I need some expert opinions on mounting solar panels to a fiberglass roof

I am new to this forum and wish I had known about it months ago. We have ordered a new fifth wheel trailer that should arrive in about a month. I had the trailer manufacture and solar equipment supplier get together and are installing all the needed equipment. I am lacking in knowledge when it comes to solar but am trying to learn. All I will need to do when the trailer arrives is get the panels mounted and hooked up. The roof on this fifth wheel is one piece fiberglass and I have read conflicting information on this topic. To use stainless screws or mounting tape. I am concerned about drilling holes in a new roof and am also concerned about having a panel blow off while driving down a crowded freeway. I am looking at 600 watts on the roof (37 foot long) and would love to hear what brand panels you would buy. Thanks in advance for any help. I did a search but couldn't find a thing on fiberglass roofs.


  • VicVic Solar Expert Posts: 3,152 ✭✭✭✭
    Re: I need some expert opinions on mounting solar panels to a fiberglass roof

    Hi tv,

    Welcome to the Forum.

    Well, is it safe to assume that you have asked the manufacturer of the trailer, exactly how to do this? They should know. Wonder why THEY are not mounting the PVs and running the wiring with coaching from the eq supplier. Suppose that they might want to avoid any liability ... but I would become insistant and see what happens .. you may have already tried this. I have not mounted any PV modules on any RV, so cannot really add anything. Good Luck, Vic
    Off Grid - Two systems -- 4 SW+ 5548 Inverters, Surrette 4KS25 1280 AH [email protected], 11.1 KW STC PV, 4X MidNite Classic 150 w/ WBjrs, Beta KID on S-530s, MX-60s, MN Bkrs/Boxes.  25 KVA Polyphase Kubota diesel,  Honda Eu6500isa,  Eu3000is-es, Eu2000,  Eu1000 gensets.  Thanks Wind-Sun for this great Forum.
  • PhotowhitPhotowhit Solar Expert Posts: 5,824 ✭✭✭✭✭
    Re: I need some expert opinions on mounting solar panels to a fiberglass roof

    The whole prospect of mounting on a moving vehicle scares me, vibrations with screws, not good, tape against wind shear for 90-100 MPH (70 MPH and 30-40 MPH head long gusts...) Sound like the trailer manufacturer should have the greatest knowledge.

    I will suggest NOT flush mounting them, as heat building up under them won't be good, also they will be harder to keep clean. If I was doing it on an older motor coach, I'd plan a roof mount attached from the sides of the coach, 5-7" above the roof. Problem is they can create pressures that might cause noises or vacuum under or over the panels, so you'd likely want a scoop in front of it...

    I would want the 'array' to be able to raise on angle from the ground, hydrolics?
    Home system 4000 watt (Evergreen) array standing, with 2 Midnite Classic Lites,  Midnite E-panel, Magnum MS4024, Prosine 1800(now backup) and Exeltech 1100(former backup...lol), 660 ah 24v Forklift battery(now 10 years old). Off grid for 20 years (if I include 8 months on a bicycle).
    - Assorted other systems, pieces and to many panels in the closet to not do more projects.
  • ywhicywhic Solar Expert Posts: 621 ✭✭
    Re: I need some expert opinions on mounting solar panels to a fiberglass roof

    I've seen posts on the net with some people using bolt/nuts (permanent on the roof).. then mount the panels once in the stationary position with just wing nuts on top of the 'permanent mount' listed above.. store panels inside the RV while in motion..

    They make tilt RV mounts for like $80.. once in position THEN tilt them up.. (not while moving obviously)..

    Some people do mount to RV roofs.. they also use extra roof rack 'rails' over the length of the panel frame/edges for added security in knowing the panel won't blow off..

    The flex on a fiberglass or poly/plastic roof may not be good and cause CRACKING near your drilled bolt locations..
    (you can see this on fiberglass boats and there railing areas sometimes)..

    Does the RV roof have a roof rack?? maybe mount the panels to THAT fixture..

    Thats all I got.. I'll all suggest to try contacting the RV mfg..
  • CariboocootCariboocoot Banned Posts: 17,615 ✭✭
    Re: I need some expert opinions on mounting solar panels to a fiberglass roof

    If you're going to bolt through fibreglass you need some backing. The material itself is too thin and fragile to take the load. Normally they put wood or metal behind any point that needs to have something connected to it. Since the interior of the camper is no doubt finished, this means ripping out the ceiling and epoxying some wood along the space where the mounts will go to spread the load out over a larger area, preferably solidly connecting to whatever is used for the structure of the roof.

    Not a project for the faint of heart.
  • solarixsolarix Solar Expert Posts: 713 ✭✭
    Re: I need some expert opinions on mounting solar panels to a fiberglass roof

    I mounted uni-solar PV flexible panels on a camping trailer with good success. These are the 16' long x 15" wide "mats" designed for use on standing seam steel roofs. They have adhesive backs and I used Through-the-Roof roofing sealer around the perimeter as well. Only hole was for the wiring. Uni-solar recently went bankrupt though so am not sure how available there are and may be more expensive than crystal PV, but worked slick. Can't even see that they are there (theft protection) and no wind drag.
  • Jim45DJim45D Solar Expert Posts: 102 ✭✭
    Re: I need some expert opinions on mounting solar panels to a fiberglass roof

    Don't sweat the fiberglass roof. I have 5 panels mounted on mine and they have been there for going on 10 years. Either use the roof rack, if you have one installed, or simply mount a length of aluminum square tubing. A panel is roughly (depending on what you get, I use Kyocera exclusively) 42" in length. Mount the aluminum, 1" square in four places, then mount the panel to that. Yes, use stainless steel screws, and also Dicor sealent. Using anything else will rust, and or leak. If driving at 65 mph with a head wind of 45 to 50 mph is not enough to rip them off. If the wind is stronger, park it. Otherwise if that was going to happen, it would tear off the TV antenna, vent lids, etc. Mine are mounted on a 33' foot MH, and if you like, PM me and I'll send you photos of the mount procedure I use.

    I don't know about your underlying roof support, but mine is 3.5" thick, that's just the wood between the fiberglass. It has to be strong to support you, and someone else walking around on the top of it also. If the wind is going to rip them off a RV, it surely will rip them off a house too. Incidently, I use 2", 1/4" dia. stainless steel bolts for anchoring mine. Enjoy. Oh don't let anyone run the wiring down the reefer vent either. Mount the panels permanently, leaving room for tilting, don't take them down at night. If someone is going to steal them from your roof while you're sleeping, then either they're nuts, or on meth. It ain't gonna happen.
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