Yamaha Motor explores flax fiber for PWCs

While many manufacturers have used fiber-reinforced plastics (FRP) for over 60 years in boat hulls, swimming pools, and other products, there is still room for further development of composites using materials and construction methods in terms of recycling.

Amidst such developments, Yamaha Motor has begun new R&D projects to explore using plant-derived composites such as flax fiber in PWC hulls.

As a textile, linen is a flax fiber often used for clothing. Flax is a plant actively cultivated in France, Belgium, and other eastern European countries. The flaxseed oil extracted from seeds is used as a raw material for paint and ink, but it has also drawn attention in recent years for its health benefits.

“Flax has a wide variety of applications, but when it comes to using it in industrial products, the hurdle suddenly shoots up,” says Tomoki ITO from Yamaha’s manufacturing technology center. Ito is working with senior engineer Kenjiro FUJII to develop fiber-reinforced plastic (FRP) using flax fibers.

FRP is a strong, lightweight composite material for boat hulls and many other applications. It generally uses glass fiber or carbon fiber. Yamaha Motor has been working with this material for over 60 years, but “FRP still has room for development in resource recycling and other aspects,” says Fujii. “We believe that using plant-derived materials is one effective approach to pass the FRP machining expertise and technologies we have amassed thus far to the next generation.”

Recyclable Composite Materials

Flax fiber, which is used as a raw material, easily retains air and moisture, frays irregularly, and has other characteristics that make it difficult to handle in ways common with natural materials.

As a raw material for composites, flax fiber presents several disadvantages. Some examples are that it frays irregularly—something typical with natural materials—or it absorbs moisture more easily than glass fiber.

“It’s already a difficult material to handle, but we envision adapting it to a wide range of product categories. By setting strict requirements and a difficult target to reach, we believe we can expand the possibilities for the material across Yamaha’s many different business fields,” explains Ito.

That “difficult target” is the SuperJet stand-up personal watercraft. On top of the material not being very water-resistant, it must also be strong enough to withstand heavy water pressure. After repeated trial and error, they eventually made some headway. Their first step from there was to exhibit their results at an in-house technical exhibition to other Yamaha engineers. The high level of interest from peers working in other businesses gave Ito and Fujii added confidence, and their work was also exhibited at the Japan International Boat Show 2024.

Flax fiber is laminated using a process called vacuum infusion, in which resin is injected into a mold and impregnates the fiber via vacuum pressure.

“The reason we can do this in the first place is because Yamaha’s commitment to these processes gives us so many options,” says Fujii. His colleague Ito feels they are progressing well: “By closely examining what we’re working with, we’ve discovered what’s key to handling this material. We’re getting a better idea of how to make the most of the material, like its gentle appearance or elastic qualities.”