Fiberglass Repair for RVs, Campers and Caps

A front or rear cap is a single molded piece, not an assembly. It is laid up in a female mold: gelcoat sprayed into the mold first, then chopped strand mat and woven roving with polyester or vinyl ester resin, then core material in the areas that need stiffness, then more laminate. When it comes out of the mold the gelcoat surface is the exterior finish, already glossy, with no paint on it at all from the factory on many units.

That construction has consequences for repair. First, the gelcoat is the outermost layer and it is only about 20 thousandths of an inch thick. Sanding through it exposes raw laminate, which will not gloss back. Second, the cap is a compound curve in every direction, so a repair cannot be blocked flat against a straightedge; it has to be shaped against templates or against the surrounding surface. Third, the cap carries structural load. It ties the roof to the sidewalls and it holds the windshield frame on a Class A. A cracked cap is not just a cosmetic problem.

Repair sequence is laminate first, then filler, then gelcoat or paint. Laminate repair means grinding the damage back to sound material in a long scarf, typically twelve to one, so the new glass has a large bonding area. Layers are built back matching the original schedule. Skipping the scarf and filling with body filler produces a repair that cracks in the same place next season.

Full band detail is on the price sheet. Cap replacement, when the damage is beyond repair, runs $4,500 to $25,000 across 30 to 120 hours.

Delamination is adhesive failure between the outer fiberglass skin and the substrate behind it. Three things cause it: water, impact and heat cycling. Usually all three in sequence.

Water gets in at a seam, a window frame, a clearance light, a screw hole or a roof edge. It reaches the luan plywood substrate under the fiberglass. Luan swells when wet and it loses stiffness, so the adhesive bond that was holding fiberglass to luan is now holding fiberglass to a soft, swollen surface. The bond releases.

Once released, the spread is mechanical. Every time the wall flexes over a bump, the boundary of the released zone works. Every time the sun heats the black-backed fiberglass to 150 degrees and it expands against a substrate that expands at a different rate, the boundary works again. The released area grows outward from wherever it started, which is why a bubble that was the size of a dinner plate in spring is the size of a door in autumn.

You find it by hand and by ear. Run a flat palm across the sidewall and feel for the ripple. Tap across the panel with a plastic-handled tool and listen: bonded panel gives a sharp tick, released panel gives a dull thud. Map the dull zone with tape and that is your repair area.

Repair means opening the panel, removing failed substrate, drying the cavity, replacing luan and any rotted framing, then re-bonding the skin under vacuum or under mechanical pressure with a structural adhesive and holding it until cure. Injection-only repairs, where adhesive is syringed through drilled holes, work on small isolated areas and fail on large ones because the wet substrate is still in there. Delamination repair runs $1,500 to $20,000 across 10 to 100 hours.

Matched, yes. Matched invisibly on a heavily oxidized surface, rarely without additional work. Gelcoat is pigmented polyester resin, and the pigment ages differently than paint pigment does. White gelcoat ambers. Colored gelcoat chalks and shifts. A tinted gelcoat mixed to the original formula lands noticeably brighter than the surface next to it.

The working method is to tint against the vehicle rather than against a code. Small batches are mixed, cured on a card, wet sanded and buffed to the same finish the repair will have, then held against the panel in daylight. Gelcoat cures dull and only reaches gloss after sanding and compounding, so judging a match before that step is meaningless.

Application is different from paint too. Gelcoat is air-inhibited, meaning it will not fully cure with an exposed surface, so it is sprayed with a wax additive or covered with film during cure. Then it is sanded through progressive grits, typically starting around 400 and working to 1500 or finer, and compounded back to gloss.

The alternative is refinishing the repair area with urethane paint and blending across adjacent panels, which is often the better answer on a coach that already has paint over the original gelcoat, or one where the surrounding gelcoat is too far gone to polish. That decision is made with the owner, and it hands off to paint and refinishing. Restoration and refinishing carries the full paint band of $5,000 to $35,000 when it goes that route.

• RV and Camper Fiberglass Repair: general laminate and gelcoat work across caps, sidewalls and roofs.
• Delamination Repair: bond failure between skin and substrate on sidewalls, roofs and slide faces.
• Crack, Hole and Impact Repair: scarfed laminate repair on punctures, spider cracks and stress fractures.
• Full Fiberglass Panel Replacement: when the panel or cap is past repair, at $4,500 to $25,000.
• Fiberglass Restoration and Refinishing: oxidation correction, gelcoat restoration and full refinish.

Sibling lines are collision repair and frame and structural repair, both under collision and structural services. Aluminum-skinned units, Airstream and similar, follow a different path entirely through aluminum skin and sidewall replacement at $2,500 to $25,000.