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Old 01-07-2021, 12:31 PM   #1
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Question Water Sealing Plus Nuts on the Roof

Hi Folks,
I did a quick search in the forum for how folks are sealing their roof fasteners, but didn't see anything.
So, sorry if this is a repeat question and I just missed it.
I plan to use plus nuts on my roof to fasten down my solar panel support frame.
We will apply a roof sealer to the entire roof after the plus nuts are in, so all around them should be leak proof.
Yes, I know that God laughs when we say, "So this work out just fine" or "this is how it's going to go...".
Anyway, I was concerned that water might leak through the threads.
Will locktite fix that, or should I try to squirt some caulk in there before I add each bolt?
Sounded silly, but I just don't know what to do.
Maybe I'm worrying about nothing?
Not sure.
Thx.

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Old 01-07-2021, 12:49 PM   #2
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I used stainless steel Carriage bolts with the head on the inside, neoprene-backed fender washers and UV resistant Sikaflex urethane sealant.

The entire stack was this

Bolt, sikaflex around bolt, neoprene backed washer, unistrut, thick fender washer, nylock nut
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Old 01-07-2021, 12:58 PM   #3
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Thanks, Danjo.
So in your case, it sounds like you think that the nylock nut will keep the threads water tight.
How long ago was that and have you noticed any leakage?
Thx.
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Old 01-07-2021, 02:59 PM   #4
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Originally Posted by Michael_Grumbach View Post
Thanks, Danjo.
So in your case, it sounds like you think that the nylock nut will keep the threads water tight.
How long ago was that and have you noticed any leakage?
Thx.
There’s a neoprene seal created by the washer around the threads on the bolt and on the surface of the roof. Under that there’s a plug of sikaflex. The nylock wouldn’t stop water.

No leaks.
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Old 01-07-2021, 05:46 PM   #5
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I've never used plusnuts but they appear to be basically rivnuts or rivet nuts. The plusnuts themselves need to go in "wet" (meaning a bead of sealant around the hole before you insert the plusnut), and then since they're open you also need sealant around the inner hole before you screw in the bolt. Basically, water can get in between the bus roof and the plusnut and also between the plusnut and the bolt, unless you seal both of those gaps.
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Old 01-07-2021, 10:31 PM   #6
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Oh, I totally missed the rivnut aspect. The best I have seen are “blind” with a sealant preapplied.

Pricey!
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Old 01-07-2021, 10:46 PM   #7
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Regarding thread locker, I would suppose that if you get it all around the threads, it would make the bolt-rivnut gap watertight and there would be no need to use sealant there. However, Loctite makes it difficult to ever unscrew the bolt (obviously) so this would be more or less a permanent attachment method. If you're currently at the stage where your factory ceiling is off and you have access to the underside of the roof, you'd probably have an easier and cheaper time just bolting your supports through the roof.
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Old 01-07-2021, 11:40 PM   #8
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Regarding thread locker, I would suppose that if you get it all around the threads, it would make the bolt-rivnut gap watertight and there would be no need to use sealant there. However, Loctite makes it difficult to ever unscrew the bolt (obviously) so this would be more or less a permanent attachment method. If you're currently at the stage where your factory ceiling is off and you have access to the underside of the roof, you'd probably have an easier and cheaper time just bolting your supports through the roof.
Yeah, and probably the most secure and cheapest
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Old 01-08-2021, 12:01 AM   #9
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Have you considered well nuts? Used on kayaks, holding tanks....liquid tight....

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Old 01-08-2021, 08:40 AM   #10
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Thanks so much folks for all of your feedback.
Yeah, I think I'll go with some semi-permanent blue loctite for the water sealing affect.
I looked at the well nuts.
These mostly look like they have rubber jacket.
I like the metal on metal plus nuts.
Compared to the rivet nuts, they seem to have a larger span of folded metal after tightening.
This makes me feel the most secure for holding down 40"x80" solar panels to the roof of my bus.
I'll definitely apply them wet.
Thank again.
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Old 01-08-2021, 09:07 AM   #11
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I keep reading this title as "sealing pine nuts on the roof". I wonder how well pesto would work as a roof covering.
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Old 01-08-2021, 11:26 PM   #12
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Funny🤣
Probably wouldn't work well after a few rainy days, but maybe...
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Old 01-23-2021, 05:10 PM   #13
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Have you considered well nuts? Used on kayaks, holding tanks....liquid tight....


These look spiffy for lightweight applications, but I'm not sure if I would trust it to hold several hundred pounds of solar panels at highway speeds.


How much weight/resistance does your application have? Is it decking or solar panels?
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Old 01-23-2021, 06:19 PM   #14
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I'm aiming for eight 40"x80" solar panels.
I'm attaching them to channel struts.
The struts will be connected to 3/8" bolts and plusnuts, about 28" apart, over each bus rib.
And with 5 parallel channel struts providing 5 points of contact on two sides of each panel.
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Old 01-23-2021, 10:30 PM   #15
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Quote:
Originally Posted by Michael_Grumbach View Post
I'm aiming for eight 40"x80" solar panels.
I'm attaching them to channel struts.
The struts will be connected to 3/8" bolts and plusnuts, about 28" apart, over each bus rib.
And with 5 parallel channel struts providing 5 points of contact on two sides of each panel.

Are you building supports on the outer channels to make a level plane for the panels? I'm assuming that your panels are running perpendicular to the length of the bus.


I've seen someone on this forum that used wedges cut from composite decking to level out their channels.
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Old 01-23-2021, 10:54 PM   #16
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Sorry, I didn't follow exactly what you were asking.
The panels will be parallel across the entire roof. They will not follow the curve of the bus.
I've come up with an original design using channel struts, corner post from a chain link fence and 3/8" threaded rods.
I'm laying 6" sections of post along the struts, to provide naturally leveled anchor points, for the struts and the panels.
All using 3/8" hw.
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