Fabricate Fiberglass Parts
Fabricating your own fiberglass parts is a useful skill when restoring an older boat because replacement components may be unavailable, expensive or simply not suitable for what you’re trying to build. For this project, I needed custom fiberglass end caps to protect the vulnerable aft corners of my trawler’s new rub rail. Rather than adapting an off-the-shelf rubber dock fitting, I fabricated parts specifically shaped to fit the boat and cover the exposed ends of the rub rail.
Making a Plug for a Fiberglass Part
The basic process begins by creating a plug that establishes the shape of the finished part. I formed scrap acrylic around a section of the rub rail to reproduce its profile, then joined two pieces at approximately 90 degrees to create the corner shape. Acrylic provided a smooth surface that would release the cured fiberglass while allowing me to reproduce the exact cross-section of the rub rail without laminating directly over the newly installed rubber.
Laying Up the Fiberglass Part
I start the fiberglass layup with lightweight cloth that conforms closely to the plug and captures its shape. Successive layers of heavier 5- to 7-ounce fiberglass cloth and epoxy provide the structural strength, with at least three heavier layers used for these end caps. I intentionally laminate beyond the final dimensions so the cured part can be trimmed to its finished shape afterward. Between layers, sanding and inspection reveal gaps, voids and weak areas that need additional attention.
Fairing and Finishing the Fiberglass
Once the fiberglass structure is complete, the weave, pinholes and surface imperfections have to be filled before primer and paint. I initially use thickened epoxy and then progressively finer fairing compounds to develop the final surface. This is where the quality of the original plug becomes important: the better the plug, the less finishing work the fiberglass part requires. The objective is a smooth, fair surface without visible weave, pinholes or sanding defects before the part is painted.
Installing the Finished Fiberglass Parts
After final sanding, priming and painting, the completed fiberglass end caps are dry-fitted and installed over the rub-rail corners. I used 3M 4200 marine adhesive/sealant to secure these parts. The finished end caps protect a vulnerable area of the hull-deck joint while giving the cut ends of the rub rail a clean, purpose-built appearance. The same basic plug, fiberglass layup, fairing and finishing process can be adapted to fabricate many one-off fiberglass parts for an older boat.
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