S.J. Byrus of Auburn, New Hampshire, asks:
"My Bristol 32 was built in 1980 and its hatches are molded fiberglass with gelcoat on the outer edges. The center of the hatch is translucent, so light can pass through. After 30 years of it being exposed to the sun, I’m starting to see some fibers in the translucent portion of the hatch, although no fibers have come loose. What can I do to protect the glass?"
Don Casey replies:
Omitting gelcoat in the center portion of a fiberglass hatch does allow sunlight to pass below. It also avoids having to buy a manufactured hatch with a metal frame and a clear lens. That saves the builder, and hopefully the buyer, a few dollars. Unfortunately the resin in fiberglass typically gives translucent panels like yours a somewhat unattractive yellow tint that darkens over time to a more toxic-looking brown.
While the rest of the fiberglass laminate on the boat is screened from the sun by pigment in the gelcoat, a bare laminate doesn’t enjoy this protection and surface corrosion can occur. That your hatches have endured the sun for almost three decades is a testament to the durability of polyester. But now that the fibers are starting to show, your hatches need attention.
Start by cleaning the translucent portion of the hatches and then wipe them thoroughly with a dewaxing solvent. Mask off the gelcoated portion and sand the translucent area with 60- or 80-grit sandpaper in two directions. When the surface is uniformly frosted, paint on a fresh coat of polyester finishing (surfacing) resin. Polyester resin is air-inhibited, which means that it won’t cure fully while exposed to air. Finishing resin also contains an additive that floats to the surface and seals the resin to produce a tack-free cure.
Considering how well your hatches have held up, this fresh application should work well for at least another decade. To protect it, let the surfaces “age” for a couple of months and then spray them periodically with a UV screening product like 303 Aerospace Protectant (303products.com).