JEC COMPOSITES MAGAZINE - Issue #93 - December 2014 - 40

testimony

are now appearing on everybody's boats
because it allows having less weight aloft,
so less keel weight and less draught, making
boats that can be manoeuvred more easily
into friendly moorings. Depending on the
user, the carbon fibre quality is more or less
important.
JCM: Are there other characteristics that give
composites an advantage?

M.D.: Another crucial factor in the marine
environment is corrosion, and composite
materials do have an advantage over aluminium or steel. There are good reasons why
the military also has produced boats made
out of composites. It's not to save on grey
paint, it's because composites do not rust.
So that also contributes to our preference
for composites, so much that today, most
structural parts - like the keel connecting
system - are made almost entirely of
carbon fibre. It is also simpler, and you get
better cohesion between the materials, in
this case of the connecting system with the
keel.

JCM: Do you think you can push the envelope in terms of performance?

M.D.: We've been experimenting with

different moduli for a number of years, for
example, the masts are in high modulus.
We also tried to make masts out of pitchbased carbon fibre, but that is so difficult to
implement that we stopped. So depending
on the part of the boat, we use different
fibre moduli. We've also created parts by
mixing different moduli, for example our

centreboard beams made in multi-modulus. We do that for maximum optimization
of the strength and deformation properties,
as a function of what we want to do with
the part. I'm not sure that those are issues
you find in other composite applications.
Of course, we don't do that alone. There
are people who build, people who calculate
and others who give these people the
means to work together. Our approach
is to seek performance, not necessarily
without factoring in cost issues, but we
certainly do try to get the best. Basically,
for the same strength, we try for the lowest
possible weight at reasonable cost. It's up
to us to make use of all types of technology
and available means. However, compared
to much of what I was able to see at the
JEC Europe, we are more in prototype
construction. There are many proposals
at this trade show that are very interesting, but simply not adapted for our field,
because when we do two or three identical
parts, that is already a very large series
for us! Our world includes a lot of "hand
made" and still very few machines.

of metal. It is also easier to repair. When
we are hit by a floating object, whether
identified or unidentified, it is relatively
easy to fix. Either the damage is minimal
and we rebuild our sandwich locally, or it is
more extensive and we make a new piece to
reintegrate it into the entire boat structure.
And that poses no problem at all.

JCM: As you use them, do you see further
advantages to the use of composites?

that we are close to reaching the limits of
the materials. The proof is that we break
things fairly often... even given that we
operate in an aggressive environment that
is hard to control. These days, an America's
Cup boat is designed for the San Francisco
sailing area, and if it ever leaves the Bay on
a day when the water is rough, it will break.
We know that, and of course the boats that
participate in this type of regatta in relatively calm sailing areas are not the same as
the ones we use to cross the Atlantic. Simply because it is a different use, and we are
at that level of precision in safety factors.
And also in the multiplicative factors for
static and dynamic loads, because both are
present.
However, what we aspire to is the post-carbon fibre, or a matrix that would result in a
composite with the same specific features
and mechanical properties as carbon along
its longitudinal axis. An isotropic material
with the same mechanical properties as
carbon fibre along its longitudinal axis.
That would be the dream. And if we find it,
demand for it will be high.

M.D.: Of course, the crucial factor is weight
reduction for the same strength. But there
is a "plus" for me: compared to metal structures, composites are much easier to use.
In our context, and given the tools we use,
when we have a zone that needs reinforcing,
to take one example, it is much easier to add
layers or plies than to shape a thicker sheet

Vendée Globe 2009 winner Michel Desjoyeaux arriving at the Sables d'Olonne. Composites can be repaired
in extreme conditions - the patch at the end of the bow was applied during the race
© Yvan Zedda

40 jec composites magazine / No93 December 2014

Composites are also interesting when you
want to make changes to an existing boat.
For example, rather than rebuild a complete
hull when there is only part of it that you
have redesigned, you can "cut and paste".
It is easy and pretty much "transparent" in
terms of robustness. With a slight weight
gain, but of course that is correlated to the
lower outlay in terms of money than you
would make if you had to rebuild the entire
hull. With composites, I keep what is of
interest to me and redo what I don't like any
more.
JCM: Do you expect the improved boat performance to come from the design or from
the materials?

M.D.: In the field of competition, I think

JEC COMPOSITES MAGAZINE - Issue #93 - December 2014

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