JEC COMPOSITES MAGAZINE - Issue #96 - April 2015 - 19

trimaran

Lightweight design: key to the Ocean Eagle 43's
rapid acceleration & long-range fuel efficiency

Commissioned by the Mozambique Government,
the Ocean Eagle 43 is an innovation in maritime
surveillance. The three 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. Sicomin played an integral part in
this challenging project and 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.

ll the parties worked
closely to achieve
a truly outstanding
result and the project has
now received the accolade
for being the largest ever
infusion of an epoxy hull in a
single shot.

The trimaran design
In order to effectively
undertake its patrol duties,
the Ocean Eagle 43 must be
able to cruise for many hours
and then accelerate quickly
and pursue. Legendary naval
architect Nigel Irens was enlisted to produce a sleek and
fast design.
"It has taken many years for
the world to warm up to this
design for an efficient surveil-

lance vessel," notes Irens, "but
it is a perfect application for a
trimaran." The long, slender
main hull and diminutive
outer hulls (called amas)
provide exceptional stability, yet are lightweight and
experience a lower 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

Destined for naval duty, the
Ocean Eagle 43's 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,
they drew on their 20-year
relationship with Sicomin
to identify an appropriate
matrix.

specified for the Ocean Eagle
43 was 120°C to140°C, a
carry-over from the initial
design that called for prepreg.
However, that would have
doubled the cost of the resin
and also increased the cost of
tooling and post-cure requirements."
Fortunately, the H2X design
and build teams converted
to a more economical resin
infusion process, allowing
Sicomin to specify a system
with a lower Tg of 90°C.
"Infusion epoxies with a Tg
of 80°C are available but in
our experience this is too low
for dark hulls, risking not only
print-through but a loss of mechanical properties over time
that could result in laminate
or structural failure", states
Denjean.

Sicomin has extensive experience with other multiple
dark-coloured, epoxy-infused
boat projects. Marc Denjean,
Sicomin's Export Manager
comments, "The original Tg

To support this evidence,
Sicomin gathered scanning
calorimetry (DSC) and
dynamic mechanical analysis
(DMA) test data.
With time, the Tg will de-

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."

The challenge of dark
hulls

The Ocean Eagle 43 and before final painting

No96 April 2015 / jec

composites magazine 19

JEC COMPOSITES MAGAZINE - Issue #96 - April 2015

Table of Contents for the Digital Edition of JEC COMPOSITES MAGAZINE - Issue #96 - April 2015