That’s less of a problem on small fixes, but if you’re repairing a big area it can cause a major headache. Polyester shrinks as it cures because the styrene molecules evaporate.
And while you can add a catalyst like MEKP (methyl ethyl keytone peroxide) to polyester resin to tailor curing times in cold temperatures, using a catalyst creates a less effective bond. Epoxy works well in hot conditions too – with the WEST SYSTEM 105 Epoxy Resin®and 209 Extra Slow Hardener® specifically designed for extremely warm and humid conditions.īy using different hardeners – such as WEST SYSTEM 205, 206, 207 or 209 Hardeners– you can tailor how quickly epoxy cures, giving you more control over your repair. Use the right hardener in your epoxy mix, however – for instance WEST SYSTEM 205 Fast Hardener® – and you can work on repairs at temperatures as low as 5☌ by following our guidelines for using epoxy in cold conditions. Polyester resin manufacturers typically recommend that you use their products in temperatures of 15☌ or higher, which can be a problem if your workshop drops below that. It works as an adhesive, coating and laminating resin even when used as a thin film – and it’s less likely to develop micro-cracks too. As a result, it has limited use if you want to repair well-cured fibreglass laminates using only a thin film. So when it’s used as a thin film it stays sticky and tacky, because a higher percentage of the resin you’re using is exposed. Polyester resin struggles to cure when it’s exposed to air. Which means less time working, and more time eating toast. Brush the surface you want to wet out, leave it, and the resin will get to the right places and wick right into the fibres. With epoxy, it’s like using warm butter – the epoxy does the work for you. You need to work hard to get an even, consistent coating – normally using a foam roller, brush or metal paddle roller.
If you’ve ever tried to spread cold butter on a piece of toast, you’ll know roughly what it’s like to wet out fibreglass using polyester resin. Polyester resin struggles in comparison.Įpoxy is ideal for wetting out fibreglass It creates a resilient bond to fibreglass, cured polyester laminates, wood and metals – even when you only use a thin film.
One reason that an epoxy product such as WEST SYSTEM® Epoxy is so useful for fibreglass boat repairs is that it’s an incredibly effective adhesive. But as hulls have become thinner, lighter and more flexible, they’ve become harder to repair – especially with polyester resin. And longer-term problems like water osmosis, delamination and blistering can leave you frustrated and off the water too.įor many years, the automatic response to many issues was to reach for polyester resin. Collisions and groundings cause everything from small nicks to serious structural damage. Not sure whether epoxy has what it takes to fix your fibreglass boat? “It’s versatile, strong, reliable – and more than a match for polyester resin”, says Hamish Cook, Technical Guru at Epoxycraft.įibreglass boats – like all boats – get damaged.