Gelcoat

A pigmented surface resin applied to the mould before a fibre-reinforced composite hull or component is laminated.

Gelcoat is commonly based on unsaturated polyester or vinyl ester resin. It provides a smooth coloured finish and a protective surface barrier, but it is not the structural laminate and should not be assumed to remain completely impermeable throughout its life.

Impact, flexing, ultraviolet exposure, poor application and water ingress can lead to chips, fading, crazing, blistering or separation. Repairs require compatible materials, sound preparation and control of thickness and cure so that the surface bonds properly without concealing damage to the laminate beneath.