Linen dense chassis for Class40 . Champion

Sicomin fibres, fabrics, epoxy resins and adhesives were used by Grand Largue Composites (GLC), based in Mondeville, France, to build the first Class40 racing yacht to feature a large amount of flax fiber reinforcements.

Crosscall won the Class40 World Championship in June 2022 and is a prototype of the new Lift V2 design by Marc Lombard, one of the leading naval architects in the field.

Class40 is one of the most competitive fleets in yacht racing. The hulls of a Class 40 yacht must be lightweight, strong, rigid and durable in the harshest conditions. Furthermore, to keep costs down, they cannot be reinforced with carbon fibres. Therefore, the quality and reliability of the resins used for pumping and lamination of structures are of paramount importance.

Crosscall’s owner, Aurelien Ducroz, was keen to use as much flax as possible in building the yacht, but Lombard—who had to certify and guarantee the boat’s hull in ocean racing use—was more careful. So a compromise had to be found.

shock loads

The Crosscall’s cockpit is designed to be effectively non-structural, with a main cover, which can generate massive, separately supported shock loads. This allowed the cockpit to be made of a hybrid biaxial fabric comprising 50% flax fibres. Other parts of the boat that contain flax fibers include the tunnel, bonnet, ballast tanks and cover. The rest of the boat is reinforced with 100% fiberglass fabrics.

To help realize this ambitious design, GLC, a highly skilled infusion specialist, turned to longtime material supplier, Sicomin. The hull is shaped and grooved into one piece, and the deck – including the flax-fibre hybrid cockpit – is grooved as one. The inner hull was then laminated into the hull by hand before the hull and deck were finally bonded together.

The infusion resin of choice is Sicomin SR 1710, a high modulus structural epoxy. Specifically designed for use in infusions and injections, it has an exceptionally low viscosity and low reactive hardener that makes it suitable for large part production. The composite components made of SAR 1710 have a high shear strength between the plates and the resin retains its mechanical properties in wet environments.

Both the hull and deck are machined and implanted as single parts.  © Sicomin

Sicomin low toxicity SR 8200 was used to laminate the internal structures onto the hull skin. Ideal for manual lamination, this system incorporates a selection of tempering materials with a wide range of reactions, making it equally suitable for making large or small parts. The structure and surface were bonded with Sicomin Isobond SR 7100, which shows extremely high compressive strength and extreme resistance to microcracking.

A bonding epoxy primer called Undercoat EP 215 HB+ was used and supplied by sister company Sicomin, Map Yachting was first applied to the molds to facilitate the mold removal process. It also acts as an undercoat in a polyurethane exterior coating system that is used in place of gelcoat to protect the epoxy structure from UV damage.

Since Crosscall’s launch, GLC has begun building a second V2 Class40 lift and a third is now planned. Sicomin will supply the material for both.

“We’ve used Sicomin products from the start, never had a problem and wouldn’t want to risk trying another supplier,” said Xavier Gosselin, managing director of GLC.

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