The Draeger Atlantis 1 rebreather, reviewed here last October, turns out to have the additional virtue of delivering warm breathing air. By John Bantin
February. Freezing fog on the motorway. Snow lying in the Leicestershire fields. lush in the car park at Stoney Cove. Water temperature: a crystal clear 3C. My new drysuit has a cuff dump with a severe leak. These are perfect conditions for trying the Draeger Atlantis 1 rebreather.
When I last reported on this exciting new developmen in leisure diving equipment, I had extensively used an Atlantis 1 in its pre-production prototype form. Now, at last, I got my hands on the finished product, complete with its BC and open-circuit bail-out rig.
One of the advantages of a semi-closed-circuit rebreather (SCR) is the exothermic (heat-producing) reaction of the CO2 scrubber unit. This promises to eliminate any risk of the mechanism freezing up and to offer a warm, comfortable breath when every other part of your body screams: "brass monkeys".
However, until the beginning of February, I had no evidence to support this theory.
I had already put an additional 4kg over and above what I'd normally wear in the weight pockets of the integrated wing-style BC. This is because, with a rebreather, you need to weight for both your own lung volume and that of the counter lung - and I've got a big one!
I cursed the fact that I'd decided simply to wear my undersuit over the clothes I'd driven up in, since they were getting wetter by the minute.
As we descended, my suit began to fill with the freezing cold water. I persevered. Ten minutes into the dive I was aware that my arm was completely numb past the elbow. After 15min this numbness had worked its way past my left arm pit. By 20 it had passed my groin and I knew my foot was wet. But was I cold?
Strangely I was not cold in the way that you would expect. I was losing heat from my periphery, but my body otherwise felt quite comfortable. Even my head did not have that brain-crushing ache so familiar in such cold conditions. What was the reason?
I can only put it down to the fact that, instead of filling my lungs continually with chilling air from a normal open-circuit scuba set, I was breathing air which was at the same temperature as my body core. Any cooling caused by the cold water while the air was in the corrugated breathing hoses was probably counteracted by the scrubber unit's heat production.
Since my body core was not being cooled, I found I was able to look at the progressive numbness caused by the cold water entering my leaking suit with a degree of detachment. When I did decide to call off the dive, I was surprised to discover that my open-circuit-equipped buddy, in a perfectly functioning drysuit, was suffering from the cold more than I was - confirmation that the SCR Atlantis 1 is ideal for diving in cold conditions.
How else did the unit perform? I enjoyed the perfect buoyancy control afforded to me and crept almost imperceptibly from 15m to the surface, hovering to watch the odd crayfish and other forms of aquatic life on the way. With an SCR there is no change in buoyancy caused by breathing. Nor does gas consumption vary much with changes in breathing rate. If you breathe heavily, you just circulate the gas through the system faster. The 4l cylinder provided was so sufficient that checking its contents gauge was irrelevant. I used a nitrox mix which gave me 40 per cent O2 at the mouthpiece, with a consequent maximum depth limit of 25m.
The BC is in the style of a wing, and clearly betrays its AP Valves parentage - since it is almost a replica of their new Buddy Trimix jacket, right down to the front mask pocket and stainless steel D-rings. The integral weight pouches are 'as well as' not 'instead of' a normal weightbelt. Weights can be dropped by undoing the Fastax retaining clips to each individual pouch. This looked to be a perfectly viable emergency option.
The open-circuit bail-out rig consists of either a 2l or 3l air cylinder with either international A-clamp or DIN fitting for a standard regulator equipped with its own pressure gauge. Uwatec, the distributor, assumes that its customers will already own such a piece of equipment. However, the Atlantis 1 supplied for me to use came equipped with a Draeger scuba regultor and 3l cylinder.
The hoses are easily and conveniently arranged, but I noted you really need an extra long hose to the direct feed of the BC. My drysuit was also fed from this regulator, and I stowed the pressure gauge alongside that of the nitrox cylinder. I checked during the dive to see if I could easily change to the open-circuit regulator if necessary. I didn't actually breathe from it because of one small problem.
In order not to flood the unit it is essential to close off the twin-hose SCR mouthpiece valve using a lever before removing it from your mouth. In the warm waters of both the Bahamas and the Red Sea, I found this lever to be very stiff, needing two hands to use successfully. In the near-freezing waters of Stoney Cove, I was completely unsuccessful at closing it, such was the increased stiffness of the mechanism.
Uwatec tell me that they have solved the problem, but I await the evidence. In the meantime, I kept the mouthpiece firmly in place and waited until I was back on dry land with the supply cylinder turned off before I let it go.
When I did finally get out, let go of the mouthpiece, and took a breath of Stoney's crisp winter air, I appreciated just how warm and comfortable the Atlantis' supply had been. It's a pity I had to spend the next few days nursing an arm that ached from the cryogenic effects of the leaking suit valve. That apart, I found myself once more enthusing about SCRs and pleased that at last there is an example available to buy.
When it comes to trying suits, on behalf of Diver readers, I get to use a lot. However, the one aspect of a suit I rarely get the cance to check is that of longevity.
My wife has a 4mm Hydrotech Explorer 2 semi-drysuit. She's had it, it seems, for years. It was only when the neoprene wrist seals began to lose their elasticity that she decided to replace it with a new one, and got one for me too.
Made-to-measure, it fits me perfectly, and hopefully it will prove to last as long as her previous suit lasted her. A suit for warm water use, it's made of 4mm lined neoprene - cup-stitched (which I am told is the secret of its strength). There are seals at both wrists and ankles, together with a wide smoothskin neoprene flap to back up the zip. This zip runs from the base of the back to the neck and makes entry to the suit exceptionally easy - although I always needed help from my buddy to do it up.
As someone who prefers to cover up completely while diving, no matter how warm the water, I've already used this suit extensively. It's kept my skin protected from the rusty metal of wrecks, man-eating plankton and stinging hydroids, as well as underwater heat loss and boat-ride sunburn. It has shown no sign of fraying at the knees, something which has seen the death of so many of my other suits.
Two new ideas from the Italian company Technisub are the Idea3 (pronounced 'Idea cubed') fins and mask. The fins (bottom) are constructed from three different materials: a soft, black rubbery material for the foot pocket; a stiffer coloured plastic for the main structure; and a flexible, ribbed blade. The Italians have always had a flair for things like this, and they make a very sexy-looking item. They're available in three colour combinations of black/navy/light blue, black/pink/purple, and black/silver/lime. They come in three sizes: compact, regular and big.
The foot pockets are long. Surprisingly, though, these are not as long as those of some other fins; and I can't understand why Technisub choses to leave the diver's heel overhanging. There are Fastax-style clip-on buckles for the straps, which makes undoing and adjusting them easy. Their importer, Aqua-Lung UK, optimistically claims that these are the most efficient fins available. Hard to quantify, but they certainly are smart. The Idea mask has similar colours, enabling the style-conscious diver to be perfectly co-ordinated.
It is a low-volume design which gives a wide angle of view. A key feature is a totally new buckle design, intended to make strap adjustment easy. I found this not to be the case. In fact, it was just as difficult to adjust the strap as with any other design.
There's a choice of silicone skirts in either crystal clear, black, or metalised finish. Skirts which do not allow extraneous light to reflect back from the inside of the mask glass give a clearer view, but are not so seductively attractive as clear silicone in the dive shop - so they're less popular.
Technisub Lumen 4 and Lumen 6 torches take either four or six D-cells. These emit 105 and 130 lumens respectively. Both give six hours of burn time.here's also a Lumen 6 rechargeable, but this doesn't last as long and costs much more. Personally, I was hard pushed to tell the difference in light output, and I opted for the Lumen 4.
It comes in a choice of four different colours, including black, titanium (a sort of grey), blue, and a rather unmistakeable lime yellow.With a claimed maximum depth rating of 120m, it should be sufficient for any diver; although, being old rather than bold, I tried it in considerably shallower water!
It's switched on by a simple mechanism which passes through the one-piece moulding of the torch. The reflector unit unscrews, giving access to both the bulb and the batteries. The seal is made water-tight by a single, slim O-ring.
I found it rather fiddly to remove the bulb unit to change the four batteries. This is not something I recommend you do in a small boat while at sea.
It didn't flood. What more can you ask of an underwater torch?
The Spiro late deployment surface marker buoy, Deco Stop, is a 1.20m-long, bright orange sausage. It rolls up into a handy 15cm-wide bundle which fits into a pouch. The pouch has a karabiner clip to allow it to be attached to a loop on the BC. It comes with 12m of cord.
To avoid it falling over on arrival at the surface, it has a small lead weight built in to its base. The user should be aware that he will be letting go of this weight at a crucial moment for buoyancy control during the dive (in the shallows and at a time when his cylinder is at its lightest), and should be sure to have sufficient weight on his belt.
Its 16l volume means that it could be used as a small lifting bag - its bottom loop looks strong enough. It is a low-tech item, but a very strongly made one. It should give years of service.
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