Onesails 4T Forte
Unfortunately there’s no way to recycle a sail that’s made out of a mix of material such as carbon, aramid, Mylar and glues. However, in 2013 Piercarlo Molta, Onesails’ R&D coordinator and CEO of Flexon Composites, producer of 4T Forte sails, set out to develop a new material that can be recycled, without compromising shape retention, longevity and reliability.
“At that time I decided to get rid of carbon and Mylar and move towards materials and processes that would be more sustainable,” he told us, “but we still had to ensure the performance would be the same.”
Conceptually the general idea is straightforward: to build the structure of the sail using a single material, plus a layer of thermoplastic melting matrix in the sandwich. These are vacuum bagged and then heated over a shaped air suspension surface, so that when the thermoplastic melts it flows through all the other layers, bonding all the elements together in exactly the right shape.
At the end of its life the sail can be recycled locally in a standard industrial recycling plant. The first stage is to mill it into small pieces, heat to extract the thermoplastic, then heat further until the fabric is molten and can be extruded into pellets. As an example, one of the sails Pip Hare used in the Vendée Globe has already been recycled in this way.
On the downside, you can’t get back to a pure polyethylene, so this is not a full circular economy model in which old sails provide the raw materials for new ones. However, the pellets can be used to create a variety of other new injection moulded products.
The engineering involved in creating such a sail is not simple. The fabric is a composite made of 16-20 micro layers, all of which are fine tuned for each sail and each boat. In addition to the structural fibres and thermoplastic melting matrix, they include a secondary grid for support and stability, a honeycomb that increases stiffness while keeping weight as low as possible, plus UV and abrasion resistant outer layers.
Other than the thermoplastic matrix, the base material for every layer is pure high modulus polyethylene (UHMWPE), a part of the same chemical family as Dyneema. This has a very similar modulus to carbon, but crucially enables the sail to be constructed from a single material – a prerequisite for recycling.
Molta is keen to point out that the thermoplastic film used is not a conventional glue. Its chemical properties are not changed at any stage of the process, which means it can be recovered entirely by heating.
In addition to producing sails for racing and cruising yachts of all sizes, he’s “very involved” in emerging technologies for wind powered shipping, developing sails for vessels with a total sail area of around 4,000m2 and individual sails of around 600-700m2 each. To give a sense of scale, a 4T Forte mainsail for the Clubswan 125 Skorpios is around half that size at 380m2.