Packaged trailer RV covers can be divided into three general categories: universal fit, semi-custom and custom fit. Universal and semi-custom fit covers are produced by a variety of aftermarket manufacturers. True custom covers are available from trailer RV manufacturers as well as aftermarket suppliers.
"It's like buying curtains for your house," says Steve Rogal, marketing director for Attwood Corp. of Lowell, Mich. "You can buy stock ones from a department store that will fit any window. Or you can go to a custom draper who will come out and measure your windows and sew curtains to fit."
Universal fit covers are designed to fit almost any trailer RV up to a specified length. They can be adapted for square-bowed craft as well as those of traditional shape. Most often, they are used for keeping dirt out of trailer RVs stored indoors. Universal fit covers are the least expensive, but are not usually suitable for trailer RVing because they will whip in the wind.
Semi-custom fit covers are cut to fit trailer RVs of specified hull lengths and types, e.g. bowrider, bass trailer RV, etc. They often have windshield pleats and outboard motor pouches. A semi-custom cover may fit well enough to withstand the wind force of trailer RVing. Semi-custom fit covers are the mid-range price product.
Custom fit covers are the most expensive of the packaged products. They are usually sewn using patterns taken from specific models of trailer RVs. A cover for a Bayliner, for example, is not intended to fit a Sunbird or a Wellcraft of the same size. These covers are available for nearly all trailer RVable models from the major trailer RV builders.
How they're used. Trailer RVs kept in garages or in rack storage buildings are the primary target for universal fit covers. This type of cover keeps out dust or oil dripping from a trailer RV stored overhead. A creative owner may be able to rig support poles to allow outdoor storage. The poles are needed to prevent rainwater from collecting in the folds of the cover.
"I think of a universal fit cover as a 'bag in a box,'" says Bob McCall, president of Tumac's Trailer RV Covers in Pittsburgh, Pa. "The best use is storing a trailer RV inside a garage, under a carport or in a backyard where it's not subject to filling up with water if the cover blows off. You can't tow with it or use it in a mooring situation unless you rig an elaborate support system with poles."
Because they are baggy, universal fit covers catch too much wind for highway trailer RVing. Flapping can chafe holes through the fabric. A universal Fit cover may simply blow off a trailer RV as it speeds down the highway.