The latest vehicle to emerge from the workshop of all-terrain vehicle developer Supacat is a strange looking beast.
Part tractor, part tank and part submarine, the machine has attracted some incredulous looks as it trundles along the country lanes surrounding Supacat’s Devon headquarters.
But while startled motorists might fear they’ve come face to face with some strange new weapon in the war on terror, the bizarre contraption has an altogether less sinister application — the launch and recovery of the RNLI’s next generation of all weather, high-speed lifeboats.
Developed specifically for the Fast Carriage Boat (the vessel which will replace the hugely successful Mersey class vessel) Supacat’s launch and recovery system (L&RS) has been designed to automate a process that hasn’t changed for years. Although there is currently just one prototype of the Supacat system, the project’s chief engineer Simon Turner believes that a whole fleet of around 20 vehicles could enter service as early as 2010.
The key elements of the system are a tractor and a carriage, both of which are equipped with caterpillar tracks. The tractor contains the engine and cab while the carriage incorporates a turntable that enables the lifeboat to be rotated from its bow forward recovery position back into launch position in just under two minutes.
Powered by a Mercedes-Benz V6 12-litre engine producing 422bhp the system has a top speed of 10.5mph and, with a lifeboat onboard, weighs around 47 tonnes.
Said to be simple to operate, control centres around two joysticks: one for direction and speed and the other for shifting the power between the front and rear sets of tracks.
Supacat has spent the past two and a half years putting the vehicle through rigorous tests, beginning with dry trials at Qinetiq’s facility near Bournemouth, moving on to the steep shingle banks of Dungeness and the sands of Wells-Next-the-Sea in Norfolk, and culminating this winter in rough weather trials on the Cornish coast.
During launch the vehicle reverses when it reaches the water’s edge, freeing the coxswain on the boat to guide the tractor driver while the rest of the crew prepare the vessel
One of the big attractions of the system is the way in which it automates what’s currently an extremely labour-intensive process, typically involving a dozen people on the ground accompanying a conventional tractor and trailer on its journey to the sea. ‘Our system can be managed with about two or three — two on the ground and one driving, with the crew staying on the boat,’ said Turner.
During launch, the system first transports the boat from the boathouse to the shore. When the vehicle gets to the water’s edge it turns round and reverses towards the water. While the coxswain on the boat guides the tractor driver to the most suitable launch position and depth the rest of crew prepare the vessel and start the engines.
Taking his cue from the coxswain the driver can control and adjust hydraulic rams to alter the angle of the carriage. ‘You can have either a very steep entry, which means the boat travelling faster, or you can drive out and try and float the boat off which we usually do in reasonably calm conditions,’ explained Turner.
When ready for launch the coxswain pushes a button which releases the strop attaching the boat to the carriage. The boat is then free to power away. Turner said this represents a fundamental difference over the traditional approach where the cue to launch comes from the tractor driver. ‘The coxswain has full control over where he goes, whereas previously it was the tractor driver — who can’t really see very much,’ he said.
By putting the authority in the hands of the coxswain and enabling the release of the boat with a single button, the system is expected to get round one of the potential pitfalls of the conventional lifeboat launch process. ‘On the existing system when the boat’s ready to be released the tractor driver blows a horn at which point four men on the boat’s deck hit catches with hammers which release the chains holding it. Timing is critical. If they’re not released at the same time you end up with a boat lashing about in the water attached to the trailer.’
For recovery, the new system also has considerable advantages over the traditional approach. ‘Currently they have to recover the boat stern first so they reverse up to the back of the boat and drag it backward on to the trailer.’
But thanks to a turntable arrangement the new launcher is able to turn the boat round once it’s on the carriage, meaning it can be winched on to the vehicle bow-first.
The Cat can launch a lifeboat into deep or shallow water
The launcher is prepared for recovery by positioning the carriage facing the sea and rotating the cradle through 180°. Depending upon conditions the boat either runs gently to the shore and heals over typically with the stern still partially afloat, or, in particularly rough conditions, is driven at speed on to the beach to clear the water.
The launcher is then reversed to the bow of the boat, and uses a winch capable of pulling 27 tonnes to drag it on to the cradle. The cradle is then turned back through 180° so that the system is ready for relaunch. According to Turner the technology can recover the boat and turn it back around into launch position in around five minutes.
If an immediate relaunch isn’t required, the boat is transported back to the boathouse, which, at many of the UK’s lifeboat stations is a far from straightforward task. ‘In places such as Dungeness it’s very difficult,’ said Turner. ‘they have to release the carriage from the tractor unit, leave a winch rope attached to the trailer, drive the tractor unit to the head of the beach up on top of the gravel and then winch the carriage with the boat on it up to the tractor.’
Turner explained that the ability of the L&RS to shift the power between the front and rear tracks helps it surmount obstacles such as these with relative ease. ‘For example, if you were going up an icy slipway with the tractor on the slipway and the carriage on the beach behind and the tractor started to slip you could shift the power to the rear and push the tractor up the slipway.’
Constructed from marine grade stainless steel and steel treated with a zinc coating, the vehicle is designed to resist the worst the corrosive marine environment can throw at it.
Indeed, while it is designed to regularly operate in water up to three metres deep the vehicle can also withstand complete immersion up to nine metres deep — hence the cab’s resemblance to a submarine’s pressure-resistant conning-tower. Turner stressed that while the vehicle couldn’t actually be used underwater, this feature would enable operators to lock the vehicle down in the event of a breakdown at low tide.
With the RNLI’s chief naval architect Steve Austen recently praising the design for ‘taking into account a demanding technical specification and operator feedback after each trials stage,’ the institute is impressed with the vehicle and has asked Supacat to produce a pre-production vehicle.
This, said Turner, will incorporate a redesigned electrical system as well as improvements to the cockpit design, but will effectively be the same vehicle.
He said the next iteration of the vehicle should be ready in around a year, and following more extensive trials hopes the RNLI will buy around 20 to smooth the passage of its next-generation lifeboats in and out of the water.