Carbon fibre and sailboats

Developments
Future
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 in 2001).
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 boats.

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 sailing.

They are the successors to our racing boats, and are gradually replacing them.

Baronessa V photo G. Finot ADP 52 photo Tresco 6,50 open 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 or aluminium).
The result is greater strength for lower weight.

This leads to greater speed (from 15% to 50% higher) and a more stable boat.

The greater impact strength contributes to greater safety, as well.

And a sailboat can be capable of righting itself with a leak tight carbon mast

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 polyester one.

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 prepreg.

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 or prepregs.

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 that avenue.


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 sailboats

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 stable.
It is possible to have small sailboats and fast cruisers that can right themselves.
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 remains.

The 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.

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