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Old 10-06-2021, 11:39 PM   #1
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Mounting solar

Hey all, finding lots of info on mounting solar panels but nothing that really jumps out at me. Got a few questions if anyone has ideas

1. I'm pretty sold on unistrut, but some people say they wouldn't bolt it through the channels.. why is that? is it a thermal bridging kind of issue?

2. There's already holes in my panels and I'm not under warranty so should I go that route and bolt straight to the aluminum? I see some people use some kind of clamp thing but that just makes me nervous.. thoughts?

3. any tips on unistrut hardware in general would be great, bolt sizes, names of things etc. It seems like unistrut can do just about anything so I want to make sure I'm getting the right stuff

Thanks everybody

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Old 10-07-2021, 12:05 PM   #2
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-bumping for bump reasons-
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Old 10-07-2021, 12:57 PM   #3
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One advantage of Unistrut is the ability to offset the strut attachment points from the panel mounting points...in other words, if your ribs don't line up with the panel mounts Unistrut is a good option. If you can line up the ribs with the mounts, you wouldn't need the Unistrut. But it is a good, sturdy option.

Personally, I like to make mounts with a larger footprint so we can add a permanent bonding adhesive like 3M 5200 to the structural anchor. I'm afraid I can't speak to the actual Unistrut hardware options.

I also don't like clamp methods, where a loosened clamp could release a panel. So, we drill through the side frames and use locknut hardware.

I know these didn't address your questions directly, but I hope it's of some help.
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Old 10-07-2021, 01:14 PM   #4
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McMaster-Carr has these great saddle washers that go over the strut nut and make a nice clean setup IMO.

Bolting through the hat channel is the way to go. Use carriage bolts from the inside to have a low profile bolt head on the ceiling. Use a fender washer with generous UV-resistant polyurethane sealant around the bolt, under the washer.
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Old 10-07-2021, 09:44 PM   #5
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I'm mounting with aluminum brackets secured with VHB. Very impressed with those rigs who've done that and reported back after a year or so, no issues.

Because VHB will deteriorate under UV light they cover the whole assembly with the white elastomeric tape. It does nothing to hold the bracket, just protects the VHB.
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Old 10-08-2021, 03:27 AM   #6
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Quote:
Originally Posted by Rucker View Post
I'm mounting with aluminum brackets secured with VHB. Very impressed with those rigs who've done that and reported back after a year or so, no issues.

Because VHB will deteriorate under UV light they cover the whole assembly with the white elastomeric tape. It does nothing to hold the bracket, just protects the VHB.
I wouldn’t and I sure would t want to be behind you!

https://www.skoolie.net/forums/f49/s...res-37534.html
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Old 10-08-2021, 07:55 AM   #7
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Quote:
Originally Posted by Rucker View Post
I'm mounting with aluminum brackets secured with VHB. Very impressed with those rigs who've done that and reported back after a year or so, no issues.

Because VHB will deteriorate under UV light they cover the whole assembly with the white elastomeric tape. It does nothing to hold the bracket, just protects the VHB.

mmmm, I like a mechanical attachment myself. VHB only seems like it would be sketchy.
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Old 10-08-2021, 10:59 AM   #8
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Quote:
Originally Posted by Danjo View Post
McMaster-Carr has these great saddle washers that go over the strut nut and make a nice clean setup IMO.

Bolting through the hat channel is the way to go. Use carriage bolts from the inside to have a low profile bolt head on the ceiling. Use a fender washer with generous UV-resistant polyurethane sealant around the bolt, under the washer.
Now that looks nice! I think I'll be going that route.

And I have to agree about VHB tape.. after welding and screwing and bolting everything else tape no matter how sciencey would just make nervous

Thanks everyone for chiming in
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Old 10-16-2021, 05:04 PM   #9
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Rivet Nuts

I used 1/4-20 rivet nuts on mine.The rivet nut has a lip around the top,and when crimped,leaves a lip under the roof like having washers.
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Old 10-16-2021, 05:34 PM   #10
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You Danjo,
on those saddle washers, does the bolt go thru and into a regular unistrut nut?
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Old 10-16-2021, 09:49 PM   #11
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Originally Posted by DoubleO7 View Post
You Danjo,
on those saddle washers, does the bolt go thru and into a regular unistrut nut?
Yes, they are standard gold “galvanized” strut nuts
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Old 10-17-2021, 03:05 PM   #12
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I don't get it. Sticking PV panels onto the paint is NOT a secure and reliable way to attach them. Please, if only for the sake of everyone driving behind your bus, through-bolt your panels to the roof's structural elements. If (when?) one of the glued-on panels decides to fly off the roof at 60+ MPH and it hits a car behind, now just imagine what the police report will say, and what the other party's lawyers will say, and what the judge will say, and what the relatives of those injured or killed will say.

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Old 10-17-2021, 10:09 PM   #13
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Why is it that solar racking with the hold down clamps does not seem to be used on schoolies? Ross mentioned his concern of clamps coming loose.

It looks like there are several styles of track from different manufactures and many mounting brackets and clamps available.

Ted
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Old 10-18-2021, 12:17 AM   #14
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Why is it that solar racking with the hold down clamps does not seem to be used on schoolies? Ross mentioned his concern of clamps coming loose.
Hi Ted. My concern might be pointless. I've used the clamp systems on lots of ground-based installations in some pretty harsh environments. Buy they're all stationary and not subject to the vibration we get in our buses. I through bolt the frames to the brackets...just out of personal preference...but I would guess the clamp systems might be okay with some thread locker to keep the clamps tight.
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Old 10-18-2021, 01:07 PM   #15
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I used the same stuff danjo did ...it works great I used 2 20ft lengths about 2 ft from center line of roof. I had to add 1.5in square tube spacers where the uni bolted thru the hat channels to give the hight need for the curve of the roof then the danjo method hardware to mount z brackets to uni and some bolts and lock nuts for the z to panel mount ...each panel has a stainless safety wire bolted thru a hat Channel and to the panel just for peace of mind

Use locktite on the uni strut flat rectangle nuts
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Old 10-18-2021, 01:32 PM   #16
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I didn’t loctite anything. I think that’s a good addition and I’m going to revisit before my next trip. Don’t want to end up on the Panel Installation Failures thread!
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Old 10-31-2021, 11:24 AM   #17
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Quote:
Originally Posted by Danjo View Post

[Rucker said]
I'm mounting with aluminum brackets secured with VHB. Very impressed with those rigs who've done that and reported back after a year or so, no issues.
[end of Rucker quote]

I wouldn’t and I sure wouldn't want to be behind you!

https://www.skoolie.net/forums/f49/s...res-37534.html
Update on my solar panel install. I was a passionate advocate of VHB-only installations, and I didn't want to risk a roof leak with screws?

Even old dogs can learn new tricks.

I finally got around to installing the two 240 watt panels on the roof of the shuttle bus yesterday. I used the aluminum bracket approach, but instead of four brackets per panel I added two for a total of six brackets. I used high temp loctite on the stainless bolts holding the panel to the bracket, and VHB to secure the brackets to the gelcoat roof.

I'm glad I followed my own advice and bought more brackets then I thought I needed, just in case. Too much is always better than not enough.

Another thing about applying VHB: that VHB comes with a plastic backing on one side and a paper backing on the other. I pulled the plastic backing off first (a pain), and applied the VHB on the brackets on the ground, then hauled them up onto the roof. With the paper tape on the bottom it was very easy to push them around and get them located. Then I lifted up one side, pulled the paper backing off the three brackets and lowered the panel back down-worked perfectly. Repeat for the other side. There's enough flex in the panel and brackets that you can lift on side three or four inches even if the other side is already secured. It would have been incredibly challenging (I think) if I had to try and get that plastic backing off while bouncing around on the roof

Up until this point I' still felt the VHB would be sufficient to hold the panels, especially with six brackets. I've read the specs and watch the videos, and VHB alone is a good, permanent method of securing panels. (with the usual caveats-clean surfaces, smooth and secure paint, flat contact surfaces etc.)

But when I stood back and admired the work I looked at those little holes in the brackets and my OCD side said 'hey, those could use a couple of #10 SS screws', so I made another trip to the hardware store, predrilled and installed 24 screws through the perfect, flawless fiberglass roof. Two trips, because I bought exactly 24 screws, breaking my own rule (see above) and one of them was a misfit.

A little bit of Eternabond over the top of the bracket with some overlap for UV protection of the tape, and all done!

I feel really good about the install, and not at all concerned (now) that I machine-gunned two dozen holes in a perfectly good fiberglass roof. I got fixated on no holes in the design stage, but all of your comments to the contrary and being willing to stay open to changing things up during build gave me a better product.

Thanks everyone for that discussion!
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Old 10-31-2021, 01:53 PM   #18
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If it were me, I'd have put strips of metal on the inside of the fiberglass for backing support and used bolts with nuts and washers through the brackets and fiberglass and metal strips. And the "glue" or "tape" (?) VBH stuff? Nice for sealing stuff. Helps hold it on the roof. But depend on it? I, also, would certainly not want to ride behind you.


My plastic rooftop AC cover blew off somewhere in Nebraska, I think. It was screwed on, but the plastic cracked. There is a LOT of continuous force up there from air-flow at highway speeds. Respect it. Don't be that dweeb in court for involuntary manslaughter.



A screw through fiberglass will easily strip out, or even crack the fiberglass, unless the fiberglass is 1" thick or more.


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Old 10-31-2021, 09:14 PM   #19
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If it were me, I'd have put strips of metal on the inside of the fiberglass for backing support and used bolts with nuts and washers through the brackets and fiberglass and metal strips. And the "glue" or "tape" (?) VBH stuff? Nice for sealing stuff. Helps hold it on the roof. But depend on it? I, also, would certainly not want to ride behind you.

My plastic rooftop AC cover blew off somewhere in Nebraska, I think. It was screwed on, but the plastic cracked. There is a LOT of continuous force up there from air-flow at highway speeds. Respect it. Don't be that dweeb in court for involuntary manslaughter.

A screw through fiberglass will easily strip out, or even crack the fiberglass, unless the fiberglass is 1" thick or more.

for caring.
Not seeing it.

The fiberglass is about an eight or three sixteenths thick. That is pretty darn rigid. And I did some experimentation with the pilot holes to pick the right size for bite. With fiberglass, too small a pilot hole will reduce the grabbing strength of a screw.

I did a quick back of the napkin calculation for VHB alone: each bracket has about 400 lbs of tensile strength (without the screws). I looked up the wind forces at 60 mph and it is nowhere close to what's needed to pull the panel up.

The solar panels are light but pretty rigid. Looking at my setup, I think if I grabbed the front center of the panel and lifted up, the aluminum frame of the solar panel would bend before the VHB-secured brackets and screws came out.

Here's another factor: the panels are only about an inch and a half off the roof, and both panels are all the way to the back of the bus. Probably pretty constant and laminar flow back there, at least compared to the front.
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