How to Repair a Hole in the Side of a Camper or Motorhome

Object:  To repair without using a body shop and saving hundreds, if not thousands of dollars by doing it yourself – for under $30.

This is a short article on how to repair a damage hole in the sidewall of a camper or motorhome. My particular hole came from a rock or tree on the side of a mountain when I was forced off the road by a large truck while rounding a blind curve in the Nantahala gorge in western NC.

The tree or rock hit the awning on the side of the motorhome and forced the upright support to dig into the side of the motorhome, thus ripping a gapping home in the side about 2 inches wide and 10 inches long. The side wall of this motorhome is fiberglass instead of aluminum, so these instructions are for a repair on this type of “hard” walled vehicle.

First of all, take a small knife (I used my pocket knife) and clean away the loose and broken pieces of fiberglass and wood. Be sure to keep a small piece of the broken fiberglass sidewall for later use. The side wall of this type of motorhome is made up of a sandwich of fiberglass over what appears to be a thin sheet of luan plywood, then a layer of Styrofoam, followed by the inside wall paneling. 

Next, if the Styrofoam is damaged or gouged out, get a can of expandable foam insulation from a hardware store and squirt some into the opening. Be very careful not to overfill the opening since this foam greatly expands while curing. This will fill in any gaps in the Styrofoam caused by the gouging. 

After the foam has cured (probably the next day for safety), obtain a small can of auto body filler such as Bondo and mix it with the hardener per the instructions that come with it. Use a small plastic disposable putty knife to spread the body filler onto the foam insulation, making sure to cover all cracks and crevices.

Fill it completely full and build it up a little higher than the surrounding undamaged siding. You will not be able to smooth it very well because it sets up in just minutes. As it begins to cure, you will notice heat coming from it. This is a normal reaction caused by the hardener reacting with the filler.

Allow another day to pass so as to insure that the body filler is completely hard and cured. The next step is to grind or sand off the excess body filler down to level or just below level with the surrounding undamaged side. Use a course sander to get the bulk of the build up off and switch to finer sandpaper as you finish up.

Now is the time to apply fiberglass. From an auto parts house, obtain a small fiberglass repair kit. It should contain some fiberglass cloth, a container of resin and a tube of hardener. The resin and hardener should be mixed according to the instructions on the can. 

With scissors, cut a piece of cloth the same shape as the damaged area, but slightly smaller. Coat it with the mixed resin and place it onto the body filler which you have already sanded. Smooth it out with your disposable putty knife. Now cut a second piece of fiberglass the exact same size as the damaged area and coat it with resin and place in over the first piece. Smooth it as best you can and leave it alone to cure.

The next day use your sander to sand down the fiberglass and get it as smooth and flat as you can. You might be able to use hand-powered sanding blocks, but a power sander will work better and be easier.

After this is finished, mix a final batch of body filler and thinly apply it over the fiberglass, smoothing it out as best you can and leaving only a thin coat over the fiberglass.

After this has hardened and cured, it will require sanding with progressively finer sandpaper to blend it down to the original undamaged sidewalls while getting the surface as smooth as glass. 

Finally, take the small piece of damaged sidewall fiberglass you saved in the first step and take it to an auto parts store and try to match the color to a small aerosol can of auto paint. Use that paint to spray the repaired area, trying to match to the surrounding undamaged paint. If you cannot find an exact match, ask the shop clerk about other options for spraying.

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