Produce stable pattern from timber, fibreglass, or any material that will produce a stable shape observing release angles to allow a rigid mould to come off the pattern easily.
Brush or Spray Polyester spray filler. This highbuild product is quick drying & easy to rub down which makes it ideal for resurfacing the pattern to achieve a smooth even surface ready for gloss coat if rubbed down to 1000 grit wet & dry paper.
Gloss coat for high finish should be done with any good quality 2 pack paint system such as polyurethane “International Perfection”. Follow the manufacturers instructions and always allow the paint to fully cure before proceeding. Cellulose paint is best avoided. If specs of dust or other imperfections are present the surface can be carefully rubbed with 1000 wet & dry or finer then buffed with a fine grade buffing compound taking care not to rub through the gloss layers of paint. A G-mop polishing head attached to low speed machine will speed up this process. All compound residue should be polished off. Wash surface with warm soapy water, rinse & dry thoroughly.
Apply release agent wax system following manufacturers instructions after all paint has fully cured (3 - 7 days).
Making the Mould. This should be done in stages building up the layers slowly to avoid heat build up and distortion. The first coat to be applied is gelcoat which can be pigmented. A minimum amount should be added as pigment degrades the gelcoat slightly. Better still is to keep the gelcoat clear. Standard isophthalic brushing gelcoats are suitable for general moulding & mouldmaking. Catalyst should be added at the rate of 2% by weight and stirred thoroughly. Apply an even coat by brush and allow to dry. Touch the gelcoat in the lowest part of the surface, it should be dry but slightly tacky.
Apply the skin layer of chopped strand mat taking particular care to remove all air bubbles. Air bubbles at this stage will cause the mould surface to blister. Allow to dry hard, lightly sand any rough areas then apply more layers to the desired thickness (Approx. twice the thickness of the finished product to be made). 2 layers at a time can be laminated together wet.
Extra fiberglass reinforcement can be added to mould edges along with timber or foam ribs to help avoid distortion during use of the mould. Allow to cure preferably for 1 week in average temperatures.
Release mould & allow 2-3hrs for vapours to escape, wash surface with warm soapy water, rinse & dry thoroughly. Apply PVA release agent by spray or sponge for the first few pulls to break the mould in, The surface finish with PVA is not as good as with waxes but does guarantee successful release on new moulds. A release agent wax system can then be used following manufacturers instructions to produce high gloss finish mouldings.
Temperatures in the work area should be kept as even as is possible. Do not work in very hot, cold or damp conditions. Inexperienced moulders should not try to rush the work or cut corners. Catalyst levels should be kept at 2% by weight throughout. Follow manufacturers instructions of all materials.
The same materials as used for making repairs to cars and other vehicles are used for making repairs to boats. CFS resins and fibreglass are approved by Lloyds.
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