Please inform me as to ultimate fastening of mounting rack for solar on my RV’s solid surface/fiberglass roof. Most outfits just use screws or bolts into most solid surface roofs, which soon loosen from vibrations or wind loads. I’d like a more permanent fastening system. Would epoxy screw-in fasteners work better? That way you rely on metal threads to grip the bolt or screw and not the solid surface roof material to hold. Thank you. —Bruce, 2015 Jayco Precept 29 Class A
We have installed quite a few solar panels on a variety of surfaces and have yet to have any loosen due to vibration. The first thing you need to look at is the actual materials used in the construction of your roof and the assembly.
This is a mockup of a Winnebago Class A, which would be very similar to what your rig would have in the layers of the roof. It starts with the one-piece fiberglass outer skin, then a thin wood panel which is typically a 1/8” lauan panel, and block foam insulation with perimeter framework and metal cross members in strategic locations. It is almost impossible to actually find the framework in the roof. According to a brochure I found online, the fiberglass is actually a pebble grain version that has small bumps of gelcoat that help strengthen the material, especially on the sides where it has to make a 4” bend over the roof to sidewall joint.
I don’t think that using a screw fastener even with epoxy would be the answer as it would be mostly stuck in the block foam insulation.
Best way to mount items to RV roof
What really holds most items mounted to the roof is the self-leveling lap sealant. Since you have a fiberglass roof, I would suggest 311 or a similar product. A good amount of the sealant completely covering the base of the mounting bracket will hold the panels securely and they will not work loose. I use a little butyl tape underneath and clean the fiberglass very well, then cover the entire base of the mounting bracket overlapping on the roof at least 2”.
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With all the ads on TV about getting free solar panels put on your home, I wonder if anyone has considered the offer be extended to the RV market?
If your roof is flat like my fiberglass roof is, mount 8 ft angle pieces across the width of the roof, anchored on the edges in the framing. The solar panels then lay in the aluminum angle piece. You’ll put about half the holes in your roof & the holes you do drill will be in the framing on the edges of the roof. I’ve had seven 100 watt panels on my roof for 13 years & 175K miles, with no issues.