Carbon fibre and sailboats
Example of autoclave moulding
| Jean Marie Finot's Conférence
, on 2003 april, 2, at the JEC Composites Show 2003.
The use of carbon fibre for mono- and multihull racing boats has
helped enormously to advance boat speed and safety.
Our 60 footers have won the last three Vendée Globe races and the
last three Around Alone races (Alain Gautier in 1991 and 1993, Christophe
Auguin in 1995 and 1997, Giovanni Soldini in 1999, and Michel Desjoyeaux
Fifteen carbon racing monohulls have been built on our drawings.
The trend in carbon prices, developments in processing techniques,
the increase in productivity, and demand are encouraging the mass
production of rapid sailboats using carbon.
||The challenge is to succeed in making
reasonably priced mass-produced boats in carbon that
offer a new way to sail, whether it is just for sailing about, or
for regattas, or fast cruising. If this does succeed, it will mean
building a new type of boat that will represent from 5% to 15% of
the yachting market.
A bit further off in the future, if prices continue to drop, the proportion
of the market share could rise. For the time being, carbon
masts are about to win the market for fast
With all this in mind, we have been developing carbon sailboats, including
a 40 footer (Open
40), a 50-foot fast cruiser (ADP
52), and a 6.5-metre-long boat for regattas. All these boats are now
They are the successors to our racing boats, and are gradually replacing
photo G. Finot
photo G. Finot
1 - The advantages of carbon
The advantages of using carbon lie in its mechanical strength and fatigue
strength, which are much higher than those of other materials (polyester/glass
The result is greater strength for lower weight.
This leads to greater speed
(from 15% to 50% higher) and a more stable
The greater impact strength contributes to greater
safety, as well.
And a sailboat can be capable of righting
itself with a leak tight carbon
2 - Sailboat structure
The boat is subject to overall stress
(from the sea and its own weight) and to localized
stress (the rigging, waves, ballast and rudder loads,
stress due to crew movements, etc.).
To withstand all these stresses and any trouble with water-tightness,
the sailboat is generally made of a one-piece-moulded or sandwich
skin over a structure.
For the same stiffness and strength, a one-piece-moulded
carbon panel weighs only half as much as a glass-fibre reinforced
There is less weight saving for sandwich, as it is applicable only
to the skin - thus, savings of only 15-30%. One-piece construction
is suitable for large structures and all parts of the boat that
are highly subject to impact.
3 - Processing methods used for building
The first open 60 footers were built in sandwich
material over a positive mould,
the following ones in sandwich material
over carbon prepreg female mould.
The front part that is subject
to a lot of impacts was one-piece-moulded
; the skin and sometimes
the stringers, in oven-cured
The transverse structures were
sometimes assembled by wet lay-up or prepreg.
construction de PRB (Isabelle Autisser)
construction de CCP Cray Valley
These time- and labour-consuming processing methods are suitable
for racing boats that are built by the unit, but not for mass production.
The current challenge is to build
these hulls in series relatively rapidly and mould the skins and
stringers/frames in a single step.
It is possible to use infusion injection moulding
We worked with the CRITT in Toulouse to test several different solutions
- these were infusion moulding,
- vacuum prepreg in a curing oven,
- prepreg in autoclave.
Setting up the infusion process for one-step construction takes a long
time and requires a lot of consumables for large parts. It is no doubt
a promising solution.
However, the prepreg in autoclave
rapidly gave good results and, since
we had an 8m x 4m autoclave available at Latécoère, we decided to explore
hull of the 6,50 just out
of the mould
photos jm finot
Following the tests at the CRITT, the
Grillons Workshop in Toulouse succeeded in producing
several hulls for a 6.50-m
sailboat called the "Open 6.50".
The skin and the longitudinal
stringers and transverse frames
were done in a single curing step.
The technique required investing in complicated moulds and cooling
jigs for holding the fabrics and stringers/frames in place, but
the result is promising.
After carrying out strict quality controls, the next step will
be to carefully calculate the time savings obtained.
the open 6,50 in
the golfe du Morbihan, photo jm finot
4 - The evolution of processing methods
Consistent results with respect to strength, weight, higher productivity
and, especially, savings on consumables are the potential gains from the
advances made in processing.
5 - Future developments in the use of carbon for
|Masts (built using
prepreg, filament winding, or pultrusion techniques), hulls,
and ballast fins, in that order,
are the areas that benefit the most from carbon. The
more weight savings achieved in the upper works, the more it is profitable
6 - Development
Developing the market and the use of carbon will depend on
lowering the processing costs and the price of the boats.
There are some very interesting avenues: using carbon produces rapid cruising
sailboats that sail 20-50% faster. Thanks
to these new cruisers, it becomes possible to sail the Mediterranean by
day (150 km in 16 hours).
The boats are more robust and more
It is possible to have small sailboats
and fast cruisers that can right
For light sailing, a number of craft are currently being designed that
are possible only with the use of carbon.
The technique is now reliable, although the problem with price still
cost price of a glass-fibre reinforced composite is about 8 euros/kg,
or 16 euros/kg with respect to its equivalent in carbon, which weighs
half as much. The hull represents one-third of the price of a boat.
The current price of carbon prepreg is 150 euros/kg. The new processing
methods make it possible to lower that price to 75 euros, or 50 euros
in the medium term. Its use is limited, however, because the boat
costs 85% to 100% more than a standard boat.
The new customers will have to be motivated
by speed and a heightened sailing pleasure.