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BACK IN 1992, I did a rebreather course with Peter Readey and took the unit to the Red Sea. My subsequent article was entitled "I Have Seen The Future - And It Works!"
Unfortunately, Peter had no manufacturing capacity at that time. Everyone wanted a rebreather but he and other pioneers could not supply what came to be known as "vapourware". Dräger had a fire-fighting rebreather which it quickly adapted and made available for sale as a semi-closed circuit unit, the Atlantis. But this also proved to be something of a false dawn.
We had to wait until the idea of a closed-circuit rebreather (CCR) caught the imagination of a diver who was both an engineer and a manufacturer - Martin Parker. In 1996 I dived prototypes with him. Eighteen months later, the finished production version of the Buddy Inspiration CCR was launched.
I went with Martin to the Maldives for some intensive diving with it. My article was entitled Now He's A Believer. Today a lot of other divers are, too.
Meanwhile, Ambient Pressure Diving, the Inspiration manufacturing company associated with AP Valves/Buddy, has been developing a second-generation rebreather, the Evolution.
At first glance, special examples put together as conversation-pieces for dive shows simply looked like smaller versions of the Inspiration.
But under development alongside the unit (which featured a smaller scrubber unit and smaller gas cylinders) was the Vision electronics system. Vision is revolutionary to the extent that adding it to a full-scale Inspiration or the smaller Evolution turns either into an entirely different proposition. We've waited a long time for this second-generation rebreather and finally, just before Christmas, I was able to take a pre-production example away for some concentrated diving. But where to take it?
Cocos seemed an ideal destination. A remote island set in the Pacific 350 miles from the Costa Rica mainland, it's a location famous for its large population of sharks, including skittish hammerheads which are easily frightened off by the exhaled bubbles of open-circuit divers.
You need a certain degree of stealth to get close to them. A closed-circuit rebreather gives you that stealth, and long bottom times that allow you to out-wait your prey.
This is combined with short ascent times that often see you back in the pick-up boat at the same time as the open-circuit divers.
Undersea Hunter and Sea Hunter, two dive-support vessels that operate around Cocos, are rebreather-friendly boats with supplies of scrubber material and oxygen on board.
One of their owners has dived exclusively with closed-circuit scuba for many years. It's an operation favoured by film-maker Howard Hall, another CCR fan. Many confirmed CCR divers have since discovered these boats.
As the Evolution lent to me was still in pre-production format, Martin Parker decided to send his CCR production manager and erstwhile test-diver, jolly giant Mike Etheredge, to accompany me, using a second pre-production Evolution.
Both units had the counterlung and wing configuration with direct-feeds for diluent and oxygen that are familiar to Inspiration users. But that is almost where similarities with the original Inspiration end.
Big Mike is known not to suffer fools gladly, so I found it comforting when his first words to me were that the Vision electronics fitted to the Evolution were such a sophisticated development of the original Inspiration (now to be known as the Inspiration Classic) that even a fool could use one. I was off the hook!
The two Evolutions were easy to send as checked baggage to Costa Rica because, with mere 2 litre twin cylinders and a 2kg scrubber unit, each weighed in at around 23kg. We were able to pack other diving equipment alongside each unit in its crate without exceeding the all-up 32kg per item airline weight limit.
Big Mike had evidently taken a lot of ribbing from other members of APD staff before taking his leave, including being given a label to wear on the back of his diving suit: "Big Mike and Fries".
As someone normally more at home in a drysuit, he had even got hold of a wetsuit. He may have been an expert rebreather user, but there would be aspects of the trip that were unfamiliar to both of us.
mv Sea Hunter was waiting for us in Punta Arenas, immaculate as usual, and 36 hours later we arrived at her mooring next to Manuelita Island in Cocos waters. At least one of us was gagging
to get in the water with the sharks.
Our first dive saw us swimming alongside multitudes of whitetip reef sharks and clusters of enormous marble rays. It was our check-out dive and it revealed to me a flaw, possibly the only flaw, in the choice of the smaller Evolution for the trip.
Because you still need to use the same size of counterlungs, the weight-saving advantage of the smaller cylinders was negated by having to add more lead to compensate. With my thick wetsuit,I needed a massive 15kg, and at first, with some of this on a weightbelt, severe backache ensued.
On my next dive, I stowed 3kg in the trim-weight pockets provided, 8kg in the ditchable integrated-weight pockets, and 4kg in the top part of the unit.
I understand that a top weight-pouch, as fitted to Inspiration Classics, may well be installed on Evolution production models - or there may be an even more elegant solution to getting the weight up high.
Diver preparation of the new unit is very much in line with the original. Better ergonomics within the case makes precise installation of the scrubber unit and two cylinders far easier than before.
The scrubber top, where the electronics are stowed, is much neater, and there is a connection lead for downloading information to PC and connecting to the optional scrubber-use gauge. Packing the scrubber with Sofnolime or Sodasorb will be familiar to any existing Inspiration user.
In fact, this is where I offend all the technical diving agencies which, naturally, are in the business of selling further courses. I would say that an Inspiration user will find the Vision electronics much easier and hence less fraught by unintended mistakes than any Inspiration Classic, so no extra course, only sufficient time with the on-board simulator to get familiar with its use, would qualify them to use it. It's like changing cars, from one with a manual gearbox to one with an automatic.
The single handset of the Evolution is much neater than the twin handsets of the old Inspiration and it imparts a lot more information, including full deco requirements.
Mike used a trimix version (with air as a diluent), setting the gradient factors accordingly. I used a nitrox version set to a caution level of 2 out of a possible 1 to 5. Simple "gauge" versions will also be available, but these can be upgraded at a later date.
The handset display shows current diluent, dive time, current depth and maximum depth, and, once into deco, time-to-surface (TTS) and ceiling depth. Sometimes, during a 50m dive, I would see a TTS of only four minutes with a deco-ceiling of half a metre, such is the speedy off-gassing offered with a fixed ppO2 of 1.3bar and nitrox mixed automatically on-board.
The display also shows the chosen set-point and the three read-outs from the O2 sensors. You still need to start off with the unit at 0.7 bar ppO2 and switch to the higher set-point at depth.
Regular readers might remember my trip to Cocos with an early Inspiration when I forgot to change to the high set-point and did a whole dive at 0.7 bar ppO2. I'm told that some Inspiration trainers still derisively refer to this as "doing a Bantin". The important part of the story, however, is that with the CCR I was able to rectify the mistake by staying in the water.
There's no chance of making that error with the Vision electronics. You pre-program your switch-point depths, and they're taken care of automatically during the dive.
On the way up, the unit will try to maintain a low set-point that equates to breathing 100% oxygen in the shallows.
You can over-ride this manually at any time, just as you can change a set-point on the old Inspiration. I did so, because the big Pacific swells at Cocos made a lower set-point of 0.7 bar more comfortable in terms of buoyancy control when in less than 5m of water.
The handset is very robustly built and readily viewable because it's handily strapped to your left wrist. I didn't have to grope around to find it.
What else did it display? It initially fires up much like an Inspiration, with all the usual questions, and confirmations by button-pushing. It's quick, slick and comprehensive, with pre-dive self-checks.
The buttons are no longer magnetic, and use a crystal contact to generate a current, rather like a Pietzo lighter.
The Vision electronics measure ambient air-pressure and, although I never tried it, you can evidently jump into the water before firing it up and still get a performance from it. The Evolution with Vision is pretty foolproof, but I suggest that going in with it switched off is about as foolish as you can get.
The batteries last so long that it's not worth switching off just to save power. By the way, they've designed out any possibility of battery-bounce with under-sized batteries. Once up and running, the three readings from the oxygen sensors are permanently on display and seen to vary from moment to moment when you breathe off the unit, as they should. You can switch between controllers 1 and 2 at any time.
The condition of each of the batteries is displayed (they are used separately at first and, once the second drops voltage, the two are combined), as is the current dive time in minutes and seconds, depth, and any appropriate warnings.
The optional scrubber display gives a graphic representation of which part of the scrubber is generating heat and so being used. As it progresses up the stack, it effectively monitors scrubber use and gives a warning of CO2 breakthrough.
I never saw that last part, because I changed my scrubber content every three hours of use regardless. This scrubber display is very comforting and, once enjoyed, becomes indispensable. Don't go without one!
Brilliant news for photographers and those with other work to do under water is that your dive is no longer dominated by continual reference to the handset display, conveniently placed as that may be. A set of LEDs for each of the controllers in the scrubber lid is linked via very flexible modern fibre-optics to a head-up display (HUD) mounted on the mouthpiece.
In normal use, you see two green lights. If a warning is generated, you get one or two reds. You could learn the codes for flashing red, red and green, steady red and so on, but in reality any flash of red at the HUD had me referring to the handset instantly. Green meant good, and red meant check.
Lesser warnings can be turned off once given, but crucial warnings such as high or low O2 and CO2 break-through cannot.
During my 21 test dives at Cocos, I saw a red light once that indicated "Low Battery", a flash of red that resulted from a "High O2" from descending too rapidly, and another from a "Cell Warning".
The latter came after I had been lying on my back photographing hammerhead sharks above me, and had presumably allowed a bead of condensation to drip onto a cell face.
A too-quick ascent rate meant that both controller greens went out (because the controller could not maintain a ppO2 set-point) and the word "Slow" appeared on the handset.
On one occasion, while chasing up through a massive school of horse-eye jacks at Submerged Rock and looking where I was going through the viewfinder of my camera, I did almost lose control of my buoyancy. Nigel Dunkley, a fellow-passenger on conventional scuba and from Barnsley, observed later that at that moment I looked like a "reet novice".
I found myself wondering how an auto-dump valve could be fitted to the wing (though you probably won't use the wing if you use a drysuit and you probably won't find such interesting subjects near the surface).
However, I soon got up to speed with buoyancy-control with an Evolution, wetsuit and wing.
The very audible alarm, as already fitted to the Inspiration, remains.
I heard Mike screech down with a long oxygen peak to where I was at the beginning of our second dive. He was still getting used to the idea of diving in "shark-infested waters" and didn't want to be alone. Bless!
To be certain, and because we were using pre-production rebreathers, we backed up our decompression computations on each unit with a separate Buddy Nexus CCR computer. I never like to dive with only one deco computer, however state of the art.
The Evolution was a dream to use. Only 100 bar fills of oxygen were available, which meant refilling the cylinders after every dive. For each hour-long dive, I found I used about 50 bar of each, oxygen and diluent-air, from the 2 litre cylinders, even to around a 50m maximum depth. So gas consumption was not important, even in Cocos's arduous conditions.
The warm breathe provided because of the chemical reaction taking place in the scrubber made my 7mm semi-dry suit slightly too hot, and I dispensed with the hood.
The famous Cocos night dive, where divers find themselves escorting literally hundreds of reef sharks in a constant feeding frenzy, made buoyancy control crucial. I didn't want to unintentionally touch down into those open mouths and gnashing teeth, so I waited until later in the week, when I was entirely competent, to enjoy this spectacle.
You can vary the contrast and intensity of the handset LCD to suit ambient light conditions together with the intensity of the HUDs. I used the lowest setting at night. The automatic diluent valve (ADV) made it easy to keep the volume of the counterlung comfortable during descents, and this now has a sleeve-type cut-off valve fitted.
Controlled ascents were easy, too, because expanding air in the counterlung could be dumped by simply blowing back against the "hamster-cheeks" effect to open the dump-valve.
On ascent you can also, of course, either pull on the cord of the dump-valve or blow out through your nose to keep the counterlung at minimum volume.
Mike regularly dives past 80m in UK waters but a visit to Silverado was a life-changing experience for him. This is a shallow rock where silvertip sharks congregate to benefit from the attention of hard-working cleaner wrasse. We eventually watched three of these impressively large creatures enjoying the equivalent of a manicure.
Initially, when he heard that it was only 10m deep, Mike could hardly be bothered to launch himself into the water. But once he found that he had a large, angry shark hurtling around his head, he started to look impressed. The shark had been irritated by a group of would-be cleaner reef-runners.
At Cousteau's Alcyon, a sea-mount that tops out at about 30m, we waited for the air-expelling divers to retreat and the scalloped hammerhead sharks to rise from the depths to be cleaned by willing barberfish and king angels. After getting a few good images, we made our way back to the shotline anchor. Here we found a boisterous group of mating whitetip reef sharks tumbling together.
A few metres up the line, I broke away to photograph a very large manta-like mobula, overloaded with enormous remora suckerfish, that danced around us joyfully. Meanwhile the others had seen a marlin near the surface. That's diving at Cocos.
Mike never stopped talking about the incredible visibility. It's not Falmouth!
There were places such as Dos Amigos where barberfish were abundant, but no sharks turned up and they had to clean Creole wrasse instead. Galapagos sharks passed by, but never close enough for a good picture. We often saw eagle rays - once, I found one swimming around my legs, but it knew I was out of film. There were no flashes from my camera to put it off. Giant marble rays were everywhere.
By the way, despite his original misgivings about sharks, Mike is solid as a rock to dive with. I couldn't have wished for better company, and he had instant answers to any queries about the Evolution.
Each night, we would download our dives onto a laptop PC. It recorded every detail, and the on-board computer would remember our last eight hours of diving. It was limited to eight hours because the factory had increased the sampling-rate on our pre-production models to get as much information as possible. And there was a lot.
I could display the time/depth chart of a dive against the decompression ceiling. I never came anywhere near it.
I can imagine some divers spending hours going over dive profiles. It's especially useful if something goes wrong on a dive.
The facilities afforded by the new Vision electronics, combined with the ability to download all the information from the dive, have added a huge amount to the safety of CCR diving.
Finally, I can hear you asking about open-circuit bail-out. We dived with the 2 litre cylinders, the breathable diluent was pumped past 200 bar and the oxygen was always filled past 100 bar. We used no bail-out. Mike has been diving to 85m (with trimix) in the UK and 1 litre cylinders. Do your pre-dive checks. Think closed-circuit.
The APD Evolution rebreather starts from £4695.
Ambient Pressure Diving, 01326 563834, www.ambientpressurediving.com
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Back from a dive
Big Mike prepares an Evolution on mv Sea Hunter
The head-up display will be available on a stalk for those without a deep-lens mask
Apart from good visibilty and predictable diving conditions, this is the point of coming to Cocos Island to test a new rebreather. Will the unit allow the diver to get close to big animals, and to stay with them for as long as required, without undue technical distractions? These hammerhead sharks provide the evidence - the Evolution helps turn you into a human fish!
A pregnant whitetip reef shark
wrist unit with scrubber display included
A night dive is no occasion for poor buoyancy skills!
The downloaded computer display shows time/depth graph and handset display at any given part of the dive. The upper horizontal line is the deco ceiling
Instead of inhaling breathing gas and then exhaling into the water, as divers do with conventional open-circuit scuba, the rebreather diver's lungs become part of a closed loop with the equipment.
Breathing gas is inhaled, part of the oxygen within it is metabolised, then the gas is exhaled back into the loop. A counterlung takes up the volume when the diver's own lungs are deflated.
This gas now contains the carbon dioxide that is a by-product of breathing, plus a great deal of unused oxygen. The poisonous CO2 is removed by passing it through a chemical scrubber and the oxygen level is topped up automatically before the breathing-gas returns to the diver's lungs.
It is not the percentage of oxygen in the breathing gas that's important, but the partial pressure (ppO2). As the CCR diver goes deeper, he needs less and less oxygen to achieve the same ppO2. The rebreather automatically maintains the ppO2 at a chosen set-point, weakening the breathing mix as the diver descends and enriching it as he moves back upwards.
The amount of gas consumed is minimal. Dive times depend more on the duration of the scrubber material than on gas supplies, hence the need for only small cylinders.
There are two cylinders. The oxygen from one is mixed with a diluent gas such as air or an air/helium mix to give it sufficient volume in the loop. Because the rebreather maintains the ideal gas mix for any given depth, the amount of inert gas absorbed by the diver is kept to a minimum. For example, the no-stop time for a diver using a set-point of 1.3 bar ppO2 with air as a diluent gas at 20m is around three hours.
The electronics of the Evolution take care of giving the diver the right mix of gases at any time, and track the deco status of someone breathing those different mixes at different depths.
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