drilling holes in bigfoot roof for solar panels

[Raspy]

I had things bolted to the bottom of my 42' Ketch with through bolts. No leaks. A bit of rain is not going to leak past some 5200 or similar on a sloping roof.

[wallnut1234]

i see there exists bulb style rivets specially made for plastic and fiberglass

[redbarron55]

Originally Posted by wallnut1234

i see there exists bulb style rivets specially made for plastic and fiberglass

But they are not like rivnuts al all.

https://www.youtube.com/watch?v=gmZBVSMBs0E

[wallnut1234]

the only differences I see would be that the rivet nut would be a lot easier to remove than a rivet that would be more permanent. Also the diameter of the holes would probably need to be a bit bigger for a rivet nut than for a rivet.

[Flydog]

The rubber (with brass insert) wellnuts are easier to install than the rivnuts and are self-sealing.

[Flydog]

Here's a video.

https://youtu.be/QIOf-7WAZ5E

[wallnut1234]

Originally Posted by Flydog

Here's a video.

https://youtu.be/QIOf-7WAZ5E

those seem pretty nice

[ZachO]

If nothing else, don’t just put simple screws into the fiberglass. Completely ineffective.

If I bolt mine, the bolt will go all the way through.

The problem with VHB that someone is bound to mention so I’ll be the one is that yes, it’ll bond for life. But bond to what? If on a painted surface, the paint. On fiberglass, the gelcoat or thin fiberglass layer. Both can break. You can have a panel fly off and take a chunk of fiberglass with it.

You could install with only VHB and never have a problem. Or, like many Escape owners found when Escape was installing this way, they may fly off while driving.

I think VHB is perfect for flexible panels, but a gamble for rigid panels.

Full disclosure: my rigid panels are on my roof with VHB, then a layer of eternabond over the feet for a little more surface area and stability. If I did it again, I’d also use bolts, and I’ll probably put bolts in two of the feet at some point.

I thought it was interesting that one prominent YouTuber promoting VHB and clearly frustrated about people telling him that using VHB-only was dangerous...made videos explaining how VHB is more than enough. BUT always stressed that you need to anchor the panels with a chain connected to something which is bolted to the roof...

[redbarron55]

One important thing to consider if mounting something rigid with tape is that when these things get hot and cold the fiberglass and the "thing" may expand and contract at different rates. Also even if the glue line holds 100% the thin line of foam between might just fail and test the safety chain.
To some extent I feel the same about the well nuts with the rubber that could (as the British call it) perish and come loose. I have replaced a number of these on my Kubota hood hinge pins and other places where they were used by Kubota.
Of course the nutcerts etc. could rust out they could pull out of the fiberglass etc. as well.
I love the rivet nuts and nutcerts etc, but they cannot completely replace nuts and bolts, but then the nut could vibrate off...
Personally I have a hard time understanding the angst about drilling a hole through the shell. These things already have a bazillion holes with pretty poor fasteners through them.
The floors don't rot out from a screw holding down a solar panel leaking, just saying.

[ZachO]

I agree. I think it's pretty natural for us to cringe at the thought of holes in the roof, but if we think it through, it's nothing to be afraid of. Just like with the roof vents (I've got 4 of them), a little sealant is 100% effective in stopping leaks, assuming you take any time at all the learn how to use it.

I didn't watch the rivnuts videos to get a sense for scale, but in my mind, something with a footprint only centimeters wider than the hole you drilled isn't going to hold any better than VHB tape, in the sense that if a crazy enough gust of wind came along to tear the VHB or the fiberglass underneath it, it's a strong enough gust of wind to tear out the rivnuts. This thin fiberglass layer on the outside of our trailers is really not very strong.

[redbarron55]

You have an excellent point about the contact point and the stresses that might be applied in case of a gust etc. This is the reason that I used screws and fender washers on my installation.
However the rivnut or Nutcert would serve to anchor the corners to keep the VHB tape from peeling.

[ZachO]

Most likely, yes.

If/when I get back to this on my trailer, I'll have long bolts (Bigfoot roofs are thick), upside down as Raspy suggests, with wide washers inside on my ceiling.

The VHB on my roof is solid. It will not detach from my roof. But unlike videos I've watched where the guys says you could grab the panel with a crane and the entire trailer would lift before the tape separated, I disagree. The fiberglass would crack and tear off under the tape long before the wheels left the ground. From what I've read, this is what started happening to Escape owners. It wasn't the VHB bond that separates, it's the fiberglass itself.

[Raspy]

This VHB discussion is not new. 3M 5200 glues things to fiberglass, such that the bond is stronger than the fiberglass itself. I have pried things off the boat and taken layers of glass with it, while the 5200 held. The only way you are going to beat that kind of hold, is with a through bolt large washers. If the glass itself is not strong enough to hold the thing, something serious is happening. Air conditioners are only held on with four screws that pinch it to the roof, and sticky tape (not VH. And they don't routinely fly off. Neither do the typical roof vents until they are UV damaged and crack apart.

It seems natural to be concerned about simply gluing things to the roof, but how strong does it have to be?

In my case, I'm adding two more solar panels. But I can't glue the down because the roof is an aluminum sheet. I need to bite into the substructure instead of relying on the aluminum sheet.

Maybe we just need big wingnuts inside. We can bolt stuff down by screwing on a big wingnut inside and painting the wings to look like upside down bunny ears, or something. Nobody will ever notice them. And when you bump your head on it, it will just torque it up a bit tighter for added safety. Win-win.

[Mooncusser]

I just installed a big 300 watter using VHB tape and wired it down thru the fridge vent, along the side to the front left under dinette storage area where it connects to the charge controller, and from there to the batteries on the the tongue. 8 anchor points all using VHB tape. No screws.

If you do use screws I would use butyl underneath the mounts and lap sealant overtop

You can't get much bigger than the solar panel I installed with just VHB tape.

To each their own as long as it doesn't leak or fly off

[redbarron55]

Personally I wouldn't mind if the solar panel flew off other than if it hit someone.
That possibility of a solar panel coming off and through a windshield of an innocent traveler means that I will drill holes in my Scamp and install screws and washers with elastic stop nuts.

[ZachO]

Well this is all good to know. To me solar panels are different than AC because air gets under them causing a lot more force than on something flush with the roof. If it wasn’t for the Escape stories I wouldn’t be worried. But they have me figuring I should add a couple bolts.

[redbarron55]

Actually the AC is retained with a great big washer called the inside mounting frame, not just a few screws into the fiberglass.

[redbarron55]

Just thinking for those with rat fur interiors you could get someone to weld the head of a screw or bolt to a fender washer and grind it relatively smooth and then cover it with rat fur to match. Then you could just hold it while it is tightened on the outside. This would make it blend into the interior better if that is an issue.
Obviously I have been too lazy to take my own advise but here are some pictures of my installation

[wallnut1234]

I was thinking on using both well nuts (or rivnuts) and VHB tape to which I would add sealant. Only thing that makes me hesitate is water getting past the sealant... I guess that's what butyl tape would prevent...

[ZachO]

For roof vents, the butyl tape goes between the vent and roof, sandwiched there. Screws go through it. This alone is possibly enough of a seal, and is all that is used for windows. But on the roof, people typically then cover the joint with something like Dicor lap sealant.

I'm sure there are all sorts of ways to do this, but if I were using butyl tape for solar, it would go between the feet of the panel brackets and the roof. The screws/bolts would go in, then the whole thing would get covered with Dicor or Eternabond tape.

I don't have a picture of your installation in my mind, but with VHB tape, I'm not sure where butyl tape fits in. It would go where the VHB tape goes. Seems like it's one or the other.