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Lightweight Construction is Key to the Ocean Eagle 43’s Rapid Acceleration and Long Range Fuel Efficiency

Lightweight Construction is Key to the Ocean Eagle 43’s Rapid Acceleration and Long Range Fuel Efficiency

  • Tuesday, 5th May 2015
  • Reading time: about 4 minutes

Sicomin has played an integral part in the Ocean Eagle 43 trimaran project which has received the accolade of the largest ever infusion of an epoxy hull in a single shot.

Sicomin explains that the Ocean Eagle 43 is an innovation in maritime surveillance commissioned by the Mozambique Government. The 3 trimaran vessels will conduct multiple missions throughout the Indian Ocean, including anti-piracy operations and the safeguarding of fisheries, oil, gas and other maritime resources. It says that it supplied a range of advanced resin systems during the build programme that was secured by renowned French shipbuilder, CMN. The trimaran shells were produced at Chantier Naval H2X’s facility in La Ciotat, France. All parties worked closely to achieve a truly outstanding result.

In order to undertake its patrol duties effectively, Sicomin claims that the Ocean Eagle 43 must be able to cruise for many hours and then accelerate quickly and pursue. Naval Architect, Nigel Irens was enlisted to produce a sleek and fast design.

“It’s taken many years for the world to warm up to this design for an efficient surveillance vessel,” notes Irens, “but it is a perfect application for a trimaran.” The long, slender main hull and diminutive outer hulls (called amas) are designed to provide exceptional stability, yet are lightweight and experience a reduced amount of drag than other hull forms of comparable displacement, including twin hulled catamarans.

The laminate design mainly consists of a glass fibre and epoxy sandwich construction – a well proven composite structure according to Pierre Lallemand, Head of Composites at H2X. “Everything is cored and infused, except for the monolithic areas near the bottom of the hull at the front of the boat. Carbon fibre was used in the high load areas such as the stringer caps and the arms that connect the amas to the main hull.”

According to Sicomin, the Ocean Eagle 43 is destined for naval duty, its hulls must be painted grey to reduce visibility on the horizon but unfortunately this means the hulls will also absorb significant heat from sunlight. This made the glass transition temperature (Tg) of the resin a key concern for H2X. To achieve a sound solution to this potential problem, Sicomin was challenged to identify an appropriate matrix with a Tg of 90°C.

Sicomin assisted with a series of infusion tests completed on a large glass table to ensure all the cored laminates would infuse completely without issue. With the designer and naval architect’s approval, Sicomin and H2X subsequently made numerous changes to maximise the infusion process such as altering the laminate plan and switching the direction of the fibre to achieve the best flow and wet out possible. Sicomin also developed 150mm and 300mm wide unidirectional tape for the infusion of the critical arm structures. Stitching was designed to leave open paths to encourage resin flow but was balanced to achieve sufficient fibre volume for the required mechanical parts. H2X used 10 layers of these tapes in the arms.

To keep construction time to a minimum, the hull, amas, arms and deck parts were laid up and infused in parallel. The main hull took 5 hours in total to infuse and a vacuum was maintained for a further 4 until gel was completed. This was followed by a 16 hour post-cure in a 43m long oven at 60°C. The 11 metre amas were infused in two halves and then joined along the centreline.

Following the infusion and cure of the first boat, the assembly of the Ocean Eagle’s 106 parts could commence. It took several weeks to build the structure inside the main hull. Parts were joined by conventional wet lay up tabbing using glass reinforcements supplied by Sicomin and their SR8500 hand laminating resin. Sicomin’s Isobond SR1170 was used for enhanced bonding strength in high stress areas.

The first fully assembled boat took 3 months in total to complete and Sicomin and H2X’s overall attention to process control and material selection paid dividends. “The weights of the first and second boats’ main hulls differed by less than 5kg – impressive for such a large structure,” comments Lallemand of H2X.

Sicomin comments that CMN is so pleased with the design concept of the Ocean Eagle 43 that the company is developing a mine-hunter version. Sicomin continues to work collaboratively with H2X on the remaining 2 boats.

Photo provided by Sicomin.

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