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Rigid-hulled inflatable boat
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A rigid-inflatable boat (RIB) or rigid-hulled inflatable boat, (RHIB) is a light-weight 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.
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Encyclopedia
A rigid-inflatable boat (RIB) or rigid-hulled inflatable boat, (RHIB) is a light-weight 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. The RIB is a development of the inflatable boat.
Zodiac is a tradename for a make of inflatable boat, but often has become a genericized tradename used to mean any inflatable boat or RIB.
History
- See Inflatable boat - History for earlier history.
The combination of rigid hull and large inflatable buoyancy tubes seems to have been first introduced in 1967 by Tony and Edward Lee-Elliott , and patented by Admiral Hoare in 1969 after research and development at Atlantic College in Wales. RIBs were then introduced for the first time as lifeboats on the Solent, England in 1970 by the League of Venturers Search and Rescue and also the Gosport and Fareham Inshore Rescue Service.
Today there are about a thousand manufacturers of RIBs and inflatables. Common brands include Walker Bay, Avon, Ribtec, Ribcraft, AB & Apex. About fifty RIB manufacturers are in the UK but only a few now produce all of their components locally. It is becoming more common for hulls to be produced cheaply in South Africa and China to be shipped back to the UK for outfitting.
General characteristics
RIBs are commonly 4 to 9 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 horse power (4 to 220 kW). In some cases multiple engines can be installed either as outboards or as inboard engines.
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 7 metres in length can be towed on trailers on the road, making them attractive as leisure craft.
Performance
RIBs are designed with hydroplaning hulls. Due to their low weight RIBs often out-perform other similarly sized and powered boats, and can also cope with rougher seas.
The maximum speed of the RIB depends on its weight, power, load, and sea conditions. A typical 6 metre RIB, with six passengers, engines, in the sea in Beaufort force 2 is very likely to have a top speed of around . High performance RIBs may operate with a speed between 40 and , depending on the size and weight. Certain companies operating out of holiday destinations use RIBs as a "wave jumper". This is a standard RIB of about 10 metres in length, with two parallel rows of seating down the centre of the craft. It is propelled by two engines, with the aim being to get the craft to roughly 30-40 knots before jumping off the tops of waves.
Construction
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 "Planning 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 over pressure. Common materials for the tubes are Polyvinyl chloride, Polyurethane and Hypalon.
As a material for building tubes, polyvinylchloride (PVC) has the disadvantage of lacking flexibility. To make it supple, an additive is used with the polymer. This additive vaporises as the material ages, making the PVC brittle and allowing it to crack easily. A PVC tube is the cheapest option and lasts approximately five years.
Tubes made of polyurethane (PU) are difficult to manufacture and hard to repair. PU has the great advantage of being very tough, it can be made knife-proof or bulletproof. Unfortunately to make PU airtight, it has to be used in layers, combined with neoprene. The biggest disadvantage with PU is that it ages quickly: thermal and mechanical wear-and-tear and exposure to ultraviolet-light are problems. A high quality PU-made tube lasts 10 to 15 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 of the complete RIB.
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 30 years or more.
Although early in its life a PU tube will be stronger than a Hypalon / Neoprene tube, by the age of 5 years they have similar levels of durability, which is why Hypalon/Neoprene tubes are often to be found on RIBs that are owned by commercial and high value leisure users. Hypalon is probably the most popular material used for the construction of RIBs manufactured in the UK.
A 3 part instructional video of RIB Tube construction may be viewed at
Wheelhouse/cabins
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 2 people and in some cases sea toilets or chemical toilets), widening the application of RIBs as cruising craft.
Images
Rigid Buoyant Boat (RBB)
Based on the concept of a RIB but with a tube/sponson manufactured from a solid material such as moulded polyethylene or aluminium and therefore being much more robust than the fabrics commonly used. Boats with foam filled collars such as the secure all-around flotation equipped (SAFE) boats employed by the US Coast Guard can also be classified as Rigid Buoyant Boats rather than "true" RIBs as the collar is solid foam rather than inflated. The handling tends to be very similar to a RIB; likewise they will remain afloat (buoyant) even if completely flooded. Aluminium RBBs tend to be bespoke (custom-made to specification) or low-volume products whilst the tooling cost of rotomolded polyethylene boats tends to require these to be higher volume products. At least three manufacturers are producing rotomolded boats of this type. One supplier demonstrates the robustness of the boats by dropping one from a crane onto a concrete car park. The U.S. Navy’s small unit riverine craft and the Coast Guard’s Defender class boats are examples of RBBs.
See also
External links
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