Rigid Inflatable Boat

The rigid inflatable boat (RIB) is an incredibly versatile craft, in fact it's the SUV of the sea, reports Kevin Green.

Invented by the British Royal National Lifeboat Institution in the early 1960s, it has become synonymous with rescue agencies worldwide. Versatility and seaworthiness are the main attractions for rescue services and naval military units.

Commercially, it was the British Avon company that began marketing them to the general public – mostly as a way of selling more of their rubber/neoprene material – before pioneering builders such as British Humber, French Zodiac and others joined the fray. The first commercial RIB is believed to be the Avon Rubber Searider which was launched at the January 1969 London Boat Show.

RIB Design

Major milestones in the RIB's evolution include the moulded hulls and the use of Du Pont's Hypalon material, the latter creating strong tubes and allowing multiple fabric colours to be used and thus make design more commercially appealing. This was one reason why Italian design flair nowadays means that they are a leading nation for commercial/recreational models. Smaller and cheaper models are made of PVC and glued, with better ones using welded seams. Some companies, such as Zodiac, use derivatives of PVC to improve this material.  Both materials suffer from UV exposure in harsh climates such as Australia, requiring special care and treatment to ensure longevity. Cost has always been a factor with the RIB because of the labour-intensive build required, which meant that production was often moved to developing countries. However, the downside was lower quality, which gave RIBs a bad reputation among recreational users, especially in harsh climates that further degraded them.

RIB Characteristics

Australian users have been relatively limited but include rescue agencies and most prominently surf life-saving organisations. However Australian builder and leading global brand Brig is one company that is expanding this perception locally. Its Ukraine-made boats are high quality and innovative.

So, during my 20 years of working as yachting journalist here, I have seen a steady rise in their popularity among recreational users. The reasons are the same as commercial users – flexibility, versatility, seaworthiness, good power-to-weight and safety. Safety comes from the surrounding air tube in a deep vee hull that has a low centre of gravity, and is usually unsinkable. Versatility includes a relatively lightweight vessel, easily trailable or hoisted on a davit. Hull design is a major factor in the modern RIB, allowing it to handle effectively in displacement and semi-displacement mode due to its flat aft section but with enough deadrise aft to soften the ride. Flexibility includes the ability to be buoyant despite the air tubes deflating. The result is an extremely seaworthy vessel that is often sturdier than the steerer. As RIB expert Dag Pike told me once when we were boat testing, the weak link in the modern offshore RIB is often the inexperienced steerer.

Handling a RIB

Recreational boaters use RIBs for a variety of inshore activities such as hooning about, pulling skiers, sub-aqua diving and ferrying crew to the mothership. To achieve any of these activities safely, a few handling characteristics are worth highlighting:

Slow speed handling is often more predictable on an average 20-foot RIB than the equivalent tinny or runabout because of the deep vee hull and the longshaft motor that is generally fitted. Throttle response is often quick, so like a sports motorbike on land, it has to be graduated to the situation. Going astern is done simply by following the direction in which the motor is pointing but in chop the lower transom of some RIBs can ship water.

At speed, the smooth ride comes from the linear stability of the deep vee, running strakes and lateral stability from those wide air tubes which also absorb shock. Turning is predictable due to the good grip of the hull yet controlled by those air tubes, while planing is promoted by the warped vee shape of many RIBS. Just like a 4WD scenario, these tubes can be slightly deflated to ease the ride. In mild conditions, the novice skipper can simply point and go. However, once conditions deteriorate, more interaction is required to manage the throttle, change the trim (with tabs or engine angle) and typically adjust the hull-angle for the oncoming seas.

Oncoming seas are the most challenging, even for a rugged RIB, because both objects (you and the waves) are moving quickly towards one another. Facing steep, short seas is tough in any boat but the RIB can tackle them if the right speed is chosen for the wave. Typically done by throttling forward (bow up) and then back (bow down), while ensuring to maintain momentum. As the seas rise, the RIB will follow their contours, which can become dangerous. One solution is tackling them at an angle to slow the ascent and then descent into the trough, where more throttle is generally required to lift the bow.

Running with the seas can be a fun experience on a RIB as its immense buoyancy compensates for even the novice steerer. However, a sobering thought is that RIBs, like most vessels, are mostly designed for meeting oncoming seas, so following seas can find weaknesses. So, once wave height rises, dangers lurk when waves can move faster than the RIB, causing a loss of steerage and threatening a broach – going sideways to the waves.

The rule here, is to outrun them, especially the breaking crests following you. Getting the speed right in large following seas requires constant adjustment of the hull-angle and throttle speed. Too slow could result in a broach or being pooped. Too fast and air-time followed by the prop spinning- out and a severe crash or even a pitch-pole is possible. Apart from the RNLI with their gantry air bags, there are few ways to recover an upturned RIB.

Beam seas are another common scenario, but the RIB's inherent characteristics generally cope well with these conditions, such as their lower centre of gravity. However, breaking wave crests require evasive action such as running off or slowing to avoid.

Heading shoreward in following seas is the classic beach landing for trailer boats. Typically done by watching the wave sets then coming in on the back of mid-set wave before roaring up the beach on the rugged fibreglass or alloy hull that most RIBs have.