On this page I have tried to explain in basic, but understandable terms how to make something out of fibreglass. This is not as hard as it may seem so if you want to have a go, read on. Please note: The production of fibreglass gives off fumes. Therefore always where a decent mask, with carbon filters to extract any vapours. Dust masks will not do, it needs to filter the air. Be prepared to spend around £25 on a semi decent mask, more if you can afford it.
The following list is the things you will need to make something out of fibreglass.Gelcoat resin, (comes with own catalyst.)Polyester Resin, (comes with own catalyst.)Colouring, (this is optional.)Mould release wax. (I use Meguiarís Mirror glaze No 8)Fibreglass mat or CSM as it is also known. (I use 600gram mat, but it comes in different weights. I find 600gram is best as it can be separated into thinner layers if needed.)Cheap disposable brushes. Plastic jug, (1 litre capacity.)Small mixing cup, (For gelcoat.)Medicine syringe. (Can be got from most chemists, comes in 5ml size.)Consolidation roller. (I use a small roller, as I find it better, but again they come in different sizes.)Mould. (These can be bought off ebay if you look. Or you can make your own when you get the hang of it.)
Now the fun begins. Gelcoat can be bought in clear or white, (you can get other colours also.) I buy clear as colour can be added to it. I have one tin of clear and lots of tins of colours, which saves having to have lots of tins of colour gelcoat lying around, which would take up far more space. For car accessories I tend to use beige if its one I will be selling in general, but I do whatever colour is required if itís a special order. I mix up 50ml of gelcoat and just dip my mixing stick in the colour pot. (This is enough to colour the gelcoat.) Mix thoroughly, and then add the appropriate amount of catalyst. (It has on the tin the percentage to use, which can vary depending on the make.) Brush the gelcoat on starting round the edge, then filling in the middle. Make sure itís evenly coated, but not to thick or in lumps. Mixed correctly it goes tacky in a couple of hours.
This picture just shows the mould after the gelcoat has been applied. I will just mention about adding colours. This is quite strong dense colouring so not much is needed. As I said I just dip the stick in and thatís enough. The only one that needs a bit more is white, which I always use what is called super white colour as it seems denser still than just normal whiteNow obviously its better to make things in a colour that matches the car, and then in the event of it getting scratched, the underneath is still the correct colour. You can get dozens of colours, so most cars can be matched up, with something close enough. Things like black and racing green if also mixed in with the polyester resin can be used without painting. I also add white to the resin when doing stuff in white, so it just makes it a more solid colour. For general stuff I sell, I use beige as mentioned, as this matches up to high build primer just right, which makes for easier covering.
The first thing to do is polish the mould. Now if you have bought this off ebay or itís a brand new one, it needs to be polished with mould release wax. Even if itís a second-hand one, donít assume it has been thoroughly waxed, treat every mould you acquire as new and wax it properly yourself so you know itís waxed up properly.If I buy a mould second-hand I clean it with mentholated sprit first, which removes any wax build up, then polish it from scratch.This is the boring it. A new mould needs wax applying and polishing off 25-30 times. Yep that might sound a lot, but trust me, if its not properly waxed, and the gelcoat sticks to the mould, because you got bored applying the wax after the first few times, the mould goes in the bin. I wax a new mould 30 times, and then each time I use it. Some may say thatís over doing it, but better to be safe than sorry.
With the gelcoat tacky, its now time to add the matting. As I mentioned before I use 600gram CSM, so a single layer overlapped on the corners is strong enough for a car bonnet vent such as this.I cut three pieces. One to go down the centre, with just enough to go up each side, and two additional strips to go either side. I then mix up the resin. For something this size 100ml of resin is just about right. I pour resin into the jug, then add 3ml of catalyst via the medicine syringe, and stir thoroughly. Once the catalyst is added and stirred in, you can see just a slight change of colour in the resin. I find adding 3ml for this amount gives you plenty of time to work with it, but the larger the quantity of resin, the great the thermal build up, and the shorter the setting time. This is trial and error, till you get the hang of it. Also temperature has a lot to do with it, but I have my workshop set at 65 degrees c, so I know how long it takes to set depending on what I am doing.
First of all brush resin onto the gelcoat. The reason for this is the CSM will draw up the resin from under it, then place the centre piece of CSM in place and wet it out. Donít be impatient here, as when you first brush the resin on, it doesnít look like it is doing much. However brush resin all over and by the time you have finished you will notice the white matting turning resin colour. Where white spots still show brush a bit more resin on, working it into the CSM with the brush.Now with the consolidation roller carefully roll back and forth starting from one end and moving towards the other, rolling the CSM. You will see as you go, any air bubbles underneath, get pushed out, and the resin well massaged into the cloth. When you have gone one way, go back and forth in the opposite direction.If needed brush in a little more resin, and re- roller it, till you are left with a even coloured surface.
Once the side are roughly the same colour as the base, and you have gone back and forth with the roller, removing any air bubbles and massaging the resin well in, get the brush and a piece of paper towel, (Kitchen towel will do.) wipe the brush out removing as much resin as you can, then dab at the wet CSM at random, wiping the brush every so often. What this does is pick up any access resin, leaving just the right amount on the CSM to form a nice strong construction.Too much resin and you will see it pool in the lowest spot. If you get it to pool you have used far too much resin. A good indication, is it will be wet looking, but you will be able to see all the fibreglass strands clearly.If you use too much resin it's not the end of the world and on something of this size it wonít really make any difference. However the bigger the item, the stronger it needs to be, so the resin to CSM ratio is far more critical. The dabbing the brush is a easy simple way to get the ratio about right.
In this picture, you can see better what I meant about seeing the fibreglass fibres clearly. While they are coated in resin, they are still visible. At this stage when the resin is applied pick the mould up and have a close look at it to make sure its ok. Sometimes up close you can see air bubbles, and with the resin still wet, now is the time to get rid of them.Once you are happy with the finished item, place it on one side, away from direct sunlight or heat source to cure on its own. While adding heat will speed up curing time, I find it better to let it set at its own speed.You can also see I have overlapped the outer edge slightly. By pre cutting the matting to shape avoids wastage, and also minimises trimming when itís cured.
Once set its time to get it out the mould. Now this is where all that waxing and polishing pays off. I use a mini pallet knife, as itís thin but not sharp. I run this right round the edge making sure itís between the mould and layer of gelcoat, to release the edge from the mould. I then twist the pallet knife and if you have polished it correctly it will pop out the mould.If itís being stubborn, use a blunted flat screwdriver and put this just under the edge and prise it up a little. If you damage the edge, itís not going to matter as it will be cut off and sanded later.All being well, it came out nice and easy. This is why I said to wax the mould such a lot, and then re-wax it each time you use it. The more wax on it, the less chance of it sticking. However there should be no visible signs of wax build up on the mould prior to use. Each coat should be applied then polished till shiny.
With the vent out the mould it just needs cleaning up. I use a dremel with diamond cutting disc to take it back to nearly the edge line, then sand the edge back by hand or workbench sander as I have.As this is to go on a bonnet, the bottom is not flat. There is a slight curve from front to back so it can be placed on a bonnet better. However I always recommend placing a old sheet on the bonnet where itís to go, then a sheet of abrasive paper on top of that and move the vent from side to side to sand it to get a perfect match to the curvature of the bonnet prior to sticking it on.You may also find there are sharp bits of fibreglass on the underside. Just sand these smooth with a 320 grade paper.Also fibreglass can produce sharp edges, so just go round the edge with the 320 grade paper smoothing them off.
So thatís it. If you read this and had a go, you should now be left with a fibreglass item of your choosing.Donít worry if it didnít come out as well as expected, practice makes perfect. The more you do, the more you will become familiar with the process and your confidence will increase.As I said at the start, this is not as hard as it seems, or some people would have you believe.One last tip, once itís out the mould it might have a slightly waxy surface. This wonít be anything you can see, but you might be able to smell it. Just give it a good clean with mentholated sprit to remove any wax prior to painting.However it you are going to paint it, you will find itís much better to sand it with 1000 grade abrasive paper first, just to take the shine off it, and give the paint something to key to.
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