Hello everyone, newbie here. I am mounting some solar panels to the roof of my cargo trailer. I do not want to drill holes in the roof. I have already purchased the glue on mounts from Rich Solar. What is the best adhesive to use so these will stay in place? i know about VHB tape. Im talking about the caulk. Thanks in advance.
Best adhesive for no drill roof mounted panels?
- Thread starter Bigdaddy
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Critter350
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Hi. Won’t try to tell you it’s the best (I’ve not tried any others) but I’ve used a product called ‘toolbox’ to stick a semi flexible panel to 17year old corrugated fibreglass canopy. Been on since August, and have done a trip around the tropics here in WA. Satisfied it’s rock solid.
Bit of a pain to work with - very thick (hard to squeeze out) and short work time, so with manual calling gun I was squeezing like heck to get the stuff out as quickly as possible, gave myself a tension headache. (Getting old eh).
Bit of a pain to work with - very thick (hard to squeeze out) and short work time, so with manual calling gun I was squeezing like heck to get the stuff out as quickly as possible, gave myself a tension headache. (Getting old eh).
mikefitz
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Carry out a risk assessment using plastic mountings with adeshive. Without using mechanical fixings there is a chance the panels will fall off. Which has less risk, glue or bolts?
In the UK there have been many reported panel detachments and a number of serious accidents worldwide,
diysolarforum.com
rvdaily.com.au
Plastic is a difficult material for many adhesives to bond successfully, not helped with the release agents that may have been used in the manufacturing process of the bracket. Can you be confident that long term exposure to water and UV will not degrade the plastic.
I have first hand experience of failure between the vehicle paint layers leading detachment of the mounting bracket.
Mike
In the UK there have been many reported panel detachments and a number of serious accidents worldwide,
Fatal accident caused by loose panel on road
Just seen a post on another forum about a fatal road accident in Tasmania, Australia police believe was caused by a solar panel on the toad that had fallen from a caravan roof Here is a news article about the accident...
diysolarforum.com
Flying Solar Panels - The danger lurking on your RV's roof
Flying solar panels are the dangerous new threat that could be literally just sitting on the roof of your caravan or motorhome right now.
rvdaily.com.au
Plastic is a difficult material for many adhesives to bond successfully, not helped with the release agents that may have been used in the manufacturing process of the bracket. Can you be confident that long term exposure to water and UV will not degrade the plastic.
I have first hand experience of failure between the vehicle paint layers leading detachment of the mounting bracket.
Mike
I have no issues trusting the glue but it is the paint peeling off the van roof I would worry!
and there ya go!
bolts do not care about the paint.
i sure as hell don't want to be the cause of others pain and suffering for my mistakes.
that's the stuff of nightmares.
acdoctor
Solar Enthusiast
I mounted 12 100 watt panels on the roof of my cargo trailer using tamarack mounting. I believe the engendered wind rating was 120 mph. I covered the mounts with dicor RV sealant. Most cargo trailers are metal frame with a skin of aluminum or sheet metal over that. I ordered mine with 3/4 plywood on top of the frame but I still found the frame to anchor to. My roof design is flat with a frame around the edge that produces a 1/2 in lip. It is raining now and 1/2 of the mounts are under water. They have been there for a year and no leaks. If you aren’t going to have them secure just store them when you are on the road. I don’t want to get hit by them.
acdoctor
Solar Enthusiast
I forgot to mention I am in north Arkansas in the winter I get about 40% of the rated output in summer about 60%. So ground mounted portable maybe a better solution you could have 1/2 the number of panels. I put 12 expecting a low output.
Bill Taylor
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I have used adhesives to attach solar panels to the roofs of two cargo trailers. One was 18 years ago, the other one 7. They are both still on there very tight. Clean the roof VERY well. Use alcohol on the roof and the feet to make sure it is absolutely clean. When it is dry, use E6800 adhesive. It's available at craft stores, or online. (Do not use E6000, it is not sunlight resistant.) After it has dried several days put some paint over the plastic parts of the mounting brackets. That will reduce Sun cracking and yellowing, it will make the brackets last longer. Those trailers get hauled across several states every year, I hope you have good success like I have had.
MisterSandals
Participation Medalist
So exactly what is the roof of your cargo trailer? Bare metal? (type: steel?, aluminum?) Paint or coating on metal? Some type of composite material? Fiberglass?
How is the roof fastened and supported?
I think the best solutions would depend on your answers to these questions.
Bill Taylor
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It's reasonably solid. Galvanized steel over steel beams inside. Typical interstate cargo trailer. I was assuming that anyone who would attempt to use adhesive to mount a panel would make sure that the roof was solid. But it never hurts to clarify things.
MisterSandals
Participation Medalist
Super! My thought is that since steel is so durable and easy to work with that I would strongly consider drilling and sealing (there are probably water tight grommets or something equally clever). Attaching to the beams is a big advantage too, especially if your rack had hauling capabilities. Even if you removed the rack, it would not be difficult to plug/seal the holes easily.
On my Winnebago View (big fiberglass cap), I put VHB on the cleaned and scuffed fiberglass and its mighty permanent (10 years now!). 8 brackets with a 2" x 3" surface for each 165w panel.
There isn't a good way to locate beams under the roof cap so thats one strike against drilling. Also, the fiberglass greatly weakened when cut or drilled and is very susceptible to splintering and fraying on the edges created by drilling and cutting (strikes 2 and 3).
I have used VHB tape and it is some serious sticky. Would I use it to attach panels to the roof of a vehicle? No....
After seeing the gent down in California that used VHB to attach panels to the roof of his RV. It held fine on all but one of the panels. That one panel came off while he was driving down the highway.
It hit another car, caused an accident that killed a young lady. The RV driver was arrested and charged with manslaughter.
The panels on my RV are bolted down with 28 - 3/8" bolts. I was reluctant to put holes in my roof but with it done, I am glad I went that route.
I used polyurethane sealer quiet liberally on every penetration, bolted everything down and then covered the top of the bolt & bracket with self leveling roof sealant.
After seeing the gent down in California that used VHB to attach panels to the roof of his RV. It held fine on all but one of the panels. That one panel came off while he was driving down the highway.
It hit another car, caused an accident that killed a young lady. The RV driver was arrested and charged with manslaughter.
The panels on my RV are bolted down with 28 - 3/8" bolts. I was reluctant to put holes in my roof but with it done, I am glad I went that route.
I used polyurethane sealer quiet liberally on every penetration, bolted everything down and then covered the top of the bolt & bracket with self leveling roof sealant.
Factory400
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VHB has always been my go-to adhesive for things I care about. When applied properly - it can not only be strong, but very reliable over time.
A. Make sure you get real 3M VHB
B. Make sure you are very methodical in its application
C. The wind loading on a panel at 65mph is pretty extreme sometimes, so a little extra is not a bad idea.
D. In aerospace applications, adhesives are sometimes used because they can be stronger than mechanical fasteners.
In the context of 'D', that is not always true, but on an RV where the structure underneath can be unknown or your fasteners can miss - this could hold true. Using VHB requires some understanding of how to estimate the loads and then translate that to the contact surface. You must have a margin of safety, probably around 5x for this. If you are thinking in more simplistic terms - perhaps you need to be thinking about screws and bolts.
Of course those are not infallible either.
VHB 4910 at room temp is about 100psi tensile and 70psi shear. I am using 4x5 plates (2000lbs tensile and 1400lbs shear)
That gets de-rated for heat and cold of course but in the worst of situtations will be easy to maintain a large factor of safety.
I am currently planning a VHB install on my travel trailer and will be using custom aluminum plates to make the bond. The leading edge sees the most pressure, so I am going to add additional plates along the front.
A. Make sure you get real 3M VHB
B. Make sure you are very methodical in its application
C. The wind loading on a panel at 65mph is pretty extreme sometimes, so a little extra is not a bad idea.
D. In aerospace applications, adhesives are sometimes used because they can be stronger than mechanical fasteners.
In the context of 'D', that is not always true, but on an RV where the structure underneath can be unknown or your fasteners can miss - this could hold true. Using VHB requires some understanding of how to estimate the loads and then translate that to the contact surface. You must have a margin of safety, probably around 5x for this. If you are thinking in more simplistic terms - perhaps you need to be thinking about screws and bolts.
Of course those are not infallible either.
VHB 4910 at room temp is about 100psi tensile and 70psi shear. I am using 4x5 plates (2000lbs tensile and 1400lbs shear)
That gets de-rated for heat and cold of course but in the worst of situtations will be easy to maintain a large factor of safety.
I am currently planning a VHB install on my travel trailer and will be using custom aluminum plates to make the bond. The leading edge sees the most pressure, so I am going to add additional plates along the front.
Bill Taylor
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Surface Prep goes a long way. But I sure love that E6800. And I live in Arizona, so anything that is plastic gets painted. Between those two things, the first panel I did has probably got 50,000 miles on it and still looks tight.
But even with that success, everything else I put on the roof get screwed and covered with Dicor. I feel so much better knowing there is a mechanical attachment on there in addition to the sealer.
But even with that success, everything else I put on the roof get screwed and covered with Dicor. I feel so much better knowing there is a mechanical attachment on there in addition to the sealer.
Factory400
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My biggest hesitation with screws is not leaks - I think I can manage that. I am worried about what I am screwing into.
How do you know what/if you are screwing into something worthy of holding the panel. How do you know you are not going to damage something on the other side?
MisterSandals
Participation Medalist
Drill your pilot holes from the inside?
Or, is there anything on the outside (rivets?) you can use as guides/offsets?
I guess the question I have is what the inside looks like. What can you see and measure from the inside?
Factory400
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The roof of my Micro Minnie is smooth with no obvious signs of mechanical fasteners. I can sort of make out the ribs if I push on it while looking for the most rigid area.
I do not, however have any idea what the ribs are made of, therefore no way to know what fastener to use or how strong the fastener will be in tensile pull out strength.
I would hazard a guess that the roof is attached with adhesive like many trucks and trailers these days. It is a lot less labor to use adhesive to build the things. Either way, if I have not idea what I am screwing into - the adhesive on the exposed surface seems like a good idea. Adhesive plates also allow the load to be spread out over a large area.
I would love to learn more about the structure, but don't know where to get that information.
Bill Taylor
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I know a few guys who install solar panels on RVs for a living. Seriously. They do it 5 days a week. I've known them for years, I'm an electrical contractor and we pick each other's brains a lot. That's where I get my information.
Cargo trailers and unfinished vans are easy, you can see from the inside. Use the shortest screw possible, (1/2" self tapping sheet metal screw.) All you're trying to do is get some bite. As far as the traditional RV roof goes, number 14 x 3/4 inch screw works fine. Any wiring is far enough away where the screw will not hit it. And there's no plumbing up there, you may tap into an A/C duct but you'd never know it. And you don't need to use dozens of screws. I've seen plenty of people just put a few screws on the leading edge to make sure the panel stays down and use adhesive on the rest of the feet. No matter what, you can use a drill to get the screw started, but always finish it by hand with a screwdriver. You will not strip them out that way. Don't ask how I know this....
I can't honestly say they have *never* hit a wire. It has happened. Maybe twice in the last 15 years. So I think the odds are in your favor.
Cargo trailers and unfinished vans are easy, you can see from the inside. Use the shortest screw possible, (1/2" self tapping sheet metal screw.) All you're trying to do is get some bite. As far as the traditional RV roof goes, number 14 x 3/4 inch screw works fine. Any wiring is far enough away where the screw will not hit it. And there's no plumbing up there, you may tap into an A/C duct but you'd never know it. And you don't need to use dozens of screws. I've seen plenty of people just put a few screws on the leading edge to make sure the panel stays down and use adhesive on the rest of the feet. No matter what, you can use a drill to get the screw started, but always finish it by hand with a screwdriver. You will not strip them out that way. Don't ask how I know this....
I can't honestly say they have *never* hit a wire. It has happened. Maybe twice in the last 15 years. So I think the odds are in your favor.
Hey MisterSandals- what is the material of your 2x3 pads? Looking to do a similar install. Thanx, ken
MisterSandals
Participation Medalist
2” right angle aluminum, probably from Home Depot as an 8’ length.
(2) 3” pieces per side so 24” per panel.
Whinny
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Factory 400:
My Micro Minnie (2016) has aluminium truss and osb sheeting with epdm membrane glued on. I took out a speaker and poked around to find the truss. Don't think the epdm is glued on too well, wouldn't trust it for a panel. Any wiring I saw was laying on the ceiling paneling.
My Micro Minnie (2016) has aluminium truss and osb sheeting with epdm membrane glued on. I took out a speaker and poked around to find the truss. Don't think the epdm is glued on too well, wouldn't trust it for a panel. Any wiring I saw was laying on the ceiling paneling.
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Perfect! That is exactly what I have in mind. Thanks
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