handlayup

Hand layup is a manual composite fabrication process in which reinforcing fibers are laid into a mold and resin is applied by hand. It is commonly used with woven fabrics such as fiberglass, carbon fiber, or aramid, and with resins including unsaturated polyester, vinyl ester, or epoxy. The method is simple, versatile, and well-suited to large parts and low- to medium-volume production, such as boats, architectural panels, and prototype components.

Process steps typically begin with preparing the mold with a release agent or gel coat. Reinforcement plies are cut to fit the geometry and placed into the mold. Resin is then applied by brush, roller, or pour-and-saturate methods, and excess resin is removed with squeegees to reach the desired fiber content. Layers are built up to the required thickness, followed by curing at room temperature or with heat. After cure, the part is demolded and trimmed. Variants include wet layup, where resin saturates the fiber during placement, and dry layup, using preforms with resin added later; vacuum bagging or other compacting methods may be used to improve consolidation and reduce voids.

Advantages of hand layup include low equipment costs, adaptability to complex shapes, and suitability for custom, low-volume production and repairs. Disadvantages include labor intensity, variability in resin content and compaction, longer cycle times, and greater exposure to volatile organic compounds from resins such as styrene.

Common applications span marine vessels, architectural and automotive components, and repair or refurbishment tasks where geometries are irregular or production volumes are small. Safety considerations include adequate ventilation, personal protective equipment, and proper handling and disposal of resin systems.