Practical Boat Owner – May 2018

60 Practical Boat Owner t http://www.pbo.co.uk

PRACTICAL

THE SECRETS OF

VACUUM INFUSION

Jake Kavanagh joined a course to learn about

vacuum epoxy infusion and helped build a

canoe hull. Here he shows how it’s done

T

he 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.
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.

The infusion process is well within

reach of the DIY enthusiast, with all the

materials and machinery available from

a network of composite suppliers

Hand layup is effective but can lead to

thick and heavy mouldings