“The marine industry is very open to natural fibres materials”

JEC Composites Magazine: Whilst natural flax and hemp fibres have been used onboard ships for ropes, sails and sealing between planks for hundreds, even thousands of years, the use of these fibres in what we would call true lightweight composite applications is much more recent. Can you give us a short introduction to some of these early natural fibre applications in the marine environment?
Brice Roussel, Materials and Innovation manager, Alliance for European Flax-Linen & Hemp: That’s absolutely right, flax and hemp have been used in fibre and textile format since some of the earliest seafarers set sail. It wasn’t really until 1937 when probably the first true flax composite material, and one of the first fibre reinforced plastics ever recorded, a flax phenolic composite called Gordon Aerolite was created in the UK as a potential replacement for aluminium. At this time, a host of new composite resins and fibres were appearing and, from about the 1950’s, glass fibres, then later on carbon fibres in high-performance applications, remained the preferred reinforcements of choice for marine sector composites. Over the last ten or fifteen years, several innovative flax fibre boats have been built as flax has started to gain significant traction in marine applications.

Friedrich Diemann, founder of natural fibre composite specialists Greenboats, built his first flax boat – a two-person kayak – over 10 years ago having become dissatisfied with the unpleasant fumes and skin irritating dust produced when working with typical composite fibres and resins. Since then, Greenboats has gone on to develop a flax version of the popular 24’ Bente yacht and a larger Judel and Vrolijk design, the Flax 27 day sailor using Bcomp’s ampliTex™. The company is currently building a 30’ one-off cruiser racer with a strip planked construction using flax, balsa and larch.

Another early flax project was the mini 6.5 class yacht Araldite, built for skipper Thibault Reinhart to race in the 2011 mini transat race. Using flax fibres infused with epoxy resins from the sponsor Huntsman, Araldite was built to a Julien Marin design at the IDB Marine shipyard. Around 75% of the reinforcement fibres for the yacht’s hull and deck were flax.

In 2013, Roland Jourdain developed the first trimaran “Gwalaz” sailing since then, demonstrating long term benefits of flax fibre use in marine applications. Other builders quickly noted the potential for flax in composites and flax has become more and more visible in marine structures ever since.

JEC Composites Magazine: Why are flax composites becoming more popular in marine projects? What are the drivers for naval architects, skippers and boat owners making the switch to flax from more typically used fibres?
Brice Roussel: We would say that there are 3 main factors that are influencing the switch to flax from other fibres more conventionally used in marine. Of course, we talk a lot about the environmental benefits but just as important in the decision-making process are the technical and processing benefits that manufacturers are also realizing with flax fibre composites.

Flax is a very low-density fibre, with a high specific stiffness. It can be used to manufacture composite laminates with mechanical properties not dissimilar to typical E-glass composites. The coefficient of thermal expansion of a flax fibre epoxy part is also quite close to that of a carbon fibre part, allowing the materials to work well in combined assemblies such as flax hatches in a carbon fibre bulkhead. Flax parts are also highly impact resistant.

Flax fibres provide impressive acoustic and vibration damping in composite applications. As well as providing a warm and aesthetically pleasing appearance below decks, flax yacht interiors can create a more pleasant environment for passengers with less noise and harshness than standard composites.

In addition to making a strong technical argument for their use in boats, flax fibres also have several advantages throughout the production process. Easily compatible with established composite resin systems such as polyester, vinylester and epoxy, flax fibres are well suited to a host of common boatbuilding techniques including hand lay-up, infusion, and prepreg lay-up. When cured flax parts are cut, trimmed and drilled, the resulting dust doesn’t cause the same skin irritation and itching that can be found from glass fibre composite dust. Working with flax composites makes for a cleaner and safer workshop.

Overall we have found the marine industry to be very open and receptive to natural fibre materials. The relative lack of qualifications and legislation within the racing and leisure marine market definitely puts fewer barriers in the way than might be found in say aerospace or some automotive applications. Many sailors now seem to share our passion for reducing the impact that composite structures have on the environment and want to build more sustainable boats from materials with a reduced CO2 footprint. That has to be a good thing.

JEC Composites Magazine: How can designers, builders and project managers ensure a successful construction of their flax reinforced marine projects?
Brice Roussel: As with any composite project, good pre-production preparation and a thorough understanding of the raw materials involved is important when working with flax composites. Fortunately, high quality reinforcements optimised for composites are now available from a wide range of suppliers and Alliance for European Flax-Linen & Hemp has compiled a comprehensive directory of suppliers that is freely available on our website: https://flaxandhempdirectory.com/

Manufacturers are often concerned about moisture sensitivity when they first start to work with flax. We would definitely encourage builders to review the complete set of guidelines and recommendations about coping with moisture sensitivity in our recent publication even if immersion is not addressed in the document – http://news.europeanflax.com/en/outils/.

It is also useful to check for further updates on the Alliance for European Flax-Linen & Hemp website as the European Scientific Council are constantly working on new technical literature for Alliance for European Flax-Linen & Hemp members and flax users. Alliance for European Flax-Linen & Hemp remains available to provide further technical information and support. We would definitely recommend that users who are still unsure on any particular flax related processing issues should get in touch with us directly to discuss the specific requirements of their project.

JEC Composites Magazine: Are flax composites limited to a particular type of vessel? Do you see their benefits and potential being applied more in race boats and one-off builds than in series production boats?
Brice Roussel: There does not need to be any limitation on the type of vessel or marine craft that can use flax composite components. We have seen boatbuilders working successfully with flax for both series production and one-off projects. Sometimes the craft are for racing, other times they can…

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