Feature 4 | COMPOSITE CONSTRUCTION
forward sections may incorporate up to 15 carbon plies. Forward hull areas are further fortified by moulding in carbon fibre beams. Tese stiffen the hull against the high
tension exerted by the forestay when the rig is fully tuned and laterally, since the Extreme 40 lacks the secondary crossbeam that joins the bows on many other catamarans. Each hull is further stiffened by an inside ‘middle’ deck and six bulkheads. Tese items are prefabri- cated and autoclave cured before being introduced into the hulls via the cockpit and bonded in place. For each major item, prepreg fabric
is laid up into the female mould to the required thickness and then vacuum bagged. Bagged items are then placed in the autoclave and heated to 125°C for about 90 minutes, although it takes a similar time to ramp the laminate up to temperature initially. Because a high-temperature cure regime is used, comparable with that used in aerospace fabrication, no post cure is necessary. The mast is similarly produced by
laying up carbon prepreg laminate in female moulds. Among other critical items are the twin main dagger boards, which are highly stressed when sailing at speed and have profiles that are optimised for high hydrodynamic eff iciency. Marstrom produces these parts with high fibre volume fractions using its one-shot technology. Te vessels are built so that they can be
dismantled, enabling each to be stowed in a 40ſt container, along with its road trailer, for shipping to various parts of the world. Accordingly, the hulls are 12.19m long, and the 18.89m mast has a sleeve joint at the halfway point so that it can be disassembled into two halves for container stowage. Assembled, the craſt has a 7.92m beam and displaces 1250kg.
Record world girdlers Dwarfing the Extreme 40s are the latest breed of circumnavigating multihulls including the IDEC 2 maxi trimaran, in which Frenchman Francis Joyon recently sailed solo and non-stop round the world in 57 days, 14 hours, averaging 19knots and smashing Ellen MacArthur’s B&Q Castorama record by two weeks. During his voyage, Joyon created a
42 Inside the hull of an Extreme 40 during build (courtesy TornadoSport).
new 24-hour record run of 616miles. Tis was subsequently beaten by fellow Frenchman Tomas Coville who covered 619miles in the same time in his slightly bigger trimaran Sodeb’O. However, the crash box of one of Coville’s bows tore off shortly aſterwards, and he was forced to abandon his non-stop round the world record attempt. IDEC 2 and Sodeb’O are both about 30m
long and 16m wide, approximately a third of the dimensions of a football pitch, and both were conceived by the same design team of Nigel Irens and Benoit Cabaret (they are well known for having also designed a number of other performance multihulls including MacArthur’s B&Q). However, there are interesting differences between the two vessels. Both craſt are composite but whereas
Coville’s boat was built by Boatspeed, Australia, in high-tech prepreg carbon, Marsaudon Composites, of Brittany, used a more affordable resin infusion process to fabricate the carbon/foam sandwich IDEC 2.
Samuel Marsaudon believes IDEC to
be the largest multihull ever produced by infusion and regards this approach, developed in response to Joyon’s need for a tough yet affordable vessel fit for tackling the world’s oceans at speed, as a good way of producing strong carbon craſt at reasonable cost. Carbon plies and core are laid up by
hand into female moulds for each major part, and vacuum bagged. Reducing the pressure behind the membrane then serves to draw liquid resin, injected at inlet ports, fully into the lay-up. Aſter a period curing at ambient temperature, de-moulded parts are post-cured in a large oven - for approximately 16 hours at 70°C for IDEC 2. A considerable testimo- nial to this affordable technology was that an inspection aſter Joyon’s voyage revealed no cracking or other significant damage. Boatspeed Performance Sailcraft, of
New South Wales, on the other hand, used a wet-preg epoxy/carbon system from ATL Composites to produce the
Ship & Boat International May/June 2008
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