Engineering:Rigid-hulled inflatable boat

RNLI inshore rescue boat during Falmouth Lifeboat Day, August 2006

A rigid-hulled inflatable boat (RHIB) or rigid-inflatable boat (RIB) is a lightweight but high-performance and high-capacity boat constructed with a solid, shaped hull and flexible tubes at the gunwale. The design is stable and seaworthy. The inflatable collar allows the vessel to maintain buoyancy if a large quantity of water is shipped aboard due to bad sea conditions. The RIB is a development of the inflatable boat.

Uses include work boats (supporting shore facilities or larger ships) in trades that operate on the water, military craft, where they are used in patrol roles and to transport troops between vessels or ashore, and lifeboats.

History

See Inflatable boat – History for earlier history

Origins in Britain

The combination of rigid hull and large inflatable buoyancy tubes was initially conceived by a Royal National Lifeboat Institution (RNLI) team working under Inspector of Lifeboats Dag Pike in 1964 as a means of reducing the wear and tear of the fabric bottoms of the existing inflatable inshore lifeboats. Although working versions were built, the plywood rigid hulls were not strong enough and broke up in waves. Development was being simultaneously undertaken by students and staff at Atlantic College in South Wales, where the rigid section was formed as a deep vee hull to add strength and which worked. The Atlantic College RIB's were developed to be an effective rescue craft for the college's fleet of sailing boats on the often perilous Bristol Channel, and the college had become an Inshore Lifeboat Station for the RNLI in 1963, carrying out countless rescues over the next 50 years. The first commercial RIB was introduced in 1967 by Tony and Edward Lee-Elliott of Flatacraft, and patented by Admiral Desmond Hoare in 1969 after research and development at Atlantic College.

In 1964, Rear-Admiral Hoare and his students at Atlantic College replaced the torn bottom of their 12-foot-long (3.7 m) sailing activity rescue inflatable boat with a plywood sheet glued to the inflatable tubes. This proved a successful modification but was rather uncomfortable at speed offshore, and so the floor was rebuilt with a deep-vee bow blending to a nearly flat section stern. This boat was named Atlanta and later that year an Atlantic College RIB was displayed at the London Boat Show.

By 1966 the students had built a further five rigid inflatable boats – Aphrodite (15 ft), Triton (16 ft) and X1–X3. Aphrodite and Triton were for the College’s own use. X1 (16 ft) and X2 (22 ft) were launched in 1965 by Queen Elizabeth II and made under a development agreement with the Royal National Lifeboat Institution (RNLI). They were taken by the RNLI for trials at Gorleston (X1) and Great Yarmouth (X2) from which they returned to Atlantic College in Spring 1967. X3 was an experimental vortex-lift hull funded by a private developer and was not greatly successful.

By that time Hoare had concluded that for the conditions under which they operated a boat of around 18 feet long was optimum which led to X4 (launched 1966), X5 and X6 (launched 1967), and X7 to X8 (launched 1968). These boats were used to support the college's sailing activities and also to fulfil the college's responsibility as an inshore lifeboat station for the RNLI – a responsibility it still discharges to this day. At the same time, work started on a smaller series of beach-launchable boats (10 – 12 ft long, designated MX1 – MX6) to support lifeguards on local beaches.

All the above boats’ hulls were built from plywood. In summer 1968, student Paul Jefferies designed and constructed a hull (X10) from fiberglass, which was not a success due to lack of strength. However that development led to the building of Psychedelic Surfer, a twin-engined 21 ft RIB, for John Caulcott, Graeme Dillon and Simon de’Ath to race in the 1969 Round Britain Powerboat Race, in which it was one of the few boats to finish.

From that time, the RNLI transferred development to its research centre in Cowes, who took the Atlantic College designs and developed from them the 21 ft Atlantic 21 class of inshore lifeboats which entered service in 1972 and continued for the next 30 years or so.

The first commercial RIB is believed to be the Avon Rubber Searider which was launched at the January 1969 London Boat Show.

The 108th Engineering Heritage Award by the Institution of Mechanical Engineers was presented to UWC Atlantic College on 30th July 2017 by Carolyn Griffiths, President of the IMeche for its development of the X Alpha Rigid Inflatable Boat ||

Introduction to North America

RHIB deployed from a US Navy Destroyer operating in a littoral area

In the mid-1970s a hull mould and tubes for 21-foot R-HIBs were sent from Atlantic College to their new sister school being established on the west coast of Canada, the Lester B. Pearson College of the Pacific, at Pedder Bay, British Columbia. Three graduates of the Atlantic College who were also trained as RNLI inshore lifeboat coxswains worked at the school during its inaugural year and coached some Pacific College students to build a pair of boats, designated X-27, propelled by twin outboard engines and X-28, propelled by inboard-outboard stern drive. These students were also trained by the graduates to operate these craft as safety boats in support of the college's coastal sailing and diving programs.

During summer, the college loaned their fast rescue craft to the Canadian Coast Guard (CCG), which was introducing rigid-hull inflatables into its new summer seasonal inshore rescue boat service operation. Meanwhile, CCG stations in the Great Lakes began introducing 5.4 metre (18 ft) Avon Seariders at seasonal inshore rescue boat operations in the late 1970s. The CCG inshore rescue boats hired university students to serve as crew, in part due to the success of the student crews operating these ever-buoyant rescue craft at Atlantic and at Pearson College.

Origins in the Southern Hemisphere

The first inflatable boat manufacturer in the Southern Hemisphere is Lancer Industries Ltd, of Auckland, New Zealand in 1971. The founder Chris Marks had visited Europe and brought the concept to NZ. He pioneered many of the initial inflatable boat construction and material methods. Lancers innovate designs and engineering approach to inflatable design still applies and the company holds many patents. Lancer is noted for manufacturing large RIBs, in 1987 it provided tubes for a 17m RIB and then 19 the late 1990s Protector (Rayglass) of New Zealand built two 20m RIB support boats for the Americas Cup which were tubes by Lancer.

In 1976 Steve Schmidt introduced the RHIB concept to New Zealand under the brand Naiad. While it was slow to be accepted for the first few years, it gained momentum with Police, Rescue, marine farmers and Government agencies.

The Naiad RHIB developed by Steve Schmidt differed from the existing RHIB designs in two ways. It had a twin skin, incorporating an air retaining inner and a robust replaceable outer. These were held in place by tracks. This system allowed for easy removal of the outer or inner for repair or replacement. The other feature was the unusually deep variable V hull with extreme turned down chines aft.

In 1978 the demand grew for more protection in the form of an integral cabin and outboard well to better protect the crew in adverse conditions. Though basic to start with cabins soon became popular and more sophisticated. Naiad were one of the early pioneers in designing RHIBs and models range from 2.5m to 23m.

In South Africa

In 1979, Gemini Marine based in Cape Town started building RIBs for the local market. Early on they joined forces with the NSRI and started to design and build rescue craft for the South African Sea Rescue Institution.

In New Zealand

These, as well as Zodiacs, are also used in New Zealand, and Naiads in particular were used in the Marlborough Sounds as water taxis, and their use features in the case of Scott Watson, accused and convicted of the 1998 New Year's Day disappearances and believed murders of Olivia Hope and Ben Smart.

General characteristics

Side view of hull assembly

Forward hull assembly of RHIB prepared as an emergency boat on a ferry in British Columbia, Canada

RIBs are commonly four to nine metres (13 to 28 ft) long, although they can range in length between 2.5 and 18 metres (7.5 and 55 ft). A RIB is often propelled by one or more outboard motors or an inboard motor turning a water jet or stern drive. Generally the power of the motors is in the range of 5 to 300 horsepower (4 to 224 kW).

Small RHIB being used as a dive boat

RIBs are used as rescue craft, safety boats for sailing, dive boats or tenders for larger boats and ships. Their shallow draught, high maneuverability, speed and relative immunity to damage in low-speed collisions are advantages in these applications.

RIBs up to about seven metres in length can be towed on trailers on the road; this, coupled with their other properties, is making them increasingly attractive as leisure craft.

Performance

High-performance RHIB from the Danish Navy

RIBs are designed with hydroplaning hulls. Due to their low weight, RIBs often outperform some types of similarly sized and powered boats.

RIBs can also generally cope better with rougher seas, although this may be partially due to an increased level of confidence in knowing that a RIB is hard to sink, and better absorption of heavy loads by the flexible tubes, which therefore make heavy seas less unpleasant.

The maximum speed of the RIB depends on its gross weight, power, length and profile of hull, and sea conditions. A typical seaborne 6-metre (19 ft 8 in) RIB, with six passengers, 110 horsepower (82 kW) engines, in Beaufort force 2 is very likely to have a top speed of around 30 knots (56 km/h). High-Performance RIBs may operate with a speed between 40 and 70 knots (74 and 130 km/h), depending on the size and weight.

Construction

Clear view of a "Deep-V" rigid hull

Hull

The hull is made of steel, wood, aluminium, or more commonly, a combination of wood for the structure and glass-reinforced plastic (GRP) composite for the shaped and smooth surface. Some manufacturers also weave Kevlar into the GRP sheets for extra strength. The hull of a RIB is shaped to increase the performance of the boat in the water by optimising its hydroplaning characteristics. "Deep-V" hulls cut through waves easily but require greater engine power to start planing than "shallow-V" hulls, which plane at lower speed but with a more uncomfortable ride. As with the design of most boat hulls they represent a compromise of different design characteristics. Modern "all round" RIB hulls combine a deep v hull at the bow which flattens out to present a broad planing pad. This is a flat area on the rear of the hull designed to allow the boat to have a stable surface to plane on.

Tubes

The tubes are usually constructed in separate sections to reduce the effect of a puncture, each with a valve to add or remove air. Larger boats (7m+) have 6 or more chambers with a valve for each chamber. The more chambers a boat has the more redundancy the boat is considered to have. This is because if only one chamber is damaged then the impact the damage has on the boat is much less. Dark tubes often have pressure relief valves as the air inside them expands when exposed to sunlight. This prevents the tubes bursting from overpressure. Common materials for the tubes are Hypalon and uPVC (Polyvinyl chloride), though some manufacturers use PU (Polyurethane).

Hypalon

Tubes made of Hypalon are easy to manufacture and can be repaired with simple puncture repair kits. Hypalon is not airtight and so must be combined with Neoprene when used to build tubes. Tubes made with Hypalon and Neoprene layers can last up to twice as long as PVC tubes and have been known to last 20 years. Hypalon is probably the most popular material used for the construction of RIBs manufactured in the UK.

PVC (Polyvinyl chloride)

As a material for building tubes, polyvinyl chloride (PVC) has the disadvantage of lacking flexibility. To make it supple, an additive is used with the polymer. This additive vaporizes as the material ages, making the PVC brittle and allowing it to crack. A PVC tube is the cheapest option and can last approximately 10–15 years.

PU (Polyurethane)

Tubes made of polyurethane (PU) are difficult to manufacture and are consequently not often used for RHIB construction. PU has an advantage of being very tough, it can be made knife-proof or bulletproof. Earlier PU had a disadvantage of aging quickly but newer types are much more resistant to degradation when exposed to ultraviolet-light. A high-quality PU-made tube lasts over 20 years. PU tubes are often to be found on commercial RIBs, in applications where strength and durability are needed. Replacing the tubes when they wear out usually costs one third as much as the complete RIB.

Wheelhouse/cabins

RIB with a small wheelhouse

Larger RIBs can have hard-tops or wheelhouses made of GRP or aluminium. Wheelhouses offer protection from the elements to both the crew and passengers – and can also protect equipment such as suspension seats and navigation equipment. Some RIB manufacturers, particularly those popular in Ireland and the West Coast of Scotland provide optional canopies which form fabric and perspex wheelhouses but can be easily removed in good weather. Increasingly, RIBs are becoming available with small cabins (usually with accommodation for two people and in some cases sea toilets or chemical toilets), widening the application of RIBs as cruising craft.

Seafari setup

Seafari boats are set up to accommodate tourists for a typically smaller duration. Typical setups use jockey seating to accommodate passengers. Coding in the UK and the EU typically limits the number of passengers to 12 while in some countries, such as Poland, more seats are placed on the boat. Thrill rides are common with high speeds and turns adding to their lure.

Foldable-rigid-hulled inflatable boat (FRIB)

A foldable rigid hull inflatable boat has a 3-section articulated folding rigid hull. The hull sections have interlocking tabs and slots, held together by the pressure in the tubes. Once assembled it’s difficult to tell they fold. Once inflated, they are fully rigid.

Flying inflatable boat (FIB)

Polaris AM-FIB

A flying inflatable boat or FIB is a RIB with microlight-type wings and air propeller. "FIB" is used as a model name by Polaris Motor of Italy for their Polaris FIB.

See also

• Inflatable boat
• Luxury yacht tender
• Outboard motor
• Subskimmer for a RIB that can transform into a submerged Diver Propulsion Vehicle and back.
• LCRS
• Rigid buoyant boat

External links

• AllInflatable's History of Inflatables