“For the last 40 years or so, hand and spray lay-up have been the predominant manufacturing processes for the production of GFRP boats. They are relatively easy to work, allow the use of female molds and, until recently, the regulations regarding emissions were fairly relaxed. In fact, until the advent of stricter emissions regulations, there was very little motivation for the vast majority of boat builders to change their working process.

Resin infusion done at our shop

The most commonly used matrix for GFRP boats is undoubtedly polyester resin. Polyester resins are produced through a process of polycondensation between poly-basic acids and polyvalent alcohol.
If the acid is unsaturated, these polyesters can
co-polymerize with styrene, the unsaturated monomer obtained out of de-hydrogenation of the ethyl benzene at atmospheric pressure and at about 600°C. The product that is created is a polymer with a three-dimensional structure that
is inhible and insoluble.
Evaporation of the styrene during hand or spray laminating process is a harmful chemical-physical process that is almost completely eliminated by the use of infusion molding techniques.
However, in addition to the environmental issues, there are many negative aspects to the hand/lay-up process, particularly in terms of quality as the finished laminate is heavily dependent on the relative skill of the individual.
Moreover, even when the skill level is high, it is difficult to achieve fiber fractions of more than 40 percent and to eliminate the problems associated with air entrapment.
Regarding mechanical properties, it is clear that laminates manufactured using the infusion process are considerably superior to those produced by hand lay-up. Four point bending tests to ASTM 790 Norm show that infusion laminates have 20 percent higher flexural strength than an equivalent hand lay-up laminate.”