Crest of the Royal National Institution of Naval Architects - Click to return to the homepage

The Royal Institute of Naval Architects

Jotun 09/11/2016

Bentley Systems 10/11/16

New wave movement

Ship & Boat International: March/April 2016

Considering its modest dimensions, a new 13m RIB design by Camarc may not seem momentous, initially ­ but this vessel could well hold the key, at least in part, to the future of marine renewables.

Iain Hill, owner of offshore renewable energy support vessel operator Seafari Marine Services (SMS), explains: “As well as the current offshore construction industry, I’m aiming at the upcoming tidal operations, which are starting to get close to commercial deployment.” SMS has been working with this nascent sector to design the kinds of vessels needed to support the process; for instance, the company has been collaborating with a major player, OpenHydro (part of DCNS), since 2012.

Therefore, the RIB, Celtic Guardian, which has been designed to transfer crew and cargo to tidal turbine installation vessels, is “the first of its kind” says Hill, although it incorporates some well-proven design elements.

Alastair Cameron of Camarc explains: “It’s a hull shape we have used very successfully before; it has a fine entry at the bow with a double chine aft: this gives good seakeeping and stability during turns, and it also results in that bit extra beam further aft, for load carrying.”

Despite the proven hull form, Cameron continues: “The design was reasonably challenging; it has to carry, alongside the two crew, 12 passengers and 1tonne of cargo and have a top speed of over 40knots. So we had to work on making sure it trims well, even when fully loaded.”

Further, the RIB has been certified to comply with the UK MCA Workboat code Category 2, and so, although it will probably be deployed less than 20nm from shore, it is actually classed for operations 60nm offshore, “since this adds to the flexibility of the vessel,” says Hill.

Unlike many of SMS’ vessels, Celtic Guardian was built and fitted out entirely at aluminium specialist AluTec Marine’s yard in Argyll, Scotland. Cameron explains: “This was partly due to time constraints ­ we got the commission in early spring 2015, but the build time was very short, delivery being scheduled for last October. AluTec rose to the challenge.”

Celtic Guardian’s 5m-long and 2.9m-wide superstructure takes a lot of the 4.1m overall beam; this allows for three rows of four shock-mitigated seats, supplied by Scot Seats, as well as a toilet and galley, Hill says.

RIB advantages
Which prompts the question, why opt for a RIB at all? Surely a more traditional wind farm support vessel (WFSV)-type build would have given more room for the technicians? Hill points out: “We are working with installation vessels and cable layers and, as these aren’t fixed, if you had a WFSV the thrust needed to keep it ‘nosed on’ means you’d end up pushing the installation vessels around.

“Also, RIBs are the four-by-fours of the sea ­ light, nimble and much faster than other boats, which is necessary given the tight installation windows.” So, in contrast to the slower and heavier WFSVs, this RIB design has a 40knots max / 28knots cruising pace courtesy of three Yamaha 224kW outboard motors. This arrangement also adds important redundancy, as the vessel can still operate with just two engines.

Overall, the aluminium design is extremely sturdy: it has an 8mm shell bottom to its 0.8m draught and, above, the vessel benefits from ManuPlas’ D-section foam-filled fenders. These fenders have an outer sleeve which is sprayed with elastomer coating, “creating a more robust boat than the traditional RIB,” Hill adds ­ an important point, given the nature of the work involved.

Interchangeable bow
However, one of the most interesting elements is the interchangeable bow. “The main design specification we gave to Camarc was ‘versatility both in use and bow loading’,” says Hill.

The answer sprang in part from existing wind support operations; a tailored bow fender section ­ separate to the main collar itself ­ that allows the RIB to nib in, “so that just a little push from the engines will keep the two vessels together,” explains Cameron. And while this boat is designed to mate with the first of these deployment vessels already on site off the coast of France, Hill has an eye to the future. “If a client had a specific access system on their vessels / offshore structures, we’d simply be able to go to ManuPlas and order a shaped bow to fit,” he says. In this way, redeployment would be measured in terms of a few weeks rather than months.

Further, the RIB is useful for a number of roles. The craft has clear cockpit decks forward and aft to carry cargo, while diver access is provided by bulwark gates port and starboard; when open, these gates allow for casualty recovery without the fender getting in the way. It also can cover a wide area; below decks, three 400litre-capacity stainless steel fuel tanks grant the vessel a range of 280nm but further, as the mast on the cabin roof hinges down, the RIB can fit on a low loader without major disassembly, Cameron explains.

If this design is as successful as predicted it will pave the way for many more like it ­ but, as SMS has the advantage of getting to the market early, the company may have a hand in how these support roles develop in the future.

Alfa Laval 260x120

Stone Marine 260x120

Rolls Royce Marine 2016

JETS VAC July 2015

KnudNoSMM2

Drew Safety