A
rigid inflatable boat ( Rib Boat )
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 means that buoyancy is not lost if a large quantity
of water is shipped aboard. The Rib Boat is a development of the inflatable
boat
General characteristics
Rib Boat's are commonly
4 to 7 metres (13 to 24 ft) long, although they can range in length
between 2.5 and 18 metres (7.5 and 55 ft). A Rib Boat is often propelled
by one or more outboard motors or an inboard motor turning a water jet
or z-drive. Generally the power of the motors is in the range of 5 to
500 horse power (4 to 400 kW).
Rib Boat s 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.
Rib Boat s up to about 7 metres in length can be towed on trailers on
the road, making them attractive as leisure craft.
Performance
Rib Boat's are generally
designed with hydroplaning hulls. Due to their low weight Rib Boats
often out-perform other similarly sized and powered boats, and can also
cope with rougher seas.
The maximum speed of the Rib Boat depends on its weight, power, load,
and sea conditions. A typical 6 metre Rib Boat, with six passengers,
110 horsepower engines, in the sea in Beaufort force 2 is very likely
to have a top speed of around 30 knots. High performance Rib Boat s
may operate with a speed between 40 and 70 knots, depending on the size
and weight. Certain companies operating out of holiday destinations
use Rib Boat s as a "wave jumper". This is a standard Rib
Boat 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 75 knots before jumping 10 ft
off the tops of waves.
Rib Boat 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. The hull of a Rib Boat 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.
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. Common
materials for the tubes are Polyvinyl chloride, Polyurethane and Hypalon.
- Polyvinyl chloride
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.
- Polyurethane
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 Rib Boat s, in applications
where strength and durability are needed. Replacing the tubes when they
wear out, usually costs one third of the complete Rib Boat.
- 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
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 Rib Boat
s that are owned by commercial and high value leisure users.
Deck house
Larger Rib Boats can have hard-tops or deck houses made of GRP or aluminium.
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.
Rib Boats then were introduced for the first time as lifeboats on the
Solent, England in 1970.
After the Zodiac patent
on the inflatable boat expired, the Rib Boat business boomed. Today there
are about a thousand manufacturers of Rib Boats and inflatables. Some
of the most common brands known worldwide are Zodiac, Walker Bay, Avon,
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