Painting Fiberglass
GRP (glass reinforced plastic) is a polyester resin strengthened by glass fibres. When combined in the correct proportions under controlled conditions, these high strenght low weight materials require little maintenance and can be produced for relatively low cost.
A model hull or plug is produced from which a female mould is laminated. A wax mould release agent is first applied to the inside of the mould and then a polyester gelcoat is applied in liquid form.
The gelcoat is then strengthened from behind by the application of chopped strand or woven roving reinforcement saturated in polyester resin. This combination of gelcoat and laminate provides a high resistance to water, chemicals and impact.
Timing of the various applications, the control of base resin and catalyst additions and the avoidance of air bubbles are all critical in determining the quality of the final moulding.
After a curing period the hull is removed from the mould. This is made possible by the mould release agent which was initially applied. An amount of release agent will remain on the hull and it is essential that this is removed prior to painting.Â
Painting of GRP may be necessary for a number of reasons. It has no antifouling properties and will require protection. It can be affected by ultraviolet degradation and general wear and tear over a period of time which may cause the cosmetic appearance to deteriorate.
Painting Glassfibre Glassfibre, or GRP (glass reinforced plastic), is a polyester resin strengthened by glass fibres, creating a high strength, low weight material which requires little maintenance. The outer shell of the glassfibre has a layer of gelcoat.
Over time gelcoat and glassfibre can be affected by UV (ultraviolet) degradation and general wear and tear which will cause the cosmetic appearance to deteriorate and eventually it will need painting to protect the surface. GRP is susceptible to a condition called osmosis – see Osmosis section.
Particular tips when painting glassfibre New gelcoat contains large residues of wax and mould-release agents which must be removed before painting. These residues can be extremely persistent and old gelcoat will probably still have traces, so it is important to carry out a degreasing procedure to remove them.
• Old and weathered gelcoat and GRP can become porous and may need extra attention.
• For advice on repainting glassfibre see the section on Repainting.
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