BOV-less rEvo

Mark Chase

I have never had an air bag deploy on a car but I am glad they are there.

I did over 500 hours on CCR before my first caustic cocktail. Mainly 50m+ mix dives. I am still waiting for my first C02 hit but I expect it to happen one day especially with the depths and run times occasionally do.

I just look at incidents others have suffered and try and work around the problems they encountered. This could be with protocols or it could be with equipment.

The BOV appears to solve some fairly critical problems with ease. I find it odd that some divers don't see any benefit. I envisage all units in the not too distant future coming as standard with HUDs and BOVs. I cant see it being any more difficult to engineer the WOB on a BOV than it is to engineer the WOB on a loop mouthpiece.


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
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paulraymaekers

Hi Mark,

give it a try

the fact that there is not yet a very small BOV available that breaths super both in OC and in CC tells me it is not so easy
perhaps with the new AP??
I have drawings in my computer... but not easy to achieve!

I fully agree if the above mentioned conditions are met at reasonable cost, it can become more of a standard on any rebreather

paul

__________________
www.rEvo-rebreathers.com

.... the earth is flat, Elvis is alive, and radial scrubbers give longer dwell time than axials...

Dave Sutton

Agreeing with Mark here while fully understanding Paul too.

I've have 2 'unearned' C02 hits in the last year. Both were on easy dives, both were between 100 and 130 feet, and both went from being 'everything just fine" to "I'm gonna die NOW" in less than 15 seconds. One waqs without a BOV and one was with a BOV. In the first one, I 'just barely' made it onto the second stage. If *anything* else had gone wrong I would be dead. I'm not kidding: If the second stage of the bailout bottle had not worked perfectly I would have had no options and I *could not* have held my breath for 5 more seconds. It was SCARY. In the second one it was effortless to recover. Flip the BOV (which happened to be hooked to onboard diluent), and then a no-struggle retrieval of the second stage on the bailout bottle, and a no-sweat switch to that regulator.

The contrast is black and white. It could be life and death. I will NEVER EVER dive without a BOV if one is available.

I realized after the fact why I had two "unearned" C02 hits. It both cases I was at "vegatative workload' just hanging out and not moving a muscle. My breathing pattern went very shallow and I was not passing a good tidal volume thru the scrubber. You would never suspect that LOW metabolic rates could drive this pattern... I've never had any issues at moderate to high workloads, but TWICE at near-zero workloads. Both with fresh scrubbers. Both shallow. Go figure. Had a third one in 250 feet that was also scary, but it was "earned" due to a flooded scrubber.


Dave

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RAL

Should have known you where already looking at the options. I understand you feel that rEvo really does not need a bov. Yes it is a bit more bulky but I can not see complicated to setup & use. If anything it simplifies things a good bit when things hit the fan. With the twist of a nob you are breathing a gas with a known PPO2 & no co2. The very fact that is so easy to switch promotes safety by a great deal IMHO. There is no reason to hesitate to switch & sort out gremlins, after all if there is nothing wrong just a simple twist of the nob & off you go. The longer one ignores that nagging little voice that is telling you something is out of square it brings you closer to the edge of the slippery slope that turns a uhm into a emergency situation.
I do not find the wob CC or OC bad on my Jetsam with a SP G-500, when it had the dreaded pargon it was another story. I plumb my BOV to one of the offboard bottles, it makes little sense to me to hook it up to a tiny dil bottle that can be drained in a flash if breathing hard.
I have not dove a rEvo, haven't seen one for that matter. Maybe when they are more common here I will get a chance to dive one, looks to be a topnotch rig....if it only had a BOV


RAL

Mark Chase

[quote]
Again i fail to understand the issues. Looking at the mouthpiece on the inspo / rEvo / Meg etc they appear to be straight tubes with mushroom valves on the end. So how hard is it to put a ball in the tube that once rotated redirects the flow to a regulator. (Kiss V4Tec Golum). In loop mode it would still be a continuous tube so I see zero problem with designing that.

The AP mouthpiece is significantly bigger bore than the Dragger type or the Meg type.

Does this mean its the correct size for CE and the others are not?

If this is the case i can see the problem because a barrel the size of the AP one will make the BOV pretty big.

As you rightly say the AP BOV looks excellent and its light weight too. This demonstrates it can be done. The V4Tec and Golum offerings are an engineers answer to the problem. Big, solid, hewn out of granite type lumps, that work great but by God they are heavy.

AP will no doubt be slagged for the cheep plastic design on their BOV but if it works??? then It will be on my shopping list.

As for breathing resistance on the OC unit? OK the Paragon was rubbish but all the other BOV second stages i have used were fine. V4Tec, Golum, Dive mattic?? All of them perfectly good enough at any depth to use till my deep bailout was empty.


BOVs (apart from the KISS unit which wasn't a glowing example of the state of the art) are very much in their infancy. As with all small batch designs the only way to get it done is machining individually. This makes it expensive and heavy. Moldings will always be cheaper and lighter but only in bulk.

Its not a design limitation, its a front end cost issue. As a business man I fully appreciate the problems but it seems to me that at present CCR designers are focusing their skills on the CCR scrubber hand sets etc and the bailout options are very low on the priority list


My 2p is do what Keven did and just use someone else's design. If that was a Golum or a V4tec id be very happy. If AP or Pelegan offer a light weight compact that performs as well.. then id be ecstatic.

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
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