SHAPE SHIFTER
systems that scan the sea bead ahead and relay the information in real time to the mothership. Presumably, the idea is for them both to take up positions ahead of the superyacht (red to port, green to starboard) and map a safe channel between them through uncharted waters which is safe for the mothership to follow. To do this effectively they must provide a safe, stable platform for the crew even in the inhospitable seas around the Antarctic. The lengths some superyacht owners go to…
While the Explorer yacht wasn’t available for testing (if only!) its two Rafnar tenders were, albeit in the slightly less challenging waters of the Solent. The first thing to point out is that even without the strange hull shape, these are no ordinary RIBS. The fitout has more in common with search and rescue lifeboats than leisure RIBS let alone superyacht tenders. Treadmaster non-slip decking, black anodised grab rails, heavy duty lifting points and chunky sampson posts replace the usual warm teak and polished stainless steel fittings. The monogrammed bench seats hint at a rather more refined purpose, although the twin Ullman suspension seats wouldn’t look out of place on an SBS assault craft.
The choice and installation of engine is equally unusual, eschewing the normal petrol outboards (an OB version is under development) in favour of a single 440hp Volvo D6. This is mounted amidships under the helm console and linked to the DPI sterndrive with the aid of a short jackshaft. This keeps the considerable size and weight of the big 5.5-litre diesel as low and close to the centre of gravity as possible while still benefitting from the speed and efficiency of a slippery sterndrive leg. The internal structure of the hull also deserves a mention, comprising a seriously hefty grid of criss-crossing GRP stringers that must make for one of the stiffest hulls around.
Then there’s the shape itself. As you can see from the photos the usual V-shaped forefoot evolves into a deeper bowed keel that gradually flattens off towards the stern. The sides of this are gently scalloped and framed with a pair of shallow chines and two larger spray rails leading up to vertical topsides that raise its freeboard forward and give it that distinctive kinked sheerline. Rafnar is very cagey about explaining exactly how all these different elements interact to deliver that promised slam-free ride for fear of revealing the secret of its multiple patents but the effect is to keep the hull sucked down onto the surface, rather than skimming over the top of it, without the penalties of excessive drag and a hefty bow wave that normally accompany a semi-planing hull.
Fire up the engine and it welcomes you with a distinctive diesel thrum that while noisier than an outboard, sounds in keeping with its semi-commercial roots. Thankfully, Volvo’s new electronic throttle and drive-by-wire gearbox ensure that it slips smoothly and effortlessly into and out of gear. The electronic steering is equally refined, although there’s a very slight delay between applying lock to the rather small, go-kart like wheel and the computer relaying that information to the sterndrive. On the plus side it makes for a nicely weighted and geared helm without any hint of stickiness or friction in the system. There also seems to be a slight list to starboard at slow speed which Rafnar UK’S Tom Bettle, sitting next to me, puts down to his lockdown eating habits!
WAVE-BUSTING
Put the throttle down and the torquey D6 delivers lusty acceleration but without the bow rise that you’d get with a conventional hull. Look at the performance table and you can see that both speed and fuel consumption build in an almost perfectly linear fashion without the usual hump at 10-14 knots as it clambers onto the plane, supporting Rafnar’s claim that it behaves more like a fast displacement hull than a planing one. It does throw out a fair bit of spray from those broad chines but it seems to eject it far enough out to the side to prevent it being blown back on board in anything other than a strong sidewind. But it’s the way it rides that is
most unusual. You can feel the hull being sucked down into the water rather than skimming across it. In a short chop it just blasts its way clean through, in a larger sea you can feel each wave in the form of a slight deceleration as it forces the water aside matched with a short frequency bob as it tries to rise before being sucked back down again. It’s an odd sensation that takes a bit of getting used to but because that curved keel section rarely, if ever, leaves the water, the frequency, size and particularly the abruptness of the vertical shock loadings are significantly reduced. It’s a photographer’s worst nightmare as I simply couldn’t force it to deliver the kind of wave-jumping moneyshots that we usually strive for, however hard I tried.
Admittedly, the waves weren’t particularly big on our test day but piling flat out through the other boat’s wake produced nothing more dramatic than a bigger than normal arc of spray. It’s not completely immune to any form of slamming; if you bank it hard enough over a wave so that it lands chine first you’ll still get a shudder through the hull but the combination of that immensely solid structure and the Ullman suspension seats ensure both the boat and your spine stay intact. A study by the University of Iceland comparing a conventional deep-vee 10.5m RIB with Rafnar’s 11.0m equivalent over the same stretch of water in 0.5-0.75m waves found that the deep-vee RIB experienced 517 impacts of more than 1g whereas the Rafnar suffered just 189. By the same token the highest impact for the regular RIB was between 4-4.5g whereas the Rafnar was between 3-3.5g. Nor does this come at the cost of stability or sea-keeping; the Rafnar 850 gripped like velcro through the turns, refusing to budge an inch off line even when provoked and leaning far enough over to feel natural without ever submerging the tubes.
VERDICT
The Rafnar 850 delivers on its promise of providing a safe, stable, soft-riding platform without a major compromise in speed or efficiency – 39 knots flat out and 1.56lpm at 31 knots is on par with an 8m planing RIB and a 300hp outboard. That said you’ll need to value these assets highly as they do come at a financial cost – €342,000 for a D6 330hp Rafnar 850. Nor is the current boat particularly well suited to leisure use, although the layout can easily be changed. There’s also the question of whether it’s actually more fun to drive than a planing hull. You can certainly push it harder through rougher seas than an ‘ordinary’ RIB but not many leisure users go out in those conditions and in calmer seas that feeling of skimming over the surface with the occasional jump is all part of the fun. Rafnar UK knows this and is instead targeting the kind of customer where delivering precious guests, cargo or troops swiftly and safely regardless of the conditions is everything – a brief which the 850 fulfills almost to perfection.
Rafnar UK Tel: +44 (0)1243 682080; www.rafnar.uk