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Old 09-13-2021, 07:53 PM   #1
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Solar Panel Mounting Sanity Check

Hey yall. Mostly have figured out how I wanted my solar panels mounted but wanted to run it by a few more eyes before I bit the bullet.

Running Unistrut on My 1984 MCI MC-9

22 Ft of Unistrut running in parallel. fastened with bolt down 1/2" fasteners (see picture strut 2)

Plan of attachment: I am copying this video almost exactly,
due to the similarity in bus and need for unistrut.



To attach the unistrut to the bus, I will use brackets. Brackets held in place by 3/8 - 1/2" lag bolts screwed into the metal support square tubing. Lag bolts will have a flat and lock washer combo underneath but obviously no nut on the through side, since there wont be one. Unistrut will then be affixed to the brackets via bolts and 1/2" unistrut receiving inserts (see picture)

Solar panels will then be screwed down with square washers and a rubber washer underneath held in place by 1/2" bolts. (see picture)

The reason I chose this attachment method is the ceiling is already installed earlier than I had anticipated. (brother in law surprised me with some tongue and groove installation, but didnt know I had a need to mount the solar first!

Questions:
Thoughts on use of lag bolts for this situation for bracket install? He mentions they have held well for several years of use.

Would you use 1/2" or downsize to 5/16" or 3/8'' ?

Anything that you would do differently or change knowing that the ceiling cannot be removed? The middle support beam IS still accessible for the meantime.
Attached Images
File Type: png Strut 1.PNG (834.8 KB, 12 views)
File Type: png strut 2.PNG (56.2 KB, 131 views)

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Old 09-19-2021, 03:13 PM   #2
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Originally Posted by MaxnMag View Post
...I am copying this video almost exactly...
.
To anybody considering becoming a YouTuber...
.
Suggestions:
* work from a script
* rehearse
* edit ruthlessly
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Old 09-19-2021, 04:01 PM   #3
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Well I hope that technique works, because I plan on doing essentially the same thing. I also jumped the gun on finishing the ceiling.

Lag bolts may work fine, but you might consider rivnuts as an alternative. They make closed-end varieties that seem like they might keep water out better. Yet another option is blind bolts. These ideas were both stolen from members here, but I can't remember who's they were.

Using a regular square washer to level out the bracket like in the video seemed to work, but looked a little crude. A beveled washer might work better for that purpose, depending on the angle of your roof (Link to Fastenal). Somebody here cut shims from Trex and that also looked like it worked very well. Simpler still would just be to put in a little more oomph than the Youtuber and just bend the brackets to the correct angle.
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Old 09-19-2021, 04:49 PM   #4
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A rivnut would be much stronger. A self tapping screw or bolt will not hold much on thin sheet metal.

Ted
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Old 09-19-2021, 07:24 PM   #5
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In addition to the mechanical fastener you choose, consider getting a tube of 3M 5200 and bedding each foot/bracket in that stuff. It's the closest thing to a permanent panel bond that I've had experience with.
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Old 09-19-2021, 08:50 PM   #6
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A rivnut would be much stronger. A self tapping screw or bolt will not hold much on thin sheet metal.

Ted
If Youíre only Attaching to sheet metal then the strength of a rivnut will be about the same as a thru-bolt in sheet metal: if youíre installing lengths of strut, thru-bolt to the hat channel for a much stronger connection.
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Old 09-19-2021, 09:08 PM   #7
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can anyone tell me the benfeits of unistrut over just using metal angles? Being as its stationary I can't really figure the difference.
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Old 09-19-2021, 09:20 PM   #8
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can anyone tell me the benfeits of unistrut over just using metal angles? Being as its stationary I can't really figure the difference.
The strut letís you offset from the sturdy place where the strut mounts
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Old 09-19-2021, 09:24 PM   #9
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The strut letís you offset from the sturdy place where the strut mounts
My panels are predrilled where the manufacturer says to bolt to them. Itís not where the hat channels are so bolt to the channel with the strut and then wherever you want with the panels.

Itís kind of a moving target though if you replace your panels
In a few years and they are a different size
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Old 09-20-2021, 07:13 AM   #10
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Lag bolts may work fine, but you might consider rivnuts as an alternative. They make closed-end varieties that seem like they might keep water out better. Yet another option is blind bolts. These ideas were both stolen from members here, but I can't remember who's they were.

Using a regular square washer to level out the bracket like in the video seemed to work, but looked a little crude. A beveled washer might work better for that purpose, depending on the angle of your roof (Link to Fastenal). Somebody here cut shims from Trex and that also looked like it worked very well. Simpler still would just be to put in a little more oomph than the Youtuber and just bend the brackets to the correct angle.

We used Blind Bolts and they've held fine for the past 3 years. I'd be hesitant to just use lag bolts or self-tappers, personally. I also bent the brackets to the correct angle instead of using shims. The solar racking was one of the simpler projects on the build.
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Old 09-25-2021, 03:15 PM   #11
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Similar install

I had a similar install. I used some residential solar racking product. I bolted the angle bracket through eaxh rib or hat. Then bolted the solat panel down with the bolts that were ment for that track. Now it was supose to hold up to 150 mph wind but I had panels come loose twice In the first 1000 miles. I went back and replaced the thread glue that came with the bolt with the loctite perminate version and they have travel 7000 more miles without adjustment. I also safety wired the back side with some 1/8 in galvanized wire they sell in the fencing section just incase the bolt ever came loose again..

Bottom line invest in some loctite.
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Old 09-25-2021, 03:36 PM   #12
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Photos

Here is photos of the safety wire. My pannels already had a couple hole in them so I just used those
Attached Images
File Type: jpg 20210925_142341.jpg (200.1 KB, 14 views)
File Type: jpg 20210925_142333.jpg (149.3 KB, 10 views)
File Type: jpg 20210925_142321.jpg (146.5 KB, 14 views)
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Old 09-25-2021, 04:53 PM   #13
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I have used thousands of feet of unistrut for installations for the Navy.
Never seen side bolted connections like pictured.
Why not use the extra tall unistrut and eliminate the brackets for the outside struts and one lower profile strut at the crown?
Fasten struts directly to the roof structure into every roof rib.
I am guessing there are two panels end to end or side by side covering across the roof?
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Old 09-25-2021, 05:41 PM   #14
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Wouldnít the outside unistrut end up at a weird angle without a brace or shim?
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Old 09-25-2021, 05:51 PM   #15
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You can shim under the strut instead of bracket.
You could use one fastener into each roof rib vs two fasteners per bracket, reducing leakage points by 50%.
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Old 09-25-2021, 07:10 PM   #16
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You can shim under the strut instead of bracket.
You could use one fastener into each roof rib vs two fasteners per bracket, reducing leakage points by 50%.
A single fastener would introduce the potential for movement far in excess of two fasteners. Something to be avoided.
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Old 09-25-2021, 07:51 PM   #17
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LOL
Millions of miles worth of unistrut installed with one fastener every few feet along it's length.
That is what those oblong holes punched in the strut bottom by the factory are for.
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Old 09-25-2021, 08:43 PM   #18
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LOL
Millions of miles worth of unistrut installed with one fastener every few feet along it's length.
That is what those oblong holes punched in the strut bottom by the factory are for.
The image I got was of a 90 degree angle bracket and then only putting one fastener through it. THAT is what I was talking about.
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Old 09-25-2021, 08:54 PM   #19
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Given your strut experience, can you weigh in on this idea:

- Three struts running in a nose to tail orientation, one midline (with a low profile) and the outside two the taller profile and shimmed.
- Attach two low profile struts perpendicularly to the nose to tail struts and attach panels to that.

I have eight 100W panels but want to create a structure that can be updated without having to open the interior ceiling back up if I do so. Based on spec sheets this idea should be ok, but I’m curious what your hands on experience has taught you.
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Old 09-26-2021, 08:36 AM   #20
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I would ask what are the low profile perpendicular struts accomplishing?
The panels are rigid being framed with an aluminum frame. Under any other "normal" install they would be clamped down outside the frame in four places. The panel adjacent sharing the clamping bolts.
Perpendicular struts installed on top of the three lengthwise struts would be more robust for sure.
But perhaps overkill.
But your idea brings up this....
I would look at installing two of the 1-5/8 square struts lengthwise. Space apart so that same size perpendicular struts could be installed on top of the lengthwise struts and clear the crown of roof. The cross struts could be low profile or the 1-5/8.
A ten panel array would only need eleven cross pieces and the two long pieces.
Would likely work out to be cheaper then using the taller struts and cheaper using all 1-5/8 sg struts as that is the most common size by far.
The above assumes all panels installed on the same plane.
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