Fibreglassing is a trade that anyone can pick up the basics of very easily. Many little projects (or even quite major jobs) can be accomplished without too much stress. However, as is the case with any skilled trade, to learn all the tricks of the trade takes many years in the proper environment, with the proper equipment and training. What we outline here are just some basic steps to allow those who prefer to do it themselves, to do so.

Materials

POLYESTER RESIN - General purpose resin can be used for normal laminating and a special casting resin is available for pouring solid objects. There are many different resins but the variations are mostly to do with gel time and cure times. Obviously for some jobs a long gel time is needed to allow you the time to lay in the glass fibre and roll the air from the laminate. In casting resins, occasionally a very fast cure is needed for turn around of very small objects such as chess men. In most cases a very long, slow cure is required so that there is no distortion or cracking of the casting. When attempting other than general purpose laminating seek advice from your supplier.

CATALYST or MEKP - Catalyst is normally a liquid and must be handled with extreme care. Un-catalysed resin simply will not harden. The measurement of catalyst in the resin is critical and it cannot be stressed enough that all safety precautions must be followed. MEKP (Methyl Ethyl Ketone Peroxide) is very dangerous to the eyes and can self ignite when mixed with other products. It is normally used in a ratio of 1-2% by weight of the total polyester resin. A rule of thumb, 20mls of catalyst is usually needed for 1kg of resin. Accurate measurement is important because a small increase or decrease of the amount of catalyst can have a large effect on the gel time or working time of the polyester resin.

GELCOAT - Gelcoat is a pigmented resin which forms the smooth outer surface of the finished laminate and is therefore applied first to the mould. Usually 450-600gms of gelcoat is needed for each square metre of mould surface. It is not normally used for castings. Gelcoat is available in virtually any colour including clear.

GLASSFIBRES - There is a large variety of glassfibre materials which are available for various needs. The most common one is chopped strand mat and probably 90% of all home handyman jobs are done using chopped strand mat. This is a mat comprising of small fibres held together with a binder to allow them to be laid into the mould. Another common product is woven roving where the glass strands are woven into a mat to give extra strength. It is usual in boat building for instance to use a combination of chopped strand mat and woven roving to get bulk plus strength.

Chopped Strand Mat and Woven Roving

RELEASE AGENTS - Release agents are applied to the mould prior to laminating to prevent the laminate from sticking to the mould surface. They are not normally required for casting where RTV rubber flexible moulds are normally used, They come in many shapes and types for various products and it is best to seek advice as to the best type for the project that you are currently engaged in.

FILLERS - Inert fillers can be added to resin to produce a general purpose body filler stopper paste, or to make a slurry for resin casting. They are not usually needed for many laminating projects but it is very common to use fillers for casting projects. Two common fillers are calcium carbonate and Q-Cels. However Q-Cels are normally used in conjunction with epoxy resin to make a coving filler in right angle corners and for ease of sanding.

COLOUR PIGMENTS - Although laminates and castings can be painted, it is often simpler to colour the resin before laminating. By adding pigment paste to the resin in a small amount you can tint the resin into a suitable colour. It is wise to seek advice from your supplier before doing this.

BARRIER & CLEANSING CREAMS - In some cases the skin can be irritated by polyester resin and it is wise to wear a barrier cream in conjunction with gloves when handling resins and glass fibre. Low cost disposable gloves are available and the cost is largely offset by the reduction in using cleaning liquids, such as acetone, which are not recommended for cleaning resin from skin.

SPECIALIST RESINS - Apart from the normal laminating resins there is a large variety of other resins available for specialist uses, such as making chemical resistant tanks or fire retardant laminates, clear encapsulating castings, adhesion to acrylic panels, etc.

SPECIALIST REINFORCEMENTS - Reinforcements other than glass fibre are sometimes used in high performance laminates. A typical example is Kevlar, a synthetic aramid material which is even stronger than glass fibre, and has excellent impact resistance (it is used to make bullet-proof vests) and carbon fibre which gives greatly increased rigidity to the laminate. It is used for applications requiring a strong but lightweight laminate e.g. race car bodies. It is advisable to seek advice before using these specialist materials as they are more difficult to use than the standard glassfibre and their characteristics while strong in some areas, can be weak in others.

Carbon fibre and carbon kevlar cloth

STYRENE - Styrene can be used to thin resins in certain cases but not normally recommended, again advice should be sought before adding to resin.

WAX SOLUTIONS - Wax is often added to resin or gelcoat to reduce the tackiness that is often left on the surface of the resin. The addition of wax to resins or gelcoats makes it easier to sand that surface without clogging the sand paper. This is especially useful when doing small gelcoat repairs. However, for large jobs it is advisable to use fully formulated flocotes or top coats.

CORE MATERIALS - Core materials come in a variety of types and are used to increase the stiffness of particularly flat panels. Coremat, divinycel, klegecel, and balsa to name just a few. Again advice should be sought before using these materials.

Foam and balsa

For further information on the materials used in producing composites, please contact composites@nuplex.co.nz

Tools & Accessories

Mixing Cups or Buckets - For mixing resins, pigments, gelcoats, flocotes etc. polythene containers are ideal. A typical one is ice-cream containers. Do not use Polystyrene - it can be dissolved by polyester resin. While some cardboard containers can be used, it is advisable to try a small amount to see whether or not the polyester will attack it. It wouldn't do to have it all fall out the bottom five minutes after you had started!

Brushes and Rollers - For applying the resin. Use tools specifically made for fibreglassing - conventional decorator tools often use adhesives which are attacked by the resin. For brushes, unpainted or plastic handles are more desirable as washing the brushes in acetone often causes the paint to come off and so colour the resin itself.

Laminating Rollers - come in both plastic and metal and a variety of shapes and sizes. They are needed to consolidate the resin glassfibre laminate and remove any air from that laminate. Do not use conventional rollers for this purpose.

Laminating Rollers

Catalyst Dispenser - A purpose-made dispenser is essential for measuring out liquid catalyst. For small amounts a measuring syringe can be used.

Working Tips

Use a brush or polyester roller to cover the mould surface evenly with gelcoat. Wait for at least an hour until the gelcoat becomes tacky (it will feel slightly sticky but will not actually adhere to the touch) and make sure there are no corners or crevices where the gelcoat is still wet.

Catalyse a working quantity of resin. Polyester resin is usually blue and when properly catalysed changes colour to opaque in 3-5 minutes. Blue streaks indicate poor mixing. Paint the resin over the gelcoat

Lay down a piece of glass fibre and push it gently into the wet resin with a brush. If using chopped strand mat, use a stippling action - DO NOT 'paint' to and fro as this tends to separate the glass fibres. Make sure the glass fibre is thoroughly impregnated with resin (keep the brush well loaded to add more resin if necessary). When the fibres are properly wetted out they should go clear. Any white patches remaining are dry spots.

Once completely 'wetted-out', use a metal laminating roller to consolidate the layer and force out air bubbles. This also forces resin through the fibres from beneath which makes for better impregnation.

A further coat of resin and another layer of glass fibre can then be added, repeating the process. Any number of layers can be built up depending on the thickness and strength required. For many jobs, two layers will be adequate.

The exposed surface of a chopped strand mat laminate will be rather rough - this will not normally matter, but if necessary it can be covered with a layer of surface tissue. Surface tissue is fine glass fibre material - it has a smooth side and a 'hairy' side. While the laminate is still wet, apply the surface tissue 'hairy' side down, wet out with more resin and stipple down lightly.

When the required layers have been built up, leave the laminate to cure. It will soon reach the 'green' stage when it becomes quite firm, at which point you can trim off rough edges with a trimming knife. Once fully hardened you will have to use a hacksaw with a metal cutting blade. Cutting, sanding and drilling cured laminates produces harmful particles - to avoid these you should wear a breathing mask and goggles.