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Drysuits

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Drysuits

Thu, 13/10/2011 - 23:23
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All the questions about drysuits you always wanted to know the answer to but never dared to ask: Why dive drysuits? Neoprene or membrane type? Purchasing a suit. Zippers and care. Getting the Bouyancy right. Diving the suits. Special training and tips.

Factfile

Why you should stay warm

The recent rise in popularity of technical diving with mixed gasses, rebreathers and advances in computer technologies have enabled us to vastly increase the time we can remain underwater.

Consequently, the requirements for thermal protection are higher than ever. If the protection is insufficient, our bodies will react by increasing metabolism to compensate for the loss of body heat. This in turn increases our breathing rate and gas consumption, sometimes depleting our supplies prematurely and forcing us to finish a dive early. Being cold also increases the risk of decompression illness. In the beginning of dive, when the body is still warm, the tissues saturate with nitrogen relatively fast. But once the tissues have cooled, the off-gassing occurs much more slowly.

Most people can do one dive and stay comfortable, but, the second or third dive of a day is when heat loss becomes very noticeable. Even in the tropics, after a week of heavy vacation diving, many people start getting chilled during the last few days.

Also, water temperature in many dive areas can change up to ten degrees or more between winter and summer, so this factor must also be considered when choosing a dive suit. ■

 

Not that I mind diving in wetsuits, which I often have to do whenever I go traveling with a limited luggage allowance, and I gladly admit that diving in wetsuits does tend to give you a more real experience of being in the wet element, whereas a drysuit does tend to isolate you, which, by the way, also has its advantages. Some would even say that this is the very point of using drysuits. My point is, aside from the range of obvious technical advantages over wetsuits, there is this unique feeling of diving the suit, almost as in driving a car and becoming one with it through the seat of your pants.

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Diving the suit

Diving the suit

My drysuit is a vehicle too. It can be finely controlled and maneuvered to the point where I can ultimately come to rest and relax totally outstretched as if I was lying on a mattress. I have, in fact, often amused myself by the thought that the suit was like a waterbed that was just wrapped around you. It is all about comfort.

Being comfortable may mean a lot of things and most of them applies to diving drysuits. It is about protection from the environment, thermal protection first of all, but also against abrasion from sharp rocks, jagged wrecks, spiky sea creatures. And it is about taking as much of the strain out of the dive as possible, making it a pleasurable excursion or exploration into the underwater realm.

As for the thermal protection, there is a lot to be said. As most are well aware, unlike wetsuits, which are almost solely manufactured in neoprene, drysuits comes in two main types (with some overlaps and cross breeds):  Neoprene and membrane suits (such as tri-laminate, rubber or nylon). Membrane suits are sometimes also called shell suits. The main difference being that neoprene provides thermal insulation in itself whereas membrane suits require an undergarment worn underneath for thermal protection.

Entry level training taught us that the body loses heat 20 times more quickly in water than in air. This makes proper thermal protection priority-one in a good suit. Not only do we want to have a good time down below being cozy rather than cold and miserable, but once we get cooled off, our air consumption also goes up, risk of DCS increases, not to mention, dedicated hypothermia is dangerous and ultimately fatal. In all types of drysuits, air plays the dual role of both providing thermal protection and buoyancy, and fulfilling these two requirements simultaneously is the key.

 

I am a confessed drysuit nuttie. I prefer my drysuit anytime, even on a hot summer day where I, while kitting up, will subject myself to bystander’s snide comments about my apparent lack of Viking genes and tolerance to the elements. Not that I mind diving in wetsuits, which I often have to do whenever I go traveling with a limited luggage allowance, and I gladly admit that diving in wetsuits does tend to give you a more real experience of being in the wet element, whereas a drysuit does tend to isolate you, which, by the way, also has its advantages.

Some would even say that this is the very point of using drysuits. My point is, aside from the range of obvious technical advantages over wetsuits, there is this unique feeling of diving the suit, almost as in driving a car and becoming one with it through the seat of your pants.  

Diving the suit

My drysuit is a vehicle too. It can be finely controlled and maneuvered to the point where I can ultimately come to rest and relax totally outstretched as if I was lying on a mattress. I have, in fact, often amused myself by the thought that the suit was like a waterbed that was just wrapped around you. It is all about comfort.

Being comfortable may mean a lot of things and most of them applies to diving drysuits. It is about protection from the environment, thermal protection first of all, but also against abrasion from sharp rocks, jagged wrecks, spiky sea creatures. And it is about taking as much of the strain out of the dive as possible, making it a pleasurable excursion or exploration into the underwater realm.

As for the thermal protection, there is a lot to be said. As most are well aware, unlike wetsuits, which are almost solely manufactured in neoprene, drysuits comes in two main types (with some overlaps and cross breeds):  Neoprene and membrane suits (such as tri-laminate, rubber or nylon). Membrane suits are sometimes also called shell suits. The main difference being that neoprene provides thermal insulation in itself whereas membrane suits require an undergarment worn underneath for thermal protection.

Entry level training taught us that the body loses heat 20 times more quickly in water than in air. This makes proper thermal protection priority-one in a good suit. Not only do we want to have a good time down below being cozy rather than cold and miserable, but once we get cooled off, our air consumption also goes up, risk of DCS increases, not to mention, dedicated hypothermia is dangerous and ultimately fatal. In all types of drysuits, air plays the dual role of both providing thermal protection and buoyancy, and fulfilling these two requirements simultaneously is the key.

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Which suit

Neoprene or membrane?

This is a matter of a probably never ending dispute. Not quite as bad as a religious quarrel but the two camps each have their outspoken proponents. Speaking in very general terms, neoprene suits are generally more hydrodynamic due to their smoother surface, and as neoprene allows for some stretch the movement of joints, are less restricting. The downside is that neoprene drysuits compresses with depth, just like wetsuits, whereby they suffer from a loss of both buoyancy and thermal protection exactly there where you need it most. As the suit’s buoyancy changes with depth, it also calls for slightly more precision in controlling the buoyancy at any stage. Finally, neoprene suits are generally viewed as requiring more weights than membrane suits, but ultimately, this depends on the undergarment used.

Membrane suits, on the other hand, don’t compress. They are light-weight and easy to enter, but do require additional protective underwear, for example, Thinsulate underwear from 100 up to 400 gram or some of the special garments advertised on these pages. 

Membrane suits generally require less lead, but the amount of needed weights will also depend on the choice of undergarment. Another and less important consideration is that membrane suits tend to be baggier and have a wrinklier appearance causing more drag, which however, to be fair, I haven’t been able to really notice. Also, the membrane material doesn’t stretch, which, depending on the design and ‘tailor cut’ of the suit, can limit movement in some directions, for example, if you try to reach out for a tank valve behind your head (a maneuver you should be able to execute in technical diving).

Finally, there are some high-end hybrid models aimed at combining the best of both worlds. Foremost and best known of these models are suits made out of compressed neoprene, a special neoprene in which the characteristic air bubbles have been compressed or ‘collapsed’.  This produces a much thinner, yet flexible material, but obviously also far less insulating, for which reason an undergarment is necessary for thermal protection. These suits are generally more expensive. We have also seen suits lately where a thin metalfoil that reflects body heat are incorporated into the fabric.

 

Choice of material is ultimately down to personal preference and the type of diving you want to do - and perhaps also the size of your wallet

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Neck seal

Seals & Hoods

Air is kept inside the suit by seals or cuffs at the wrists and either a neck seal or a hood with face seal. It is inflated through the inlet valve and deflated through an exhaust valve or by air escaping out under the cuffs. The amount of air in the suit is thus variable. How much will always be a compromise. Put more air in and the insulation improves but this also makes the suit more buoyant, calling for the addition of more weights to maintain overall neutral buoyancy.  Conversely, if you can do away with less air in the suit—i.e. by using high quality undergarments—you can save on weights. As compared to diving with wetsuits, most will need at least 5kg extra weight for starters.

However, the extra air and the added weight also calls for better buoyancy skills. A drysuit is less forgiving and requires more compensation than a BCD once you start to sink or ascend... more on that on page 74.

Neoprene suits require more weights than membrane suits to compensate for their relatively higher buoyancy at the surface. But as they compress with depth and lose buoyancy this has to be offset by adding extra air. Therefore the air pressure inside a neoprene suit will often be slightly higher. This puts a stronger pressure upon neck and wrist seals.  These seals can be made of either latex or neoprene.

Neoprene seals have to have the outermost 1-2 cm folded inwards like an inverted turtle neck collar and tucked down along the skin to provide a tighter seal.

When air tries to get out of the sleeve, it gets trapped under this fold and presses the folded-down flap against the skin.  It is not always necessary to fold down latex seals as this material is more elastic than neoprene but many do anyway.  A word of caution however, a neck seal should hold tight but not be so tight that it restricts the blood flow in the veins leading to the head nor should it be pressing on the vagus nerve. This can lead to increased blood pressure in the head, causing headaches and perhaps even unconsciousness. This can be avoided by using an isolating latex hood, which seals around the face. This latter option is more often seen with commercial divers who have to work for many hours under water, while recreational divers seem to favour the neck seal with either a fixed or separate hood.

 

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Drysuit zipper

 

Zippers - Configurations & Care

The zipper is the most expensive feature on a dry suit. It requires both protection, careful handling and maintenance. But with proper care the zipper could outlast the suit.

How exposed the zipper is to wear and tear, grit and dirt depends on the design of the suit and whether it is protected under some flap or cover. The zipper needs to be kept clean and lubricated to ensure that it doesn’t jam and damage itself and remains watertight. It should open and close smoothly.  

Keeping the zipper clean may include rinsing the zipper off after the dive before unzipping. Divers who dive off beaches may get sand grains deposited as they scramble ashore, which must be rinsed off or swept off before the buddy opens the zipper.  An old toothbrush may also come in hand to clean out dirt and salt crystals from between the zipper teeth.

Lubrication

It is also important to keep the zipper well lubricated. Wax or liquid are the main choices. Silicone should never be used as it causes problems with glue used in repairs. Some manufacturers recommend sticking with the wax only. In any case, follow their recommendations – otherwise you might void the warranty. Liquid does seem to seep better into the corners, but it may also attract and trap dirt particles.

Some manuals also state that only the outside teeth should be lubricated. Lubricating the zipper, once for each diving day, should suffice. But once it feels tight to open and close, it’s time for another lubrication or cleaning. Apply the correct lubricant, open and close the zipper twice, then store the suit with the zipper open ready for the next use.

 

 

Dry gloves

Dry Gloves

The head, neck, hands and legs can be responsible for up to 70 % of the loss of total body heat.

Dry glove systems should be considered when diving in water temperatures below 12°C to minimize the risk of non-freezing cold injures.  Inside the membrane, you wear gloves of wool or Thinsulate. There are two main types—with or without a coupling.

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