Raw materials from the forest can be used for much more than boards, timber, pulp and fuel.

Dellencat, a modern catamaran

Sweden is a major innovator when it comes to developing technology to find new uses for wood. Recent research and development focuses for example on construction products, bio fuels, food, chemicals, products for surface treatment, bio-composites, clothing, nanotechnology and much more.

The competence Center EcoBuild (see box below), at the SP Technical Research Institute, has as a mandate to develop bio- and forest-based raw materials into innovative, eco-efficient and durable wood-based products.

EcoBuild’s ambition is to cooperate with industry and universities, and at the moment is cooperating with more than 30 large and small companies.

One of the smallest is boat builder Dellencat.

To build wooden boats is hardly new, but Dellencat stands for innovation and environmental compatibility in the design of wooden catamarans.

Modified wood as construction material

A key component to Dellencat’s success has been the use of ‘modified wood.’

“Wood impregnated with conventional wood preservatives has never been popular among boat builders,” says Jan-Åke Malmqvist, one of the founders of Dellencat.

“But modified wood can be the starting point for a new approach in the boat building industry. Our goal is to build environmentally friendly boats in terms of material selection, surface protection (coating), and propulsion. One example is that solar cells on the sails supplement electric motors for propulsion.”

Weight, strength and stability are of utmost importance in construction materials for boats. Additionally, the materials must be flexible and resistant to degradation by rot, shipworms and UV light.

“With modified timber, we see no obstacles to meeting those requirements,” says Malmqvist. “In the catamaran, we use modified wood in a laminate with fiberglass and epoxy resins. In development, we also have marine optimized fittings made of recycled PET plastics that yield an even higher weight to power ratio.”

The choice of materials was made together with EcoBuild. The following methods for the modification of wood is recommended:

  • Heat treatment (thermal modification). Heat-treated wood is heated to high temperatures (180-240 ° C) in an oxygen-free environment. The result is a dimensionally stable material with high resistance to rot.
  • Furfurylation. In this case, treated wood with an aqueous solution of Furfury alcohol and catalysts is cured in a subsequent drying step. As an example, this process gives Swedish maple the appearance and characteristics of tropical woods like teak and mahogany. This process provides dimensional stability, strength, hardness, and resistance to rot and insect pests.
  • Acetylation. With this process, the wood is modified through pressure treatment with acetic anhydride, which react with the wood at elevated temperatures and residual chemicals (mainly acetic acid) is driven off by drying processes. The method gives results similar to furfurylation but does not affect the wood’s color.

Different companies working with EcoBuild manufacture this modified wood for the catamaran. The competence center also provides the opportunity to test material properties. The center has a unique pilot plant for wood modification, which among other processes, includes innovative microwave technology, to streamline the acetylation process to make it cheaper and better.

The catamaran’s eco profile

Dellencat’s first catamaran under construction is 11 meters long, 6 meters wide, weighs 3.5 tons and has a sail area of 55 square meters. Despite its large dimensions, its draft is only 0.9 meters.

The catamaran has four staterooms, a lounge, a kitchen, one bathroom, a large sun deck and can accommodate up to 12 people.

Hull platting consists of a 12 mm-thick strip of knot-free pine from Hälsingland, not a modified wood material.

In this case, it is first and foremost about learning the special hull construction techniques with strip-plank. The plan is to implement and supplement the concept of modified wood as the structural hull material. All the wood is sealed with epoxy and then reinforced construction with epoxy-impregnated fiberglass. This wood material yields hull strength, insulation and buoyancy, and the epoxy is a very dense and strong material.

Boat builder Richard Woods designed the Flic 37 boat model. It has already been built in about 25 copies at other shipyards in the world, but with the new catamaran from Dellencat it has the thoughtful environmental profile. Another feature is that the boat hull is continuously monitored using 16 measurement points with moisture sensors that are placed in the hull below the waterline. The sensors alert to moisture or water entering the hull.

What are the advantages of a catamaran compared to a traditional single-hulled boat? A catamaran’s advantage with buoyancy on two hulls puts the superstructure between them. The large distance between the hulls in relation to the length makes the construction very stable. One simply has more square meters of usable space at a lower cost than the equivalent single-hulled boat. A catamaran also has a very shallow draft and can navigate shallow bays. A catamaran is usually faster and easier to sail than a single-hulled boat with the same sail area and weight.

EcoBuild Showcase

“Dellencat is a showcase for EcoBuild. When completed, this will be the first boat built with modified wood and become a symbol for many of the projects aimed towards eco-efficient use of forest resources, “says Jan-Åke Malmqvist.

“We are part of Project 9 within EcoBuild and the vision is to develop and build catamarans with hulls made of thin planks of modified wood, bio-based acrylic-based binders and strong cellulose fabrics. One possibility is to include panels and moldings from modified wood fibers and bio-based resins. Another possibility is to use fiber reinforced thermoplastic elastomer (TPE) reinforced with nano-cellulose, “says Malmqvist.

The article was published in January 2012