How to Fabricate Fiberglass Door Panels

Cover with fabric. Start by taking a large sheet of continuous fabric, and use it to cover the entire panel where you want to add the fiberglass. The panel must be removed from the car doorframe. Use staple guns to attach the fabric to the panel. Add staples on the depressions and grooves of the panels so that you will be able to shape the surface of the panels.

Apply the resin and hardener. Combine the fiberglass resin and the hardener in a large bowl, and mix well together. Add a little bit of acetone, if you are working in a sunny area where the mixture may quickly dry out. Fiberglass resin usually comes with a packet of hardener, but you can buy additional hardeners separately. Apply the first layer with a paintbrush and allow it to dry before adding the next layer. Let dry again and add another layer, until you get the desired thickness for the fiberglass on top of the door panels. Make sure that you use a fiberglass mask while applying the mixture. Fiberglass has a very strong odor.

Add the mat. Once the layers of fiberglass has been applied , take strips of fiberglass mat and attach it to the surface of the panels, using leftover resin to get the fiberglass mat to stick. The mat is important, since it is what actually keeps the resin intact over time.

Sand the panels and add the filler. The fiberglass will change into a lighter color when it has fully dried. After drying under the sun, get fine-grit sandpaper and use it to polish the surface of the fiberglass. There will naturally be small bumps and holes in the fiberglass panel. You can add fiberglass body fillers like Rage Gold to smoothen out the surface. Let the filler dry out and sand again. Once the filler has dried, you can add a layer of primer on the door panel and paint it with whatever color you want.