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>Return-Path: <owner-techdiver@opal.com> >Errors-To: owner-techdiver@opal.com >Errors-To: owner-techdiver@opal.com >Precedence: bulk >Errors-To: owner-techdiver@opal.com >Date: 26 Jan 1995 23:40:51 U >From: "Roger Carlson" <Roger_Carlson@at*.sp*.tr*.co*> >Subject: 2/2 Offgassing from a tek.d >To: "aquaCorps" <aquacorp@sh*.ne*>, > "Michael Menduno" <73204.542@co*.co*>, > "List TechDiver" <techdiver@opal.com> > >part 2 of 2 > > On Monday, the final day of the show, I spent most of the day on the >exhibition floor, studying the four rebreathers present, but after Nuytten's >talks, I didn't want to miss the tek.Banquet luncheon, at which Graham Hawkes >would speak on his submersibles: the Wasp, Deep Rover, and his new concept >submersible, Deep Flight. > Hawkes was another wonderful speaker. He warmed us up by telling a few >stories about the fun you can have with a Wasp when there are divers in the >water with you. One story was about the time he was in a lock with a diver, >since the diver was the biggest animal in the lock, he was naturally the most >fun to play with. Hawkes decided to see how noisy the thrusters really were by >seeing how close he could sneak up on the diver. > Very close. > Hawkes ended up giving the diver a bear hug with the Wasp's arms. "He >went rigid, and then he went limp. At first, I thought I'd killed him, and >that might have been better. Now, I don't know about you, but when I turn my >head, it only goes about this far, but somehow, the diver got his all the way >around...." > Then on the set of the Bond movie, For Your Eyes Only, that's Hawkes >in the Jim suit and the other submersibles again. They asked him to fly a >submersible up and over the camera for one shot. Hawkes didn't want to; the >camera was so valuable, only a few people were even allowed to touch it. >Hawkes was afraid of hitting it with the submersible. Somehow, they talked him >into it, and set the camera up on a tripod, with two big lights behind it, and >five divers in attendance. > The submersible hit the camera square on. > This knocked down several divers, and the wash and confusion brought >down the lights, and pinned down the rest of the divers. Hawkes was afraid of >what the thruster blades would do to all the arms and legs, so he killed the >throttle in the submersible. > And gently set down on the pile of divers. > He was concerned, of course, but by the time the divers fought the >battle for regulators, got themselves together, and looked in the dome, Hawkes >couldn't control his laughing. "They were pretty certain I'd done it on >purpose, but they asked me to do it again. So I did it again. The whole thing. >Now they were confused. I wouldn't do it on purpose twice, so we did it a >third time." > This time, even though he blew ballast early, he was still heading for >disaster, praying the divers would scatter like sane people, and give him room >to maneuver. One finally broke ranks and fled. Hawkes dipped a wing, made it >through the gap, on to safety... and the diver stopped and turned around, and >got folded over the dome and carried on. > I happened to be sitting with Ross Saxon, head of the Association of >Diving Contractors; he shook his head a lot. If I am ever in the water with a >great white and Graham Hawkes in the Wasp, I'd rather take my eyes off the >shark than Hawkes. On the other hand, I'd put up with a lot for a ride in one >of Hawkes' submersibles. > > Hawkes finally told us about the new stuff. He just built two new Deep >Rovers, the submersibles with the big bubble for a cabin (there's one in the >movie The Abyss), for a French filming company. They should have some new >films for us to watch soon. Hawkes said he hates when customers take away his >toys, so he's building one just for himself: Deep Flight. Here, I refer you to >Hard, for pictures and an interview. It looks like a stub-winged fighter jet, >and Hawkes says it should do about 12 knots, but right now, it's batteries >only last 7 minutes. It isn't quite done yet. > The pilot lies down in the body of the short craft, and his head and >shoulders are entirely out in a clear bubble on the front of the plane. Hawkes >said that the clear material vanishes underwater; in Deep Rover, he reaches >out, and isn't sure when (or if) his finger will touch glass. "You wouldn't >believe it. You really should see it." Well, I'd like to, now that you mention >it. > > I did get to see a NewtSuit. The US company that contracts with Hard >Suits and is using the NewtSuit was there, with one of theirs in a rack. >They're right: it's smaller than you think outside, bigger than you think >inside. Like most of the tools there, it was being used for some unexpected >purposes: it was often being used to find and recover rare WWII aircraft for >museum restoration. Some of the pictures he had of rotten fuselages didn't >look like much, yet somehow, they could be turned into museum pieces worth >hiring a NewtSuit for. > Another item that was seeing some unexpected usage was a software >package called Melian, from Webster Associates. Pretty simple stuff, actually: >you told the software about your sensors, sidescan sonar, magnetometers, >whatever, you told it how close to space tracks, how tight to make turns to >keep the sensors flying, you plugged the sensors and the autopilot into it, >and then you waited while it drove your boat and mapped the bottom for you. >They just developed it for some contracts they had, and it worked so well they >thought they'd see if anyone else liked it, so they came to tek. I liked it. I >just need a boat and some sensors, and I'll get it. > Beuchat was there. I haven't seen their 190 cuft tank before. It >seemed a lot bigger than my OMS 120. > Cochran was there, with their newest Nemesis. There were posts about >it earlier. It still looks good, the software interface keeps growing, it may >one day work with the Abyss software, and there is an upgrade plan for old >Nemeses. > Force Fin was there. I said above that Nuytten's putting Force Fins on >the light NewtSuit. I mentioned this to Bob Evans, the inventor, and he got >all excited. He said he just thought of something a day or two ago that's even >better, hasn't even told Nuytten about it yet and couldn't tell me. Evans is a >mad scientist, and a lot of fun. He loves what he is doing, and his brain >won't stop churning out new ideas. However, he's gotten pretty tired of some >of the dive industry politics. He said that one big chain stopped selling his >fins and is telling people that somebody drowned in them. He said it made him >think about quitting. He was really excited and happy to be at tek with some >real divers. It was a lot of fun talking to him; his excitement was >contagious, and if I said something he liked, he'd get even more excited. He >had a pile of fins in the corner of his booth, all kinds of concepts, many >brands with skegs on them, all kinds of ideas. You'd start talking to him, and >he'd pull one out of the pile and have all the ideas embodied right there to >show you. I told him I noticed that each level of Force Fin had a certain >power band that it worked best in, and to prepare for emergencies or current >or lots of gear, I wanted a stiff fin, but was afraid it would be too >inefficient at low power. He was thrilled. He showed me the new fin, the stiff >one with the adjustable skegs. The most powerful, the fastest fin on the >market, he hoped. The skegs even adjust its power. Turn them out, and you can >cruise along. Turn them in above the blade until they are almost touching, and >when the fin flexes, a venturi forms in the pocket under the skegs. He was >getting more excited when I knew what a venturi was, that somebody understood >his stuff. I asked him if the cleats on the bottom were to make turbulent >flow, to keep it attached, and I thought he was going to bust. I asked him >about cave divers using his fin, since they can't scull or frog kick with >Force Fins, and he got excited again. His fin directs flow backward, not out, >so a normal kick, the most powerful kick, won't churn up silt. Cave divers >don't have to torture themselves with weird kicks anymore, and benefit more >than anybody from his fin. > Bob Evans is lots of fun. I want to try his new fin out. I'll let you >know how it is. And if you see him at a conference, talk to him. He'll cheer >you up. > >**************************************************** > > OK, finally, the rebreathers. There were four at the show: two fully >closed, the Cis-Lunar and the Oceanic Phibian; two semi-closed, the Prism and >the BMD. The Phibian and the BMD were new to me, and I spent some time with >each of them. > > If you don't understand semi- and fully-closed, let's start there. If >you do, skip down. I know we've got some new subscribers who want to learn >about rebreathers, so here we go. > Fully closed systems typically have two gases on board, pure oxygen, >and the diluent, which can be any gas: air, nitrox, trimix, heliox, pure neon, >whatever. An onboard computer fills the breathing loop with diluent and oxygen >to a life-sustaining level. By keeping the O2 level high, there is less inert >gas to load your tissues, so on the way down, your computer would be mixing >you nitrox. At the bottom, your computer will have you on a low O2 mix, >perhaps pure diluent, to keep O2 partial pressures below toxicity range. On >the way up, the computer will mix oxygen in as quickly as is safe, to speed >decompression, until near the surface, you are breathing pure oxygen. > For bailout purposes, it would be nice if the diluent was something >with oxygen that could sustain you if your computer died and couldn't mix for >you any more. > On the way down, the computer will be adding both gases, to keep the >loop full. On the bottom, the computer will be adding only oxygen, since the >only gas lost is metabolized oxygen. Oxygen is metabolized and CO2 is produced >at the same rate, regardless of depth. So little gas is used overall that >fully closed systems are typically limited in duration not by gas supplies, >but by the amount of CO2 that the chemical scrubber can remove from the loop. > On the way up, the loop will be overpressurized and vent gas. Divers >with bad buoyancy control will waste gas, and may find themselves limited by >gas supplies. > Semi-closed systems have only one gas on board. It had better be >breathable. As you breathe and gas flows around the loop, oxygen is lost, but >rather than add pure O2 to replace it, gas is added. Let's say the gas is >EAN50, to keep the math simple. If you've consumed a liter of oxygen, you need >a liter of oxygen. To get it, you have to add two liters of EAN50, by dumping >an additional liter of gas from the loop. Semi closed systems actually achieve >this by keeping a steady flow at a *critically* measured rate into the loop. >Semi-closed systems are actually constantly bubbling, although more quietly >than scuba. They are typically limited in duration by gas supplies, but you >might be able to simply bring more. Some manufacturers argue that since divers >rarely stay at one level, semi-closed is as efficient as closed, since both >systems will be constantly dumping gas on a sawtooth profile. Semi closed >systems are simpler, and do not need to be computer controlled. I'm making >some sweeping statements here, oversimplifying a lot, but this should be >enough to get you through the rest of the post. I know there are exceptions. >Ask me questions or flame me as you choose. If you want more, I'll help, but >the first thing I'd recommend is getting an aquaCorps back issue, C2. > > The Cis-Lunar was well described in Steve Millard's recent post, so >I'll be brief on it. It is everything you've heard, maybe everything you want. >It has the look of a really well built, really durable, really efficient tool. >This unit in particular had the marks of standing up well to some really heavy >use. This was not a concept mock-up. This thing works. The Mark IV is not that >streamlined; the new Mark V should be better. > The Oceanic Phibian was there in concept form. It should be out later >this year. There are two models, and a few options, so pricing is uncertain, >but my guess is it starts higher than the semi-closed, uncomputerized units, >and lower than the Cis-Lunar. If you buy the redundancy for the Phibian that >the Cis-Lunar has, it may cost as much. > Like the Cis-Lunar, the Phibian is fully computerized and will keep >you at a high PO2 to speed decompression. The rebreather, including the >breathing bag and 2 or 4 small cylinders, is entirely housed in a hard shell >that slips into what is basically a large pocket on the back of a BC. The >whole package is about as streamlined as a rebreather can get. This is the >rebreather with the most inside the case; all four have some kind of BC >bladder outside, and the other 3 have their breathing bags outside. The >breathing bag inside on the Phibian may be a little high, and since it will be >displacing water inside a case, it might be a little hard to breathe on. It >will be interesting to see. The Phibian was not going to be available in the >pool sessions, and I couldn't stay anyway. > The base Phibian comes with one computer, which hides under the stack >in the shell, and one display, a solid case with a large LCD display. The >displays looked good, clear and complete. The computer listens to 3 oxygen >sensors; a CO2 sensor can be added. The 4 cylinder model can handle mix. The >cylinders are mounted inverted, with valves and purge controls on the bottom, >where the user can easily reach them. Flooding is recovered from by hitting a >purge and overpressuring the loop; there is a vent on the bottom of the stack, >the lowest point in the system, to vent water. Duration, as in most fully >closed systems, is limited by the absorbent, and should be 4-6 hours at any >depth. > > The BMD and the Prism are semi-closed systems. However, there are >several differences between the two. The Prism is a very simple system, and >the least expensive. It consists of a breathing bag, a canister of absorbent, >and enough plumbing to get air to your mouth. You attach the system to your >own BC and cylinder; the canister rides on back next to your tank, and the >breathing bag goes on your chest. The canister looks large and not >streamlined, something like 8 inches across and perhaps a foot high, like the >lower half of a scuba tank. > The BMD unit comes with its own cylinders and vest; the stack, >cylinders, and plumbing fit into a shell which rides on back of the vest. I >was very impressed by the BMD's breathing bags: there are two of them, toroids >around each arm inside the vest. With this layout, whatever the diver's >orientation, there should be a breathing bag available at lung level for easy >breathing. There are four small cylinders inside the backpack; I was surprised >to see that they were composite and perhaps high pressure. I can't get fills >at pressures high enough to justify composites, and they probably add expense. >The BMD also had an Orca Phoenix attached; I'm not sure how it handles mixes >other than air. > The biggest difference between the two is the flow control used to add >gas to the loop. The Prism uses a mass-flow valve, basically setting a flow >rate. The BMD, as I understand it, uses another kind of valve that simply >dumps 25% of each exhaled breath overboard and out through a nice diffuser to >keep things quiet. > You know, if all you fish guys want is silence, that's not hard. > Anyway, by my math, the BMD unit very simply stretches air consumption >by 4 times. The Prism's consumption rate is based on flow, but is probably >similar. The Prism's flow rate is adjustable; it didn't sound like the BMD >is. Here's an interesting note on semi closed: you are actually breathing a >lower PO2 than what is in your cylinder, if you think about it. The BMD people >had worked out the math, and were quick to tell me that if you use air in >their system, you are actually getting EAN17. Nice to know. Since a lower >percentage of O2 is consumed at depth, I bet the O2 level is higher at depth, >and lower near the surface, kind of opposite what you want. Perhaps not >significant, but this is a forum where we split hairs. > Anyway, one final note, and I'll wrap this up. I've heard that more >than one Prism rep based his sales pitch on what's wrong with the Cis-Lunar: >it's sooo high maintenance, so expensive, uses just as much gas on sawtooth >profiles, blah blah blah. Well, at his booth, Peter Readey, the Prism's >inventor, gave me the same negative sales pitch. This attitude starts at the >top. I hope somehow he reads this. It really turned me off. I like the Cis-Lunar. >I like the Prism. I like all the rebreathers. They are all different. I wanted >to hear what was right with the Prism. There is a lot right with the Prism. It >will probably sell more than the others, based on price alone. I wish Readey >had answered my question instead of jumping on the competition. He's built >rebreathers before, including fully closed, and he knew exactly what he was >doing when he made the Prism. He had a world of options when he built it, so >he I know he knows all it's good points. I wish he'd told them to me. > > I hate to end on that note, but I've finally run out of things to say. > This show was so worthwhile that I plan on making the long trip to New >Orleans next year. I did my best at the show to try to get a job in the >industry so I'd have an excuse to. I hope other people, and the industry, got >as much out of it as I did. I'd really like to thank Michael Menduno and >everyone at aquaCorps for calling everyone to this party, and then working so >hard throughout it. > > >#----------------------------------------------------# > Roger Carlson H 310-frogger > Somewhere off Hermosa Beach, CA W 310-813-0858 > Roger_Carlson@at*.sp*.tr*.co* F 310-812-1363 >#----------------------------------------------------# >-- >Send mail for the `techdiver' mailing list to `techdiver@opal.com'. >Send subscription/archive requests to `techdiver-request@opal.com'. > > ---------------------------------------------------------------------------- Scot Anderson <scot@bt*.co*> http://www.btg.com/~scot/
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