RV and Camper Fiberglass Repair, From Grind to Gelcoat
11 October 2026
RV fiberglass repair is boatyard work on a thinner panel: grind the damage back to solid glass, laminate chopped strand mat (CSM) and cloth with polyester resin catalyzed at 1.5 percent MEKP, fair it, and finish in white gelcoat. The structure is the easy part. What separates a repair that disappears from one that looks patched is the last step, two coats of gelcoat and a wet sand.
This is the sequence printed on the sheet inside our RV fiberglass repair kit. It covers cracked end caps, holed sidewalls, broken corners, wheel well trim and wet-bath or shower pan fiberglass.
First, make sure it is a fiberglass repair
If the panel is cracked, holed or broken, keep reading. If the wall has bubbled or gone wavy with no break in the surface, that is delamination: the skin has let go of the wall behind it, and laying glass over it does nothing. That is an adhesive job for the RV Delamination Repair Kit.
What an RV fiberglass repair takes
| Material | Amount | What it does |
|---|---|---|
| Polyester layup resin with MEKP | 1 quart | The structural resin for every glass layer |
| 1.5 oz chopped strand mat, 38" wide | 1 yard | Bulk, and the first layer against the repair |
| 6 oz woven cloth, 38" wide | 1 yard | Strength and a smooth outer layer |
| Fumed silica | 1 quart | Thickens resin into fairing putty |
| Pure white gelcoat with MEKP | 1 quart | The gloss white finish coat |
| Surfacing wax | 2 oz | Lets the last gelcoat coat cure tack-free |
| Chip brushes, mixing tubs, spreader, sticks | Wetting out, measuring and fairing |
That list is the RV & Camper Fiberglass Repair Kit, portioned for about 2 square feet of built-up patch or several smaller repairs. You supply nitrile gloves, eye protection, a respirator with organic vapor cartridges, acetone, a grinder or 80 grit block, sandpaper from 120 to 400 grit, masking tape and plastic sheet.
The kit for this job
RV & Camper Fiberglass Repair KitQuart of layup resin, quart of white gelcoat, mat, cloth, fumed silica and tools.See the kit
MEKP ratio for the resin and the gelcoat
Both the resin and the gelcoat are catalyzed with MEKP, and each quart ships with its own 1 oz bottle.
| Batch | MEKP at 1.5 percent |
|---|---|
| 4 oz | 1.8 mL (about 1/3 tsp) |
| 8 oz | 3.6 mL (about 3/4 tsp) |
| Full quart | 14 mL (about 3 tsp) |
That 1.5 percent is for 65 to 85°F (18 to 29°C). Above 85°F drop to 1 percent. At 60 to 65°F go to 2 percent. Below 60°F wait for a warmer day. Working time is 15 to 20 minutes, so mix small batches you can use right away. The MEKP catalyst calculator does the math for any batch size.
The repair, start to finish
1. Prep and grind
Wash the area with soapy water, dry it, then wipe with acetone. Grind or coarse-sand the damage back to solid glass and dish the edges out wide and shallow, about 12 times the panel thickness. On a 1/8" (3 mm) end cap that is a taper 1-1/2" (38 mm) wide all the way around. Scuff 2 to 3 inches beyond that with 120 grit and mask off the surrounding finish.
2. Cut your glass
Before mixing anything, cut CSM to fill the dished area and cloth patches slightly larger to cap it. Mat goes down first, cloth on top. Lay the dry pieces in place to check the fit. A through hole needs a backer first: tape plastic sheet or waxed cardboard behind it.
3. Laminate
Mix a small batch of resin with MEKP. Wet the repair, lay in the mat, and stipple resin through it with a chip brush until it turns translucent. Lay the cloth over it, wet it out, and chase the air bubbles to the edges with the spreader. Let it cure hard, 2 to 4 hours.
4. Fill and fair
Stir fumed silica into a fresh catalyzed batch until it stands in peaks like peanut butter. Spread it over the patch slightly proud of the surface. Once cured, sand it fair with 120 then 240 grit until the patch feels flush under your flat palm.
5. Gelcoat and finish
Stir the gelcoat well, catalyze it the same as the resin, and brush on the first coat about the thickness of a business card. For the second and last coat, stir surfacing wax into the gelcoat first, about 3/4 teaspoon per 8 oz, then catalyze it and brush it on 30 to 45 minutes after the first. The wax rises as the coat cures and lets it cure tack-free. Next day wet sand with 320 then 400, and for full gloss keep going with finer grits and a polishing compound.
What it works on
Fiberglass and Filon RV skins, end caps, wheel well trim, and interior wet-bath or shower pan fiberglass. Filon is a polyester fiberglass sheet, so polyester resin bonds to it once the surface is ground clean and dull. One thing to know going in: gelcoat cures to a smooth gloss, so on a pebbled or textured wall the patch will read smoother than the panel around it.
It will not bond to aluminum-skinned campers, EPDM or TPO rubber roofs, or polyethylene tanks.
If something goes wrong
| Symptom | Cause and fix |
|---|---|
| Laminate feels tacky | Normal. Layup resin stays tacky on top so the next layer bonds to it. It sands fine once it is hard underneath. |
| Nothing hardened | Too little MEKP, or under 60°F. Scrape it off, warm the space and remix. |
| It kicked in the cup | Too much MEKP, or too hot out. Cut back and mix 4 oz at a time. |
| Gelcoat stayed sticky | No wax in that coat, or it went on too thin for the wax to rise. Add another full coat with surfacing wax stirred in. |
| Patch shows through | Gelcoat is translucent when thin. Two coats minimum over a faired patch. |
Frequently asked questions
Can you repair fiberglass on an RV yourself?
Yes. A crack or hole in an RV panel is the same laminate repair done on a boat hull: grind a taper about 12 times the panel thickness, lay chopped strand mat then cloth in polyester resin catalyzed at 1.5 percent MEKP, fair with fumed silica putty, and finish with two coats of gelcoat.
What is the best resin for RV fiberglass repair?
Polyester layup resin, when the patch will be finished in gelcoat, because gelcoat cures properly over polyester and does not cure reliably over epoxy. Catalyze it at 1.5 percent MEKP between 65 and 85°F, which gives 15 to 20 minutes of working time per batch.
How do I match the white on my RV?
Start with pure white gelcoat and judge the color on a test dab after it has cured, because gelcoat shifts shade slightly as it kicks. Many coaches have yellowed with age, so a bright white patch can read lighter than the wall. Wet sanding and polishing a foot or two around the repair blends the edge.
How long does an RV fiberglass repair take?
Plan on two days. The laminate needs 2 to 4 hours to cure hard before fairing, the putty needs to cure before sanding, and the gelcoat goes on in two coats 30 to 45 minutes apart and is wet sanded the next day with 320 then 400 grit.
Will this fix a bubble in my RV sidewall?
No. A bubble or wave with no crack is delamination, where the fiberglass skin has come loose from the wall behind it. That needs thin epoxy injected behind the skin at about 4 fl oz per square foot and the wall braced flat until it cures, not a fiberglass patch on top.
What You Need For This Job
- RV & Camper Fiberglass Repair Kit: resin, gelcoat, MEKP, mat, cloth, fumed silica, surfacing wax and tools for one repair
- Marine-grade polyester layup resin: more resin for a repair bigger than 2 square feet
- Pure white gelcoat: extra finish coats, or a larger area to blend
- Surfacing wax: stirred into the last gelcoat coat so it cures tack-free
- Fumed silica: thickens resin into fairing putty
- RV Delamination Repair Kit: for a bubbled or wavy sidewall, which is not a fiberglass repair
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RV Fiberglass Repair: Crack, Hole or Delamination? Which Kit You Need
Updated on 11 October 2026
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How Much Epoxy for RV Delamination Repair? Sizing by Wall Area
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