Things You'll Need
Fiberglass epoxy resin
Fiberglass sheets and mats
Pan spray or mold release
Fiberglass is a very versatile building material. Unlike metal or wood, it isn't simply cut and screwed or welded into place. Fiberglass sheets are shaped to form the product, and a two-part resin hardener is used to transform the flexible sheet into a strong, durable product. Finished fiberglass has a texture that feels much like plastic, but has strength that rivals some metals.
It is used to make a very wide range of products, such as cases for mechanical components, automotive panels and body kits. Marine applications also commonly use fiberglass, due to its durability, water-tightness and resistance to corrosion.
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The concept of working with fiberglass is not incredibly challenging, but in reality it can take a great deal of practice to get things right.
Use cardboard or high-density foam to form a rough shape of the object you're trying to make. Cardboard can be cut, curved, folded and pieced together to form a shape that resembles the finished product. Foam can be used when more detail is required. Cut or carve it into the shape you need, filling in any precise details using an X-Acto knife.
Prepare the object to receive fiberglass by covering it with a single layer of aluminum foil. Use masking tape to hold the foil in place and to seal any gaps at the edges where two sheets overlap. The foil will protect the object and allow the fiberglass to be easily removed. Spray the foil with a coating of pan spray or a commercial mold release product.
Mix the two-part epoxy resin in a container such as a plastic cup. Follow the manufacturer's directions to ensure an even consistency. Stir the epoxy using a disposable stirrer. Be aware that the epoxy will only stay liquid for a matter of minutes before it begins to harden.
Using a paint brush, lightly coat one side of a fiberglass sheet with epoxy resin. Place the sheet on the object, with the epoxy coated side touching it. Thoroughly coat the exposed side with resin, making sure enough is applied to soak all of the way down into the fiberglass material. Allow this layer to dry overnight (or at least 12 hours) before moving on to the next step.
Wearing gloves, gently pull the fiberglass sheet off of the object. It will be somewhat fragile at this point, so handle it with care and avoid dropping it. The fiberglass will now need to be strengthened. On the inside of the fiberglass part (the side that was previously touching the mold), lay another layer of fiberglass. This can be either a regular sheet or a thicker fiberglass mat. Follow the same process used to lay the first sheet. You can lay as many as you feel are necessary, allowing around 30 minutes between each layer. The final number of layers needed will be up to you, since it depends on the strength your specific application calls for.
Allow the fiberglass to dry overnight (or for another 12 hours) before handling. Once dry, the edges will likely be very jagged and will have exposed glass fibers that could embed in the skin in the form of splinters. Wearing gloves, eye protection and a breathing respirator, use a metal file to hone the object to a smooth edge. Once finished, begin sanding the visible surface of the fiberglass. Start with a very rough sandpaper, around 80 grit, followed by a medium grit such as 200, and finish things off with a fine grain paper in the 600 grit range. Switch to a finer paper when you can no longer feel the surface getting smoother with the sandpaper you're currently using.
Prime and paint the object, following the instructions printed on the products you are using. One to two layers or primer works best to ensure that the paint won't peel off over time. Use as many coats of paint as needed to completely cover the fiberglass. If it will be exposed to the elements, consider placing one to two layers of clear coat over the finished product to prevent the paint from fading or chipping.
The fiberglass mold can be used to make as many parts as you need.
Never sand or file fiberglass without protective equipment.