Mounting solar on RV roof

[TimC]

Not sure if this is the right section for this question but it is electrical related.

I'm mounting two 260 watt panels (about 40lbs each) on the flat roof of the RV my wife recently bought. I've seen folks use Unistrut/Superstrut but the added weight worked out to be too much. So I made brackets. I have VHB tape and thought I would use that to help secure the brackets, adding two #14 x 1" screws to tie it all to the OSB under the rubber roof membrane. There will be a total of nine brackets. The roof appears to be a sandwich two sheets of ~1/2" OSB with 2x2 frame inside. Plenty strong enough to walk on.

My question is should I through-bolt some or all of the brackets or will the panels be secure enough with the tape and #14 screws? I don't mind having a couple bolt heads showing on the interior ceiling but would prefer not to do that.

I realize the rubber membrane is only lightly glued to the OSB. The VHB tape will mostly help keep everything aligned during installation.

[John61CT]

Without inspecting / testing

I have to say bolt through, with big fender washers or even more sq in of plate to spread the load on the inside as well as out.

Lifting force at highway speed can be much greater than the static weight at rest.

[TimC]

If my footprint of the brackets calculation is correct... 9 x 6 sq inches = 54 sq in. 78 lbs / 54 sq in = 1.44 lbs per square inch.

I removed an air conditioner that weighed about 110 lbs. I feel that I am not adding a lot more weight than the AC was.

[TimC]

Lifting force at highway speed can be much greater than the static weight at rest.

I plan to provide a deflector across the front of the panels, 78" across. That won't eliminate the lift but should help reduce it.

[flboy]

Do not need to be concerned with lifting force if you block the wind in the front so it cannot get underneath as mentioned. After panels are mounted, get some 1 inch angle aluminum cut to width of front, and use self taping screws into solar panel frames an flush it up with the roof.

If you do that. I believe wood screws into the OSB is all you would need. Just seal well with Dicor self leveling caulk.

That's how I'd do it in any case. You could epoxy the screws in also for extra measure.

Sent from my SM-N970U using Tapatalk

[saltydawg]

I put a bead of marine glue under the bracket, then run the screw down thru it. The glue does help it hold the screw in plus seals it.

[TimC]

I put a bead of marine glue under the bracket, then run the screw down thru it. The glue does help it hold the screw in plus seals it.

Thanks. The plan is to put a small dab of Dicor over the screws when finished. I'll either use VHB tape or butyl tape under the brackets. Not sure which. My original plan was to VHB tape three five foot sections of Unistrut to the roof (as well as screws) so I bought a big roll. Now that I have steered away from Unistrut I don't have a use for the tape except maybe under the brackets. That'll use less than 2'. I've never had trouble with properly applied butyl and it is easy to remove down the road. Nothing wrong with Unistrut. I just want to save as much weight as possbile.

The biggest step is going to be lifting the two panels up on top of an eight foot roof. I'll be knocking on my neighbor's door for that.

Because of the design of the frame I had to fab brackets to fit under the panel instead of a simple angle bracket. A buck twenty each and easy to add a bend and drill holes. The Unistrut spring nuts alone would have been more $ that these.






The assembly. I'll attach temporary braces to keep it rigid while lifting.

[TimC]

Finished up the installation of the two panels. After tying them together with the modified 12 ga. Simpson Strongtie brackets I attached three temporary 2x4s across the panels to keep them from flexing while lifting them on the roof. The center brackets are spaced just wide enough to place #14 x 1 screws. Under each bracket is butyl tape and then the screws are covered with Dicor self leveling goop. I'll fabricate a wind deflector on the front edge to minimize lift while running down the road.

It was a little bit of a figure it out as I go project but the results are good. 520 watts of solar is more than I need but for a hundred bucks a panel I just couldn't pass on them. Ordering new Renogy 100 watters would have cost me about the same with only two fifths the potential.

[Gulfcoast]

Looks real good.... are those Santa solar panels? Where do we buy the brackets? Thanks

[TimC]

Looks real good.... are those Santa solar panels? Where do we buy the brackets? Thanks

They are Rec Solar REC260PE panels. Used, about six years old. Probably no longer available new.

The brackets are available at HD and probably other stores with lumber hardware offerings. They are modified angle brackets. Easy to bend in a good bench vise and drilled for more convenient holes. Yeah, I could have bought solar brackets but their buck twenty price each beats light gauge aluminum at twenty bucks for a set of four.. My dad always told me, "You have more time than money".