce a water trap in the exhale CL and would simplify the head design.

Thanks for reminding me Pete, since we spoke about this I picked up a spare CL in a camp shop sale with this in mind.

Was thinking of doing it for the exhale side only, a perforated T inside the bag, incoming gas/liquid priority straight in/down and a dump at the bottom (need to make sure the dump can't get caught and jammed open) Would have to block the head turret with a "plug"

Sorry this is WAY off topic for the thread

SimonK · 19th October 2007, 19:34

To jump back a few posts.

Kevin said that the single lung significantly reduced heat loss from the gas.

The actual scrubber is approximately the same size as an inspo scrubber, just a much bigger air gap around it.

I think Kevin also said that Molecular Products would be making sofnolime cartridges for the unit.

Simon

19th October 2007, 06:15	#31 (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: 1,740	Re: New CCRB Sentinel Rebreather aka Baby Boris Quote: (Originally Posted by jhaaja) How could that work? How would you stop the gas in the inhale CL from flowing to the exhale CL? Pressure difference between those CLs would make the gas flow to the exhale lung. Or is there something that I don´t get? JH Good question, maybe I wasn't clear or I'm being mush brained, but wouldn't the check/one way/flapper valves take care of that as it does in any dual CL design?
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19th October 2007, 06:20	#32 (permalink)
jhaaja Custom Title Allowed! Current Rebreather/s: Inspiration Classic Other Rebreather/s: Join Date: Mar 2005 Location: Finland Posts: 867	Re: New CCRB Sentinel Rebreather aka Baby Boris But isn´t it so that the one way flapper valves are supposed to allow flow from inhale to exhale but not the other way? JH
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19th October 2007, 07:01	#33 (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: 1,740	Re: New CCRB Sentinel Rebreather aka Baby Boris Quote: (Originally Posted by jhaaja) How could that work? How would you stop the gas in the inhale CL from flowing to the exhale CL? Pressure difference between those CLs would make the gas flow to the exhale lung. JH OK, now I see what you're getting at. But, if the hydrostatic head is not so great as my BM CL buddies would have me believe, maybe it would not be enough on it's own to open the flappers? Or maybe it doesn't matter if the flapper valves are open a bit at all times as long as the gas is always moving in the right direction, maybe it would be effortless, hmm. Or if the DSV had slightly stiffer flapper valves, then maybe the cracking pressure of those valves could be made the same as a loop with CLs on the same side of the body with nice, thin flappers. I didn't mean to make things more complicated than they were already, maybe I should have left well enough alone, duho!
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19th October 2007, 07:05	#34 (permalink)
jhaaja Custom Title Allowed! Current Rebreather/s: Inspiration Classic Other Rebreather/s: Join Date: Mar 2005 Location: Finland Posts: 867	Re: New CCRB Sentinel Rebreather aka Baby Boris I was thinking the same idea of stiffer valves, but that might be too bad for the WOB. Maybe the issue can be addressed with correct placement of the lungs so that they are in nearly the same pressure. It is always nice to think JH
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19th October 2007, 08:18	#35 (permalink)
dave t Custom Title Allowed! Current Rebreather/s: Inspiration Classic Inspiration Vision Evolution Sport Kiss Classic Kiss Dolphin Ray Azimuth Home Build Other Rebreather/s: Dolphin Ray Azimuth Home Build Join Date: May 2005 Location: UK Posts: 610	Re: New CCRB Sentinel Rebreather aka Baby Boris sorry this is confusing, my answers are in the white box with the quote text. its a bit early ) Quote: (Originally Posted by silent running) Hello Dave, thanks for all the info. I'd like to ask you some more about it: I'm asuming by "mechanical" you mean the hydrostatic head created by whatever position the CLs are relative to the diver's lungs, yes? And is it also true that the drive pressure needed to move the gas around the loop is lower with 2 CLs than with one due to this mechanical assist and thus increases dwell time by slowing the gas flow? By mechanical I mean as one lung expands (exhalation) the other colapses and creates a "servo assist" to the gas flow. This can be very evident if you watch twin lungs on a breathing machine at high rmv. Yes I think it slows gas down. I'm gessing that the reason for this is that in a single CL loop, the volume of gas outside the scrubber will be greater at any given moment than with a dual CL loop and thus be more directly exposed to the water temp longer, yes? Yes but after having a close look at Kevins design he has increased the size of the outer cannister, not the actual pack of sorb so he will use the outer can as a second lung volume and achieve extremely good insulation of the sorb thus giving long duration at depth. see I said he was smart I'm not sure how this is possible. My understanding about back mounted CLs placement is that it should be high and as close to the diver's body as possible, yes? This would explain why I found the Atlantis/Dolphin to have better WOB than the CK. But I have always been concious of the hydrostatic head while diving a BM CL unit in any postion other than the optimal one while I have not noticed any big difference in the hydrostatic head while diving the Prism. If my perception is accurate, is there any way to offset this difference btw OTS and BM units? I ask because I dive in places where I am sometimes tossed into odd positions and always at a time of stress and high exertion, when high RMVs make the WOB shoot up and create potential for CO2 retention. I have had some bad experiences on Drager units in high RMV situations and am thus wary of BM CL units, but happy to stand corrected as it gives me more options. IF the bmcl's are place properly you will get no hydrostatic imbalance in any position except maybe laying on your back. Most of the bmcl's I see today are set to low, the important thing is to get the tee/top of the lung correctly placed at your shoulder. And one last question if I may: Has anybody designed a dual CL unit with the inhale CL on the front and exhale CL on the back? I realize this design might be awkward, but it would seem to take maximum advantage of the hydrostatic head in all but the belly up position. And if we are maintaining mimimum loop volume as we should, the profile of any given CL placement other than one which wraps under the arm-ala Pelagian-should not be any more or less with BM or OTS CL units, volume is volume, yes? volume is volume, no not always take OTS lungs, the top half is in fact only where the gas is hydrostatic pressure flattens the bottom half while the diver is swimming in normal position. I have tried laying one lung on top of another if thats what you mean but its quite restrictive and raises WOB and reduces mechanical access for buttons, dumps and such. But I think the closest to what you mean is the IDA series setups and breathing wise they work well. best Dave Thanks, -Andy Last edited by dave t : 19th October 2007 at 08:30.
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19th October 2007, 09:48	#36 (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: 1,740	Re: New CCRB Sentinel Rebreather aka Baby Boris Dave, thanks for the clarifications and walking me through it. I think I understand the servo assist idea, maybe a bit like a bellows works. And if 2 CLs do slow down gas velocity and incresase dwell time, wouldn't 3 lungs slow it down 1/3 more than 2 CLs? As for the widening of the Sentinel scrubber helping with insulation, which in effect is functioning like a 2nd lung in a single lung design, would you take a guess at how much the gap is between the inside scrubbber stack and the outside housing? This design sounds a bit like the Prism radial-about .5 inch between the scrubber stack and the housing, thus providing insulation for the exhaled gas which travels in-out and up through the gap. Not sure of the gas flow direction in the Sentinel. The next question is: which is the best direction from an insulation scrubber efficiency standpoint-gas flowing in through that gap, or out through the gap? By the hose t's being on the shoulder, do you mean resting them at the highest point, or on the front of the shoulder, or somewhere else?
(Offline)

19th October 2007, 10:09	#37 (permalink)
dave t Custom Title Allowed! Current Rebreather/s: Inspiration Classic Inspiration Vision Evolution Sport Kiss Classic Kiss Dolphin Ray Azimuth Home Build Other Rebreather/s: Dolphin Ray Azimuth Home Build Join Date: May 2005 Location: UK Posts: 610	Re: New CCRB Sentinel Rebreather aka Baby Boris Yes well maybe three lungs would be better from a dwell time point but then WOB would be much higher, I guess its a compromise! Its only a guess as I only got a quick look but I would say an inch to an inch and a half. The best direction is debatable, if you look at the test results of the classic kiss the exhale gas goes down a centre tube thus warming the sorb from the inside out (there is no outer gap on the kiss) and this appears to work very well. What one would think works very well is the exhale gas surrounding the sorb before being drawn into the actual pack. Kevin has proved this works on the sentinal but the inspiration is of the same design all be it a smaller gap and that didnt work quite so well. At the moment I am not decided on which way is best. the tee's should sit almost on the top of your shoulder but just a little to the back, when you are in the swimming position or the upright position the tees will be almost level with your mouth and balance the hydrostatic effect. Any backmounted lung(s) should be adjustable to suit the individuals body shape and size Dave
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19th October 2007, 12:44	#38 (permalink)
Scubascooby Better Off Out of the EU Current Rebreather/s: Classic Kiss Other Rebreather/s: Join Date: Nov 2005 Location: Great Britain Posts: 321	Re: New CCRB Sentinel Rebreather aka Baby Boris I have wondered if the Kiss Classic would benefit from extended lungs that have L-pieces where the hoses connect, instead of the current arrangement of connecting the hoses and the CL's to the head separately. This would also produce a water trap in the exhale CL and would simplify the head design. __________________ "dove" is NOT the past tense of "dive"
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19th October 2007, 13:20	#39 (permalink)
Ben Field CK+Shearwater Current Rebreather/s: Classic Kiss Other Rebreather/s: Sport Kiss Join Date: Aug 2005 Location: London, England Posts: 1,442	Re: New CCRB Sentinel Rebreather aka Baby Boris Quote: (Originally Posted by Scubascooby) I have wondered if the Kiss Classic would benefit from extended lungs that have L-pieces where the hoses connect, instead of the current arrangement of connecting the hoses and the CL's to the head separately. This would also produce a water trap in the exhale CL and would simplify the head design. Thanks for reminding me Pete, since we spoke about this I picked up a spare CL in a camp shop sale with this in mind. Was thinking of doing it for the exhale side only, a perforated T inside the bag, incoming gas/liquid priority straight in/down and a dump at the bottom (need to make sure the dump can't get caught and jammed open) Would have to block the head turret with a "plug" Sorry this is WAY off topic for the thread __________________ www.hugsac.org.uk Beware Fridge Suck
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19th October 2007, 19:34	#40 (permalink)
SimonK Custom Title Allowed! Current Rebreather/s: Inspiration Classic Other Rebreather/s: Join Date: Oct 2005 Location: Cumbria UK Posts: 231	Re: New CCRB Sentinel Rebreather aka Baby Boris To jump back a few posts. Kevin said that the single lung significantly reduced heat loss from the gas. The actual scrubber is approximately the same size as an inspo scrubber, just a much bigger air gap around it. I think Kevin also said that Molecular Products would be making sofnolime cartridges for the unit. Simon
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