10 Essential Repair Supplies For Fixing Cracked Trailer Fender Skirts

Spotting a crack in an RV fender skirt is a rite of passage for anyone towing a travel trailer or fifth wheel down highway miles. These thin plastic guards bear the brunt of road debris, wind drag, and harsh UV exposure, making failure almost inevitable over time. Having the right tools on hand transforms a potentially expensive replacement job into a straightforward, long-lasting DIY fix.

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Why RV Fender Skirts Crack and How to Fix Them

Most factory RV fender skirts are made from vacuum-formed ABS plastic or thin polyethylene, materials chosen more for their low cost and lightweight properties than their durability. Years of sun baking, cold winter highway runs, and constant wind vibration fatigue these plastic panels until they snap around mounting screws or along body lines. A stray tire fragment or road pebble is often all it takes to trigger a structural split.

Leaving a cracked fender skirt unaddressed does more than just ruin the trailer’s aesthetic. High-speed wind gets trapped behind the loose plastic, pulling it away from the camper body and potentially tearing out surrounding fasteners or damaging the underlying wood framing. Rainwater then sneaks into these open mounting holes, leading to hidden sidewall rot and costly structural repairs down the line.

Repairing these skirts successfully requires more than just slapping duct tape over the damage. The goal is to weld or chemically bond the cracked edges back together while reinforcing the back of the repair area to handle future road vibrations. Selecting the right adhesive, welding element, or reinforcement substrate depends on whether the skirt is made of thermoformable ABS or highly slick polyethylene.

Plastic Welding Kit – Polyvance 5700HT Mini Weld

When adhesives cannot bite into stubborn plastics like polyethylene, thermal welding is the only reliable way to fuse a cracked fender skirt back into a single piece. A dedicated plastic welding kit melts the damaged seam while introducing new plastic filler material, creating a joint that is often stronger than the surrounding material. It turns a weak, separated seam back into a solid, continuous panel.

The Polyvance 5700HT Mini Weld is the premier choice for trailer owners because of its precise temperature control and highly portable design. Unlike standard soldering irons that burn the plastic, this unit delivers consistent heat through specialized tips designed to smooth and feed welding rods. It comes with a variety of plastic rod types, including polyurethane, polypropylene, and ABS, allowing for precise material matching.

Operating this tool does require a steady hand and a bit of practice on scrap plastic before tackling the trailer’s exterior. It is essential to identify the plastic type of the fender skirt—often stamped with a recycling code like ABS or HDPE—to ensure the matching rod is used.

• Power: 200W ceramic core heating element
• Includes: Standard welding tip, airless welder tips, and assorted plastic rods
• Best for: Deep splits in polyethylene (PE) and ABS skirts
• Who it is for: DIYers who want a permanent, professional-grade fusion on stubborn plastics.
• Who it isn’t for: Quick-fixers who prefer simple peel-and-stick solutions or those working with highly delicate, paper-thin plastics.

ABS Cement – Oatey Medium Body Black ABS Cement

For fender skirts made of ABS plastic—which represents the vast majority of towable trailers—chemical solvent welding is incredibly effective. Instead of simply gluing two parts together, solvent cement temporarily dissolves the plastic surfaces, allowing them to fuse on a molecular level as the solvent evaporates. This creates an incredibly strong, seamless bond that will not pop loose under highway-speed wind shear.

Oatey Medium Body Black ABS Cement is the go-to standard for this specific repair task. Its black color blends seamlessly with typical black fender skirts, minimizing the need for extensive painting or cosmetic cover-ups later. The medium-body viscosity is thick enough to fill small gaps and cracks without running down the side of the trailer during application.

Keep in mind that this solvent only works on ABS plastic; attempting to use it on polyethylene or polycarbonate will result in zero adhesion. The working time is exceptionally fast, meaning parts must be aligned and clamped within seconds of application. Always use this product in a well-ventilated outdoor space due to the strong chemical fumes.

• Color: Black
• Material Compatibility: ABS plastics only
• Set Time: 1 to 2 minutes; cures fully in 24 hours
• Who it is for: Owners of black ABS trailer skirts looking for a fast, chemical-fusion repair.
• Who it isn’t for: Anyone working with non-ABS plastics like polyethylene or fiberglass.

Reinforcement Mesh – J-B Weld Tension Wire Mesh

A plastic repair is only as strong as its reinforcement, especially on a trailer skirt that undergoes constant vibration and flexing on the highway. Simply gluing a crack from the front will fail if road bumps place tension on the seam. Embedding a metal wire mesh into the backside of the plastic repair bridges the gap, distributing structural stress across a wider surface area.

J-B Weld Tension Wire Mesh is specifically engineered to act as a skeletal structure for plastic adhesives and welds. This fine aluminum screen is highly pliable, allowing it to conform easily to the complex, curved contours of molded trailer fenders. It holds its shape once bent, preventing the repaired plastic from sagging while the adhesive or weld cures.

When using this mesh, cut it to overlap the crack by at least an inch on all sides using heavy utility shears. For plastic welding, use the welder tip to press the mesh directly into the molten plastic until it is fully embedded. For epoxy repairs, sandwich the mesh between two thick layers of adhesive to prevent moisture from reaching the metal.

• Material: High-strength aluminum
• Dimensions: 5″ x 10″ sheet
• Grid Size: Ultra-fine weave for maximum adhesive grip
• Who it is for: Anyone needing structural backing for high-stress cracks near mounting holes or sharp curves.
• Who it isn’t for: Minor hairline cracks that do not experience heavy structural tension.

Plastic Adhesive – J-B Weld PlasticBonder Epoxy

J-B Weld 50139 Plastic Bonder Body Panel Adhesive and Gap Filler Syringe - Black - 25 ml

When thermal welding is not an option, a specialized structural adhesive is the best way to mend cracked plastic. Standard household glues lack the sheer strength and flexibility needed to survive outdoor temperature swings and road vibrations. A dedicated plastic-bonding epoxy chemically anchors itself to the material, creating a rigid yet slightly flexible patch.

J-B Weld PlasticBonder Epoxy stands out because of its high-strength, two-part urethane formula designed specifically for DIY plastic repairs. It cures to a tough, sandable finish that can be painted over to match the trailer’s original color scheme. The convenient syringe packaging ensures a perfect 1:1 mixing ratio every time, reducing the risk of a weak cure due to improper mixing.

Prep work is absolutely critical when using this adhesive; it will not bond to greasy, dusty, or un-sanded plastic surfaces. The formula sets in just fifteen minutes, meaning all clamps, backing mesh, and alignment tools must be ready to go before mixing. It works exceptionally well on ABS and PVC, but requires an adhesion promoter if used on slick polypropylene surfaces.

• Set Time: 15 minutes; fully cured in 4 hours
• Strength: 3770 PSI tensile strength
• Color: Tan or Black options available
• Who it is for: DIYers wanting a highly reliable, high-strength structural adhesive that can be sanded and painted.
• Who it isn’t for: Quick repairs on highly slick, untreated polyethylene skirts that repel standard epoxies.

Repair Tape – EternaBond RoofSeal MicroSealant

Sometimes a crack happens mid-trip, and a full structural plastic weld is not immediately feasible. In these mobile scenarios, a heavy-duty, weatherproofing repair tape is a lifesaver to prevent the crack from spreading or letting road spray behind the skirt. It can also be applied to the inner side of the skirt as a permanent, flexible backing layer for an epoxy repair.

EternaBond RoofSeal MicroSealant tape is legendary in the RV community for its aggressive adhesion and unmatched durability. This tape utilizes a specialized microsealant adhesive that fuses to plastics on contact, creating a completely waterproof barrier that tolerates extreme heat and freezing temperatures. Its UV-resistant backing means it will not dry out, crack, or peel away after a summer of exposure to the elements.

The extreme stickiness of this tape means there are no second chances during application; once it touches a surface, it is permanent. Users must carefully peel the backing and roll it down firmly with a roller to activate the pressure-sensitive adhesive. It is best applied to the hidden, inner side of the fender skirt unless the trailer owner does not mind the industrial look on the exterior.

• Width: Available in 2-inch to 4-inch rolls
• Adhesive Type: MicroSealant technology
• UV Resistance: Rated for 10+ years of direct exposure
• Who it is for: RVers needing an instant, waterproof, long-term backing strip or emergency roadside repair solution.
• Who it isn’t for: Aesthetic-focused exterior repairs where paintability and seamless cosmetics are required.

Sanding Sponge – 3M Utility Sanding Sponges

Adhesives and plastic welds require a rough, textured surface to mechanically lock onto the plastic. Skipping the sanding phase is the number one reason DIY fender skirt repairs fail within the first few highway miles. A good sanding tool removes oxidized plastic, road grime, and paint, exposing fresh, raw plastic for the bonding agent.

3M Utility Sanding Sponges are far superior to standard sandpaper sheets for this task because of their flexible foam cores. They conform seamlessly to the compound curves, molded ridges, and tight corners typical of trailer fender skirts. The durable backing resists tearing when working over sharp, cracked plastic edges and can be rinsed and reused multiple times.

Using a medium grit (around 80 to 120) is ideal for scuffing the backside of the fender skirt where structural reinforcement is applied. For the exterior cosmetic side, a fine grit (220 or higher) prepares the cured epoxy or plastic weld for a smooth coat of primer and paint. Always wet-sand when finishing plastic to prevent heat buildup from melting the material during hand-sanding.

• Grit Range: Fine, Medium, and Coarse options
• Material: Aluminum oxide on flexible foam
• Use: Wet or dry application
• Who it is for: Anyone doing plastic prep or finishing work on curved trailer body parts.
• Who it isn’t for: Large-scale paint removal projects where an electric sander is more efficient.

Degreaser Cleaner – Spray Nine Heavy Duty Cleaner

Highway travel coats the lower sections of an RV in a film of diesel exhaust, road oils, tire dust, and wax. If these contaminants are not completely stripped away before starting a repair, they will act as a barrier, preventing epoxies or weld material from bonding. A dedicated heavy-duty degreaser is mandatory to prepare the surface for surgery.

Spray Nine Heavy Duty Cleaner is the ideal choice because it cuts through tough petroleum grease and road grime without leaving behind a soapy residue. Unlike some household cleaners that leave behind oils or scent agents, it leaves the plastic surgically clean. It also sanitizes the area, removing mold and mildew that often build up behind damp fender skirts.

This is a professional-grade chemical cleaner, so wearing protective gloves is highly recommended during use. Spray the product generously on both sides of the cracked area, scrub vigorously with a stiff nylon brush, and rinse thoroughly with clean water. Ensure the plastic is 100% dry before applying any sanding blocks, adhesives, or plastic welds.

• Formula: Water-based biodegradable degreaser
• Action: Triple-action cleaner, degreaser, and disinfectant
• Container: Spray bottle or gallon refills
• Who it is for: Trailer owners who need to quickly and completely strip road grime, wax, and oils from repair zones.
• Who it isn’t for: Delicate interior plastics or finishes that are sensitive to alkaline-based cleaners.

Fiberglass Cloth – 3M Bondo Fiberglass Cloth

For repairs on fiberglass or rigid ABS fender skirts, fiberglass cloth provides unmatched tensile strength when layered with structural adhesives. It behaves like rebar in concrete, preventing the cured resin or epoxy from cracking when the trailer chassis twists on uneven ground. It is the best choice for spanning wide holes or missing sections of a fender skirt.

3M Bondo Fiberglass Cloth is woven from high-quality glass fibers, offering a uniform weave that absorbs epoxy resins quickly and evenly. It is incredibly thin and lightweight, meaning it adds structural integrity to the backside of the skirt without creating a bulky bulge that interferes with trailer mounting brackets. Its flexibility allows it to drape over complex, compound curves with ease.

Working with fiberglass cloth requires a bit of care, as cutting it releases tiny glass fibers that can irritate the skin and eyes. Always wear a mask and gloves, and use a pair of dedicated heavy shears to cut the cloth to size. Make sure the cloth is fully saturated with epoxy so that no dry, white patches remain, which would represent weak points in the repair.

• Material: Woven fiberglass strands
• Size: 8 sq. ft. pack
• Compatibility: Works with epoxy resins, polyester resins, and structural adhesives
• Who it is for: DIYers fixing large cracks, punctures, or missing plastic pieces on rigid skirts.
• Who it isn’t for: Flexible, soft polyethylene skirts that reject rigid fiberglass and epoxy bonds.

Rotary Tool Kit – Dremel 3000 Variable Speed

Simply gluing the flat sides of a crack together rarely lasts because there is not enough surface area for the adhesive to grab. Creating a “V” shaped groove along the crack line exposes more surface area and allows the weld filler or epoxy to sit flush with the plastic panel. A rotary tool is the perfect instrument for carving out these channels and trimming away frayed plastic fibers.

The Dremel 3000 Variable Speed rotary tool kit is the industry benchmark for detail work on alternative dwellings and RVs. Its variable speed range (5,000 to 35,000 RPM) allows users to dial back the speed to prevent melting the plastic while cutting or grinding. The kit comes with a variety of sanding bands, grinding stones, and cutting wheels perfect for tight plastic repair steps.

When working on plastic, keeping the RPMs low is vital, as excessive speed will melt the material instead of cutting it, creating a gummy mess. Gently run a conical grinding bit along the crack on both sides of the panel to create the V-groove. Wear safety glasses, as small plastic shavings will fly during the carving and trimming process.

• Motor: 1.2 Amp variable speed
• Speed Range: 5,000 to 35,000 RPM
• Attachments: Includes 28 accessories and a carrying case
• Who it is for: DIYers who want a precise tool for prepping plastic cracks, engraving grooves, and finishing repairs.
• Who it isn’t for: Heavy-duty, high-volume cutting tasks where full-size angle grinders are required.

Butyl Seal Tape – Dicor Butyl Rubber Seal Tape

Once a fender skirt is repaired, mounting it back onto the trailer body requires a proper seal. Without a flexible gasket between the plastic skirt and the aluminum or fiberglass sidewall, road vibration will rub the skirt raw and allow water to seep behind the panel. A high-quality butyl tape creates a waterproof cushion that dampens vibration and prevents future cracks.

Dicor Butyl Rubber Seal Tape is the gold standard in the RV industry for sealing trim, windows, and exterior panels. It remains soft, pliable, and sticky indefinitely, allowing it to stretch and compress as the trailer moves down the road. It adheres aggressively to both plastic skirts and camper siding, ensuring a watertight seal around screw holes.

When installing, apply the tape along the mounting flange of the fender skirt before pressing it against the trailer wall. As the mounting screws are tightened, the butyl tape will squeeze out slightly; simply trim the excess with a plastic putty knife. Avoid using silicone caulk in place of butyl tape, as silicone loses its seal under road vibration and makes future removals extremely difficult.

• Material: Butyl rubber compound
• Dimensions: 1/8″ thick x 3/4″ wide x 30′ roll
• Color: Off-white/Gray
• Who it is for: RVers reinstalling fender skirts who want to prevent water intrusion and isolate road vibration.
• Who it isn’t for: Non-mating surfaces or structural bonding tasks where a high-strength adhesive is needed.

Tips for a Long-Lasting Fender Skirt Repair

To ensure a repair lasts for thousands of highway miles, never skip the “stop-drill” step. Before applying any adhesive or heat, use a tiny drill bit to make a clean hole at the very end of each crack. This circular hole stops the crack in its tracks by distributing the physical stress evenly around a circle rather than letting it focus on a single sharp point.

Pay close attention to the mounting screw holes, as this is where most cracks originate due to vibration and overtightened fasteners. When reinstalling the skirt, slide a wide stainless steel fender washer onto each screw to spread the holding force over a larger surface area. Tighten the screws until they are snug against the butyl tape, but do not overtighten them, which crushes the plastic and triggers immediate stress cracks.

Finally, respect the curing times listed on adhesive packaging, especially in cooler climates. Alternative living spaces are subject to outdoor temperature swings, and cold weather can double or triple the time an epoxy needs to reach full strength. Keep the repaired fender skirt in a warm, dry space for at least 24 hours before subjecting it to highway wind forces or road vibrations.

Conclusion

Taking the time to properly prep, bond, and reinforce a cracked trailer fender skirt saves hundreds of dollars in replacement parts and protects the trailer’s structural integrity. With these ten essential repair supplies in the DIY toolkit, restoring a damaged fender is a highly achievable project. Maintain a patient approach to the process, and the trailer will be ready for many more miles of smooth, worry-free travel.