Design and engineering are critical aspects of fibreglass fabrication. The process of creating custom fibreglass products begins with a design concept, which is then transformed into a physical product through the use of engineering principles and techniques.

The design phase for custom fibreglass fabrication involves developing a concept for the product, which includes determining its function, size, shape, and overall aesthetic. The design must consider the characteristics of fibreglass as a material, including its strength, durability, and flexibility..

Once the design concept is established, the next step is to create detailed engineering drawings. These drawings specify the dimensions, tolerances, and other details of the fibreglass product. They also consider any specific requirements or regulations that may apply to the custom fibreglass product, such as safety standards or industry-specific guidelines. During the engineering phase, various analysis tools and techniques are used to ensure that the product meets all performance requirements. These may include structural analysis, thermal analysis, and fluid dynamics analysis, among others. This ensures that the fibreglass product is designed to withstand the stresses and forces that it will be subjected to during use.