Jake Kavanagh on the epoxy infusion techniques for building ultra-lightweight mouldings that can be accomplished by the DIY-er or small-scale boatbuilder

The traditional method of glassfibre boat building has been to hand-roll liquid resin into reinforcing fibre as it sits in a mould, adding one layer after another and all the while aiming to avoid any air pockets by fully saturating the fibre with the resin, writes Jake Kavanagh.

While extremely effective for producing a wide range of composite structures, there are drawbacks: hand laminating techniques may result in laminates that are a little too thick in places, or have an uneven distribution of resin. There can also be small voids if you’re not careful.

Vacuum epoxy infusion is far more precise and works by forcing epoxy through a prepared sandwich of composites by a difference in atmospheric pressure. Modern boatbuilders are increasingly using vacuum infusion techniques to help them create composite products with a very high strength-to-weight ratio.
While still quite labour intensive in the set-up, infusion benefits from a much better dispersal of the epoxy resin, capable of creating much thinner structures with negligible voids. With strategic reinforcement, they can still be remarkably strong.

Another bonus is that fumes are kept to a minimum, as they are mostly trapped inside the vacuum bag.
Although the technique is used to build yachts as large as 120ft (36m), it is more commonly used to create a multitude of smaller parts, including those made of carbon fibre and other advanced lightweight fabrics.

So I went on a course to learn about vacuum epoxy infusion and helped build a canoe hull.