DIVING WET SUIT

A wetsuit is a garment, usually made of foamed neoprene, which is worn by surfers, divers, windsurfers, canoeists, and others engaged in water sports, providing thermal insulation, abrasion resistance and buoyancy. The insulation properties depend on bubbles of gas enclosed within the material, which reduce its ability to conduct heat. The bubbles also give the wetsuit a low density, providing buoyancy in water.

The layer of warm water normally trapped between the suit and the skin provides very little thermal insulation, contrary to popular beliefs regarding wetsuits.

Hugh Bradner, a University of California, Berkeley physicist invented the modern wetsuit in 1951. Wetsuits became available in the mid-1950s and evolved as the relatively fragile foamed neoprene was first backed, and later sandwiched, with thin sheets of tougher material such as nylon or later Lycra/Spandex. Improvements in the way joints in the wetsuit were made by gluing, taping and blindstitching, helped the suit to remain waterproof and reduce flushing, the replacement of water trapped between suit and body by cold water from the outside. Further improvements in the seals at the neck, wrists and ankles produced a suit known as a "semi-dry".

Different types of wetsuit are made for different uses and for different temperatures. Suits range from a thin (2 mm or less) "shortie", covering just the torso, to a full 8 mm semi-dry, usually complemented by neoprene boots, gloves and hood.

Insulation

Still water (without currents or convection) conducts heat away from the body by pure thermal diffusion, approximately 20 to 25 times more efficiently than still air. Water has a thermal conductivity of 0.58 Wm⁻¹K⁻¹ while still air has a thermal conductivity of 0.024 Wm⁻¹K⁻¹, so an unprotected individual can succumb to hypothermia even in warmish water on a warm day. Wetsuits are made of closed-cell, foam neoprene, a synthetic rubber that contains small bubbles of nitrogen gas when made for use as wetsuit material (neoprene as a plastic may be manufactured without foaming, and is made in that fashion for many other applications where insulating qualities are not important). Nitrogen gas (like any gas) has very low thermal conductivity with respect to water or to solids, and the small and enclosed nature of the gas bubbles minimizes heat transport through the gas by gas convection currents (this is the same principle by which air containing cloth fabrics or feathers insulate). Indeed, some modern wetsuits incorporate Merino wool and titanium fibers to add an incompressible layer of gas cells in other ways, while keeping the thickness of the suit to a minimum. The end result of all these techniques is that the fabric layer of trapped gas cavities forces heat to travel slowly by a mostly diffusive process, in a direction that mostly passes through bubbles of entrapped gas, thereby greatly reducing heat transfer from the body (or from the layer of warmed water trapped between the body and the wetsuit) to the colder water surrounding the wetsuit.

Uncompressed foam neoprene has a typical thermal conductivity in the region of 0.054 Wm⁻¹K⁻¹, which produces about twice the heat loss of still air, or one-tenth the loss of water. However at a depth of 15 metres (50 ft) of water, the thickness of the neoprene will be halved and its conductivity will be increased by 50%, allowing heat to be lost at three times the rate at the surface.

A wetsuit must have a snug fit to work efficiently; too loose a fit at water entry and exit points will allow water to escape from between the suit and the body, taking the body's heat with it. Cold water from the outside may enter the same way. Flexible seals at the suit cuffs aid in preventing heat loss in this fashion.

Foamed neoprene is very buoyant, helping swimmers to stay afloat, and for this reason divers need to calculate the need for extra weight based on the thickness of their suit to achieve neutral buoyancy underwater. At the same time, the suit loses buoyancy and thermal protection as the bubbles in the neoprene are compressed at depth.

Semi-dry suits

Semi-dry suits are effectively a thick wetsuit with better-than-usual seals at wrist, neck and ankles. The seals limit the volume of water entering and leaving the suit. The wearer gets wet in a semi-dry suit but the water that enters is soon warmed up and does not leave the suit readily, so the wearer remains warm. The trapped layer of water does not add to the suit's insulating ability. Any residual water circulation past the seals still causes heat loss. But semi-dry suits are cheap and simple compared to dry suits. They are made from thick Neoprene, which provides good thermal protection. They lose buoyancy and thermal protection as the trapped gas bubbles in the Neoprene compress at depth. Semi-dry suits can come in various configurations including a single piece or two pieces, made of 'long johns' and a separate 'jacket'. Semi dry suits do not usually include boots, so a separate pair of insulating boots are worn. They are used typically where the water temperature is between 10 and 20 °C (50 and 68 °F).

Suit creator history

 

 1960s beavertail wetsuit

In 1952, UC Berkeley and subsequent UC San Diego SIO physicist Hugh Bradner, who is considered to be the original inventor and "father of the modern wetsuit," had the insight that a thin layer of trapped water could be tolerated between the suit fabric and the skin, so long as insulation was present in the fabric in the form of trapped bubbles. In this case, the water would quickly reach skin temperature and the air in the fabric would continue to act as the thermal insulation to keep it that way. The suit did not need to be dry to be insulative. Dr. Bradner clearly understood that the gas in the suit fabric provided the thermal insulation, as his letter notes, but in the popular mind, the layer of water between skin and suit has been credited with this task. He initially sent his ideas to Lauriston C. "Larry" Marshall. Marshall was involved in a U.S. Navy/National Research Council Panel on Underwater Swimmers. However, it was Willard Bascom, an engineer at the Scripps Institution of Oceanography in La Jolla, California, who suggested neoprene as a feasible material to Bradner.

However, Bradner and Bascom were not overly interested in profiting from their design and were unable to successfully market a version to the public. They attempted to patent their neoprene wetsuit design, but their application was rejected because the design was viewed as too similar to a flight suit. The United States Navy also turned down Bradner's and Bascom's offer to supply its swimmers and frogmen with the new wetsuits due to concerns that the gas in the neoprene component of the suits might make it easier for naval divers to be detected by underwater sonar. The first written documentation of Bradner's invention was in a letter to Marshall, dated June 21, 1951.

Traditionally, most say it was Jack O'Neill who invented the wetsuit and started using neoprene, a closed-cell foam which was shown to him by his bodysurfing friend, Harry Hind, who knew of it as an insulating material in his laboratory work. After experimenting with the material and finding it superior to other insulating foams, Jack founded the successful wetsuit manufacturing company called O'Neill in a garage in 1952, later relocating to Santa Cruz, California in 1959 with the motto "It's Always Summer on the Inside".

Bob and Bill Meistrell, from Manhattan Beach, California, also started experimenting with neoprene around 1953. They started a company which would later be named Body Glove.

Neoprene was not the only material used in early wetsuits, particularly in Europe. The French-made Pêche-Sport Suit and the UK-made Siebe Gorman Swimsuit were both made out of sponge rubber. The Heinke Dolphin Suit of the same period, also made in England, came in a green male and a white female version, both manufactured from natural rubber lined with stockinet.

Suit design history

 Two scuba divers with steamer wetsuits, with one wearing a hood

Originally, wetsuits were made only with raw sheets of foam-rubber neoprene that did not have any backing material. This type of suit required extra caution while pulling it on because the raw foam-rubber by itself is both fragile and sticky against bare skin. Stretching and pulling excessively easily caused these suits to be torn in half. This was somewhat remedied by thoroughly powdering the suit and the diver's body with talc to help the rubber slide on more easily.

Backing materials first arrived in the form of nylon sheeting applied to one side of the neoprene. This allowed a swimmer to pull on the suit relatively easily since the tough nylon took most of the strain of pulling on the suit, but the suit still had the black sheet rubber exposed on the outside and the nylon was very stiff and rigid, limiting flexibility. A small strip reversed with the rubber against the skin could help provide a sealing surface to keep water out around the neck, wrists, and ankles.

In the early 1960s, the British Dunlop Sports Company brought out its yellow Aquafort neoprene wetsuit, whose high visibility was designed to improve diver safety. However, the line was discontinued after a short while and wetsuits reverted to their black uniformity. The colorful wetsuits seen today first arrived in the 1970s when double-backed neoprene was developed. Now the foam-rubber was sandwiched between two protective fabric outer layers, greatly increasing the tear-resistance of the material. An external layer also meant that decorative colors, logos, and patterns could be made with panels and strips sewn into various shapes. This growth from bare flat black rubber to full color took off in the 1980s with brilliant fluorescent colors common on many suits. The Cornwall based company GUL, started by Dennis Cross in 1962 is best known for its use of these fluorescent colours in Europe.

Suit assembly history

 

 

A modern steamer with "superflex" properties

The first suits used traditional sewing methods to simply overlap two strips of rubber and sew them together. In a rubber wetsuit this does not work well for a number of reasons, the main one being that punching holes straight through both layers of foam for the thread opens up passages for water to flow in and out of the suit. The second problem is that the stretching of the foam tended to enlarge the needle holes when the suit was worn. This meant that a wetsuit could be very cold all along the seams of the suit. And although the sewn edge did hold the two pieces together, it could also act as a perforated tear edge, making the suit easier to tear along the seams when putting it on and taking it off.

When nylon-backed neoprene appeared, the problem of the needle weakening the foam was solved, but still the needle holes leaked water along the seams.

Seam taping

To deal with all these early sewing problems, taping of seams was developed. The tape is a strong nylon cloth with a very thin but solid waterproof rubber backing. The tape is applied across the seam and bonded either with a chemical solvent or with a hot rolling heat-sealer to melt the tape into the neoprene.

With this technology, the suit could be sewn and then taped, and the tape would cover the sewing holes as well as providing some extra strength to prevent tearing along the needle holes.

When colorful double-backed designer suits started appearing, taping moved primarily to the inside of the suit because the tape was usually very wide, jagged, black, and ugly, and was hidden within the suit and out of sight.

Many 1960's and 1970s wetsuits were black with visible yellow seam taping. The yellow made the divers more easily seen in dark low-visibility water. To avoid this problem O'Neill fabricators developed a seam-tape which combined a thin nylon layer with a polyester hemming tape. Applied over the interior of the glued & sewn seam, then anneal bonded with a hand held teflon heating iron produced a seam that was both securely sealed and much stronger.

Seam gluing

Another alternative to sewing was to glue the edges of the suit together. This created a smooth, flat surface that did not necessarily need taping, but unfortunately raw foam glued to foam is not a strong bond and still prone to tearing.

Most early wetsuits were fabricated completely by hand, which could lead to sizing errors in the cutting of the foam sheeting. If the cut edges did not align correctly or the gluing was not done well, there might still be water leakage along the seam.

Initially suits could be found as being sewn only, glued only, taped only, then also sewn and taped, or glued and taped, or perhaps all three.

Blindstitch revolution

Sometime after nylon-backed neoprene appeared, the blind stitch method was developed. A blindstitch sewing machine uses a very unusual curved needle, which is designed to not go all the way through the neoprene but just shallowly dip in behind the fabric backing.

The curved needle allows the fabric backing to be sewn together without punching a hole completely through the neoprene, and thereby eliminating the water-leakage holes along the seam. Blindstitch seams also lay flat, butting up the edge of one sheet against another, allowing the material to lay flatter and closer to the skin. For these reasons blindstitching rapidly became the primary method of sewing wetsuits together, with other methods now used mainly for decorative or stylistic purposes.

Further advances in suit design

 

 Woman wearing mid-1970s O'Neill Sealsuit

Highly elastic fabrics such as Lycra/Spandex have mostly replaced raw nylon backing, since the nylon by itself cannot be stretched and makes the neoprene very stiff. Incorporating Lycra into the backing permits a large amount of stretching that does not damage the suit, and allowed suits to become closer fitting.

After the development of double-backed neoprene, singled-backed neoprene still had its uses for various specific purposes. For example a thin strip of single-backed wrapped around the leg, neck, and wrist openings of the suit creates a sticky rubber seal that greatly reduces the flushing of water in and out of the suit as the person's body moves. But since the strip is very narrow, it does not drag on the skin of the wearer and thus makes the suit easy to put on and remove.

As wetsuit manufacturers continued to design suits, they found ways that the materials could be further optimized and customized. The O'Neill Animal Skin created in 1974 by then Director of Marketing, E.J. Armstrong, was one of the first designs combining a turtle-neck based on the popular Sealsuit with a flexible lightweight YKK horizontal zipper across the back shoulders similar in concept to the inflatable watertight Supersuit ( developed by Jack O'Neill in the late 1960s ). The Animal Skin eventually evolved molded rubber patterns bonded onto the exterior of the neoprene sheeting ( a technique E.J. Armstrong perfected for application of the moulded raised rubber Supersuit logo to replace the standard flat decals ). This has been carried on as stylized reinforcing pads of rubber on the knees and elbows to protect the suit from wear, and allows logos to be directly bonded onto raw sheet rubber. Additionally, the Animal Skin's looser fit allowed for the use of a supplemental vest in extreme conditions.

In recent years, manufacturers have experimented by combining various materials with neoprene to lend additional warmth or flexibility to their suits. These include, but are not limited to, Spandex, and wool.

Precision computer-controlled cutting and assembly methods, such as water-jet cutting, have allowed ever greater levels of seam precision, permitting designers to use many small individual strips of different colors while still keeping the suit free of bulging and ripples from improper cutting and sewing.

Return of single-backed neoprene

 

 Two surfers in steamer wetsuits

As wetsuits continued to evolve, their use was explored in other sports such as open-water swimming and triathlons. Although double-backed neoprene is strong, the cloth backing is rough and creates a large amount of drag in the water, slowing down the swimmer. A single-backed suit meanwhile has a very smooth, slick exterior permitting water to slide easily over the bare neoprene. With the advances of elastic Lycra backings and blindstitching, single-backed neoprene suits could now be made that outperformed the early cousins from the 1970s. Other developments in single-backed wetsuits include the suits designed for free-diving and spearfishing. Single lined neoprene is more flexible than double lined. To achieve flexibility and low bulk for a given warmth of suit, they are unlined inside, and the smooth surface of the neoprene is removed mechanically to reveal a rougher "open cell" surface which adheres closely to the skin and reduces flushing of the suit. The lined outer surface may be printed with camouflage patterns for spearfishing.

Some triathlon wetsuits go further, and use rubber-molding and texturing methods to roughen up the surface of the suit on the forearms, to increase forward drag and help pull the swimmer forwards through the water. Extremely thin 1 mm neoprene is also often used in the under-arm area, to decrease stretch resistance and reduce strain on the swimmer when they extend their arms out over their head.

Wetsuits used for caving are often single-backed with a textured surface known as "sharkskin" which is a thin layer where the neoprene is less expanded. This makes it more abrasion resistant for squeezing between rocks and doesn't get torn in the way that fabric does.

Types

  

 A shorty wetsuit

Wetsuits come in different thicknesses depending on the conditions for which it is intended. The thicker the suit, the warmer it will keep the wearer. Because wetsuits offer significant protection from jellyfish, coral, sunburn and other hazards, many divers opt to wear a thin suit which provides minimal insulation (often called a "bodysuit") even when the water is warm enough to comfortably forego insulating garments. A thick suit is stiff, so mobility is restricted; at a certain thickness the suit would become impractical, which is why drysuits must be worn in particularly cold environments. A wetsuit is normally described in terms of its thickness. For instance, a wetsuit with a torso thickness of 5 mm and a limb thickness of 3 mm will be described as a "5/3". With new technologies the neoprene is getting more flexible. Modern 4/3 wetsuits, for instance, may feel as flexible as a 3/2 of only a few years ago. Some suits have extra layers added for key areas such as the lower back.

Different shapes of wetsuit are available, in order of coverage:

• A sleeveless vest, covering only the torso, provides minimal coverage. Some include an attached hood. These are not intended to be worn alone, but rather as an extra layer over or under a longer wetsuit.
• A jacket covers the torso and arms, with little to no coverage for the legs. Some jackets have short leg sleeves like a shorty, others feature leg holes similar to a woman's swimsuit. A third style, the beavertail or bodysuit, which was quite popular until the 1980s, had a flap which closed over the crotch and attached at the front with a fastener. It was worn with (over) or without a long john.
• A shorty or spring suit covers the torso and has short sleeves and long or short legs.
• A long john, johnny, johnny suit, or farmer john/jane (depending on the gender the suit is designed for) covers the torso and legs only; it resembles a bib overall, hence the nickname.
• A full suit or steamer covers the torso and the full length of the arms and legs.

Some suits are arranged in two parts; the jacket and long johns can be worn separately in mild conditions or worn together to provide two layers of insulation around the torso in cold conditions. Typically, two-piece cold water wetsuits have 10 to 14 mm of material around the torso and 5 to 7 mm for the extremities.

Wetsuits that fit too tightly can cause difficulty breathing or even acute cardiac failure so a proper fit is important.

A specialized kind of wetsuit, with a very smooth (and somewhat delicate) outer surface is used for long distance swimming and triathlon. These are designed to maximize the mobility of the limbs while providing both warmth and buoyancy.

Heated wetsuits are also being tested and will soon be available on the market. These suits have special heating panels integrated in the back of the wetsuit. The power for heating comes from batteries also integrated into the wetsuit.

Smaller wetsuits are even made for children in many sizes, types, and thicknesses.

Accessories

  

 Neoprene wetsuit gloves

 Wetsuit boots

Accessories to the basic suit include gloves, boots and hoods, for additional insulation and environmental protection, pockets for holding small items and equipment, and knee-pads, to protect the knee area from abrasion and tearing, usually used by working divers.

Usually a wetsuit has no covering for the feet or head, and the diver must wear separate neoprene booties and hood.

Using hoods: in the thermal balance of the human body, the heat loss over the head is at least 20% of the whole balance. Thus, for the sake of thermal protection of the diver, wearing a well-fitting hood is good practice, even at fairly moderate water temperatures. Hoods have been reported to cause claustrophobia in a minority of users, sometimes due to poor fit.

Controversy

In open water swimming events the use of wetsuits is controversial, with many participants believing that wetsuits are being worn for competitive advantage (by increasing their buoyancy and hydrodynamic curve), and not just for warmth.

Unlike triathlons, which allow swimmers to wear wetsuits when the water is below a certain temperature (the standard is 78 °F (26 °C) at the surface or up to 84 °F (29 °C) for unofficial events.), most open water swim races either don't allow the use of wetsuits (usually defined as anything covering the body above the waist or below the knees), or put wetsuit-clad swimmers in a separate category and/or make them ineligible for race awards. This differs in locales and times of the year, where water temperatures are substantially below comfortable.

Source :

http://en.wikipedia.org/wiki/Wet_suit