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March 24, 2009

Getting started with dry suits

After shivering through four 50-degree water dives in my 7mm wetsuit, I seriously began contemplating a dry suit. On the dive boat I’d been watching the divers in our group who wore dry suits smiling and being comfortable whereas the wetsuit contingent was grimacing and trying to warm up with steaming cups of hot chocolate or bowls of minestrone soup. I’d missed two dives because I simply had been too cold. Dry suits are expensive, but so is missing dives on expensive dive trips. My missed trips probably would have made a nice down-payment on a dry suit.

What are dry suits? They are the kinds of protection divers wear in cold water, 50 degrees and below (and as far as I am concerned, make that 60 and below). As the name implies, a dry suit stays dry inside and allows no water in, and that is its primary purpose. The staying warm part comes from wearing undergarments that trap an insulating layer of air. Dry suits are made of high tech components and materials, essentially technology that emanated from the space program, with some bicycle tire technology thrown in. Using a dry suit is significantly more complicated than a wet suit, and there are things that can go wrong. This is why there are special classes for dry suit diving and certification. And expect to pay quite a bit more for a dry suit than a wet suit.

Unlike wet suits that come in various configurations, almost all dry suits are full body suits, including integrated boots. They are totally sealed, and have special waterproof zippers. The seals around your wrists and neck are made of latex or neoprene, with large contact areas to provide the best possible seal. Latex seals are thinner and seal better, but they are easier to rip and some people are allergic to latex. Neoprene seals wear better, but are thicker and need to be stretched to fit. Seals are usually the first thing to break on a dry suit. They can be replaced, and some dry suits even have seals that can be zipped on and thus replaced.

As stated, the insulation provided by a dry suit comes from the air inside the dry suit. Air is a much better insulator than water, but unlike the water layer inside a wetsuit, the air inside a dry suit compresses and expands, which means the dry suit needs an air valve that allows for inflation from a low-pressure supply from the air tank. The valve is usually located on the chest. That way, the divers can add more air as they descend. There is also an exhaust valve, or “dump” valve to purge expanding air during ascent. Controlling the air inside a dry suit requires training and experience. You don’t want for all that buoyant air inside your dry suit to end up in your legs and you ascending feet first.

Dry suits can be made of a variety of different materials. Generally, they are foam neoprene, compressed and crushed foam , or membrane coated materials. Foam neoprene is the same kind of material that’s used in wet suits, which means dry suits made of it provide a bit of insulation in addition to that provided by the air layer, but their buoyancy varies with depth. Compressed and crushed neoprene dry suits use special kinds of neoprene material that has been specially prepared to strengthen the material, bonding and stitching. Membrane, or “shell,” dry suits use a waterproof coating over the fabric. The coating is usually urethane or a laminate of rubber and some tough synthetic material. They are lighter and more flexible than neoprene suits, but provide almost no insulation by themselves and have no positive buoyancy. The materials used do not stretch and are generally more loose-fitting, which makes it easier for air to move around and potentially get trapped where it shouldn't be.

It so happened that Carol had a dry suit whose arms and legs had always been too long for her, and so she suggested I try that on. I put on the thick, full-body thermal underwear first. The membrane suit itself had its waterproof zipper across the chest. I stepped into it and got my feet into the integrated boots. I then made my left hand as small as possible and squeezed it through its seal, using the fingers of my right hand to carefully stretch the seal. Same for the right hand. Then I gently used the fingers of both of my hands to grab and evenly stretch out the head seal so I could get my head through the latex seal. Carol then carefully closed the waterproof chest seal. I was now wearing a dry suit.

I had always wondered how the watertight seals worked and whether they’d feel uncomfortable and constricting around the neck. The initial answer was, “some,” but actually almost less than the neck cutout of a thick 7mm wetsuit.

I was now sealed inside the dry suit, together with a good bunch of air. Carol showed me how to hug myself with one arm, use the hand of the other to reach inside the neck seal and provide a path for air to escape, then kneel down to push out most of the air. Remove the hand so that the airtight seal re-forms, get up, and tighten the sash around your waste.

I looked in the mirror and what I saw was very different from the sleek, form-fitting look of a neoprene wetsuit. Instead, the dry suit wrinkles and crinkles and doesn’t look very elegant at all. This one had another interesting touch in that it was half black and half hot, screaming pink.

So now it was time to see how the suit worked in the water, and for that I used the pool. I got in up to my thighs and instantly felt the weight of the water compact the suit around my feet and legs. There were very small bubbles emanating from the left knee and some from the right, which Carol felt was probably air trapped underneath an outer double layer of material. I then stepped fully into the shallow end and, for the first time, experienced the weird “grab” of a dry suit as you enter water. The suit tightens around you in a weird way. Imagine one of those vacuum freezer bags where you use a machine to suck the air out of the bag so it fits tightly around the meat to be frozen. It’s an interesting and not unpleasant feeling.

I donned my fins, a dry suit hood, gloves and my mask and snorkel and began snorkeling around the pool, which was at about 58 degrees. I felt warm and, of course, dry. Water still got into my gloves, of course, but the dry suit hood almost made it feel like my head was fully protected as well. Despite having let out more air through the neck seal, I was hugely positively buoyant and couldn’t even get down to the bottom of the pool to retrieve the thermometer that had rolled down to the deepest point.

I played around for perhaps half an hour, getting used to the feeling, then got out. I still felt warm and cozy, though by now my feet were a bit cold and I wondered if my butt had gotten wet. I opened the suit and we began testing everything for dryness. All dry, including butt, but my left sock was definitely wet, and the right one a bit as well. The bottom of the thermal underwear, however, was dry, right down to the ankles. So there’s a bit of leakage in the boot region somewhere.

That was that for the day. I’d finally had my first taste of how a dry suit feels. Next we’ll hook up an inflator hose to the chest valve and try the suit with the BC and a tank.

Posted by conradb212 at March 24, 2009 05:29 AM