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143-519: A wetsuit is a garment worn to provide thermal protection while wet. It is usually made of foamed neoprene , and is worn by surfers , divers , windsurfers , canoeists , and others engaged in water sports and other activities in or on the water. Its purpose is to provide thermal insulation and protection from abrasion , ultraviolet exposure, and stings from marine organisms. It also contributes extra buoyancy . The insulation properties of neoprene foam depend mainly on bubbles of gas enclosed within

286-439: A jocking strap and the harness weights provide the ballast. The traditional copper helmet and corselet were generally weighted by suspending a large weight from support points on the front and back of the corselet, and the diver often also wore weighted boots to assist in remaining upright. The US Navy Mk V standard diving system used a heavy weighted belt buckled around the waist, suspended by shoulder straps which crossed over

429-416: A toxic hazard to users and environment, but little evidence of significant risk. Diver weighting systems have two functions; ballast, and trim adjustment. The primary function of diving weights is as ballast, to prevent the diver from floating at times when he or she wishes to remain at depth. In free diving (breathhold) the weight system is almost exclusively a weight belt with quick release buckle, as

572-402: A "bodysuit" or dive skins ) even when the water is warm enough to comfortably forego insulating garments. A thick suit will restrict mobility, and as the thickness is increased the suit may become impractical, depending on the application. This is one reason why dry suits may be preferable for some applications. A wetsuit is normally specified in terms of its thickness and style. For instance,

715-490: A 7 mm neoprene wet suit offers much less exposure protection under 100 feet of water than at the surface. A recent advance in neoprene for wet suits is the "super-flex" variety, which uses spandex in the knit liner fabric for greater flexibility and stretch. A drysuit is similar to a wetsuit, but uses thicker and more durable neoprene to create an entirely waterproof suit that is suitable for wear in extremely cold water or polluted water. Recently, neoprene has become

858-423: A base for adhesives , noise isolation in power transformer installations, and as padding in external metal cases to protect the contents while allowing a snug fit. It resists burning better than exclusively hydrocarbon based rubbers, resulting in its appearance in weather stripping for fire doors and in combat related attire such as gloves and face masks. Because of its tolerance of extreme conditions, neoprene

1001-428: A belt around the waist holding pouches for the weights, with shoulder straps for extra support and security. Often a velcro flap holds the weights in place. They have handles, which must be pulled to drop the weights in an emergency or to remove the weights when exiting the water. A weight harness allows the weights to be comfortably carried lower on the body than a weight belt, which must be high enough to be supported by

1144-399: A curved needle, which does not go all the way through the neoprene but just shallowly dips in behind the fabric backing, crosses the glue line, and emerges from the surface on the same side of the neoprene. This is similar to the overlock stitching used for teeshirts and other garments made from knitted fabrics. The curved needle allows the fabric backing to be sewn together without punching

1287-598: A favorite material for lifestyle and other home accessories including laptop sleeves, tablet holders, remote controls , mouse pads , and cycling chamois. The Rhodes piano used hammer tips made of neoprene in its electric pianos, after changing from felt hammers around 1970. Neoprene is also used for speaker cones and drum practice pads. Hydroponic and aerated gardening systems make use of small neoprene inserts to hold plants in place while propagating cuttings or using net cups. Inserts are relatively small, ranging in size from 1.5 to 5 inches (4 to 13 cm). Neoprene

1430-527: A higher percentage of gas bubbles, and are comfortable and provide effective insulation at or near the surface where they retain much of their thickness. Areas that are significantly stretched lose thickness even before they are compressed at depth, which also reduces the insulation, and long periods under pressure and repeated compression and decompression of the neoprene foam will eventually lead to loss of volume, insulation, buoyancy and flexibility. Some bubbles will also rupture under stress and lose their gas, and

1573-545: 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 stitching methods now used mainly for decorative or stylistic purposes. Highly elastic fabrics such as spandex (also known as lycra) have mostly replaced plain nylon backing, since

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1716-435: A large amount of drag in the water, slowing down the swimmer. A single-backed suit has a smoother exterior surface which causes less drag . With the advances of elastic Lycra backings and blindstitching, single-backed neoprene suits could be made that outperformed the early versions from the 1970s. Other developments in single-backed wetsuits include the suits designed for free-diving and spearfishing . Single lined neoprene

1859-405: A large lever arm for a small amount of weight and are very effective at correcting head-down trim problems, but the addition of mass to the feet increases the work of propulsion significantly. This may not be noticed on a relaxed dive, where there is no need to swim far or fast, but if there is an emergency and the diver needs to swim hard, ankle weights will be a significant handicap, particularly if

2002-797: A lecture by Fr Julius Arthur Nieuwland , a professor of chemistry at the University of Notre Dame . Nieuwland's research was focused on acetylene chemistry and during the course of his work he produced divinyl acetylene, a jelly that firms into an elastic compound similar to rubber when passed over sulfur dichloride . After DuPont purchased the patent rights from the university, Wallace Carothers of DuPont took over commercial development of Nieuwland's discovery in collaboration with Nieuwland himself and DuPont chemists Arnold Collins , Ira Williams and James Kirby. Collins focused on monovinyl acetylene and allowed it to react with hydrogen chloride gas, manufacturing chloroprene . DuPont first marketed

2145-539: A lesser extent, wind chill. Wetsuits are used for thermal insulation for activities where the user is likely to be immersed in water, or frequently doused with heavy spray, often approaching from near-horizontal directions, where normal wet-weather clothing is unlikely to keep the water out. Activities include underwater diving , sailing , sea rescue operations, surfing , river rafting , whitewater kayaking and in some circumstances, endurance swimming. Still water (without currents or convection ) conducts heat away from

2288-411: A loose fit allows considerable flushing which reduces effectiveness of insulation, so a proper fit is important. The quality of fit is most important for diving as this is where the thickest suits are used and the heat loss is potentially greatest. A diving wetsuit should touch the skin over as much of the body that it covers as comfortably possible, both when the wearer is relaxed and when exercising. This

2431-580: A marketing strategy that included publishing its own technical journal, which extensively publicized neoprene's uses as well as advertising other companies' neoprene-based products. By 1939, sales of neoprene were generating profits over $ 300,000 for the company (equivalent to $ 6,600,000 in 2023). The high tensile performance of neoprene is a result of its highly regular backbone structure, which causes neoprene to undergo strain crystallization under tensile loading. A two parameter (strain rate and temperature) hyperelastic model can accurately capture much of

2574-438: A neoprene- spandex mixture for manufacture of wheelchair positioning harnesses. In tabletop wargames, neoprene mats printed with grassy, sandy, icy, or other natural features have become popular gaming surfaces. They are durable, firm and stable, and attractive in appearance, and also favoured for their ability to roll up in storage but lie flat when unrolled. Because of its chemical resistance and overall durability, neoprene

2717-475: A plush type liner to reduce water flow. Merino wool liner fabrics have also been used. Fabric lined on one side only is more flexible than double lined. After slicing the foam slab down to the required thickness, a layer of glue is applied and the chosen lining is pressed down by the lamination rollers. A more flexible lining is chosen for most applications. Neoprene foam is also available with kevlar reinforced fabric facing for high cut and abrasion resistance. This

2860-416: A problem. Weight belts are the most common weighting system currently in use for recreational diving . Weight belts are often made of tough nylon webbing, but other materials such as rubber can be used. Weight belts for scuba and breathhold diving are generally fitted with a quick release buckle to allow the dumping of weight rapidly in an emergency. A belt made of rubber with traditional pin buckle

3003-409: A relaxed lungful of air is close to neutral buoyancy. If the air is exhaled, most people will sink in fresh water, and with full lungs, most will float in seawater. The amount of weight required to provide neutral buoyancy to the naked diver is usually trivial, though there are some people who require several kilograms of weight to become neutral in seawater due to low average density and large size. This

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3146-421: 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

3289-585: A seal with a small length of smooth surface against the skin and slightly greater contact pressure. This type of seal can also be used on neoprene dry suits as it is sufficiently watertight when properly designed. In the early 1970s Gul Wetsuits pioneered the one-piece wetsuit named the 'steamer' because of the visible condensed water vapour given off from the suit when taken off, allowing heat and water held inside to escape. One-piece wetsuits are still sometimes referred to as 'steamers'. As wetsuit manufacturers continued to develop suit designs, they found ways that

3432-450: A separate weight belt: a typical capacity is 6 kg per pocket, with two pockets available. This may not be sufficient to counteract the buoyancy of dry suits with thick undergarments used in cold water. Some BCD harness systems include a crotch strap to prevent the BCD from sliding up the wearer when inflated, or down when inverted, due to the weights. A weight harness usually consists of

3575-399: A somewhat more controlled emergency ascent. The weights are generally made of lead because of its high density , reasonably low cost, ease of casting into suitable shapes, and resistance to corrosion . The lead can be cast in blocks, cast shapes with slots for straps, or shaped as pellets known as " shot " and carried in bags. There is some concern that lead diving weights may constitute

3718-439: A suitable harness or integrated weight pocket buoyancy compensator which actually allows the weights to be placed correctly, so there is no need for longitudinal trim correction. A less common problem is found when rebreathers have a counterlung towards the top of the torso. In this case there may be a need to attach weights near the counterlung. This is usually not a problem, and weight pockets for this purpose are often built into

3861-479: A thin 2mm or less "shortie", covering just the torso, upper arm, and thighs, to thick 8mm semi-dry suit covering the torso, arms, and legs, usually complemented by neoprene boots, gloves and hood. The difference between a wetsuit and a dry suit is that a wetsuit allows water to enter the suit, though good fit limits water circulation inside the suit, and between the inside and outside of the suit, while dry suits are designed to prevent water from entering, thus keeping

4004-496: A wet suit will decrease significantly with an increase in depth as the ambient pressure causes the volume of the gas bubbles in the neoprene to decrease. Measurements of volume change of neoprene foam used for wetsuits under hydrostatic compression show that about 30% of the volume, and therefore 30% of surface buoyancy, is lost in about the first 10 m, another 30% by about 60 m, and the volume appears to stabilise at about 65% loss by about 100 m. The total buoyancy loss of

4147-418: A wetsuit is proportional to the initial uncompressed volume. An average person has a surface area of about 2 m , so the uncompressed volume of a full one piece 6 mm thick wetsuit will be in the order of 1.75 x 0.006 = 0.0105 m , or roughly 10 litres. The mass will depend on the specific formulation of the foam, but will probably be in the order of 4 kg, for a net buoyancy of about 6 kg at

4290-451: 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. Improved flexibility may come at the cost of greater compressibility, which reduces insulation at depth, but this

4433-447: Is a disadvantage in emergencies where decompression stops are required, or make the diver more negatively buoyant than necessary at the start of the dive with full cylinders, necessitating more gas in the buoyancy compensator for most of the dive, which is more sensitive to buoyancy changes with change in depth, and may make a larger buoyancy compensator necessary. These disadvantages can be compensated by skill, but more attention and effort

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4576-458: Is a good choice for supporting plants because of its flexibility and softness, allowing plants to be held securely in place without the chance of causing damage to the stem. Neoprene root covers also help block out light from entering the rooting chamber of hydroponic systems, allowing for better root growth and helping to deter the growth of algae. During the COVID-19 global pandemic, neoprene

4719-417: Is a popular material in making protective clothing for aquatic activities. Foamed neoprene is commonly used to make fly fishing waders, wetsuits , and drysuits as it provides excellent insulation against cold. The foam is quite buoyant, and divers compensate for this by wearing weights. Since foam neoprene contains gas pockets, the material compresses under water pressure, getting thinner at greater depths;

4862-431: Is a problem during the dive and reserves must be used, this could increase by up to 50%, and the diver must be able to stay down at the shallowest decompression stop. The extra weight and therefore negative buoyancy at the start of the dive could easily be as much as 13 kg for a diver carrying four cylinders. The buoyancy compensator is partially inflated when needed to support this negative buoyancy, and as breathing gas

5005-417: Is a result of the competing factors of scission of the main polymer chain and oxidative cross-linking. Chain scission leads to degradation, embrittlement , and a loss of toughness. Oxidation reactions in the presence of heating leads to increased cross-linking, which in turn causes hardening. The interplay of both these factors determines the resulting effect on material mechanical properties; cross-linking

5148-506: 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

5291-494: 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. Another reason to eliminate the external textile backing is to reduce water retention which can increase evaporative cooling and wind chill in suits used mainly out of the water. Various configurations of wetsuit are available, with varied amounts of body coverage. Most can be worn alone or in combinations to suit

5434-492: Is about 3 liters, or 3 kg of buoyancy, rising to about 6 kg buoyancy lost at about 60 m. This could nearly double for a large person wearing a farmer-john and jacket for cold water. This loss of buoyancy must be balanced by inflating the buoyancy compensator to maintain neutral buoyancy at depth. There is also a buoyancy loss due to gas loss from the bubbles over time, and the neoprene also loses flexibility with time, and tends to stiffen and shrink. This tendency

5577-528: Is actually possible. The position of the centre of buoyancy is largely beyond the control of the diver, though some control of suit volume is possible, the cylinder(s) may be shifted in the harness by a small amount, and the volume distribution of the buoyancy compensator has a large influence when inflated. Most of the control of trim available to the diver is in the positioning of ballast weights. The main ballast weights therefore should be placed as far as possible to provide an approximately neutral trim, which

5720-434: Is also manufactured without foaming for many other applications where insulating qualities are not important). Nitrogen, like most gases, has very low thermal conductivity compared to water or to solids, and the small and enclosed nature of the gas bubbles minimizes heat transport through the gas by convection in the same way that cloth fabrics, fur, or feathers insulate by reducing convection of enclosed air spaces. The result

5863-404: Is approximately 1.2 kg/m , or approximately 0.075 lb/ft ) The amount of weight needed to compensate for gas use is easily calculable once the free gas volume and density are known. Most of the rest of the diver's equipment is negatively buoyant or nearly neutral, and more importantly, does not change in buoyancy during a dive, so its overall influence on buoyancy is static. While it

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6006-581: Is called a Marseillaise belt . These belts are popular with freedivers as the rubber contracts on descent as the diving suit and lungs are compressed, keeping the belt tight throughout the dive. The most common design of weight used with a belt consists of rectangular lead blocks with rounded edges and corners and two slots in them threaded onto the belt. These blocks can be coated in plastic , which further increases corrosion resistance. Coated weights are often marketed as being less abrasive to wetsuits . The weights may be constrained from sliding along

6149-407: Is considered both an essential skill and one of the most difficult for the novice to master. Lack of proper buoyancy control increases the risk of disturbing or damaging the surroundings, and is a source of additional and unnecessary physical effort to maintain precise depth, which also increases stress. The scuba diver generally has an operational need to control depth without resorting to a line to

6292-420: 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 sufficient insulation was present in the fabric of the suit. In this case, the water would quickly reach skin temperature and gas bubbles in the fabric would continue to act as the thermal insulation to keep it that way. In

6435-412: Is difficult to achieve and the details of style and cut can affect the quality of fit. Gaps where the suit does not touch the skin will vary in volume as the diver moves and this is a major cause of flushing. Wetsuits are made in several standard adult sizes and for children. Custom fitted suits are produced by many manufacturers to provide a better fit for people for whom a well fitting off-the shelf suit

6578-448: Is exacerbated by frequent use, deep dives, and exposure to sunlight. The "compressed neoprene" and "crushed neoprene" used for hot water suits and dry suits , is permanently reduced in volume by intentional hydrostatic compression during the manufacturing process, specifically to reduce buoyancy change with depth, at the cost of reducing insulation. In 1952, UC Berkeley and subsequent UC San Diego SIO physicist Hugh Bradner , who

6721-421: Is generated. Water circulation automatically stops and body warmth builds up in moisture-laden jersey. The Seaskin suit provides both underwater insulation and above-water wind protection". Initially, wetsuits were crafted solely from foam-rubber or neoprene sheets devoid of any supporting material. Such suits demanded cautious handling during wear due to the inherent fragility and stickiness of foam-rubber against

6864-434: Is its high density, as well as its relatively low melting point, low cost and easy availability compared to other high density materials. It is also resistant to corrosion in fresh and salt water. Most dive weights are cast by foundries and sold by dive shops to divers in a range of sizes, but some are made by divers for their own use. Scrap lead from sources such as fishing sinkers and wheel balance weights can be easily cast by

7007-518: Is maintained for hours." By May 1953, the Bondi underwater equipment manufacturer Undersee Products was already distributing this singlet-like design commercially to Australian sporting goods stores, where it was described thus: "Made from heavy sheet rubber, the Sealskin suit is most effective when worn over a football jersey. When jersey becomes wet, rubber holds it firmly against body and thus warmth

7150-439: Is manufactured by foaming the rubber with nitrogen gas, where the tiny enclosed and separated gas bubbles can also serve as insulation. Nitrogen gas is most commonly used for the foaming of neoprene foam due to its inertness, flame resistance, and large range of processing temperatures. Neoprene is used as a component of elastomeric bridge bearings , to support heavy loads while permitting small horizontal movements. Neoprene

7293-464: Is more flexible than double lined. To achieve flexibility and low bulk for a given warmth of suit, they are unlined inside, and the slightly porous raw surface of the neoprene adheres closely to the skin and reduces flushing of the suit. The lined outer surface may be printed with camouflage patterns for spearfishing and is more resistant to damage while in use. Some triathlon wetsuits go further, and use rubber-molding and texturing methods to roughen up

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7436-532: Is necessary. Another significant issue in open circuit scuba diver weighting is that the breathing gas is used up during a dive, and this gas has weight, so the total weight of the cylinder decreases, while its volume remains almost unchanged. As the diver needs to be neutral at the end of the dive, particularly at shallow depths for obligatory or safety decompression stops , sufficient ballast weight must be carried to allow for this reduction in weight of gas supply. (the density of air at normal atmospheric pressure

7579-477: Is neutrally buoyant. The weight should then be distributed on the diver to provide correct trim, and a sufficient part of the weight should be carried in such a way that it can be removed quickly in an emergency to provide positive buoyancy at any point in the dive. This is not always possible, and in those cases an alternative method of providing positive buoyancy should be used. A diver ballasted by following this procedure will be negatively buoyant during most of

7722-495: Is not available. Neoprene Neoprene is produced by free-radical polymerization of chloroprene . In commercial production, this polymer is prepared by free radical emulsion polymerization . Polymerization is initiated using potassium persulfate . Bifunctional nucleophiles, metal oxides (e.g. zinc oxide), and thioureas are used to crosslink individual polymer strands. Neoprene was invented by DuPont scientists on April 17, 1930, after Elmer K. Bolton of DuPont attended

7865-435: Is of interest in the devulcanization process Finally, ultraviolet radiation is seen to decrease the mechanical properties of neoprene, which is important for outdoors applications of neoprene. Neoprene resists degradation more than natural or synthetic rubber . This relative inertness makes neoprene well suited for demanding applications such as gaskets , hoses , and corrosion -resistant coatings . It can be used as

8008-413: Is only important for diving. Foam neoprene used for wetsuits is always closed cell, in that the gas bubbles are mostly not connected to each other inside the neoprene. This is necessary to prevent water absorption, and the gas bubbles do most of the insulation. Thick sheets of neoprene are foamed inside a mould, and the surfaces in contact with the mould take on the inverse texture of the mould surfaces. In

8151-406: Is possible to calculate the required ballast given the diver and all his or her equipment, this is not done in practice, as all the values would have to be measured accurately. The practical procedure is known as a buoyancy check , and is done by wearing all the equipment, with the tank(s) nearly empty, and the buoyancy compensator empty, in shallow water, and adding or removing weight until the diver

8294-510: Is proportional to depth and the amount of gas in the bubbles, and scuba divers can correct this by inflating the buoyancy compensator . Breath-hold divers do not have this option and have the handicap of reduced buoyancy at depth due to lung gas compression in addition to suit volume loss. The suit also loses thermal protection as the bubbles in the neoprene are compressed at depth. Measurements of volume change of neoprene foam used for wetsuits under hydrostatic compression shows that about 30% of

8437-414: Is recommended to reduce downward directed fin thrust during finning, and this reduces silting and fin impact with the bottom. Trim weighting is mainly of importance to the free-swimming diver, and within this category is used extensively by scuba divers to allow the diver to remain horizontal in the water without effort. This ability is of great importance for both convenience and safety, and also reduces

8580-421: Is required throughout the dive. In surface-supplied diving , and particularly in saturation diving , the loss of weights followed by positive buoyancy can expose the diver to potentially fatal decompression injury . Consequently, weight systems for surface-supplied diving where the diver is transported to the worksite by a diving bell or stage , are usually not provided with a quick-release system. Much of

8723-524: Is sometimes used in the manufacture of dishwashing gloves, especially as an alternative to latex . In fashion, neoprene has been used by designers such as Gareth Pugh , Balenciaga , Rick Owens , Lanvin , and Vera Wang . Neoprene was also used as an experimental fabric to upholster a mirror by designer Flavia Brilli for her mirror brand Jazz Frames . Some people are allergic to neoprene while others can get dermatitis from thiourea residues left from its production. The most common accelerator in

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8866-425: Is that the gas-filled cavities restrict heat transfer to mostly conduction, which is partly 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 WmK, which produces about twice

9009-503: Is thought to dominate for neoprene. As neoprene is used to make electric cable jackets in nuclear power plants, the effect of gamma radiation on the mechanical properties of neoprene has also been investigated. Chain scission, possibly triggered by free radicals from irradiated oxygen, is seen to deteriorate the mechanical properties of neoprene. Likewise, the tensile strength, hardness, and ultimate elongation of neoprene can also be degraded upon exposure to microwave radiation , which

9152-439: Is used for reinforcing high wear areas like knee pads. A wetsuit with a very smooth and somewhat delicate outer surface known as smoothskin , which is the original outer surface of the foamed neoprene block from which the sheets are cut, is used for long-distance swimming, triathlon, competitive apnoea, and bluewater spearfishing. These are designed to maximize the mobility of the limbs while providing both warmth and buoyancy, but

9295-448: Is used to line landfills. Neoprene's burn point is around 260 °C (500 °F). In its native state, neoprene is a very pliable rubber-like material with insulating properties similar to rubber or other solid plastics. Neoprene foam is used in many applications and is produced in either closed-cell or open-cell form. The closed-cell form is waterproof , less compressible and more expensive. The open-cell form can be breathable . It

9438-410: Is used up during the dive, the volume of the buoyancy compensator will be reduced, by venting as required. The inconvenience of additional weight and managing the gas required to compensate for it in a dive that goes according to plan is the price that must be paid for the ability to decompress after an emergency which uses up most of the gas. There is little value in having enough gas to avoid drowning if

9581-405: Is usually possible by wearing the weights around the waist or just above the hips on a weight belt, or in weight pockets provided in the buoyancy compensator jacket or harness for this purpose. Fine tuning of trim can be done by placing smaller weights along the length of the diver to bring the centre of gravity to the desired position. There are several ways this can be done. Ankle weights provide

9724-410: Is usually swimming horizontally or observing the environment without making contact with benthic organisms. Ascent and descent at neutral buoyancy can be controlled well in horizontal or head-up trim, and descent can be most energy efficient head down, if the diver can effectively equalise the ears in this position. Freediving descents are usually head down, as the diver is usually buoyant at the start of

9867-537: Is usually the case with people with a large proportion of body fat. As the diver is nearly neutral, most ballasting is needed to compensate for the buoyancy of the diver's equipment. The main components of the average scuba diver's equipment which are positively buoyant are the components of the exposure suit. The two most commonly used exposure suit types are the dry suit and the wet suit . Both of these types of exposure suit use gas spaces to provide insulation, and these gas spaces are inherently buoyant. The buoyancy of

10010-492: The Siebe Gorman CDBA ) have a pouch containing lead balls each a bit over an inch diameter. The diver can release them by pulling a cord. Surface-supplied divers often carry their weights securely attached to reduce the risk of accidentally dropping them during a dive and losing control of their buoyancy. These may be carried on a weight belt with a secure buckle, supported by a weight harness, connected directly to

10153-413: The buoyancy of other diving equipment , such as diving suits and aluminium diving cylinders , and buoyancy of the diver. The scuba diver must be weighted sufficiently to be slightly negatively buoyant at the end of the dive when most of the breathing gas has been used, and needs to maintain neutral buoyancy at safety or obligatory decompression stops. During the dive, buoyancy is controlled by adjusting

10296-650: The vulcanization of polychloroprene is ethylene thiourea (ETU), which has been classified as a reproductive toxin . From 2010 to 2013, the European rubber industry had a research project titled SafeRubber to develop a safer alternative to the use of ETU. Diving weighting system A diving weighting system is ballast weight added to a diver or diving equipment to counteract excess buoyancy. They may be used by divers or on equipment such as diving bells, submersibles or camera housings. Divers wear diver weighting systems , weight belts or weights to counteract

10439-461: The BCD. The weight pouches often have handles, which must be pulled to drop the weights in an emergency or to remove the weights when exiting the water. Some designs also have smaller "trim pouches" located higher in the BCD, which may help the diver maintain neutral attitude in the water. Trim pouches typically can not be ditched quickly, and are designed to hold only 1-2 pounds (0.5–1 kg) each. Many integrated systems cannot carry as much weight as

10582-552: The British Dunlop Sports Company brought out its yellow Aquafort neoprene wetsuit, whose high visibility was intended to improve diver safety. However, the line was discontinued after a short while and wetsuits reverted to their black uniformity. The colorful wetsuits seen more recently first arrived in the 1970s when double-backed neoprene was developed. In this material the foam-rubber is sandwiched between two protective fabric outer layers, greatly increasing

10725-710: 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 and Australia. The Pêche-Sport "isothermic" suit invented by Georges Beuchat in 1953 and the UK-made Siebe Gorman Swimsuit were both made out of sponge rubber. The Heinke Dolphin Suit of

10868-482: The body by pure thermal diffusion , approximately 20 to 25 times more efficiently than still air. Water has a thermal conductivity of 0.58 WmK while still air has a thermal conductivity of 0.024 WmK, so an unprotected person can eventually 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 insulating material ( neoprene

11011-408: The body, and the change in volume of the space under the suit works as a pump to push warm water out of the suit and suck cold water in on the opposite movement. Foamed neoprene is very buoyant, helping swimmers to stay afloat, and for this reason divers need to carry extra weight based on the volume of their suit to achieve neutral buoyancy near the surface. Buoyancy is reduced by compression, and

11154-400: The bottom, and reduces the risk of striking delicate benthic organisms with the fins. A stable horizontal trim requires that diver's centre of gravity is directly below the centre of buoyancy (the centroid ). Small errors can be compensated fairly easily, but large offsets may make it necessary for the diver to constantly exert significant effort towards maintaining the desired attitude, if it

11297-445: The bottom, downward thrust can disturb the benthos and stir up silt. The risk of fin-strike damage is also significant. A further requirement for scuba diving in most circumstances, is the ability to achieve significant positive buoyancy at any point of a dive. When at the surface, this is a standard procedure to enhance safety and convenience, and underwater it is generally a response to an emergency. The average human body with

11440-434: The breastplate of the helmet, directly transferring the load to the buoyant helmet when immersed, but with a relatively low centre of gravity. Combined with lacing of the suit legs and heavy weighted shoes, this reduced the risk of inversion accidents. Trim is the diver's attitude in the water, in terms of balance and alignment with the direction of motion. Optimum trim depends on the task at hand. For recreational divers this

11583-435: The buoyancy compensator to maintain neutral buoyancy at depth. A dry suit will also compress with depth, but the air space inside is continuous and can be topped up from a cylinder or vented to maintain an approximately constant volume. A large part of the ballast used by a diver is to balance the buoyancy of this gas space, but if the dry suit has a catastrophic flood, much of this buoyancy may be lost, and some way to compensate

11726-472: The clip mechanism. They can also be used to temporarily increase the weight of a conventional weight belt. Various sizes have been available, ranging from around 0.5 to 5 kg or more. The larger models are intended as ditchable primary weights, and are used in the same way as BCD integral weights or weight harness weighs, but clipped to the backplate or sidemount harness webbing, and the smaller versions are also useful at trim weights. Some rebreathers (e.g.

11869-413: The compound in 1931 under the trade name DuPrene, but its commercial possibilities were limited by the original manufacturing process, which left the product with a foul odor. A new process was developed, which eliminated the odor-causing byproducts and halved production costs, and the company began selling the material to manufacturers of finished end-products. To prevent shoddy manufacturers from harming

12012-436: The conditions for which they are intended. The neoprene foam is available in thicknesses up to 10 mm, though 7 mm and less are most common. The thicker the suit, the warmer it will keep the wearer, but the more it will restrict movement. Because wetsuits offer significant protection from jellyfish , coral , sunburn and other hazards, many divers opt to wear a thin suit which provides minimal insulation (sometimes called

12155-437: The conditions: 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 combined thickness of neoprene over the torso and 5 to 7 mm single thickness over the limbs. Wetsuits are available in different thicknesses depending on

12298-428: 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. Sometime after nylon-backed neoprene appeared, the blind stitch method was developed. A blindstitch sewing machine uses

12441-507: 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. Jack O'Neill started using closed-cell neoprene foam which he claimed

12584-450: The dive unless the buoyancy compensator is used, to an extent which depends on the amount of breathing gas carried. A recreational dive using a single cylinder may use between 2 and 3 kg of gas during the dive, which is easy to manage, and provided that there is no decompression obligation, end-dive buoyancy is not critical. A long or deep technical dive may use 6 kg of back gas and another 2 to 3 kg of decompression gas. If there

12727-411: The dive, and must fin downwards. Professional divers usually have work to do at the bottom, often in a fixed location, which is usually easier in upright trim, and some diving equipment is more comfortable and safer to use when relatively upright. Accurately controlled trim reduces horizontal swimming effort, as it reduces the sectional area of the diver passing through the water. A slight head down trim

12870-418: The diver can surface and remain positively buoyant at the surface. The technique for shedding weights in an emergency is a basic skill of scuba diving, which is trained at entry level. Research performed in 1976 analyzing diving accidents noted that in majority of diving accidents, divers failed to release their weight belts. Later evaluations in 2003 and 2004 both showed that failure to ditch the weight remained

13013-399: The diver is killed or crippled by decompression sickness instead. Examples: Optimum weighting for scuba allows the diver to achieve neutral buoyancy at any time during a dive while there is still usable breathing gas in any of the cylinders carried, using the least amount of ballast. Deviations from this optimum either make the diver buoyant while there is still usable breathing gas, which

13156-418: The diver is marginally fit for the conditions. Tank bottom weights provide a much shorter lever arm, so need to be a much larger proportion of the total ballast, but do not interfere with propulsive efficiency the way ankle weights do. There are not really any other convenient places below the weight belt to add trim weights, so the most effective option is to carry the main weights as low as necessary, by using

13299-494: The diver's mass and body composition, buoyancy of other diving gear worn (especially the diving suit ), water salinity , weight of breathing gas consumed, and water temperature. It normally is in the range of 2 kilograms (4.4 lb) to 15 kilograms (33 lb). The weights can be distributed to trim the diver to suit the purpose of the dive. Surface-supplied divers may be more heavily weighted to facilitate underwater work, and may be unable to achieve neutral buoyancy, and rely on

13442-427: The diving safety harness, or suspended from the corselet of the helmet. Heavily weighted footwear may also be used to stabilise the diver in an upright position. In addition to the weight that can be dropped easily ('ditched'), some scuba divers add additional fixed weights to their gear, either to reduce the weight placed on the belt, which can cause lower back pain, or to shift the diver's center of mass to achieve

13585-518: The diving stage, bell, umbilical, lifeline, shotline or jackstay for returning to the surface. Free divers may also use weights to counteract buoyancy of a wetsuit. However, they are more likely to weight for neutral buoyancy at a specific depth, and their weighting must take into account not only the compression of the suit with depth, but also the compression of the air in their lungs, and the consequent loss of buoyancy. As they have no decompression obligation, they do not have to be neutrally buoyant near

13728-407: The early days of wetsuits this was often a diamond pattern or similar, but can also be slick and smooth for low drag and quick drying. The cut surfaces of the foam have a slightly porous mat finish as the cutting process passes through a large number of bubbles, leaving what is called an open cell surface finish, but the bulk of the foam remains closed cell. The open cell finish is the most stretchy and

13871-409: The emergency is life-threatening or the risk of decompression sickness is small, as is the case in free diving and scuba diving when the dive is well short of the no-decompression limit for the depth. Often divers take great care to ensure the weights are not dropped accidentally, and heavily weighted divers may arrange their weights so subsets of the total weight can be dropped individually, allowing for

14014-463: The emergency release of the weights will usually allow the diver to float to the surface even if unconscious, where there is at least a chance of rescue. The weights are used mainly to neutralise the buoyancy of the exposure suit, as the diver is nearly neutral in most cases, and there is little other equipment carried. The weights required depend almost entirely on the buoyancy of the suit. Most free divers will weight themselves to be positively buoyant at

14157-415: The environmental impact of divers on fragile benthic communities. The free-swimming diver may need to trim erect or inverted at times, but in general, a horizontal trim has advantages both for reduction of drag when swimming horizontally, and for observing the bottom. A horizontal trim allows the diver to direct propulsive thrust from the fins directly to the rear, which minimises disturbance of sediments on

14300-411: The exterior of the neoprene sheeting (a technique E.J. Armstrong developed 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

14443-412: The foam will start to absorb more water, further reducing insulation. Wetsuits for diving should be made from less compressible neoprene to keep their insulating qualities. A wetsuit must have a snug fit to work efficiently when immersed; too loose a fit, particularly at the openings (wrists, ankles, neck and overlaps) will allow cold water from the outside to enter when the wearer moves. Flexible seals at

14586-435: The heat loss of still air, or one-tenth the loss of water. However, at a depth of about 15 metres (50 ft) of water, the thickness of a typical neoprene foam will be halved and its conductivity will be increased by about 50%, allowing heat to be lost at three times the rate at the surface. The grade of foam neoprene strongly affects insulating properties at depth, and over time. Softer, lighter, and more elastic grades contain

14729-447: The hips. This is an advantage for divers who have no discernible waist, or whose waist is too high to trim correctly if a weight belt is worn. These advantages may also be available on some styles of integrated BC weights. A weight harness may also incorporate a crotch strap or straps to prevent weight shift if the diver is in a steep head down posture. These are weights which attach to the harness directly, but are removable by disengaging

14872-428: 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 1960s 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

15015-485: 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. 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, 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

15158-631: The least tear resistant. It is relatively form fitting and comfortable on the skin, but the porosity encourages bacterial growth if not well washed after use, and the foam surface does not slide freely against skin unless lubricated. The cut surfaces are usually bonded to a synthetic knit fabric, which provides much greater tear resistance, at the expense of some loss of flexibility and stretch. This fabric can be bonded to one or both surfaces in various combinations of composition, weave, weight and colour, and can be thin and relatively smooth and fragile, thicker and stronger and less stretchy,for high wear areas, or

15301-428: The leg, neck, and wrist openings of the suit creates a more effective seal against the skin than the knit fabric backing, that reduces the flushing of water in and out of the suit at these places as the person moves. Since the strip is narrow, it does not drag on the skin of the wearer much and the lining makes the suit easy to put on and remove. The strip can also be fitted with the smooth side out and folded under to form

15444-490: The material, which reduce its ability to conduct heat . The bubbles also give the wetsuit a low density , providing buoyancy in water. Hugh Bradner , a University of California, Berkeley physicist , invented the modern wetsuit in 1952. 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 spandex (also known as lycra) . Improvements in

15587-486: 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

15730-411: The mechanical response of neoprene. Exposure to acetone and heat have been shown to degrade the tensile strength and ultimate elongation of neoprene, likely due to a loss of plasticizers as well as an increase in crosslinking during heat exposure. The response of neoprene to thermal aging depends not just on the highest temperature it is exposed to, but also on the exact temperature-time profile; this

15873-488: The nylon knit fabric cannot be stretched as much as when elasticised with lycra fibres. Incorporating lycra into the backing permits a larger amount of stretching that does not damage the suit, and allowed suits to be stretched more to fit while remaining acceptably comfortable, making the tailoring less critical. After the development of double-backed neoprene, singled-backed neoprene still has its uses. A narrow edge strip of smooth surfaced single-backed neoprene wrapped around

16016-402: The nylon took most of the stress of pulling on the suit, and there was less friction between the nylon and skin, but the suit still had the bare foam exposed on the outside and the nylon was relatively stiff, limiting flexibility. A small strip of neoprene reversed with the rubber against the skin could help provide a sealing surface to keep water out around the neck, wrists, and ankles. In 1960,

16159-416: The optimum position in the water. There are several operational hazards associated with diving weights: Buoyancy and weighting problems have been implicated in a relatively high proportion of scuba diving fatalities. A relatively large number of bodies have been recovered with all weights still in place. The most common material for personal dive weights is cast lead . The primary reason for using lead

16302-442: The order of 1.75 x 0.006 = 0.0105 m, or roughly 10 liters. The mass will depend on the specific formulation of the foam, but will probably be in the order of 4 kg, for a net buoyancy of about 6 kg at the surface. Depending on the overall buoyancy of the diver, this will generally require 6 kg of additional weight to bring the diver to neutral buoyancy to allow reasonably easy descent. The volume lost at 10 m

16445-433: The popular mind, the layer of water between skin and suit has been credited with providing the insulation, but Bradner clearly understood that the suit did not need to be wet because it was not the water that provided the insulation but rather the gas in the suit fabric. He initially sent his ideas to Lauriston C. "Larry" Marshall who was involved in a U.S. Navy/National Research Council Panel on Underwater Swimmers. However, it

16588-446: The product's reputation, the trademark DuPrene was restricted to apply only to the material sold by DuPont. Since the company itself did not manufacture any DuPrene-containing end products, the trademark was dropped in 1937 and replaced with a generic name, neoprene, in an attempt "to signify that the material is an ingredient, not a finished consumer product". DuPont then worked extensively to generate demand for its product, implementing

16731-487: The rebreather harness or casing, and if necessary weights can be attached to the harness shoulder straps. All or part of the weighting system may be carried in such a way that it can be quickly and easily jettisoned by the diver to increase buoyancy, the rest is usually attached more securely. Breathhold and scuba divers generally carry some or all of their weights in a way that can be quickly and easily removed while under water. Removal of these weights should ensure that

16874-529: 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. As early as July 1951, underwater hunters in Australia were experimenting with a natural rubber wetsuit "of a 'wrap on' variety, which does not set out to be 100% waterproof (but it is claimed that) the leakage of water through it is so slow that body warmth under it

17017-420: 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. To deal with all these early sewing problems, taping of seams was developed. The tape

17160-517: The shot conforms to the diver's body. Weight belts using shot are called shot belts . Each shot pellet should be coated to prevent corrosion by sea water, as use of uncoated shotgun shot for sea diving would result in the lead eventually corroding into powdery lead chloride These are stored in pockets built into the buoyancy control device . Often a velcro flap or plastic clip holds the weights in place. The weights may also be contained in zippered or velcroed pouches that slot into special pockets in

17303-421: The skin. Excessive stretching and pulling often resulted in tearing these suits apart. To mitigate this issue, divers resorted to generously applying talc powder to both the suit and their body to facilitate smoother sliding of the rubber material. Backing materials first arrived in the form of nylon knit cloth applied to one side of the neoprene. This allowed a swimmer to pull on the suit relatively easily since

17446-406: The suit cuffs aid in preventing heat loss in this fashion. The elasticity of the foamed neoprene and surface textiles allow enough stretch for many people to effectively wear off-the-shelf sizes, but others have to have their suits custom fitted to get a good fit that is not too tight for comfort and safety. Places where the suit bridges a hollow tend to change volume when the wearer bends that part of

17589-454: The suit free of bulging and ripples from improper cutting and misaligned sewing. Further innovations in CAD (Computer Aided Design) technology allow precision cutting for custom-fit 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 surface is relatively rough and creates

17732-436: The surface at the end of a dive. If the weights have a method of quick release, they can provide a useful rescue mechanism: they can be dropped in an emergency to provide an instant increase in buoyancy which should return the diver to the surface. Dropping weights increases the risk of barotrauma and decompression sickness due to the possibility of an uncontrollable ascent to the surface. This risk can only be justified when

17875-560: The surface is delicate and easily damaged. The slick surface also dries quickly and is least affected by wind chill when out of the water. Both smoothskin and fabric lined surfaces can be printed to produce colour patterns such as camouflage designs, which may give spearfishermen and combat divers an advantage. Zippers are often used for closure or for providing a close fit at the wrists and ankles while remaining relatively easy to put on and remove, but they also provide leakage points for water A backing flap reduces leakage but can get caught in

18018-404: The surface of the suit on the forearms, to increase 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

18161-549: The surface or holding onto a structure or landform, or resting on the bottom. This requires the ability to achieve neutral buoyancy at any time during a dive, otherwise the effort expended to maintain depth by swimming against the buoyancy difference will both task load the diver and require an otherwise unnecessary expenditure of energy, increasing air consumption, and increasing the risk of loss of control and escalation to an accident. Maintaining depth by finning necessarily directs part of fin thrust upwards or downwards, and when near

18304-456: The surface, and use only enough weight to minimise the effort required to swim down against the buoyancy at the start of a dive, while retaining sufficient buoyancy at maximum depth to not require too much effort to swim back up to where the buoyancy becomes positive again. As a corollary to this practice, freedivers will use as thin a wetsuit as comfortably possible, to minimise buoyancy changes with depth due to suit compression. Buoyancy control

18447-462: The surface. Depending on the overall buoyancy of the diver, this will generally require 6 kg of additional weight to bring the diver to neutral buoyancy to allow reasonably easy descent The volume lost at 10 m is about 3litres, or 3 kg of buoyancy, rising to about 6 kg buoyancy lost at about 60 m. This could nearly double for a large person wearing a two-piece suit for cold water. This loss of buoyancy must be balanced by inflating

18590-403: The tear-resistance. An external layer also meant that decorative colors, logos, and patterns could be made with panels and strips sewn into various shapes. This change from bare flat black rubber to full color took off in the 1980s with brilliant fluorescent colors common on many suits. The first suits used traditional sewing methods to simply overlap two strips of rubber and sew them together. In

18733-642: The undergarments dry and preserving their insulating effectiveness. Wetsuits can give adequate protection in warm to moderately cold waters. Dry suits are typically more expensive and more complex to use, but can be used where protection from lower temperatures or contaminated water is needed. The primary function of a wetsuit is thermal insulation to keep the wearer warm in conditions where they would otherwise lose body heat rapidly due to heat transfer by relatively large quantities of water. Secondary, and incidental, functions are buoyancy and protection from some environmental hazards such as abrasion , sunburn , and to

18876-504: The use of a supplemental vest in extreme conditions. More recently, manufacturers have experimented by combining various materials with neoprene for additional warmth or flexibility of 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

19019-402: The volume of air in the buoyancy compensation device (BCD) and, if worn, the dry suit , in order to achieve negative, neutral, or positive buoyancy as needed. The amount of weight required is determined by the maximum overall positive buoyancy of the fully equipped but unweighted diver anticipated during the dive, with an empty buoyancy compensator and normally inflated dry suit. This depends on

19162-422: The volume, and therefore 30% of surface buoyancy, is lost in about the first 10 m, another 30% by about 60 m, and the volume appears to stabilize at about 65% loss by about 100 m. The total buoyancy loss of a wetsuit is proportional to the initial uncompressed volume. An average person has a surface area of about 2 m, so the uncompressed volume of a full one piece 6 mm thick wetsuit will be in

19305-428: The water, so they do not float off the diver's head or pull upwards on the neck, but the larger volume free-flow helmets would be too heavy and cumbersome if they had all the required weight built in. Therefore, they are either ballasted after dressing the diver by fastening weights to the lower parts of the helmet assembly, so the weight is carried on the shoulders when out of the water, or the helmet may be held down by

19448-445: The way joints in the wetsuit were made by gluing, taping and blind-stitching, 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, ankles, and zippers produced a suit known as a "semi-dry". Different types of wetsuit are made for different uses and for different temperatures. Suits range from

19591-399: The webbing by the use of metal or plastic belt sliders . This style of weight is generally about 1 to 4 pounds (0.45 to 1.81 kg). Larger "hip weights" are usually curved for a better fit, and tend to be 6 to 8 pounds (2.7 to 3.6 kg). Another popular style has a single slot through which the belt can be threaded. These are sometimes locked in position by squeezing the weight to grip

19734-406: The webbing, but this makes them difficult to remove when less weight is needed. There are also weight designs which may be added to the belt by clipping on when needed. Some weightbelts contain pouches to contain lead weights or round lead shot : this system allows the diver to add or remove weight more easily than with weights threaded onto the belt. The use of shot can also be more comfortable, as

19877-468: The work done by surface-supplied divers is on the bottom, and weighted boots may be used to allow the diver to walk upright on the bottom. When working in this mode, several kilograms beyond the requirement for neutralising buoyancy may be useful, so that the diver is reasonably steady on the bottom and can exert useful force when working. The lightweight demand helmets in general use by surface-supplied divers are integrally ballasted for neutral buoyancy in

20020-399: The zipper while closing. Jackets may have a full or partial front zipper, or none at all. Full body suits may have a vertical back zipper, a cross-shoulder zipper, a vertical front zipper or occasionally a cross-chest zipper. Each of these arrangements has some advantages and some disadvantages: Wetsuits that fit too tightly can cause difficulty breathing or even acute cardiac failure , and

20163-537: Was Willard Bascom , an engineer at the Scripps Institution of Oceanography in La Jolla, California , who suggested foamed neoprene as a feasible material to Bradner. 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

20306-493: Was identified by some health experts as an effective material to use for home made face masks. Some commercial face mask manufacturers that use neoprene have claimed 99.9% filtration for particles as small as 0.1 microns. The size of coronavirus is identified to be on average 0.125 microns. Neoprene is used for Halloween masks and masks used for face protection, to make waterproof automotive seat covers, in liquid and sheet-applied elastomeric roof membranes or flashings, and in

20449-413: 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, O'Neill founded the successful wetsuit manufacturing company called O'Neill in a San Francisco garage in 1952, later relocating to Santa Cruz, California in 1959 with the motto "It's Always Summer on

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