I bought some high quality molds, and about to embark on making parts from it. I just had a few questions about the layers of glass I would need to lay up.
After the unwaxed gelcoat has firmed up, and I am ready to start the fiberglass lay up. Do you first put down a sheet or 2 of surface veil/tissue, wet that up, get all the air bubbles out, and let it dry, then proceed to the thicker layers like .75oz (225 gram) and how many and even thicker 450gram 1.5oz, and how many.
Without giving more information as to what you plan on making, I doubt anyone can answer your questions about how many layers you need.
Regarding your molds - have they been fully prepared and are ready to use?
Yeh, totally dependent on what you are actually making.
Personal opinion though - don’t use veil. It’s awful stuff for trapping voids. Use a 100gsm if you can get it, otherwise one layer of 225 won’t print much either.
I find the veils or tissue on their own can be a real pain with air and getting caught in your rollers but I also found that if you must use it then it works really well to put the tissue and a 225g CSM down together dry and then wet through both layers in one shot, works really well like wetting through a 225 on its own.
Using solid CSM materials is great and easy but usually heavier and weaker. Once you start adding in woven materials the resin/fibre ratios get much better while your parts also get lighter too.
Like the others say it depends on what you are making. For fish ponds and simple stuff CSM is great but if you need a bit more strength or weight matters also then there are lots of ways to step up and improve your parts.
I am going to be blunt. You obviously have just enough experience to destroy a set of moulds. Get a mould surface that can be sacrificed. Maybe some melamine or sheet metal or another gelcoated surface. Apply your mould release agent to it. Make some test laminates on it. Get some sheet metal and fold it and learn how to laminate around sharp corners. Make sure your mould release application is effective. Try laminating some tissue/veil compared to 225 csm. Find out the difference between 225 chopped strand mat and 225 split strand mat. There are a heap of things I haven’t mentioned that you will learn from making some small simple test laminates. Do not risk your new moulds until you know how to do the job successfully everytime. Unless, of course, you like to throw money away.
What the items are is a front bumper and front fenders. The bumper has 4 pieces, one main piece and 3 flanges. And each fender is 5 pieces. So they are fairly intricate moulds. I practiced on replicating a car gas door lid to use as a plug. Turned out good. So I then made moulds of my factory quarter panels on the vehicle. That also turned out well. I waxed the panels about 6 times, buffing after 30 mins each time, then sprayed on PVA, 1 mist coat, let it dry, and 2 heavier coats, let them dry. Then I brushed on tooling gelcoat in a fairly heavy pass. Waited about 4 hrs, tried to dig my finger nail into it, and it wouldnt mark. So I did 1 more coat after that. The following day I laid up 1 layer of 1oz 300gram as a skin coat. Let that dry for 24hrs. The next day i did 2 layers of 300gram at once. Let that dry overnight. And the third day I did 4 layers of 450gram 1.5oz. And let that dry for 3 days before pulling the moulds off the car. It came off easy for such a large item, all edges were safe, nothing stuck to the car, I just didn’t leave a large flange around the edges. I wish i did. I only have about .5 - 1 inch of extra edges around the entire shape I want copied.
I primed the mould as some say to do, I waxed it once an hour for 8 or 9 hours. Then put regular gelcoat in it, and then did 1 hot batch of a 1oz 300gram skin coat. let that dry and pulled it out of the mould. As a sacrificial piece, not to use. Now ready to be used for regular production. 1 heavy coat of regular unwaxed gelcoat, dry, then 2 layers of 450gram. And that’s it.
Now onto the original post,
The moulds I purchased have been used for 2 years and made great parts by the previous owner. Before this venture, i have never made fiberglass items. Only used fiberglass for bumper cracks and repairs.
So the questions that I feel are important are related to the steps to make good bodykit style parts from 1 or multiple pieces moulds.
Pics attached.
These are the moulds and the parts that come from it
I’d like to make a suggestion. Buy a gelcoat cup gun. Spraying will give you a more consistent thickness and it will give you the correct thickness in one coat. If you keep using a brush for gelcoat, eventually you will encounter alligatoring and it will ruin your day. Brushing requires two coats to get the correct thickness. Alligatoring happens when the first coat is too thin in some areas and the styrene from the second coat attacks the first coat in those thin areas. The gelcoat bubbles up and separates from the mold surface. Only option is to let it cure, remove it, clean up and start over. The cheapest price I found was from U.S. Composites. $119. Well worth the investment.
That depends on the gelcoat ^
If you need 2 coats to get to correct thickness, that sounds like a very thin gelcoat, potentially one that is spray viscosity rather than brush viscosity. A brush viscosity gelcoat should make it easy to get application thickness in one coat, and you shouldn’t get alligatoring simply because you are brushing unless you are trying to brush a spray gelcoat.
The only real difference should be that spraying is significantly quicker. You can spray 1L of gelcoat in less than a minute, but try to brush up that much gelcoat within the pot-life. On larger moulds or in a production environment, there’s no way I would be brushing.