I decided to make a documentary of sorts while building the molds for my new hood vents. The goal is to produce these hood vents for sale. So the end result has to be "consumer friendly". This means the molds, and the parts produced from them, have to be built to a high standard.
Here's how I did it.
First of all, let me describe the design of the hood vents. The design is similar to the vent I built for my own hood. The general shape is based off the decklid hump on the notchback Fieros. And it's a half raised, half recessed type, just like on my car. However, I've refined the design a bit to make it more aesthetically pleasing.
The process starts with making a casting of the decklid hump. Before I started, I made sure the surface was clean and smooth. I marked off the area with a sharpie pen, and taped off the area around it with packing tape. This will keep errant drops of resin from getting on my decklid. Then I applied a liberal coat of wax, followed by a couple coats of mold release agent (PVA), using a spray gun.
Here's what the decklid looked like after the prep work:
Then I started laying on the fiberglass. I decided to use epoxy resin to make the mold. I first applied a thick coat of resin as a gel coat. After it started to gel, I started laying on the glass fiber... a couple layers of cloth weave followed by a couple layers of mat.
All that fiberglass piled on the decklid looked like this:
After breaking it free from the decklid, I cut off the excess and cleaned it up. Here's the result:
I now have a negative image of the decklid hump. But since part of the scoop will be recessed, I need to make a negative of the negative (i.e. reproduce the hump). So I used my new casting to make a copy of the decklid hump. In the photo below, I'm molding fiberglass into the casting.
After breaking it free and trimming off the excess, I now have a second casting. The two castings are mirror images of each other. One is a hump, while the other is a dip.
The next step is to chop them up, and assemble the appropriate pieces together to get that half raised, half recessed shape. I cut the parts at a 45-degree angle, so the opening in the vent would be slanted 45 degrees, instead of straight up and down. Here's what the pieces look like after a run through the table saw:
And finally, here's a shot of the complete fiberglass mold. It looks upside-down, because it's a negative image of the hood vent.
After assembling the mold, I sanded, polished, and waxed it. Now comes the real test of the fiberglass mold, using it to make a prototype part. This will tell me if all my hard work paid off. Here's a shot of the prototype hood vent being built. The new fiberglass for the hood vent has already been laid on, and is curing.
And last but not least, a shot of the raw fiberglass part, after breaking it free from the mold. The front edge of the hood vent is at the top of the photo.
This is just a prototype part. And as such, it does have some flaws (due to the procedure, not the mold itself). Now that I have the procedure figured out, I should be able to produce some high quality parts. So the hood vent mold is a success!
