Mailing List Archive Mailing List Archive
Dave, USN Dive manual quotes about 75% O2 for the standard purge (breathing down 2 bagfuls, exhaling through the nose), so I'd imagine you might get that 90% you mentioned if you wanted to do the three of four purges. Of course, nitrogen is racing out of your system the whole time, so you'd have to re-purge a few times during deco. And the electronics you add (the analyzer) just increased the complexity, and decreased the reliability. While I know next to zilch about mixed-gas rebreathers, one common complain I hear is that the electronic monitoring system, that controls the addition of O2 to the loop, is the catastrophic failure point. As for the Russian rebreathers, I've never dove one, but talked to a few (spetsnaz) who have - the one guy who was the most garrulous told me it's nickname was the widow-maker, or something like that. Whether that was the IDA-59 you're talking about or not, I don't know - I'd have to see a picture. I'd still be interested in one for shallow stuff, I'd just be hesitant to use it with mixed gas. As for the advantages of a Draeger for deco, which you described below, I agree, but my one reservation is that, even though it is a good system, it is still more likely to fail than OC. Especially if you start adding in electronics to measure the O2. Of course, since my deco diving is done in caves, I'm not too concerned about the size of my O2 bottle. Rich L ----- Original Message ----- From: Dave Sutton <pilots@na*.ne*> To: Rich Lesperance <richl@uf*.ed*>; Anthony Appleyard <mclssaa2@fs*.mt*.um*.ac*.uk*>; <techdiver@aquanaut.com> Sent: Saturday, October 23, 1999 2:58 PM Subject: Re: 02 rebreathers for deco > > > >If I could hazard a guess, why the Draeger Lar V is not used for deco, it > is > >that the fraction of O2 cannot be adequately controlled. > > > Well, that's not actually true. It's -almost- 100% as issued, > with a proper bag/lung purge of 4-5 cycles. A reduced > purge cycle results in more nitrogen, obviously. > > > > >With a proper purge, a Lar V provides something like between 40 & 70 % O2, > >but there is no way to measure what you are getting, so your deco would be > a > >guess. > > > That is true in an unmodified rig. In a modified rig you install a oxy > sensor > and the bare enough electronics to monitor the PP02. Add a trimix diluent > bottle > as well and why carry OC bottles at all??? ;-) > > > >I definitely agree about the utter reliability, though. I'd love to have > >one, myself, for shallower dives. > > > It's cool, for sure. There are a few 02 rigs available from Russia > of all places, one (the IDA-59) looks like a horsecollar BC with > the scrubber and bottles on your chest. Takes up little space > and fits with a backplate no sweat. I'm going to experiment with > using one as a bailout rig for my Mark 15 rebreather. The IDA-59 > has both nitrox/trimix bottle and pure 02 bottle so it can be used for > immediate bailout from the bottom as well as for pure 02 deco. > Cheap too. I'm getting a pipeline established and hope to have a > few on hand for sale semi-soon. I want to experiment with mine > before suggesting their use. But he rig as-is makes a cool pure > 02 rig for shallow stuff like photography etc. Figure cost to be less > than a grand all set up. There are some 'coming attractions' too > but I don't want to spill the beans. > > > >I'll stick with 100% O2 from an open-circuit system for deco, though. > > > Well, my Lar weighs maybe 15 pounds (need to weigh it) and > is chest mounted so it does not interfere. And with 4-5 hours > of 02 available it seems like carrying OC oxygen is a waste of > drag. Hanging bottles is OK but ya better find the anchor line, eh? > > > Best, > > > Dave Sutton > > -- Send mail for the `techdiver' mailing list to `techdiver@aquanaut.com'. Send subscribe/unsubscribe requests to `techdiver-request@aquanaut.com'.
Navigate by Author:
[Previous]
[Next]
[Author Search Index]
Navigate by Subject:
[Previous]
[Next]
[Subject Search Index]
[Send Reply] [Send Message with New Topic]
[Search Selection] [Mailing List Home] [Home]