Unless you own a vintage Chris-Craft or a restored steel trawler, you probably have a boat made of fiberglass that could use improvements and repairs here and there. While fiberglass work may seem daunting to a novice do-it-yourselfer – all those heavy chemicals and resins – it does not have to be.
Common polyester resin and fiberglass rolls are available off-the-shelf at just about every marine store in the country, and learning to work with these products will give you the freedom and flexibility to upgrade your boat in ways other materials cannot match.
With some basic skills and practice, you can make major cosmetic improvements, replace worn and broken parts and build entirely new structures. Electronics cases, deck boxes, access hatches and vents are all good candidates for a first-time effort.
To illustrate the process, I'll use one of my own small projects: replacing the lid of a top-loading sailboat refrigerator that was too thin and poorly insulated. My goal was to reinforce part of the existing lid with fiberglass, add foam insulation and bond the whole thing to a teak frame. It would cost me a few hours of work, but the result would be a vastly improved fridge for less than $100 in materials.
START WITH A MOLD
Modern fiberglass applications have evolved a great deal. The development of plastics reinforced with various fabrics began during World War II, spurred by a lack of aircraft aluminum and other shortages. L. Francis Herreshoff, cantankerous son of the famed designer Nat Herreshoff, called it "frozen snot." But the material grew to dominate the industry.
Fiberglass, glass reinforced plastic (GRP) and fiberglass reinforced plastic (FRP) are all basically the same thing: fibers of glass suspended in a matrix of resin. For our purposes here, that resin will be polyester. There are more exotic materials out there, but for many boat applications, good old polyester resin still works just fine. The glass fibers give the matrix its strength while the resin adds stiffness, a classic example of whole adding up to more than the sum of its parts.
Paul EsterleMost fiberglass projects start with a mold.
In much the same way that your boat was built, most fiberglass projects begin with a mold – male or female – that is used to create the structure you are building. Female molds are hollow and the project is formed inside them. With a male mold, you form the project over the exterior.
Most fiberglass boats are built in a female mold. The first step in making a hull is to thoroughly wax the mold. This wax develops the shiny surface of the hull and provides the mold release so the hull can be removed. A gel coat, much thicker than paint, is then sprayed into the mold and allowed to cure. Then the fiberglass reinforcement and resin is added.
The process is similar for small projects: build the mold, coat it with mold release, apply the gel coat and then add layers of fiber and resin.
