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An inflatable boat is a lightweight boat constructed with its sides and bow made of flexible tubes containing pressurised gas. For smaller boats, the floor and hull is often flexible, while for boats longer than 3 metres (9.8 ft), the floor typically consists of three to five rigid plywood or aluminium sheets fixed between the tubes, but not joined rigidly together. Often the transom is rigid, providing a location and structure for mounting an outboard motor.
Some inflatable boats have been designed to be disassembled and packed into a small volume, so that they can be easily stored and transported to water when needed. The boat, when inflated, is kept rigid crossways by a foldable removable thwart. This feature allows such boats to be used as liferafts for larger boats or aircraft, and for travel or recreational purposes.
The most common term for inflatable boats is "rubber boat" although rubber is usually no longer used in their construction. Other terms used include "inflatable dinghy", "rubber dinghy", "inflatable", "inflatable rescue boat", and "rubber duck".
There are ancient carved images of animal skins filled with air being used as one-man floats to cross rivers. These floats were inflated by mouth. Sometimes, these images have been wrongly described as ancient scuba.
The discovery of the process to vulcanize rubber was made by Charles Goodyear in 1838, and was granted a US Patent in 1844. In late 1843, Thomas Hancock filed for a UK patent, which was also granted in 1844, after the Goodyear patent had been granted. In 1852, while traveling in England, Charles Goodyear discovered that Thomas Hancock's company was producing vulcanized rubber and sued. It was discovered that Thomas Hancock had been shown a sample of Goodyear's rubber in 1842, but he had not been told the process that made it, and that Hancock said that he came up with his process independently. The last of the suits were settled in 1855. Vulcanization stabilized the rubber allowing it to be both durable and flexible. Shortly thereafter, several people expanded on experimentation of rubber coated fabrics.
In 1839 the Duke of Wellington tested the first inflatable pontoons. In 1840, the English scientist Thomas Hancock designed inflatable craft using his new methods of rubber vulcanization and described his achievements in "The Origin and Progress of India Rubber Manufacture in England" published a few years later.
Lieutenant Peter Halkett, an officer in the Royal Navy designed the Halkett boat in 1845 as the first successful inflatable boat. His first design was made of rubber-impregnated "Mackintosh cloth." The "boat cloak" served as a waterproof poncho or cloak until inflated, when it became a one-man boat. A special pocket held bellows for inflation, and a blade to turn a walking stick into a paddle. A special umbrella could double as a sail. Halkett later developed a two-man boat which was carried in a knapsack; when inflated, it could carry two men operating a paddle on each side, and when deflated it served as a waterproof blanket to allow the users to camp on wet ground. The Admiralty was skeptical about potential uses for Halkett's designs; on 8 May 1845, Lord Herbert, First Secretary to the Admiralty, wrote to Halkett that "My Lords are of an opinion that your invention is extremely clever and ingenious, and that it might be useful in Exploring and Surveying Expeditions, but they do not consider that it would be made applicable for general purposes in the Naval Service".
Although the Admiralty saw no use to which Halkett's designs could be put in general naval service, this larger design was extremely well received by explorers. John Franklin bought one to take on the ill-fated 1845 expedition in which the entire expedition party of 129 men and two ships vanished.
In his explorations along the Oregon Trail, and the tributaries and forks of the Platte River during the years 1842 and 1843, John C. Frémont recorded what may have been the first use of an inflatable rubber boat for travel down rivers and rapids in the Rocky Mountains. In his account of the expedition he described his boat:
Among the useful things which formed a portion of our equipage, was an India-rubber boat, 18 feet long, made somewhat in the form of a bark canoe of the northern lakes. The sides were formed by two airtight cylinders, eighteen inches in diameter, connected with others forming the bow and stern. To lessen the danger of accidents to the boat, these were divided into four different compartments, and the interior was sufficiently large to contain five or six persons, and a considerable weight of baggage."
In 1848, General George Cullum, U.S. Army Corps of Engineers, introduced a rubber coated fabric inflatable bridge pontoon, which was used in the Mexican–American War and later on to a limited extent during the American Civil War.
By 1855 there were numerous types of inflatable rubber boats in use, some made by Goodyear in the U.S. and other surprisingly modern looking boats by the Thomas Hancock Company in Britain.
In 1866, four men crossed the Atlantic Ocean from New York to Britain on a three-tube raft called Nonpareil.
From 1900 to 1910, the development of rubber manufacturing enabled attempts at producing circular rubber inflatable boats, similar to modern coracles. These were only usable as rafts, and could only be propelled by paddling. In addition, they tended to crack at seams and folds due to the imperfect manufacturing process of the rubber.
One cause of the loss of lives on the Titanic was the lack of lifeboats. Even if every lifeboat had been completely filled with passengers and crew, there would have been no way to rescue more than half of all the people on board. The first SOLAS treaty was designed to avoid such a disaster happening again. One of its provisions was to ensure that vessels had enough lifeboats to provide every person aboard the vessel with a place. Putting this rule into effect was not difficult with cargo ships: they had small crews and plenty of deck space. Passenger ships had to stack lifeboats on top of each other to carry enough to accommodate the large number of passengers and crew. Warships also had large crews and little deck space.
Between the two World Wars, Goodyear found a way to join rubber to other materials. They made life rafts of square-shaped inflated rubber tubes with a rigid floor. Such rafts were to be stacked vertically aboard warships, usually standing on deck and leaning against deck-houses.
Modern inflatable boat
In the early 20th century inflatable boats started to be independently produced by the RFD firm in England and the Zodiac company in France. This was brought about by the development of rubber-coated fabrics that had initially been used in the airship industry.
Reginald Foster Dagnall, English designer and founder of the airship manufacturing company RFD, switched in 1919 to the development of inflatable boats, using the coated fabric from hydrogen airships. The Air Ministry was impressed with trials of his boat on a lake near Guildford and began to give his firm contracts for the production of the life-saving equipment.
Meanwhile, in France a very similar pattern was emerging. The airship company Zodiac began to develop inflatable rubber boats and in 1934 they invented the inflatable kayak and catamaran which led on to the modern day Zodiac inflatable boat.
World War II
Submarine warfare in the Battle of the Atlantic led to casualties among warships and merchant ships. US warships began using rubber life rafts. Since the rubber was much higher quality than 35 years before, the inflatable returned, but this time it was boat-shaped.
In the military, inflatable boats were used to transport torpedoes and other cargo. They also allowed troops to make landings in shallow water, and their compact size and ability to be stored made overland transport possible.
The Marine Raiders were originally trained to carry out raids and landings from LCRL inflatable boats carried by high speed transports. In August 1942 the submarines USS Argonaut (SM-1) and USS Nautilus (SS-168) carried elements of the 2nd Raider Battalion who carried out the Makin Island raid from LCR-L inflatable boats. Invasions of the Battle of Arawe by the 112th Cavalry Regiment and parts of the Battle of Tarawa involved amphibious landings in inflatable boats against heavy enemy resistance.
One of the models, the Zodiac brand inflatable boat, grew to be popular with the military and contributed significantly to the rise of the civilian inflatable boat industry, both in Europe and in the United States. After World War II, surplus inflatable boats were sold to the public. A version of this boat has been adapted by the Marine Mammal Center for use in rescuing injured marine mammals at sea.
Inflatable liferafts were also used successfully to save crews of aircraft that ditched in the sea; bombing, naval and anti-submarine aircraft flying long distances over water being much more common from the start of WWII.
Also in the 1950s, the French Navy officer and biologist Alain Bombard was the first to combine the outboard engine, a rigid floor and a boat shaped inflatable. The former airplane-manufacturer Zodiac built that boat and a friend of Bombard, the diver Jacques-Yves Cousteau began to use it, after Bombard sailed across the Atlantic Ocean with his inflatable in 1952. Cousteau was convinced by the shallow draught and good performance of this type of boat and used it as tenders on his expeditions.
The inflatable boat was so successful that Zodiac lacked the manufacturing capacity to satisfy demand. In the early 1960s, Zodiac licensed production to a dozen companies in other countries. In the 1960s, the British company Humber was the first to build Zodiac brand inflatable boats in the UK.
Some inflatables have inflated keels whose V-shape help the hull move through waves reducing the slamming effect caused by the flat hull landing back on the surface the water after passing over the top of a wave at speed.
Rigid inflatable boat
The modern rigid inflatable boat (RIB) is a development of the inflatable boat which has a rigid floor and solid hull. The external shape of the hull lets it cut through waves more easily giving a more comfortable ride when traveling fast in rough conditions. The structure of the hull is capable of supporting a more powerful transom mounted outboard engine or even an inboard engine.
Some RIBs are 14 metres (46 ft) in length and include inboard steering, luxury features and full cabins.
Although most rigid multifunction dinghies are not actually inflated, they are buoyed partly by air chambers in the hull as well as by closed-cell foam inside the hull. In addition to their proactive lifeboat functionality, these boats serve as everyday tenders and as recreational boats. They are extremely buoyant and/or unsinkable and have great carrying capacity relative to length.
Today's more advanced inflatable boats are manufactured using supported fabric. They are made of rubberized, synthetic fabrics CSM Hypalon/neoprene, PVC or Polyurethane, providing light-weight and airtight sponsons. Depending on fabric choice, the fabric panels are assembled using either hot or cold manufacturing processes. Different styles of one-way valves are used to add or remove air, and some brands include inter-communicating valves that reduce the effect of a puncture. Boats are available in many floor choices, such as the ribbed air floor, High Pressure (HPP) Air Floor, fiberglass (RIB), and aluminum or wood panels for rigidity.
Inflatable boats that have transoms have an inflatable keel to create a "deep-v" along the line of the hull improving the hull's wave cutting and turning performance. Due to the light weight of these vessels, if powering with an engine, it is best to put weight in the bow area as the bow will rise while the boat is going up on plane.
A growing use for inflatables is for personal recreational use on lakes, rivers, and oceans, as well as for white water rafting and kayaking. Fabric bottom inflatable boats can be deflated, folded, and stored in compact bags, making them ideal for consumers with limited storage as well as providing for quick and easy access.
Inflatable sailboats are a small but growing niche in the recreational market. Sail rigs are now offered for inflatable dinghies, kayaks and catamarans. In keeping with the portability of the inflatable hull, the components of the sail attachment fold or come apart to fit in a compact bundle. Leeboards on the sides perform the same function as a centerboard, to enable these boats to tack into the wind.
Professional-grade inflatable boats and RIBs have existed for many decades. Modern versions are complex, and they can be rapidly inflated using SCBA or scuba tanks as well as CO2 to make them mission ready. The professional-grade RIBs are available in many sizes and styles, some sporting T-tops, cabins, and other features. Since the late 1990s, many varieties of inflatable boats, RIBs, whitewater rafts, kayaks and sea kayaks, and canoes, have been developed by Asian, European, and North American companies.
Generally, inflatable boats are manufactured with several inflatable chambers which means should one chamber be punctured the remaining chambers will keep the craft afloat. Should a chamber puncture it can be repaired while still underway with an inflatable repair kit, however it is advised that this type of repair is treated as temporary, with a permanent repair being carried out when on dry land. More extensive inflatable boat repairs are best carried out in a dry, warm, well ventilated indoor space away from dust and other contaminants. Room humidity is important for a lasting repair as specific humidity over 70% will produce a repair with a shorter lifespan.
The repair procedure for an inflatable boat is basically the same for both rubber based fabrics and those which are constructed from heavy duty PVC materials. The procedure is as follows:
- Firstly, the site of damage must be identified. If the site is already not visible the a mixture of soap and water can be sprayed onto the surface of an inflated boat, bubbles will appear where there is a puncture. Mark the site of puncture with a non-greasy marker.
- Clean and dry the surface of the inflatable boat thoroughly before proceeding.
- Create a round patch of material that has an approximate circumference of 2" (5 cm) from the centre of the hole in the inflatable boat. Use the same material of patch that the boat is constructed from for best effect.
- Prepare the site of repair with fine grit sandpaper, taking care not to rub through the coating of the fabric into the scrim of the material below. This will roughen the surface in preparation for the glue.
- Do the same preparation on the surface of the patch that you have prepared
- Clean both the site of repair and the patch with a cleaning fluid. This should be Toluene for rubber based boats (Hypalon, EPDM, Neoprene) and Methyl Ethyl Ketone (MEK) for PVC based boats if available, or rubbing alcohol if not. Wait no longer than 30 minutes between cleaning and applying adhesive.
- Mix the adhesive to be applied if this is a 2-pack adhesive. Commonly available adhesives for rubber based and PVC fabrics come as an adhesive and accelerator and whilst the adhesive can be used on its own, the accelerator gives the adhesive a faster and stronger bond.
- Apply several coats of adhesive to both the repair site and patch, waiting 10 minutes between coats.
- Use a dry, clean knuckle to press onto the surface of the adhesive to test if it is ready for application. If pressing on with a knuckle does not pull adhesive off the surface of the repair site, but is tacky then the adhesive is ready.
- Apply the prepared patch to the repair site, starting in the centre or edge, working out any air pockets. Use an edging roller to firmly press the repair together if available, or a smooth handle of a screwdriver if not.
- Wait preferably at least 30 minutes for the repair to cure before attempting inflation. Some adhesives require an overnight curing time. Read the instructions of the adhesive product you have purchased.
Subject to a great deal of wear and tear from the elements — both water and sun — inflatable boats are often replaced when they could be restored or even repaired[vague]. Products that aggressively adhere to the damaged Hypalon or PVC shell can fix virtually any surface damage[vague] through a unique chemical bonding between the undercoat and topcoat that permanently vulcanizes the two rubber coatings together to make the inflatable as good as new.
Inflatables are commonly between 2 and 7 metres (6.6 and 23.0 ft) long and are propelled by outboard motors of 2.3 to 300 horsepower (1.7 to 223.7 kW). Due to their speed, portability, and weight, inflatable boats are used in diverse roles:
When employed as life saving equipment, they should comply to the regulations set out by the SOLAS. Some life rafts also contain additional inflatable section to ensure that the raft will self righten in heavy seas.
Inflatable life rafts have also been used since the 1930s on military aircraft that operate over water.
These boats are often used by special-operations units of the armed forces of several nations, for such purposes as landing on beaches. Because inflatable craft can be stored compactly they can also be transported on midget submarines such as those operated by the Advanced SEAL Delivery System. They have also been used by other forces without government sponsorship, such as guerrillas, pirates, and terrorists.
Although rigid boats are more often employed, some cruise ships and luxury yachts use inflatable boats as tenders.
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