Launch and recovery exercise of Dungeness Shannon class The Morrell
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21st-century lifeboats: high-tech life-saving around Britain’s coastline

Image credit: Nigel Millard

From the very first ‘unimmergible’, purpose-built boat of 1785, today’s lifeboats have come a very long way, with the latest version joining the RNLI fleet using waterjet propulsion technology for the first time, making it the most agile and manoeuvrable lifeboat yet.

Lionel Lukin had a vision. A coachbuilder by trade, in 1784 he began experimenting with a Norwegian yawl (that’s not a euphemism, it’s a type of sailing boat…) in his determination to improve the safety of boats, using the River Thames to test his ‘unimmergible’. By incorporating pockets of air within watertight bulkheads, including buoyant gunwhales, and by using cork and other lightweight materials in the structure, Lukin paved the way for the first unsinkable, purpose-built lifeboat. He also included a false iron keel for additional weight to help keep the boat upright, patenting the design in 1785.

Fast-forward 200 years or so and the Shannon is the latest iteration of that original concept, the newest class of all-weather lifeboats to join the Royal National Lifeboat Institution’s (RNLI) fleet, and is making waves at lifeboat stations around the UK’s coastline. For the first time, the RNLI’s all-weather lifeboats are being propelled by cutting-edge water jets in place of traditional propellers, making the Shannon the most agile and manoeuvrable lifeboat in operation yet.

Shannon lifeboat

Image credit: RNLI

Since it was founded in 1824, the RNLI’s lifeboats have saved more than 137,000 lives and with greater numbers of people using the sea for leisure activities, RNLI crews are finding themselves responding to an increased number of incidents relating to people engaged in recreational pursuits. In 2015, the RNLI's lifeboats launched on 8,228 occasions, rescuing 7,973 people and saving 348 lives.

The RNLI fleet comprises over 350 lifeboats based at stations around the UK and Ireland, covering 19,000 miles of coastline between them, as well as some extremely busy stretches of inland water. There are also over 100 lifeboats in the RNLI’s relief fleet, ready to replace station lifeboats temporarily, whenever they require regular or emergency maintenance.

RNLI lifeboats are divided into two categories: all-weather and in-shore lifeboats. The different lifeboat classes within these categories are designed to reach people in a variety of situations and locations, with the type of lifeboat a station has depending upon the specific geographical features of that location, the types of rescue the station is generally called to and the cover provided by neighbouring lifeboat stations.

All-weather lifeboats (ALBs) are capable of high speed and can be operated safely in all weather conditions and, like Larkin’s ‘unimmergible’, they are inherently self-righting after a capsize; but, unlike Larkin’s design (although not for want of trying) they’re fitted with state-of-the-art navigation, location and communication equipment.

Designed entirely in-house by a team of RNLI engineers, the charity harnessed cutting-edge technology to ensure this new lifeboat meets the demands of a 21st-century rescue service, building on systems developed for her older, bigger sister, the Tamar class lifeboat. Measuring just over 13m in length and weighing in at 18 tonnes, the Shannon lifeboat was designed to be launched and recovered from a beach via a new faster and safer launch-and-recovery system and can also be launched from a slipway or lie afloat.

Dungeness Shannon class lifeboat The Morrell at sea during trials prior to going on station

Image credit: Mike Lavis

The new tractor-borne launch carriage operates as a mobile slipway, which solves the unique challenge of transporting, launching and recovering the Shannon over some of the most demanding beaches. After being recovered from the beach bow first, a turntable in the carriage rotates the Shannon 180º ready for her next launch meaning that casualties can be reached sooner, as well as providing better protection for the volunteer launching crews.

Faster to launch and swifter on the water, when lives are on the line, speed counts, and the Shannon brings with it the ability to travel at 25 knots, a full 50% faster than the lifeboats it replaces. As Daniel Sharp, RNLI manufacturing manager, explains: “Once the roll-out of the Shannon class is complete, the RNLI will have achieved its aim of providing a technologically advanced fleet capable of operating at up to 25 knots around the coasts of the UK and the Republic of Ireland. It’s also the smallest and lightest of the charity’s 25-knot all-weather lifeboats and is light enough to be launched and recovered from a beach. As with other all-weather-lifeboats she is inherently self-righting in the event of capsize and will be able to cope with the roughest of conditions.”

Hoylake's Shannon class lifeboat and recovery system

Image credit: Dave James

The development of the Shannon began a decade ago with an attempt to exploit the hull form of an existing pilot boat. However, the Fast Carriage Boat or FCB project only got as far as sea trials. Sharp takes up the story: “These [trials] showed that the decision to opt for a water jet propulsion system was fully justified, this technology offering distinct advantages over propeller driven craft, especially when boats were making difficult manoeuvres or operating in shallow water. But the performance of the FCB hull in rough sea conditions was disappointing. In head seas, when travelling faster than 14 knots, there was an unacceptable amount of ‘slamming’, the juddering crash when a hull that has risen upwards as it moves through a wave thumps back into the water.

“The project team members decided that a completely new hull form would have to be designed, and a competitive tendering and testing process then followed. At the time this work was in progress, the team were uncertain about the then reliability of computer simulations of the anticipated performance of hull designs, particularly those expected to operate under the exceptionally challenging conditions facing lifeboats. Some virtual model testing was actually commissioned; but while the then state of the art in computational fluid dynamics was good for eliminating some designs, and for predicting the vertical acceleration of hull movements, work on the rolling component of their movements was less advanced, with most decisions relying on the testing of physical models,” he adds.

It was during this period that one of the RNLI’s own naval architects working on the project, 24-year-old Peter Eyre, decided to have a go at designing the hull form in his own time, and was, ultimately, invited to finish his design within office hours, entering it to compete with the other shapes selected for testing.

Sharp describes the testing process: “To compare the hulls on the final shortlist the team used 1.5m-long free-running models under radio control. Much of the testing was carried out in Poole Harbour, Dorset, where the ripples caused by force 1-2 wind conditions are equivalent to the waves confronting a full-sized hull in force 7 winds. The models carried accelerometers and other instruments able to record their motion in all dimensions as they sailed through a chosen stretch of water. By testing each model side by side with a standard comparator hull, and so subjecting both to identical sea conditions at the same time, the team was able to measure their relative performance.

“Transverse motions of the hulls when they rolled were particularly important in these tests because the crew seats developed for a previous generation of lifeboats are already good at absorbing the shock of vertical movements. Transverse movement is harder to manage and, if unchecked, can leave crews with damaged shoulders and backs. Having a hull that tracks well is also important because it minimises the amount of steering required simply to keep a vessel on course. The design team also carried out tow-testing in a tank to garner more information about the performance of the hulls under specific wave conditions.”

The result of all this work was a shortlist of two, one of which was the hull design drawn up by Peter Eyre, the RNLI’s own staff member; and in a final comparison his proved to be the winner, an outcome that demonstrated the RNLI’s in-house expertise. The chosen design was a hull that is narrow at the bows, but wide in the aft section, and steeper in the mid region: a shape that presents good stability and at the same time minimises slamming.

The Shannon is described as a ‘wet boat’, as it tends to cut through the tops of waves rather than riding their crest, and it’s this aspect that reduces the slamming effect. The shape and angle of the sides of the hull also reduce broaching in heavy seas; this being the tendency for some vessels to respond to severe conditions by presenting their sides rather than their bows to oncoming waves.

And that’s the hull, but what about the water jets? The Shannon is the first modern ALB to be propelled by water jets instead of propellers, making her agile, manoeuvrable, able to operate in shallow waters and be intentionally beached. What’s more, when precision really matters, such as operating alongside a stricken vessel or navigating around hazards, the Shannon lifeboat really comes into its own.

At maximum power, the Shannon pumps 1.5 tonnes of water each second from her water jets. Chosen because of the need to operate the boat in shallower water, the jets also make the boat faster and more manoeuvrable than propeller-powered vessels. This improved performance is possible because of the moveable ‘buckets’ that alter the direction of each of the water jets, thereby changing the direction of the boat.

As Sharp adds: “Waterjet technology was not as advanced when the Mersey class was commissioned over 20 years ago. Since then, it has become more cost-effective and reliable. The advantage over conventional propulsion systems is that the boat can be held in a neutral position regardless of the throttle settings, and by changing the positions of the buckets, and therefore the direction of the water jets, it can perform a range of manoeuvres that would put impossible strain on conventional systems.”

This sentiment is echoed by Trevor Bunney, a mechanic at Dungeness RNLI, who said: “The manoeuvrability of a jet-driven boat is phenomenal – it really has to be seen to be believed. The launch and recovery equipment helps us get safely back to shore, no matter what the conditions.”

Shannon lifeboat

Image credit: Nigel Millard

The sea’s a-churning, the crew are clinging to their specially-designed shock-absorbing seats, but how ever sophisticated, fast and agile a Shannon is, how do you operate one when it’s blowing a hooley out there? It’s all down to the improved Systems and Information Management System (SIMS) and this is one RNLI innovation in marine engineering which has transformed the way crews operate.

SIMS is an electronic integrated bridge system that allows the crew to operate, monitor and control many of the lifeboat's functions from the safety of their seats, giving them access to the vessel’s intercom and other communications, displaying navigational information (radar, charts, depth, speed etc.) and also data about the performance of the engines and other machinery.

As Sharp explains: “An updated version of the system developed for an earlier class of lifeboat, the Tamar, the SIMS on a Shannon uses one screen to display all the information that a coxswain needs to operate the boat. And it’s not only the helmsman who has access to it; monitors are also visible from the crew seats. Users are spared a cluster of different instrument faces competing for their attention and instead have a tracker ball that they can use to scroll through the various screen images available in order to select just the information they need at any one moment.”

In previous lifeboat models the equipment required to run these systems was collected together in one place. In the Shannon it’s distributed around the cabin, providing two distinct advantages: weight is more evenly distributed, and less cabling is required.

SIMS needs to be reliable and able to withstand extreme weather and sea conditions and is, therefore, made with tough, rugged and salt water-resistant hardware. It’s built using solid-state technology, so it has no moving parts, making it more robust and shock-resistant. Despite its intelligence and underlying complexity, the SIMS user-interface is deliberately plain and simple for speed and ease of use: there are no touch screens and no fancy 3D maps, which can clutter the screen and hide potentially important information, and the buttons are big for crews’ gloved hands.

With six SIMS workstations on board a Shannon lifeboat, every crew member can access all of the SIMS functions to see the status of the lifeboat, but each function is commanded by one crew member at a time. Responsibility for each of the functions is determined by the crew member’s position on-board, but any member of the team can also take over the control of a function. However, the coxswain is the only person who can command all of the functions, but only if he or she takes over the control of them from the other crew members; and is also the only one who can shut-down SIMS and power-off the lifeboat when back at the lifeboat station. Just to note: although SIMS provides all the information the crew needs to operate the lifeboat, all decisions are still made by the crew, not by SIMS…SIMS is not sentient...

And if Lionel Lukin could see the Shannon? With the RNLI estimating that the 50+ Shannons in their class will rescue in excess of 56,000 people and save the lives of over 1,500 in its lifetime, let’s hope he would feel proud that his ‘unimmergible’ played an important part in increasing the safety of those at sea.

Let the music play

Shannon tech spec

Lifeboat category:

All-weather

Launch type:

Carriage, afloat or slipway

Crew:

6

Survivor capacity:

Self-righting – 23

Non self-righting – 79

Maximum speed:

25 knots

Range/endurance:

250 nautical miles

Length:

13.6m

Beam/width:

4.5m

Draught/depth:

1m

Displacement/weight:

18 tonnes (maximum)

Fuel capacity:

2,740 litres

Engines:

2 x 13-litre Scania D13 650hp engines with propulsion from twin Hamilton HJ364 water jets

Number in fleet:

Currently ten at stations and 4 in the relief fleet

Taking care of boaty business

TLC AT THE ALC

All-weather lifeboats are currently maintained on station, in local boatyards, and at the Lifeboat Maintenance Centre in Poole, Dorset, but will soon be carried out at the new All-weather Lifeboat Centre (ALC).

Still located in Poole, the ALC is where the RNLI will build and maintain the 25-knot lifeboats of the future. The completion of the building is an important milestone on a journey of innovation and engineering excellence for the charity. As well as the Shannon class builds and refits, the ALC will also maintain and refit other all-weather RNLI lifeboats.

Six Shannon class all-weather lifeboats are built every year, to replace slower and older lifeboats. By 2019, the RNLI’s own boat builders and technicians will build all of its all-weather lifeboats at the ALC, from moulding the hull to attaching the windscreen wipers.

After 25 years of service, each Shannon class lifeboat will undergo a total refit. The strong composite hull will still have plenty of life in it, but the engines, machinery, systems and equipment will need to be updated or replaced, creating a new Shannon class lifeboat ready to save lives at sea for a further 25 years.

As Sharp comments: “It’s hard out there for an all-weather lifeboat. Working at close quarters with casualty vessels in heavy rolling seas, taking on conditions that would see most mariners taking shelter, these boats need a regular dose of TLC.”

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