The largest number of reinforced plastics composite products are produced by the hand lay-up process. A few examples of this processes uses are: boats, portable toilets, picnic tables, car bodies, diesel truck cabs, hard shell truck bed covers and air craft skins and interiors. The hand lay-up process is labor intensive plus the plastic resins produce toxic fumes requiring well ventilated facilities and protective equipment for workers. And, since the workers seem to want to be paid more when around toxic things, they may want more pay.

The hand lay-up process produces parts from an open, glass reinforced, mold. The mold surface is treated with several layers of release wax and then spray coated with a pigmented polyester resin called a gel coat. The surface of the mold will be duplicated by the gel coat. Over the gel coat, glass fiber is layered. Each layer is saturated with polyester resin that is specifically formulated to cure at room temperature. The polyester resin must be catalyzed 2% by weight. The catalyst is a toxic and corrosive peroxide. Each glass layer is pressed by hand with rollers to work the polyester resin into the glass fiber. Three to nine layers are added and allowed to cure depending on the desire strength of the part. Once the polyester is cured, the part is removed from the mold. The part requires trimming and post mold surface preparation. In the production of the high performance airplane, both carbon fiber and epoxy plastic are used.

Hand lay-up parts can consist of any size or configuration. Moreover, the process does not require any special tools. Parts can be easily fabricated as a weekend backyard project. Molds can be easily modified, cut into part for prefabrication and applied to create various surface textures. The rigid properties of the final product require that under cuts and straight wall be eliminated. Any openings must be machined in post molding operations. All corners must have somewhat large radius. The structure is often stiffened with the additions of honeycomb, balsa or rigid foam blocks.