When it comes to automotive applications, fiberglass is a versatile, durable material that works well for most uses. It's lightweight and easy to work with, making it a convenient choice for many body panels and for repair work. For these reasons, it's not surprising that many automotive fenders are crafted from fiberglass. If your car has a damaged fender, you may be able to repair it on your own by patching it with fiberglass material. Here's a look at what you need to know to do the fiberglass repair work yourself.
Prep the Damaged Panel
Before you can do any repair work, you'll need to remove the damaged fender from the car for prep. Open the hood so you can access the bolts that are along the edge of the fender inside the engine compartment. Use a wrench or socket set to remove the bolts and set them aside so you can get to them later. Then, remove the bolt inside the bumper cover that's holding the bottom of the fender in position. You may need to get under the front of the car for this because it's usually behind the bumper.
Disconnect the wiring harness for the marker lights, if there are any on the panel. Remove the light assembly and set it aside. Finally, pull the fender panel off the car and lay it on a drop cloth. Use a grinding wheel to remove the damaged portion of the fiberglass. Wipe the whole fender with a rag that's been dipped in acetone. This cleans the whole surface and prepares it for the fiberglass application. Let it dry before you proceed.
Finally, you'll need to attach a piece of a thick sheet of plastic on the inside of the fender panel. The plastic should cover the hole where you removed the damage. Use a spray adhesive to keep it in place. This plastic will be the foundation that you apply the fiberglass to.
Trim the Fiberglass Mat
Cut several sections of fiberglass mat to fit the area that you need to patch. You'll want several pieces, because it's going to take multiple layers to get the job done. As you trim pieces, make each piece slightly larger than the one you cut before it, because the graduated sizes will create a taper along the edges of the repair work. This makes it easier for you to restore the panel to the same exact dimension and thickness it was originally, making it nearly impossible to know that it was repaired.
Mix the Fiberglass Resin
You'll need to mix a polyester resin to adhere the fiberglass sheets to the panel. Each resin product requires different steps to mix it, so be sure that you read the instructions carefully. You'll start with the base mixture, then add a catalyst to encourage the resin to harden. Mix the resin in as completely as possible.
Spread the prepared resin over the surface that you're patching. Make sure that the resin is even. It's often easiest to apply it with a felt roller. If you see any bubbles in the resin when you apply it, make sure you pop them and smooth them out.
Once the first coat of resin is applied, put the smallest fiberglass piece onto the surface of the resin. Then, cover that piece with more resin. Apply the next largest piece of fiberglass to the new layer of resin, and keep building up until the whole thing is level. Then, let it sit for a few hours so that the resin can harden.
Finish Things Up
After the resin hardens, you'll need to sand the surface smooth. Use auto body sandpaper to do this, then wipe the whole panel with a rag soaked in acetone. The acetone rag helps to clear away the residual dust. As soon as the surface is smooth and clean, you can repaint it to suit your preferences.
As you can see, repairing a damaged fiberglass fender is easier than you might think. If you aren't confident enough in your skills to tackle the job yourself, though, click here for more info or connect with a local fiberglass and auto body repair shop.