Inflatable boat

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 beneath it is often flexible. On boats longer than 3 m, the floor often 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 they can be easily stored and transported to water when needed. Here 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.

Other terms for inflatable boats are "inflatable dinghy", "rubber dinghy", "inflatable", "inflatable rescue boat" or "rubber duck".

Early attempts
There are ancient carved images of animal skins filled with air being used as one-man floats to cross rivers. They 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 Thomas Hancock and Charles Goodyear in 1838. 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 sceptical 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.

In 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 be propelled only by paddling, and they tended to crack at seams and folds due to imperfect manufacture of the rubber.

The Titanic
With the loss of the RMS Titanic in 1912, and World War I losses of ships to submarine-launched torpedoes, the need for inflatable boats was plain.

One cause of the loss of life 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
The modern inflatable was invented independently by the RFD firm in England and the Zodiac Marine & Pool 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 of 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.

Development continued after WW2 with the discovery of new synthetic materials, such as neoprene, and new glues, which allowed the boats to become sturdier and less prone to damage.

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 military use 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 storability 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.

Post-war inflatables
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. The PBY Catalina made by Consolidated Aircraft and Canadair seems to have been the first aeroplane to have had an inflatable life boat aboard, first as optional, later as standard equipment. A later version of that inflatable was pressurized by a gas cylinder rather than by mouth. A wire connected to the plane opened the cylinder valve in the inflatable after the life raft was thrown into the water.

Until the middle 1950s inflatables were still rafts in civilian use, hand paddled but the outboard motor came into use in the early 1950s. (The outboard motor was invented in 1909 by Ole Evinrude.)

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-hulled inflatable boat


The modern rigid-hulled inflatable boat (RHIB) 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 RHIBs are 14 m 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.

Types
Inflatable boats may have rubber floors, either plain or inflatable, or they may include steel, wood or aluminium sheets for rigidity. The tubes are made of rubberized, synthetic sheets of Thermoplastic Urethane, an advanced Polyurethane, Polyurethane, Hypalon or PVC to provide light-weight and secure buoyancy. The tubes are often constructed in separate sections, each with a valve to add or remove air, to reduce the effect of a puncture.

Some inflatable boats have an inflated keel to create a "groove" along the line of the hull improving the hull's wave cutting and turning performance. Due to the lightness, it is easy to cause an inflatable boat to start hydroplaning, thus making it faster than the engine would allow when the hull is operating in displacement mode.

A growing use for inflatables is for white water rafting and kayaking, as well as in river, lake and ocean touring. Professional-level rafts and kayaks have existed for many years; since the late 1990s, more affordable inflatable rafts, kayaks (including sea kayaks) and canoes have been developed by European and North American companies. Typically these inflatable boats contain no rigid frame members, so they can be deflated, folded and stored in compact bags.

Repairing
Should a section puncture it can be repaired while still underway. More extensive inflatable boat repairs - due to pinholes, punctures, peeling, leaks or worn fabric - can be done in dry dock using two-stage synthetic rubber coatings (SRC).

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. Products that aggressively adhere to the damaged Hypalon or PVC shell can fix virtually any surface damage 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.

Uses
Inflatables are commonly between 2 and 7 m long and are propelled by outboard motors of 2.3 to 300 hp. Due to their speed, portability and weight, inflatable boats are used in diverse roles:

Inflatable and rigid-hulled inflatable boats are often used for short scuba diving excursions.

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.

Lifeguards use inflatable boats or jet skis in order to reduce the time required to reach a swimmer in distress.

Inflatables are also used in conjunction with larger rescue craft such as the Y class lifeboat used with the Tamar and Severn class lifeboats.

They are used in a number of sporting events and for recreational purposes, such as Whitewater rafting, Inflatable Rescue Boat Racing, water skiing, Fishing

Although rigid boats are more often employed, some cruise ships and luxury yachts use inflatable boats as a tender.