I am not in the habit of commenting on the forum but thought these comments might help.
Gel cracking
This sounds like de-lamination which is different to air bubbles.
De-lamination can be caused by a couple of things; the most common is the gel coat left in the mould too long before being laminated, the other common one is a dry lay-up. There are also other less common problems; however both of the problems are generally operator error.
A dry-layup
A general rule of thumb to go by when using 450g chop strand mat is to use 1kg of resin per 1 square meter, when using 600g CSM you would use 1.2kg per meter. Gel coat would be 500g per 1 square meter.
Gel coat repair
Gel coat repair is not easy and not always successful; the problem with gel repairs is that the gel will exotherm causing very small holes on the surface. These over time will collect dirt and grime, thus giving you the discolouration. If these repairs are small, say no larger than 6mm area on a radius or in an area hidden then you would get away with it. Lighter the colour less chance of seeing the repair (black forget it).
Repairing for painting
I would recommend just standard Upol car body filler, this is polyester based filler easy to work with and easy to obtain.
In my eyes; oven baking after spraying is a big NO NO, I have always argued this with car sprayers. Polyester is a form of plastic at the end of the day. Would you put a plastic item in your oven at home ramp the heat up and expect it to survive?
Polyester will take heats of about 60 degrees for a very short time, gel coat about 80 degrees.
Not only will you distort the item you will cause any air, no matter how small, to expand and ruin the surface of your panel.
If you must bake your paints off then the temperature must be no higher than 30-35. All post curing can be done at lower temperatures it just takes longer.
Air bubbles
Yes, a lot are caused by operator error but not all can be helped. If you back up your laminate with colour to help give you a strong colour finish on your surface, you become blind to any air that may be trapped between layers and yes, a good experienced laminator would work methodically to ensure this did not happen; but sometimes it does.
Also note that CSM can hold fine air bubbles between the strands.
Fibreglass
In my 30 years’ experience in this trade I have seen patterns, moulds and items go wrong for no apparent reason. You just sometimes have to accept expectations of perfect are not always possible.
In any trade if you see a lot of items for sale cheaper marked as substandard or seconds on a regular basis, you have to question the ability of the manufacturer.
Training
I see Talon Motor says you can get a day’s training for £150-£200 to learn how to do it properly.
If anyone wants to spend a day getting an idea on how to produce items made in fibreglass then give me a call and spend the day at my factory free. You will go home at the end of it with a little bit more of an understanding but not as a skilled laminator.
I have always believed that when you buy something you should get value for money.
You won’t get a Rolex from a Sunday market.
I hope Baz-r, that this might help with the repairs of your body work.
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