drilling holes in bigfoot roof for solar panels - Fiberglass RV


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Old 08-15-2020, 06:19 AM   #1
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Name: Dominic
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drilling holes in bigfoot roof for solar panels

I'm about to install my solar panels to my roof, I'm not 100% sure if I will use VHB tape or drill holes to secure them to the roof but so far I'm leaning towards drilling holes but since I don't really know what I would be screwing into, I'm not that confident that it would be secure has anyone done this? I also read in another thread that rivets could be used instead of screws, would that be a better option?
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Old 08-15-2020, 07:38 AM   #2
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i have 2 100w "flexible" panels with one mounted on the roof of my casita and the other on the topper of my truck. both are mounted with vhb tape. i did add some gorilla tape (it's available in white now) around the edges of each panel (my ocd tendencies). i've had this set up going for about 2 years with no problems. i'm not sure i'd trust vhb tape with the much heavier framed, not flexible panels altho i've seen others that have used it. if you decide against vhb tape i'd vote for rivets with sealed holes and snap caps just like the rest of the rivets on your rig.

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Old 08-15-2020, 08:22 AM   #3
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No way would I drill holes that don't need to be drilled. Use tape!

If you're using rigid panels (personally I'm still not convinced on the long term reliability of flexible) I'd use AM Solar Products, since they've been proven over time.

Enjoy,

Perry
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Old 08-15-2020, 09:00 AM   #4
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Originally Posted by Perryb67 View Post
No way would I drill holes that don't need to be drilled. Use tape!

If you're using rigid panels (personally I'm still not convinced on the long term reliability of flexible) I'd use AM Solar Products, since they've been proven over time.

Enjoy,

Perry

I still have a few days of thinking before I do the install, I think the tape option looks pretty good. I'm also considering doing both screws and tape as the solar panels that I ordered come with some type special screw that apparently would work on a fiberglass roof. Adding the tape to that should be pretty solid.
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Old 08-15-2020, 09:59 AM   #5
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Drilling holes

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Originally Posted by wallnut1234 View Post
I still have a few days of thinking before I do the install, I think the tape option looks pretty good. I'm also considering doing both screws and tape as the solar panels that I ordered come with some type special screw that apparently would work on a fiberglass roof. Adding the tape to that should be pretty solid.
Here is some good info on sealants and adhesives
https://www.westmarine.com/WestAdvis...ants-and-Caulk
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Old 08-15-2020, 10:18 AM   #6
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Anyone that has installed vent visors on their auto motive windows know that they are held on with VHB tape and they pretty much hold for the life of the vehicle. I wouldn't hesitate to use that tape on the roof and think its a much better alternative to drilling holes in the roof.
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Old 08-15-2020, 10:30 AM   #7
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VHB tape

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Originally Posted by wallnut1234 View Post
I'm about to install my solar panels to my roof, I'm not 100% sure if I will use VHB tape or drill holes to secure them to the roof but so far I'm leaning towards drilling holes but since I don't really know what I would be screwing into, I'm not that confident that it would be secure has anyone done this? I also read in another thread that rivets could be used instead of screws, would that be a better option?
VHB is ???????? 3M alone makes about 80 types of VHB for specified uses.

I would use BOTH VHB and screws. I use 3M 5952 but not for mounting solar panels. It can be had in small rolls on Amazon, Car parts stores also sell VHB tape for holding trim on cars.

Yet another video:
https://www.youtube.com/watch?time_c...ature=emb_logo
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Old 08-15-2020, 10:51 AM   #8
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VHB is ???????? 3M alone makes about 80 types of VHB for specified uses.

I would use BOTH VHB and screws. I use 3M 5952 but not for mounting solar panels. It can be had in small rolls on Amazon, Car parts stores also sell VHB tape for holding trim on cars.

Yet another video:
https://www.youtube.com/watch?time_c...ature=emb_logo

I ordered 3M 4950 VHB tape based on a youtuber(hobotech) that has them installed for a while now and that's what he used. I plan to add some dicor around each bracket to protect the tape and probably some eternabond on top of each bracket. That plus the screws
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Old 08-15-2020, 12:24 PM   #9
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I used these rubber wellnuts and ss screws to install 2-100W solar panels to my SOB 5th wheel and they worked great. Now that i am a casita owner, I plan to use them again. However, I would only use one in each "Z" clip instead of two. Since they are rubber they automatically seal but I still covered them with Dicor. If you go this way you would probably need a smaller grip range because my roof at that time was 3/8" thick.

https://www.zoro.com/pop-avdel-well-...88/i/G3152624/
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Old 08-15-2020, 02:21 PM   #10
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One reason not to use screws is the single layer of the trailer's skin. If your using scews, they're going to intrude into the ceiling and possibly be a source of injury. I've got 4 panels on my roof mounted on PVC frames attached by VHB tape. They've been there for 5 or 6 years without a problem in very high winds.
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Old 08-15-2020, 02:42 PM   #11
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Use stainless screws with stainless fender washer inside along with acorn nuts to finish. This is what I did with my rigid panels. I made the mounting brackets from aluminum for the part mounted on the Scamp shell and used the awning box for the outside mounting, leaving space between the shell and the panels for air to help keep them cool and more efficient.
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Old 08-16-2020, 05:05 AM   #12
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Originally Posted by redbarron55 View Post
Use stainless screws with stainless fender washer inside along with acorn nuts to finish. This is what I did with my rigid panels. I made the mounting brackets from aluminum for the part mounted on the Scamp shell and used the awning box for the outside mounting, leaving space between the shell and the panels for air to help keep them cool and more efficient.

so you drilled all the way through? I'm trying to understand where you put the acron nut. I was planning on screwing from the top and not go all the way through the shell (it's pretty thick)
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Old 08-16-2020, 05:06 AM   #13
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Originally Posted by CASITA BANANA View Post
One reason not to use screws is the single layer of the trailer's skin. If your using scews, they're going to intrude into the ceiling and possibly be a source of injury. I've got 4 panels on my roof mounted on PVC frames attached by VHB tape. They've been there for 5 or 6 years without a problem in very high winds.

I wouldnt drill all the way through. I'll double check the length of the provided screws but I think they are shorter than the thickness of the shell
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Old 08-16-2020, 05:30 AM   #14
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The Scamp is a single layer shell of fiberglass with a inner lining of about 1/8" of Ensolite "insulation". I drilled all of the way through (about 1/4" or so) and put the fender washer on with the bolt cut to the right length and installed Well to tell the truth an elastic stop nut and then took a zizz wheel and cut off the excess screw length to make it flush with the end of the nut. Looks like an acorn nut. Then if I cared enough I would have painted the washer and the nut to match the interior color, but I have not gotten around to that as it has only been a year plus.
If your bigfoot (I am not familiar with how they are built) has a double skin, inner and outer with insulation between it would be a bigger problem I guess to gain access to the underside of the shell.
I would consider rivnuts installed with sealant.
I don't have a problem with the VHB tape other than I feel that the corners at least at the front should be mechanically fastened with hurricane force winds blowing over then so often. Something to resist the initial peeling.
I installed three 100 watt rigid panels on my Scamp with one side fastened to the awning cover for two and the third on aluminum brackets fabricated from angle and 1/8" plate, fastened with the stainless screws and fender washers.
Since the screws are cut off even with the rounded elastic stop nuts there is little possibility of head damage on the inside and that is important as the protective hair gave up some time ago. Later today I will try to get some pictures of my brackets and the still unpainted inside.
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Old 08-16-2020, 07:13 AM   #15
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Originally Posted by redbarron55 View Post
The Scamp is a single layer shell of fiberglass with a inner lining of about 1/8" of Ensolite "insulation". I drilled all of the way through (about 1/4" or so) and put the fender washer on with the bolt cut to the right length and installed Well to tell the truth an elastic stop nut and then took a zizz wheel and cut off the excess screw length to make it flush with the end of the nut. Looks like an acorn nut. Then if I cared enough I would have painted the washer and the nut to match the interior color, but I have not gotten around to that as it has only been a year plus.
If your bigfoot (I am not familiar with how they are built) has a double skin, inner and outer with insulation between it would be a bigger problem I guess to gain access to the underside of the shell.
I would consider rivnuts installed with sealant.
I don't have a problem with the VHB tape other than I feel that the corners at least at the front should be mechanically fastened with hurricane force winds blowing over then so often. Something to resist the initial peeling.
I installed three 100 watt rigid panels on my Scamp with one side fastened to the awning cover for two and the third on aluminum brackets fabricated from angle and 1/8" plate, fastened with the stainless screws and fender washers.
Since the screws are cut off even with the rounded elastic stop nuts there is little possibility of head damage on the inside and that is important as the protective hair gave up some time ago. Later today I will try to get some pictures of my brackets and the still unpainted inside.

Thanks for the details, no need for the pictures though, the shell of my trailler is thicker so I wont go all the way through. Those rivnuts look interesting though
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Old 08-16-2020, 07:21 AM   #16
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Use 1/4" stainless or aluminum rivnuts and they go in like big pop rivets. try to drill as clean a hole as possible where the rivet just goes through. Put some sealant on the part before you put it in and then set it. When you mount to it put some more under and over the screw and whatever hardware you use.
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Old 08-16-2020, 07:37 AM   #17
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If you are going to drill all the way through, run the screw up from underneath and put the nuts on top. This minimizes the head inside. I don't know how much headroom you have, but bumping my head on acorn nuts is not fun. With a simple round head screw, you'll minimize the intrusion inside. When sealing it on top, put a washer on, and put some sealant on the threads before screwing on the nut. With a flat washer on the inside and outside, you will not have a leak, and you will not be putting any unfair stress on the fiberglass. You can use this method on boat bottoms that are always underwater, and never have a leak.

Drilling part way through, or making a blind hole, is going to be tricky and a screw will not hold well at all. Fiberglass does not hold screws well that are just screwed into it. It's not like wood, in that it fractures next to the screw, instead of molding itself around the screw.
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Old 08-16-2020, 07:45 AM   #18
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Drilling part way through, or making a blind hole, is going to be tricky and a screw will not hold well at all. Fiberglass does not hold screws well that are just screwed into it. It's not like wood, in that it fractures next to the screw, instead of molding itself around the screw."

This is the reason for the rivnut as it installs threads through a thin substrate. The back bulges and crimps against the fiberglass. If you put a little sealant through the hole and on the rivnut the fastenet will be sealed to the fiberglass. If you use 3M 5200 it will bond quite well.
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Old 08-16-2020, 07:58 AM   #19
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But then you are looking up at a crimped rivnut and the end of a bolt, inside your camper. Pretty. And it sticks down a lot farther than a round head screw pointing up. Rivnuts are best suited to blind areas you can't reach, like inside a boxed car frame, or a tank. You'll likely be picking pieces of skin up off the floor that got peeled off as you walked under them.
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Old 08-16-2020, 08:51 AM   #20
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Leaks from screws through fiberglass.
Personally I think the problem with leaks from screws backed up with nuts on the inside is much overblown, unless they are not pulled tight .
Scamp uses screws through the fiberglass into the wood cabinets in all cases. they do not add any sealant that I have seen. I removed the rear overhead cabinets from mt 1985 Scamp and at the holes exposed to the elements for 35 years there was no sign of any water ever getting through to the wood whatever.
Modern sealants are quite good and can be trusted to continue to seal as long as the fasteners are solid and do not rattle around.
The pop rivets used through fiberglass internal fiberglass parts with reflectex and rat fur between them will never be 100% secure as the parts work in relation to each other.
If you are screwing or bolting something that will be solidly mounted to the shell I think you will be much more certain to have a goo leak free connection.
If what you are going to install will be flopping around then all bets are off no matter what you use
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