JEC COMPOSITES MAGAZINE - Issue #93 - December 2014 - 39

testimony

"In the field of competition, I think that we are
close to reaching the limits of the materials"

interview

A sailor with boundless energy and a list of achievements longer
and more colourful than a catalogue, Michel Desjoyeaux spoke
to us for a while at the last JEC Europe trade show about composites and their role in the offshore racing world. He shared
his expectations vis-a-vis these materials, and told us about his
latest project, the America's Cup with Team France: a challenge
well within his capabilities!

Michel Desjoyeaux,
Sailor,
Founder of Mer Agitée

M.D.: The weight/strength ratio is obJEC Composites Magazine: Do you know the
ropes when it comes to composites?

JCM: What motivated such a massive introduction of composite materials into racing
boats?

its centre of gravity, roughly at mid-height,
you reduce weight by about 40 kilos at
keel bottom. Which also means that if you
reduce mast weight by 10 kilos, you reduce
boat weight by 50 kilos.
And the performance factor is really there,
in the boat's capacity to carry sails. So it
is not surprising that a lot of effort went
there. People continued to sail on wooden,
fibreglass or aluminium boats, but with
carbon-fibre masts. Carbon-fibre masts

JCM: Lowering weight is a constant. What
specifically did you focus on?

M.D.: We became capable of making

carbon-fibre masts fairly early on. A lot of
people asked us about it, wondering why
we used carbon fibre because they didn't
think it was strong enough. Oh, yes, carbon
fibre is very strong. We worked on the
mast, because that is where we were trying
to reduce the most weight, and where the
safety factors are the lowest. It is normal
that the mast is the part that breaks first, or
fairly often. But in the end, it is the masts
- in fact the mast tubes - and since fairly
recently, the simplicity of the anchoring
systems, that have contributed the most to
weight reduction on boats. Basically, when
you take away ten kilos of mast weight at

The Mod 70 all-carbon trimaran designed by
naval architects VPLP
©T.Martinez

No93 December 2014 /

Feature Marine

Michel Desjoyeaux: I do - and
especially because I've been involved with
them for a very long time. We saw the first
fibreglass/polyester resin boats arrive in
the sailing world. And then carbon fibre
came along in the 1980s, and we craved it!
I made my first carbon reinforcements for
sailing models of small sailboats.
Then sandwich and honeycomb materials
arrived, with pulsed air cure, vacuum
technologies, and more recently, autoclave
cure. Each time, we had to learn "how to".
But knowing about the technologies and
how they are used isn't everything. What's
interesting is to know how to implement
them and understand all the ins and outs of
the issues.
We've seen 18-metre-long hull moulds
break when they cool down to ambient
temperature. This kind of collateral damage
is caused by expansion issues and differentials. Predictably, this did a lot to change
fabrication techniques.

viously very important in competition, but
also nearly everywhere. We always try to
make the boats as light as possible, but they
have to be strong enough so that we can
get up to the desired speeds. And the fibre's
mechanical properties are crucial. When
we saw carbon fibre arrive, and compared
it to glass fibre, the die was cast. For sure, it
cost ten times more, but it was three times
stronger. We experimented with Kevlar™
for a while, which is an interesting material,
but difficult to work with.

jec composites magazine 39

JEC COMPOSITES MAGAZINE - Issue #93 - December 2014

Table of Contents for the Digital Edition of JEC COMPOSITES MAGAZINE - Issue #93 - December 2014