RV Fiberglass Repair

Gelcoat is a resin rich surface coating roughly twenty thousandths of an inch thick, applied into the mold before the reinforcement goes in. It is not paint and it does not behave like paint. It is brittle by design, it has no primer beneath it, and it is pigmented all the way through, which is why a scratch that stops in gelcoat can be sanded and polished out entirely while a scratch that reaches reinforcement cannot.

The pattern of cracking tells the story. Fine random crazing across a broad area usually means resin degradation from ultraviolet exposure and responds to sanding and recoating. Radiating cracks from a single point mean impact, and the laminate under that point is almost always affected. Parallel straight cracks following a line mean the panel is flexing over a structural discontinuity, and coating over them without addressing the flex accomplishes nothing at all.

Delamination is the separation of bonded layers inside a sandwich wall. It is not a fiberglass problem in the strict sense; it is an adhesive failure between the fiberglass skin and the substrate behind it. The usual cause is moisture. Water enters through a failed sealant bead, a fastener penetration, a window frame or a seam, reaches the luan layer, and the luan swells. Swollen luan pushes the skin away from the core and the bond releases.

Once the bond releases, the wall stops behaving as a structural unit. The visible symptom is a bubble, a wave, or a soft area that gives under hand pressure. Owners often first notice it as a shadow across the sidewall in late afternoon light. Because water spreads laterally along the path of least resistance, the affected area is almost always larger than the visible bubble, sometimes by several feet in each direction.

Repair starts with mapping the extent. Tapping and moisture metering define a boundary beyond the visible damage, and the repair area gets cut to sound material rather than to the edge of the bubble. The skin is separated, wet luan and degraded core come out, the framing behind gets inspected and repaired if the moisture reached it, and new substrate goes in. That is the structural half of the job and it accounts for most of the hours.

The laminate half rebuilds the reinforcement. Edges get scarfed to a shallow taper so the new layup bonds over a wide overlap rather than butting against a square edge, plies go on in a schedule matched to the original thickness, and the repair cures under vacuum or mechanical pressure so no voids remain. Gelcoat or primer and paint then rebuild the surface. Cure time between steps is real and is why composite work cannot be compressed the way metal work sometimes can.

Front and rear caps are single molded pieces, often with compound curvature and integrated features like light housings, ladder mounts and roof transitions. A crack in a cap can frequently be repaired in place with a backside layup and a frontside scarf, which is far less costly than replacement and preserves the original fit. Whether that is appropriate depends on where the crack sits relative to load paths and mounting points.

When a cap is beyond repair, replacement runs into the parts problem that follows the whole industry. Caps for discontinued floor plans may not be available at all. The alternative is pulling a mold off the undamaged corresponding surface or fabricating a section, both of which the shop performs. Smaller molded components like skirts, fender flares and running board ends are usually more economical to repair than to chase through a supply chain that may not have them.

A structurally perfect repair still fails the owner if the finish gives it away. Two paths exist. Gelcoat repair rebuilds the original surface chemistry, gets color matched to the aged panel rather than to the factory formula, and then gets sanded and buffed through progressively finer grits to match surrounding gloss. That approach suits units still wearing original gelcoat with reasonable surface condition.

The other path is primer and paint, which suits units already refinished, units where gelcoat has degraded broadly, and any repair adjacent to a painted graphic. Painted finishes hold color longer against ultraviolet exposure than pigmented gelcoat does, and they permit blending across a wider area. Which path a specific coach takes is a conversation at estimate time, because it affects both cost and how the panel will look in five years.