Replacing Trailer Bunk Covers

Photo: Dan Armitage

The common polypropylene carpet material that covers most trailer bunks serves two primary purposes: a smooth surface for the hull to slide on when launching and loading the boat, and protection for the hull when the boat is supported by the trailer, in storage, or being towed. It's quick drying with built-in UV-protection, and the fibers are bound together and backed with a thin, rubber-like resin membrane called PVB (polyvinyl buteral). It shouldn't be confused with the thick, black, tar-like backing found on common indoor/outdoor carpet that some boaters use as an inexpensive alternative to material designed for the task. The cheap nylon fibers don't hold up, and the rubber backing breaks down fast in a moist marine environment.

Chris Walls, of the trailer-parts manufacturer CE Smith, says that cheaper carpeting often used for bunk use will tear more easily, or hold water, the latter promoting rot in the boards. "Quality carpeting is breathable, so it dries quickly and doesn't allow water to saturate the bunk boards," he says, adding that it's important to rinse off the bunk carpeting regularly or when you notice sand or grit caught in the fibers, which can damage the hull and cause the carpet to fail. Just as important as using carpet material made for the job, according to Steve Beaman, a marine buyer for Overton's, is how the carpeting is installed on the bunks.

"Pressure-treated pine is the industry standard for boat-trailer bunks," he says, noting that hardwoods such as oak and cypress are popular alternatives to treated pine. Composite boards such as those designed for patio decking are now being used for bunks as well, but pressure-treated pine is a proven material, strong enough to support the boat and it holds up well in marine conditions. Wood also accepts and holds the stainless-steel staples and screws commonly used to attach the carpeting to the bunks. "Fasteners should be half an inch to two-thirds of an inch long to secure the material to the bunk," says Beaman.

Unlike common carpet, bunk covering material made for the job is designed to stand up to a marine environment high in moisture and damaging UV light. (Photo: Dan Armitage)

It's important when installing bunk carpeting that the material be cut and fit on the board to allow butt seams, with no overlapping of material on the underside of the bunk. Beaman says that it's better to leave an open seam with space between each edge than to double up the carpet material because wood expands when it gets wet. An open seam allows for that expansion and doesn't stress the material and the staples or screws that hold it, as is the case when the fasteners are expected to hold through double layers of the fabric. Depending on frequency of use, quality carpeting properly installed on a boat-trailer bunk should last at least four to five years, according to Beaman.

Replacement bunk boards with carpeting already installed are available in popular sizes from several sources. Most bunks are built using pressure-treated pine or hardwoods such as oak or cypress. (Photo: Thinkstock)

In addition to traditional carpet material, boat-trailer bunks may also be fitted with various "slides" that complement or replace the fabric altogether. E-Z Slide Trailer Pads are molded from a slippery, Teflon-infused composite of polyethylene made of recycled milk cartons that reduce friction as the boat slides on and off the trailer. The pads, which cost $31 to $72, depending on the number and size, install directly over carpeted bunks and are designed for use with aluminum boats up to 4,000 pounds and fiberglass boats weighing up to 1,500 pounds.

Photo: Thinkstock

Tie Down Engineering offers full-coverage Glide On bunk slides and Bunk Slick pads made of a similar super-slick PVC material. Bunk Slicks, measuring 16 and 17 inches long, are mounted right on top of the carpet at two-inch intervals along the bunk. Glide Ons, which envelope the bunk and replace the carpet, and are also available in modular form for partial coverage. Tie Down's Jeff Minert says it's important to keep any trailer-slide surfaces as clean and free of road grime, sand, and grit as possible or you risk damaging the hull surface.

Spokespeople for every source of plastic bunk products we contacted were quick to caution how slippery treated bunks become with the addition of after-market launch accessories, compared to their plain carpeted counterparts. Because of that, care must be taken during launching and loading to compensate for how easily the boat will move across the slick bunks, an asset when you want it to, but not so much when you don't expect it.

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