How to mount solar panels thin plywood bighorn roof

Question

I've got 4 100 watt grape solar panels on order and am now wondering how to mount them on the roof of my 2016 Bighorn 5th wheel. I replaced the bathroom vent on it today with a thermostatically controlled multi speed maxxair vent and during the install I noticed just how thin the plywood on the roof is. It appears the structural strength is primarily from the Styrofoam laminated between the wood. I can't imagine this will give me a very strong anchor for screws to install brackets to mount the panels on. It also appears that the aluminum studs in the roof are few and far between so it doesn't look like I could easily hit those and still place the panels in optimal position for clearance, shading issues etc.

How are you guys mounting solar on the laminate Styrofoam roofs like used on the bighorn? I've seen some reference to using the flexible panels but don't want to go that route due to potential issues wit the panels themselves.

corvettekent · Answer

My solar panel brackets are held down with 3M double back tape and two screws.

old_days · Answer

You should have aluminum cross members some place on your roof.I went out on a frosty morning and could see all the aluminum in the camper even the side walls.  Also use 3m vhb double sided tape with stainless steel screws and dicor to seal the bracket.

goducks10 · Answer

Assuming your roof framing is 16-24" OC, why not put a piece of aluminum 2"x?x1/8"+ or equivalent to span the framing members. Then fasten the solar panels to the aluminum strips. I would use pointed sheet metal screws for the aluminum strips. Self tapers in thin aluminum could strip out too easy.
I would also run the fasteners for the solar panels up from under the aluminum strips using counter sunk machine screws. That way you only have the bare minimum required screws into the roof.

searching_ut · Answer

Thanks for the input guys. I'll probably go with something along the lines of the aluminum L channel between the studs. With the roof decking only being 3/8th inch plywood I'm not sure the bracket screws would hold going down the freeway. Historically we average about 7,000 miles a year towing, but with retirement coming up very shortly we're hoping to get a little more in. The road miles seem to be what tears up our rigs over the years.

djgodden · Answer

I did exactly what you're doing about 3 months ago. After a lengthy bit of research and practice I use 1/2 well nuts. Drill a 1/2 hole, lap sealant around the top, insert the well nut, a dab of lap sealant on top, place solar panel, screw in place (the rubber well nut expands and seals and grabs the roof, more lap sealant ontop of the screw.

Did a number of hard yank tests and there's no way these are moving. My Montana has an aluminum frame.

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How to mount solar panels thin plywood bighorn roof

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