Columbia Coronado 25 Owenrs Manual page 84

6.1.5 (continued)
Fibers of the reinforcing material, acts as a barrier to liquids, and
limits degradation that may result from ultraviolet radiation. It also
eliminates the need for painting the product after it has been built.
Although the gel coat is on the "top",or surface, of the fiber glass
product, it is applied first during its construction, usually by spraying
it on the walls of the mold. The remaining fiber glass reinforcements are
then laminated onto the gel coat, permanently bonding it to the molded
product.
Gelcoats consist of a complex mixture of several materials, including a curable
polyester resin, a colorant, and a catalyst, which are formulated according to
specific requirements.
6.1.6 Fiber Glass Laminates
Glass fibers reinforce polyester resins much like steel rods or mesh
reinforces concrete. In both instances, the more reinforcement you add, the
higher the breaking force of the end product - but only up to a point. After
that point has been reached, the breaking force remains about the same, but
the strength (pounds per square inch) actually decreases.
For glass-fiber/polyester-resin laminates, however, the percentage of glass
fibers is usually limited by other factors, such as economics and
workability. For instance, manufacturers of fiber glass boats make their
laminates just slightly stronger than what is required for normal safety
considerations. The current practice is to add from 25 to 40 percent glass by
weight to the laminate.
The choice of a particular form of glass fiber is dictated both by the properties
desired in the finished laminate and by the method of layup (discussed in Chapter
2). Generally, the continuous fiber forms (woven roving and cloth) offer the most
strength for a given thickness of laminate. Their advantage lies partly in their
continuous fiber form and partly in their capacity to be well saturated and
wetted with relatively small amounts of resin. Thus, higher glass contents with
higher strength can be achieved.
SECTION 6
Page 4