JEC COMPOSITES MAGAZINE - Issue #84 - October 2013 - 34

high-performance
Test programme
Kaïros - the racing team of Roland
Jourdain - and French Ocean Research Institute Ifremer have been
collaborating since 2009 in a joint
programme to characterize commercially available bio-sourced polymers,
composites and sandwich cores [ 3].
Several hundred specimens have
been tested since then to provide the
mechanical property database required to design Gwalaz with confidence,
focusing on three criteria:
1) The materials tested were manufactured using boatyard fabrication
techniques,
2) Within each test series, a reference
glass-reinforced composite with the
same fibre weight content was tested,
and
3) Particular attention was paid to the
influence of wet ageing on properties.
The latter point is crucial as, unless

the long-term durability of biocomposites can be established, their use in
marine structures will remain limited.
When ageing tests are performed on
traditional composites, it is common
practice to take square coupons, fully
immerse them in tanks filled with
high-temperature tap water and measure their weight gain until saturation.
With natural-fibre-reinforced composites, this approach results in a very
high weight gain and fast degradation,
as the exposed cut fibres facilitate
water ingress.
In reality, a composite boat hull will
normally be exposed to water on
one side only. There are no exposed
edges, and protective coatings such
as gelcoats and anti-fouling paints are
also present. To establish the seawater
diffusion kinetics under these conditions, a series of tests were performed using samples clamped onto the
outside of a water bath, as shown in
Figure 3a.

Figure 3b shows examples of weight
gain plots obtained under these
conditions and for similar materials
aged by full immersion. It appears
clearly that under the more realistic
conditions, the weight gains are very
limited, similar to those noted for
glass/polyester. The use of an antifouling paint was shown to further
slow water ingress.
These data and other data generated
at different temperatures make it possible to predict water ingress. Periodic
monitoring during service is also
planned to provide valuable additional information on the ageing of these
materials.

Manufacturing
Gwalaz was manufactured by Kaïros
and Tricat at the Tricat boatyard. The
moulds used for the main hull and the
outrigger hulls were provided by Tricat. Kaïros provided its expertise with
regards to the storage of flax fibre
fabric and the resin infusion process
parameters needed to achieve a highquality composite material. Figure 4
shows different steps in the manufacturing process.

Navigation

Fig. 3: Wet ageing in sea water: a) Test set-up for single-side seawater exposure of composite and
sandwich samples, b) Comparison between full sample immersion and one-side exposure to natural
seawater

Fig. 4: Manufacturing Gwalaz

34 jec composites magazine / No84 October 2013

One of the objectives of the project
is to follow the prototype's behaviour
in service, particularly as regards the
ageing of the bio-based composites.
After one month of sailing including
a tour of Brittany, no differences were
observed compared to the original
trimaran made of glass fibre and polyester. A maximum speed of 19.3 knots
was reached in those conditions, close
to the 21-knot speed record of the
classical version (see Figure 5).
The next sailing trip will be undertaken in the Solomon Islands by a
team of three sailors/surfers [4]. Five
months' sailing in 25°C water will
accelerate the ageing of materials. The
hull has been strain gauged and the
mechanical response will be compared using measurements made before

JEC COMPOSITES MAGAZINE - Issue #84 - October 2013

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