Improved Dolphin ready to roll – at last

It seems a very long time since the Dräger semi-closed circuit rebreather (SCR) was introduced to the leisure-diving market.

Its infancy has not been without problems, including an aftersales service that was often open to criticism.

Enthusiastic manufacturers have unveiled endless rebreather concepts at dive shows during the past few years.

Some even offered training programmes for their units, but among all the hype, the Dräger Atlantis 1 was unique. You could actually buy one!

Being first in the market with any product can give the manufacturer a clear advantage but the penalties can also be punitive.

 With the Atlantis 1, Dräger took the route of simplicity. Its rebreather is a semi-closed-circuit design with fixed flow rates and an over-riding demand valve which will cut in if there is insufficient volume of breathing gas in the counter-lung.

Dräger did not want any of its new-wave divers getting hurt through making the wrong decisions – so it made the decisions for them long before they entered the water.

The first year is a dangerous time for any new product, and Dräger’s was no exception. In use the Atlantis 1 was revealed to have defects. None was severe, but there were so many of them.

There remains a swathe of disenchanted owners out there, especially those who bought their units at the launch price, a whopping $5000!

The people at Dräger at last identified all the problems, and there were so many changes that they had what was almost a new product.

So they gave it a new name. Exit the Atlantis 1, enter the Dräger Dolphin. It was launched a while ago, but now you can actually get hold of one in the UK!

Dräger has got rid of those butterfly valves that go bendy if you use them in a warm climate, and those spring-clips that go rusty if you use the unit in the sea.

The Dolphin is easier to assemble before diving, thanks to arrows marking the inhalation and exhalation and the direction of the gas flow.

The mouthpiece is now colour-coded (red for exhalation, black for inhalation) and all the new screw connections are resistant to the dirt and detritus unavoidable in the real world.

The corrugated breathing hoses have been weighted to stop them floating up around your head as they once did.

The inhalation and exhalation bags are now made of a durable, reinforced material and have a water drain to make cleaning easier.

The fragility of the original bags was always a problem, and even the unit on which I was trained had a split in its exhalation bag suffered in the process of shipping.

This design defect was discovered early on (I am TDI Dräger Rebreather Diver No 004) but it took a long time for the enormous Dräger Corporation to put through these crucial design changes.

Again, all the connectors are now colour-coded and dirt-resistant. They are also removable, permitting separate bag replacement if necessary .

The scrubber unit has been re-thought – and it needed it. Gone is the cheap, flexible box that lost its shape and hence its ability to stay watertight when it had been over-tightened once too often.

In has come a unit made from a far more robust and heavier-looking material, with a lid that fits and an additional sealing frame round the filter. Arrows mark the directions for inhalation and exhalation.

Again, the connectors are colour-coded and replaceable, and sealing plugs allow the user to take the unit out of the rebreather and reinstall it later without spilling white powder everywhere.

This is naturally subject to duration limits of the scrubber material, which is around three hours if kept dry.

You choose a suitable nitrox mix, with regard to maximum operating depth (MOD), and a gas supply port to match.

The four gas supply ports, tiny orifices cut by laser, are now colour-coded for the different flow rates.

They give rates for 60, 50, 40 and 30% O2 and each is now sealed when not in use by a cover with an O-ring.

To my mind blockages of these orifices by salt crystals or other foreign bodies represented the most serious defect and insidious danger of the Atlantis 1.

A well-used but badly maintained unit could be delivering a reduced gas flow, with the diver gloriously unaware that he was about to become hypoxic.

Thankfully there seemed to be few incidents, but users were exhorted to check flow-rates before diving.

They were provided with a rather Heath-Robinson method involving a plastic bag for this purpose, so few ever did check. Now you can, with a simple little US-made flow-meter that gives an instant result.

Though the MOD depends on the nitrox mix in the tank, the decompression required has to be calculated from the mix actually breathed in the breathing circuit.

So why use a semi-closed circuit rebreather, when it offers none of the decompression advantages of the fully-closed type?

Advantages over ordinary open-circuit scuba include using a smaller amount of breathing gas and producing fewer exhaled bubbles.

There is also the constant-buoyancy effect, and essential coldwater performance.

This last is important to UK freshwater divers and happens because the user rebreathes his gas and does not fill his lungs with masses of cold air freshly decompressed from a tank.

Because of the exothermic chemical reaction going on inside the scrubber, a rebreather actually produces heat, and this warms the breathing gas too.

Nitrox use is dictated by the size of the constant-flow orifice selected. It doesn’t matter how quickly you breathe or how hard you work, every diver has more or less the same gas duration.

It’s all down to how long it takes for the tank of pre-mixed nitrox, available in 4 or 5 litre sizes, to drain slowly down through the chosen constant-flow orifice.

That’s more than one hour with nitrox 50. Big men and small women are on a par.

Excess gas bubbles off and, although this is in reduced quantities over ordinary scuba, there are still quite a lot of bubbles.

However, if you use a rebreather in the company of open-circuit divers you immediately become aware of just how noisy conventional mechanical regulators are.

So it isn’t the absence of bubbles but the absence of noise that enables you to get closer to skittish animals.

The Dolphin is also now available in “stealth” black.

The built-in BC of the Dolphin seems far less bulky than that of the Atlantis 1. This part looks very AP Valves. Weight-pockets are built in.

The BC is fed with air from a separate cylinder, which also provides a separate conventional scuba bail-out rig.

Constant buoyancy is either a joy or a curse. It depends on how well you get on with this effect. It does mean that changes in depth must be made with circumspection.

You cannot adjust your buoyancy by altering your own lung volume, as you can so quickly do with open-circuit scuba.

When, back at the beginning, the boys from Dräger asked me for ideas on improving sales of the Atlantis 1, I suggested that they avoid doing demonstrations in swimming pools, as they served only to reveal the disadvantages of semi-closed-circuit rebreathers (the preparation needed) and none of the advantages.

I also suggested that they should improve the quality, drop the price and get a distributor that could give a good aftersales service.

They seem at last to have taken my advice, and Apeks now handles the business in the UK.

The Dräger Dolphin costs £2450 in white, £2550 in black, cylinders and valves included. Drägersorb costs £84 for 18kg.

Apeks Marine Equipment 01254 692200

Mixing it by radio

Diving at Bikini atoll is mainly in the 50m-plus range. You might been one of those outraged to read recently that I got into the habit of strapping on an unused Suunto computer for each separate dive on Bikini’s wrecks.

“What a very silly thing to do,” you might have thought, and you might have been right, had I not been monitoring the week’s diving with a DiveRite Nitec3 three-mix computer and using each Suunto only as a back-up.

The problem was that, although we were using air as a bottom gas, we were using nitrox 80 as a decompression mix, which really peeled off the stop times.

But I had no way of informing any Suunto that merely had a one-mix program. Each one had to presume that I was using air all the way.

So on the first dive I stayed in until my Suunto had cleared its air deco-stop. On the second, the stop was much longer, so I made a note of the time and left it tied off to the deco bar until it was clear.

By the fourth dive, the admirably safe Suunto RGBM program had kicked in, and none of the other divers was prepared to wait it out, even though they were sitting comfortably up in the boat.

So I hauled it in, bent it and replaced it with another computer for the next dive. I went on to bend that on the next dive, and so replaced it with yet another.

I bent that and was able to replace it with the first, because 24 hours had elapsed by then; and so on.

I got away with that because the Nitec3 was my primary guide. So what to do if you don’t have a Nitec3? Use the new three-mix Suunto Vytec, of course!

The Vytec looks very like the Vyper. The display seems familiar too, but there are differences. The display lights up when any audible alarm sounds, and you can change the battery yourself.

However the main difference is that with the Vytec you can programme in three different nitrox mixes for one dive, telling it when you change gas as you go. It will track your deco requirements admirably.

You simply press one button to tell the computer that you want to change to a different nitrox mix, choose one of two other mixes predetermined before diving by pressing another button, then confirm your choice by returning to press the first button again.

You don’t have to pre-plan the depth at which you change, although it will not accept a mix that gives a greater ppO2 at that depth than the ppO2 previously chosen by you as a maximum.

The Vytec will give you all the repeat diving benefits of the standard Suunto RGBM (100) program and still get you out of the water in time for lunch.

And if the RGBM is too cautious for your taste, you can opt to use the less-cautious RGBM 50 alternative when you set up the Vytec with your personal preferences before diving.

 The Vytec does everything you would expect from a modern full-function deco-stop computer, but it does something extra, if you are prepared to pay the price.

You can opt to buy a high-pressure sensor/transmitter unit that will plug into your regulator and give you a wireless gas-integrated computer.

This displays tank pressure and remaining air time and (I am told) uses an analogue signal and a particular wavelength which appears never to be blotted out by your body getting in the way, or an underwater flashgun recycling nearby.

It updates tank-pressure information every few seconds, so even if you did lose the signal it would be back before you noticed its absence.

A permanently flashing icon confirms that the wrist unit is getting the message from the transmitter unit.

If you cannot afford this feature initially, you can always upgrade by buying the transmitter unit later. You can change the battery in this yourself, too.

I had been looking forward to spending a few hours of a plane ride figuring out from the instruction manual how to use the Vytec, but I was able to watch a movie instead.

Because it is menu-driven with three push-buttons, it is very easy to understand. In this respect, it scores heavily over the Nitec3.

I had it all sorted with my personal preferences and three chosen nitrox mixes within about five minutes. It remembers what you set for mixes two and three, and after a couple of hours defaults to air-only or mix No 1.

This saves all the embarrassment of having to return to the surface because the unit forgot your chosen mixes in the time between setting them and hitting the water.

Another unique aspect of Suunto computers is that not only do they give you a decompression ceiling through which you should not pass, but they also indicate a decompression floor.

That is the depth at which your off-gassing begins to be faster than your on-gassing, and this proves very useful when you want to use your valuable decompressing time in the shallows, on a reef for example, rather than ascending higher than perhaps is strictly necessary.

The Suunto Vytec represents the ultimate in diving-computer technology achieved by this high-tech Finnish company to date.

Watch out for revolutionary electronic developments from Suunto in the fields of golf, sailing and other sports too.

It costs £390, plus £300 for the optional wireless gas-integration transmitter.
Suunto UK 01420 587272, visit Suunto website

Not necessarily the full monty

I have to spread my favours! When other manufacturers complained that I was seen too often wearing a Mares suit, I got one from Cressi.

Now it’s Oceanic’s turn to get the limelight, and I expect I will get remarks about that too!

The Oceanic Shadow Titanium follows the trend in wetsuit systems that allow you to build up your insulation layer by layer.

You know how difficult it is to choose the right suit to take to a destination that you haven’t visited before.

Some people say: “I was OK with a 3mm shortie”, others insist that nothing short of your thick neoprene drysuit will do.

The Shadow comes as a 5mm one-piece, a 5mm shortie, a hood and interlocking boots. You can wear one part of it, some of it or all of it. The choice is yours.

In keeping with modern wetsuit design, this suit has contoured knees and elbows with high-stretch neoprene in areas at the back of the knees, the underarms and the crotch.

This means that it does not feel so restricting.

There is heavier-duty material at points of wear such as the shoulder pads of the jacket, and there are rubberised knee-pads too.

For extra warmth, the spine pad and kidney areas are of double thickness and the neoprene has a titanium layer both to the inner and outer face to add to its insulation properties.

The construction seems to be of high quality. For example, all the seam joints on the inside are reinforced with 25mm discs. This suit looks unlikely to fall apart too quickly.

A thick suit can feel cold when water flushes through it, but to prevent this, there are seals at the ankles, covered by a zipped seal.

The Shadow hood is designed to integrate fully with the rest of the suit and has a smoothskin seal long enough to mate with the collar and top seals of the one-piece base layer.

A vent at the top lets out any exhaled air gathered by the hood.

I like to have my arms and legs covered when I dive. For bathwater conditions you could use the shortie section on its own, but this is really designed to go over the top of the one-piece for winter Mediterranean-type conditions, giving you the full monty.

In fact, fully dressed with all the options, there is around 15mm of neoprene down your spine.

I felt that I would have been confident enough to use it in the sea around the coast of Britain, provided there was someone standing by with a warm towel when I took it off!

The boots, which have rubber-covered toe-caps, are also designed with ankle seals and these integrate with the ankle seals of the one-piece suit.

In this way Oceanic has almost entirely done away with water flushing through.

I had some reservations about these boots when I first saw them because I felt I would never be able to get my big feet through the small opening

My fears were unfounded, because they proved sufficiently stretchy and became the first zipless boots I have ever worn successfully.

The Shadow suit can be summed up in one word – flexibility. It is both extremely flexible to wear and gives you the flexibility to wear exactly the right amount of insulation for any conditions that you might encounter.

Of course, it’s not a substitute, in British waters, for a good drysuit!

The Oceanic Shadow Titanium suit comes in three pieces in stock sizes, in styles to suit both men and women. It costs £240.

The boots are sold separately and are available in a full range of foot sizes at £27 per pair. The hood alone costs £18.

Oceanic SW 01404 891819, visit Oceanic website