July 1998

Scubapro G500/Mk20UL Ultralight Fragile! Handle with care

The price you pay for the reduced weight of the aluminium regulator below is the risk that the first stage might snap off or corrode. But, John Bantin says, it's nicely finished, and its second stage is a delight to use.
Scubapro G500/Mk20UL Ultralight regulator (£396).
I LOVE sweeping generalisations. They emanate from simple ideas, and keep life uncomplicated. Inevitably, too, they are wrong! Here's one: diaphragm-type regulators perform better than piston designs.
"Most other manufacturers base their test performance on a diaphragm-type regulator. They cannot produce a piston-type regulator to the same spacifications as the Scubapro Mk20 because Scubapro owns many of the patents that make such a regulator great. Scubapro makes both types of regulator, but knows that the performance of the piston far surpasses the diaphragm."
So says Scubapro, and our regulator comparison (Diver March) certainly put the Mk20 in the top league. In fact I am told that it is "more balanced than any of the balanced-piston designs that Scubapro has produced before".
It has five medium-pressure ports on a turret and two high-pressure ports in the main part.
In addition to the normal chrome-plated brass version that suits most divers, Scubapro also makes a lightweight version, the Mk20UL or Ultralight, made entirely of aluminium. This weighs in at only £265 or 380gm, according to whether it is DIN-fitting or A-clamp.
Its surface treatment is said to be very durable, and is bonded to the aluminium in a scratch-resistant finish. Unlike chrome, it is never likely to peel. Polyurethane O-rings are used for internal moving parts. Weight saving is important in the divebag but is irrelevant in the water because the weight saved in the regulator is reflected only in the additional weight to go on the belt.
It is a sad fact that technological advances can be painful for those brave enough to make them, and the Mk20 Ultralight has its problems. Fragility is one. Twice now I have seen a Mk20UL snapped from its A-clamp because of careless handling by deck crews on liveaboards.
If you own one of these lightweight aluminium first stages, avoid leaving it mounted on your tank between dives - look after it.
Another problem seems to be electrolysis. Two friends of mine who bought early examples of Mk20ULs last November took them on a trip to the Galapagos and to the Maldives in March. They are broken-hearted. The electrochemical interaction between the aluminium of the first stage and the different metal of the hoses screwed into them, united in the presence of salt water and tropical heat, has led to serious corrosion. The Mk20UL first stage sent to me by Scubapro is of a later batch. The black outer coating appears to be of a different, thicker material. There are also small washer-like discs between the port plugs and the main body of the regulator that stop over-tightening. I installed these with my direct feed and high-pressure hoses.
The turret is also now enclosed in a plastic cage to prevent the coating getting knocked.
To be doubly sure, I was careful to rinse my example in fresh water after every dive, and to dry it afterwards. I would recommend removing all hoses while storing the regulator for any appreciable time.
Be aware of this problem if offered a cheap secondhand example. You cannot miss the corrosion. The port threads will be pitted and damaged, and any white powder present shows up clearly against the black finish!
The G500 second stage is one of those miniaturised designs made from technopolymer and finished in black. The diaphragm casing is a mere 7cm in diameter, and at less than 700gm is the lightest in Scubapro's range. A balanced - in fact over-balanced - design, it takes care of dropping interstage pressure as the diver inhales. This avoids that whooshy effect of some other high performers, and aims to give you as natural a breathe as possible.
To reduce wear on the soft valve seat, extending its life and performance, the balancing chamber has been designed to reduce the spring tension on the poppet valve assembly when the set is depressurised. When you open the tank valve you can detect a faint click as the valve takes up the slack. In line with most other top-of-the-range regulators, this one has a venturi +/- switch to take care of surface free-flows, and a breathing-resistance adjustment knob if you think it breathes too easily! I like Scubapro's re-usable mouthpiece clip. It saves huntinground for a cable tie every time you change the mouthpiece.
The G500/Mk20 comes fitted with a thermal insulating system that uses silicone sleeves on moving parts such as the piston of the second stage. Dupont's Delrin is used as a coating elsewhere.
The water-balancing chamber of the first stage is coated with Teflon. The idea is that water vapour in exhaled air is unable to settle on these surfaces in the form of condensation and hence form ice. Instead it is passed out through the exhaust tee still as vapour in the exhaust bubbles. The Scubapro G500/Mk20UL is beautifully finished, but then it is one of the most expensive regulators on the market. The quality of the injection-moulding on the one sent for test was first-rate - but again this is an area in which Italians excel.
European-supplied G500/Mk20UL regulators are made in Italy. I wonder whether the American ones (made, I believe, in a factory in Mexico) are as good? I do know they have had a recall because of a slight defect on the moulding of the second stage. If you have an American-supplied example, take it to your dealer. Scubapro UK will get it up to the standard of the European version.
In the water, the little second stage was a delight to use, with minimal jaw fatigue and no intrusion into my vision. It certainly appeared to provide an ease of breathing up there with the best.
In the past I have likened Scubapro regulators to Kalashnikov rifles - simple, reliable and very effective under harsh conditions.
The G500/Mk20 is the Kalashnikov once presented to President Kruschev, an exceedingly highly polished example. And owners must accept that they need to take a little trouble if they want to keep their precious aluminium UL versions in the condition in which they bought them.
The Scubapro G500/Mk20UL costs £396, as opposed to £349 in normal, tough, chrome-plated brass.
  • Scubapro UK 01256 812636
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    Enjay Marine DryDiver 2 BC Good idea, pity about the BC
    It's back to the drawing board for a new drysuit diver's BC. Enjay Marine's minimalist offering might look good on the surface, but under water it's plain irritating.
    Enjay Marine DryDiver 2 BC (£195).
    Sometimes someone comes up with a revolutionary idea. Sometimes it works. The DryDiver 2 is a BC for divers who use only drysuits.
    As you rarely put air in your BC for buoyancy control when using a drysuit, the only real reason for using one is in the event of catastrophic failure of the drysuit's ability to hold air. So the boys at Enjay Marine have come up with a minimalistic item in the DryDiver 2. Dispensing with any frills, it is designed to fold away on itself when not in use by means of generous helpings of Velcro, and to give buoyancy only should you be in dire straits.
    The backpack seems to be a standard item bought in from elsewhere, and the tank is retained by a simple camband threaded through it. The direct-feed inflation hose and over-pressure relief valve are both standard-looking items too, concealed when not in use by being wrapped in the folded bladder of the unit. The BC is fastened at the front by a single buckle on 5cm webbing, also threaded through the backpack.
    Does it work? The problem with buying in items from disparate sources is that while each might be perfect in its own way, they will not necessarily work well together.
    In the water my steel cylinder seemed to be rolling around on my back. An aluminium cylinder proved even worse, and with its own inherent buoyancy felt as if it was suspended by a couple of loose strings.
    The part that rubbed on my neck felt harsh and unforgiving too. In fact under water this BC soon became extremely irritating. The problem appears to stem from both the waistband and camband being allowed to slip at will through the plastic moulding of the backpack.
    Inflation on the surface is probably very effective (and safe) for an unconscious diver with this BC, which reminded me of an old-fashioned Mae West lifejacket. When it was folded out and fully inflated it put masses of buoyancy at the chest.
    This also meant that I could look straight ahead only, because I was blinkered by the two sides of the bladder. Trying it once in this mode was enough!
    Sorry, Enjay Marine, but I found that what was probably a good idea does not come off. And I cannot be accused of not giving this BC enough use. I was seduced by its small volume when I came to packing my bag for a dive trip, and took it away for a week as my only means of keeping a tank on my back.
    By the end of five days I had found the DryDiver 2 distracting enough to resort to hiring a knackered old BC from a dive centre. But there will be someone who likes it! The Enjay Marine DryDiver 2 costs £195.
  • Enjay Marine 01202481286
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    Cressi-sub Master Frog fins Cruising with Master Frog
    Over-length fins (right) are built for speed, but keep them out of your face.
    Cressi-sub Master Frog fins (£65).
    If you have seen pictures of Umberto Pelizzari free-diving to record-breaking depths, you might have noticed on his feet a pair of those massively over-length Gara 2000HF fins favoured throughout the world by serious snorkellers and spearfishermen.
    If you ever went diving with someone who insisted on using the same fins with scuba gear, you would soon get fed up with having them either thrust continually in your face or unavoidably stirring up silt.
    There is, however, something seductive about the light but tough polycarbonate blades and the way they are bonded to the foot-pocket. It is something at which Italian manufacturers seem very good.
    Now Cressi-sub has made available a similar product for scuba divers, with an open-heel design suitable for use with boots, and quick-release straps. The Master Frog is made alongside its scuba sibling the Frog fin, but the name is a little misleading. Where the Frog is a beautifully made but rather heavyweight item, the Master Frog has more in common with the Gara. The polycarbonate blades are lightweight and a more useful length, even though they are 20 per cent longer than other foot-pocket fins such as the Cressi-sub Ara, and about 8cm longer than the blades of the market-leading Mares Plana Avanti Quattro.
    Master Frog blades are inclined well away from the line of the foot-pocket that runs up to and includes the heels, putting the leverage on to the wearer's leg muscles rather than the ankle joints. The supporting side ribs, sole and instep are made from a rigid thermoplastic compound, and the rest from an extremely soft compound that ensures a comfortable and close fit. I found the foot-pocket of the XL version a little on the narrow side for use with the boots of my favourite drysuit, but I should reveal that I am that legendary character occasionally caught on home-movies in the Tennessee backwoods - known as Big Foot to my friends!
    My first attempts to use the Master Frog fins caused me to fear that I might break my legs, but I soon got the hang of them. As when riding a bicycle in high gear, or driving a car in overdrive. I learnt not to expect fast acceleration but to cruise.
    While the long blades did not feel clumsy, they have such a crisp line that if you did inadvertently kick your buddy he might need the resulting wound stitched!
    In sizes S/M, M/L, and L/XL, and in blue, yellow, green and black, Cressi-sub Master Frog fins cost £65.
  • Cressi-sub 01484 310130
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    Markabuoy SMB CO2 marks the spot
    Markabuoy SMB (£34.95).
    MARKABUOY is a seductively packaged SMB and line with its own inflation system provided by a small CO2 cartridge, and it all fits into a nice little pouch.
    When you want to deploy it you simply pull it from its pouch, clip it to your BC and pull the toggle. The CO2 is released into the buoy, which is sent hurtling to the surface while the line is automatically dispensed from the coil within the pouch.
    The buoy is fully enclosed and no pressure-relief valve is needed, because the amount of gas in the cartridge will not over-fill the buoy at the surface pressure. This also means that it will not deflate when it falls over at the surface.
    I have some reservations. First, although I am sure the manufacturer has the best intentions, I would avoid attaching anything like this to my person. Even though the cartridge will give only a measured amount of lift, what happens if the line snags while it is being deployed?
    I preferred to hold the pouch in my hand, so that if the worst came to the worst I could let it go.
    About 33m of line is supplied. The buoy displaces 7kg at the surface and therefore less than 2kg at 30m. I am assured that it would rise from a greater depth with an extra coil of line added, but as the gas in the buoy would be more compressed, it would displace less water and start its journey more slowly.
    I tried the Markabuoy in Stoney Cove. Once the 60cm-long buoy had safely reached the surface and the ascent began, the question arose as to what I should do with the line.
    It proved impossible to rewind it in the way it was supplied. The manufacturer's instructions say you should break off and discard the line you have used and replace an insufficiently long coil with a new one for next time. They also tell you not to discard any unwanted line in the ocean. I suggest you might do a little knitting with it during longer decompression stops.
    The importer, which also sells the MGE reel, recommended me not to use the line supplied but to use an MGE reel and its line instead! Either way, a new CO2 cartridge is needed for the next time.
    The Markabuoy costs £34.95.
  • MGE Sub Aqua 01753571831
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    Appeared in DIVER - July 1998

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