A Maritime Surveillance Vessel
When the Mozambique government commissioned Nigel Irens Design and CMN Shipyards to design and build a vessel for maritime surveillance, it sought a fuel-efficient boat that could cruise for many hours and then accelerate quickly for pursuit. Naval architect Nigel Irens designed the Ocean Eagle 43, a trimaran offshore patrol vessel (OPV) with a long, slender main hull and two smaller outer hulls to provide stability yet remain lightweight and cause less drag than other hull forms.
At nearly 143 feet long, the Ocean Eagle 43 can cruise 3,000 nautical miles and reach a top speed of 32 knots (accomplished during sea trials) while burning around one-fifth of the fuel of an equivalent single hull OPV. The first boat was delivered last September, with two others since delivered.
French boat builder H2X constructed the glass fiber and epoxy sandwich laminate hulls, main deck, helicopter deck, pilot house and structural arms. The company used CFRP in high load areas, such as the stringer caps and arms that connect the side hulls to the main hull. H2X partnered with long-time supplier Sicomin to provide a range of resin systems.
The biggest challenge was constructing the 350-square-meter main hull. The initial design called for prepregs with a glass transition temperature (Tg) of 120 C to 140 C, but using prepregs would double the cost of the resin. The tooling and post-cure also was cost-prohibitive. Moving from prepreg construction to a resin infusion process allowed for an epoxy specification of 90 C Tg, reducing the cost of the resin by half, while avoiding the risk of print-through and loss of mechanical properties that could cause delamination or structural failure.