fiberglass1

PART ONE - Materials and Safety

Having acquired your GRP bodied dream car all smothered in cracks and accident damage you have to understand what glassfibre is all about and how to go about repairing it. The most important thing to realise is that it takes an awful lot of time and you can't skimp on anything, otherwise the final repairs will look like the surface of the moon. All repair techniques are the same whether you are working on a Reliant Robin or a GT40, and why some professionals charge an arm and a leg for repairing a high class GRP car is beyond me because it takes the same amount of time to repair a crack on a Reliant Robin as it does on a 308 GTB Ferrari.

MATERIALS

Mat: this is strands of silicon (glass) chopped and laid down in various densities and chemically dressed for ease of handling. Unless you are using it for large sheet areas use only 300gm/in (the old 1oz/yd) as it bends around corners easily.

Tissue: a very fine mat looking like a Kleenex tissue to cover gel cracks etc. It gives a very fine finished surface. There are only 2 mats used, although there are glassfibre tapes and heavy mats known as woven rovings where hanks of glassfibre are woven together to give a heavy drape.

Resin: this is the other half of the GRP (glass reinforced plastic) and is a clear polyester resin. In fact resin is solid, but it is dissolved in a solvent called styrene which gives its characteristic smell.

Gel Coat Resin: used in moulds, it is a thixotropic polyester resin, much thicker than the ordinary lay up resin above and will not run on vertical surfaces.

Hardener: when you buy your resin you will automatically be given hardner either in paste or liquid form. It is actually methy ethyl ketone peroxide (MEK or MEKP for short)

Acetone: is the brush or roller and this is the only solvent. You cannot use detergent and hot water. If the brushes go solid then you throw them away. With brushes always buy the correct resin type as they are cheap and contain fewer bristles than ordinary paint brushes; this allows the acetone to get in between the bristles and clean them very thoroughly. Normal paint brushes will end up stiff in some places and become effectively useless.

Two other products which are essential are the chopped strand glass paste (Davids P40) which is as it says a paste which when mixed with hardener will form a very strong bond, and filler, found on just about every car known to man, be it metal or GRP. Filler is chalk dust in resin and, when mixed with hardener, forms a spread able paste which can cover a multitude of sins but, in our case of course, produces the perfect repair. Fillers come in all shapes and sizes but we used Davids P38 or Upol C. With all purchases but the largest quantity you want, i.e. do not buy silly tubes of Plastic Padding to do a whole car as it is a gross waste of money. With fillers buy from a motor factor in 4kg tins or so. That way you get trade. The 500gm tin in the local accessory shop costs just about the same as the 4kg tin from a factor!

Resins - again buy in 5 litre (10kg) tins along with your brushes, acetone and mat (sold by the metre). Strand Glassfibre Ltd, Brentway Trading Estate, Brentford, Middx TW8 8ER (tel: 01 568 7191) are the only retail outlet in the UK and are helpful: if you have access to a trade outlet (where I buy my stuff) it will be even less again. Failing that yacht chandlers will provide resins etc, although buying this way is unbelievably expensive. So, to recap so far, the materials needed are mat, tissue, resin, brushes (and rollers) and acetone.

TOOLS

Now the basic tools with which to attack the damage. A hacksaw, chisels, Stanley knife, plenty of tins and sticks to mix up the resin (NEVER use a glass container as the heat of the reaction between resin and hardener when it goes off will shatter the glass), a jig saw and a Grinderette - either Wolfe or Bosch. They really are essential for preparing gel cracks etc. they are expensive to buy outright but, if tackling a whole car then it is worth it; failing that hire one. If desperate you can use an electric drill with either a cintride disc on it or an adhesive disk on a backing pad.

You'll also need plenty of sandpapers in varying grades and a selection of cork, rubber blocks and the specialist files (as in the photograph) made by 3M available from motor factors - their sanding files are invaluable. recapping again; for cutting the mat - Stanley knife and scissors. for preparing the body - grinderette, hacksaw (padsaw), jigsaw for cutting and trimming. For finishing - files, rasp files, blocks and sandpapers; both production paper, i.e. carborundum chips glued on to a backing paper used dry, going from P40 course to P800 fine, and wet and dry silica chips glued on a waterproof backing paper and used either wet or dry going from 40 to 1500 which is just like newspaper. A usual selection is P40 and P80 for rubbing down filler and 360 and 600 wet and dry for final finishing prior to painting.

Rollers for use on large flat areas

All your equipment will last indefinitely, the only exceptions being the resins and fillers which have a shelf life of about nine months. In other words they may 'go off' after this time. In reality however resins will last at least two years and so will fillers if the lids are tightly on them and they are left away from sunlight in a cool place. When a crust starts to form then it's time to throw them away. Acetone lasts indefinitely. All this will be useless of course if you are allergic to resins or mat, and I suppose I should have started this article with some notes about health and safety.

HEALTH PRECAUTIONS

You are likely to get a localised rash up your arms and hands if you handle the mat with no precautions. If you are allergic do not continue. Get somebody else to do the job as the allergy can cause severe swelling, rashes and can be extremely painful. cover up your arms when cutting or handling mat and use washing up gloves if necessary. If like me you cannot stand gloves then always use a barrier cream which is available from Boots, most chemists, resin shops etc. Resins normally give people no problems, apart from the smell which may upset you. Always give yourself good ventilation when doing a job since the heavy vapour given off (styrene) can cause headaches and even unconsciousness if you are exposed to it for too long. If you ever feel drowsiness coming on you then get out immediately into the fresh air.

The warning signs for resins are an itchy nose and running eyes. When you reach this stage stop and recover. When grinding, cutting or sawing a laminate you must always wear a mask and goggles and always grind outside, never in a garage etc as very fine pure glass particles are thrown everywhere and once they are inhaled the body doesn't get rid of them. Silicosis can result (and this is similar to asbestosis). For the one off job a simple face mask is good enough provided you keep your mouth shut, because your nose is an extremely good filter. When doing long periods of grinding in an enclosed area then a full face mask must be used.

If any hardener gets on your skin then wash it off immediately as it will bleach your skin and if it is in your eyes wash them for at least 10 minutes. If resins are on your skin wipe them off immediately with a cloth dampened with acetone (you're not supposed to do this because prolonged contact with acetone may give rise to dermatitis, since it bleaches out the natural skin oils), then wash in warm soapy water and finally rub skin cream into the affected part (Nivea is very good). If any is swallowed drink quantities of water and induce vomiting - seek medical aid immediately.

If any hardener spills on the ground or clothing wash it away with plenty of water. with resins cover with earth or sand and, when soaked in, dispose of safely; wipe the residue off the ground with acetone.

SAFETY DURING WORK

Fire is a major hazard. All resins, hardeners and acetone are extremely flammable. All have low flash points i.e. temperatures at which they may ignite; resin is 25-30 deg C so do not use naked lights and do not smoke while doing a job or even when you've finished because the styrene vapour given off during curing is highly volatile. Once cured though it takes a lot of heat to make GRP burn.

Fire can also be started by throwing away your unused liquid resin in a dustbin because the heat of the reaction when it is setting is enough to set alight any paper. always place the tin in a safe place and wait till it has 'gone off' and is stone cold before you dispose of it. If a fire starts a CO2 or dry powder extinguisher will cover all possibilities. always keep an extinguisher handy. Water will not work on resins. All resins that you buy are known as pre-accelerated resins and all you do is add hardener. However, without trying to confuse the issue, unaccelerated resins are available for operatives to add their own accelerator (cobalt napthalate) to give predetermined set times. If anyone offers you unaccelerated resin do not use it. Buy the correct accelerated type. Accelerator is always added first to the resin, then the hardener. Never mix accelerator and hardener together because they form an explosive mixture. Unaccelerated resins are not usually available over the counter and, unless specifically asked for, all resins sold are already pre- accelerated so don't worry.

Working with GRP is common sense. Treat all chemicals with the respect they deserve and, if you're allergic, STOP