Marine Paints, Marine parts and House paints at trade prices direct to public – Servicing the marine industry since 1914

Painting Fiberglass

Glassfibre

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. 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.

Bare glassfibre – single pack system/conventional

Product no of coats recoating interval 
@ 10oC
recoating interval 
@ 20oC
coverage
m2/lt
thickness per coat wft tickness per coat dft thinner
ABOVE THE WATERLINE
Primer Undercoat 2 8h-6d 4h-3d 12 100 40 823
Brilliant Enamel onto Primer Undercoat 8h-6d 4h-3d
Brilliant Enamel 2 16h-6d 4h-3d 13 75 40 823
BELOW THE WATERLINE
Underwater Primer 1-2 6h-indefinite 3h-indefinite 8 125 50 823
Hempel Antifoulingonto Underwater Primer 2-3 9h-indefinite 5h-indefinite 13 70 40 808

Two Pack System

Product no of coats recoating interval @ 10oC recoating interval @ 20oC coverage m2/lt thickness per coat wft tickness per coat dft thinner
ABOVE THE WATERLINE
Light Primerthinned 5% 2 8h-60d 4h-30d 8 120 60 845
Poly Bestonto Light Primer 8h-6d 4h-3d
Poly Best 2 36h-10d 16h-5d 15 75 35 851 spray
871 brush
BELOW THE WATERLINE
Light Primerthinned 5% up tp 4 8h-60d 4h-30d 8 120 60 845
tie coat –Light Primeronto Light Primer 1 2h-4d 1h-2d 10 100 40 823
Hempel Antifoulingonto Underwater Primer 2-3 6h-indefinite 3h-indefinite 13 75 40 808