diy solar

diy solar

Airstreamer looking for some advice on mounting to a curved roof

Wait, you used double sided tape?! You are kidding, right?

That stuff is used to attach emblems etc, not solar panels on small feet, panels that can act as wings in certain circumstances once driving wind gets under and over the surface. With the frame around the panels you can create uplift much like the wing on an aircraft.

If one of those flies off and cuts through a windshield of a vehicle behind you, or a biker goes down by running over your panels laying on the highway, you will be held liable. Somebody getting killed or injured can sue you for everything you own.

Do it right and bolt them down.

PS: I used to work in aviation on S-76, Jet and Long Rangers, Engineering degree and all. What you did would never fly with the FAA.
 
A security cable is a good idea, but if you are attaching to a suitable surface like aluminum, you prep the surface by cleaning it well (I use brake cleaner), and after firmly attaching with 3M VHB tape you completely caulk with Sikaflex, there no pulling these feet off!
Please believe me... those feet will not hold.
If you insist on only adhesive for the feet, you MUST attach a security cable attaching Each panel to the cable.
The cable must attach to the frame of the vehicle.
 
The method of using vhb tape and sikaflex, isn't my idea, jump over to Airforums where it is common practice, including by professional installers, for mounting solar panels to the roofs of airstream trailers. VHB tape is designed for adhering panels on buildings, trailers, trucks, and yes even aircraft.
https://www.3m.com/3M/en_US/vhb-tapes-us/#:~:text=3M introduced 3M™ VHB,entire area of the joint.
I agree adding fasteners to each foot would add security but apparently many choose not to to avoid roof penetrations. And certainly the suitability of this method is dependent on the substrate.
 
The method of using vhb tape and sikaflex, isn't my idea, jump over to Airforums where it is common practice, including by professional installers, for mounting solar panels to the roofs of airstream trailers. VHB tape is designed for adhering panels on buildings, trailers, trucks, and yes even aircraft.
https://www.3m.com/3M/en_US/vhb-tapes-us/#:~:text=3M introduced 3M™ VHB,entire area of the joint.
I agree adding fasteners to each foot would add security but apparently many choose not to to avoid roof penetrations. And certainly the suitability of this method is dependent on the substrate.
I heard of that tape being used to hold those big panes of glass in those skyscrapers...
 
VHB tape is designed for adhering panels on buildings, trailers, trucks, and yes even aircraft.

Only tape approved by FAA for any outside application on an aircraft is P12L tape, which is an aluminum tape resistant to solvents, flame resistant, and isn’t impacted by UV degradation, to cover NON-STRUCTURAL, small holes to a certain degree. Not to be used to bond anything to any aircraft, let alone solar panels!

Don't link a useless 3M website with MARKTING videos. None of the info shows FAA approval or any ISO standards.

I know VHB tape all to well, use it in many applications, including on GoPro mounts when out on the race track. And guess what comes flying off ALL the time! GoPros from race cars and race bikes. Now compare the very small surface of a GoPro camera with a huge solar panel.


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And guess what I do know? Use a suction cup that is much stronger than your 3M VHB tape:



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Only tape approved by FAA for any outside application on an aircraft is P12L tape, which is an aluminum tape resistant to solvents, flame resistant, and isn’t impacted by UV degradation, to cover NON-STRUCTURAL, small holes to a certain degree. Not to be used to bond anything to any aircraft, let alone solar panels!

Don't link a useless 3M website with MARKTING videos. None of the info shows FAA approval or any ISO standards.

I know VHB tape all to well, use it in many applications, including on GoPro mounts when out on the race track. And guess what comes flying off ALL the time! GoPros from race cars and race bikes. Now compare the very small surface of a GoPro camera with a huge solar panel.


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And guess what I do know? Use a suction cup that is much stronger than your 3M VHB tape:



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We can also assume that in some cases the surface prep wasn't done properly or the surface wasn't something appropriate for VHB. I have suction cup things come loose frequently. The saliva dries up, the bond is lost, off it comes.
 
We can also assume that in some cases the surface prep wasn't done properly or the surface wasn't something appropriate for VHB. I have suction cup things come loose frequently. The saliva dries up, the bond is lost, off it comes.

Not in my case. I'm OCD / perfectionist / INTJ. I read the datasheet first thing, before even buying such a product, clean surfaces with mineral spirits and acetone etc. I still had 2 GoPros go flying and I lost count how many times other racers had the same issue. Some even got disqualified for not securing the cam with wire.

There are 2 effects taking place that most don't consider: heat and lateral forces.

And the same applies for the OP who added MUCH more weight and size to the mix. Guess how you remove that tape? With a heat gun. Guess how hot that shiny aluminum on the roof of his RV becomes on a southern summer day. Hot enough to fry an egg on it. Now guess what will happen with the adhesive in that heat. It gets heavily compromised and losses bond. Aluminum retains heat for a good while. Then he goes for a ride back home while the aluminum is still hot, and add those lateral forced from wind-resistance and possibly lift-off forces on the panels.

As a biker I know plenty of other bikers who crashed due to unsecured items laying on the highways. Some even died. I-95 here in SoFLa is particularly bad. I have seen it all. Ladders, matrasses, furniture, entire roof racks. If I ever go down because some idiot didn't care enough to secure his load on a truck bed, trailer or roof, he will get served quickly.
 
OP, We just got done securing 8 - 100W panels to the roof of our airstream using Scotch 4910 VHB Tape. We are very satisfied with the results. I clean the panels once a week and check that the bond is still secure. So far there is no indication of separation. Hope this helps.

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OP, We just got done securing 8 - 100W panels to the roof of our airstream using Scotch 4910 VHB Tape. We are very satisfied with the results. I clean the panels once a week and check that the bond is still secure. So far there is no indication of separation. Hope this helps.


He only used the tape on 4 small feet for each panel. Your rails offer probably 20 times the amount of strength / bonded surface.
 
This 3M VHB is good for heat? Some places on my RV I've measured at 170° F with direct sun in the summer. When I put two sided Eterna Bond to hold something a couple of ounces on this, this object slid down the side. That was 10 months after install.
 
This 3M VHB is good for heat? Some places on my RV I've measured at 170° F with direct sun in the summer. When I put two sided Eterna Bond to hold something a couple of ounces on this, this object slid down the side. That was 10 months after install.
So Eternabond isn't SW compatible :) What is the preferred or suggested method to adhere the PV cables to the roof other than when I can tiewrap them?
 
What is the preferred or suggested method to adhere the PV cables to the roof other than when I can tiewrap them?
I use zip tie mounts, and then take a piece of 4" X 4" piece of Dicor Roofing tape, and cut a hole big enough to get the zip ties through, but small enough to secure the mount to the roof. The picture on the right is after this tape has been on for months and has gathered the dust,

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I really am wondering if this VHB tape loses some of its holding power above 150. I cringe at the thought of flat panels being secured to the roof with only VHB tape. Especially towards year 10. Don't really care how good the prep is, unless that VHB is so much better than Eternabond, but to me it seems like its made of the same stuff.

I Use Dicor Roofing tape to secure the two flexible panels. I use that two sided Eterna Bond to secure the six flat panels I have as a secondary method. I use Screws as the primary method. Eight Screws total per panel.
 
I use zip tie mounts, and then take a piece of 4" X 4" piece of Dicor Roofing tape, and cut a hole big enough to get the zip ties through, but small enough to secure the mount to the roof. The picture on the right is after this tape has been on for months and has gathered the dust,

View attachment 65433View attachment 65434
I really am wondering if this VHB tape loses some of its holding power above 150. I cringe at the thought of flat panels being secured to the roof with only VHB tape. Especially towards year 10. Don't really care how good the prep is, unless that VHB is so much better than Eternabond, but to me it seems like its made of the same stuff.

I Use Dicor Roofing tape to secure the two flexible panels. I use that two sided Eterna Bond to secure the six flat panels I have as a secondary method. I use Screws as the primary method. Eight Screws total per panel.

They don't hold. Tried it 2 weeks ago when I installed a panel on my minivan camper. The black panels get so hot, the adhesive becomes almost liquid. They dropped down within 30 minutes.

I screwed aluminum square crossbars under the solar panel, into the frame, and used 250 F rated zip ties to secure the cable to the crossbars.
 

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The reason the other poster used VHB tape and Sikaflex to mount his panels is from this video.


If AM Solar uses this method to install panels on customers projects I thought it was worth looking into (especially if I don't have to drill holes in the roof). I was skeptical on the bonding surface area as stated by another poster here, but I saw another video of someone using T-Track to mount panels to another Airstream roof. They used screws/rivets plus tape, but I thought the tape might work on its own (I can always rivet them down at a later date). Each panel on the roof of my trailer has 72 square inches of bonding area which seemed to me to be a little more secure than the smaller tabs. All the research I did on similar installs on AM Solars forums and Airforums indicate zero failures so far after a few years of use. I plan to watch the install like a hawk because I'm still not 100% convinced the tape will last over time.

After reading the concerns of others here I looked up the removal procedures for my VHB tape and Eternabond.

Scotch 4910 VHB Tape:

Eternabond:

I leave any conclusions about toughness to each of you. As a side note I used the zip tie mounting squares shown above to secure the roof wiring, but i removed the double sided tape that came with it and put the VHB tape on instead. I hope this addresses some of the valid concerns with this install method.
 
They don't hold. Tried it 2 weeks ago when I installed a panel on my minivan camper. The black panels get so hot, the adhesive becomes almost liquid. They dropped down within 30 minutes.

I screwed aluminum square crossbars under the solar panel, into the frame, and used 250 F rated zip ties to secure the cable to the crossbars.
Chris was replying to my question about attaching the PV cabling to the roof, not to the panels. The white roof wouldn't be as hot so adhesives inappropriate for the back of a solar panel still could be ok for the roof.

Chris: Is the PV cable in your picture regular PV cable as it isn't red and white. Do you have PV cable in tubing? If that is regular 10ga PV cable, then the squares of adhesive don't seem to be 4x4" in ratio to the cable size. They look more like 2x2 compared to PV cable diameter?
 
Chris: Is the PV cable in your picture regular PV cable as it isn't red and white. Do you have PV cable in tubing? If that is regular 10ga PV cable, then the squares of adhesive don't seem to be 4x4" in ratio to the cable size. They look more like 2x2 compared to PV cable diameter?
Probably is 2" X 2". The first roll I used for installation was a 4" Eternabond Roof tape. That ran out and I started to use Dicor Roof tape I picked up off the shelf at a local Camping World. I Do cut the roofing tape into a square so its a bit bigger than the mount and will secure it. Got the method from this guy at 2:45 in


The PV wire I use is 10 AWG on the roof. That is here: https://www.wireandcableyourway.com/solar-photovoltaic-pv-wire. There is some 6 AWG wire in the area, but I don't think it made the pick.

Even though the PV wire was UV rated, to make the installation look better, I bought 100' of white split loom wire off E-Bay at this place: https://www.ebay.com/itm/131571481083. Could be that because the split loom is not UV resistant, I may need to replace in a few months. I may just take a split loom and paint it white.
 
. I hope this addresses some of the valid concerns with this install method.
It doesn’t address my concerns. I hope I’m not one of the unfortunates that get nailed by one of these panels flying off.

Geesh, I’ve used a lot of polyurethane adhesives over the years and I love the stuff. But I would not trust it in that application at all.
Auto body uses adhesives to affix repair panels on some models and I’m not very fond of that either.

A good fabricator can make some nice minimally invasive and esthetically pleasing crossmembers for mounting panels to on an airstream. I’m sorta morbidified about anyone using unistrut (even if aluminum) on an airstream anyway LOL so…

But to heck with “liability” I’d be stopped in my tracks over the morality of 65mph flying godzillapanels.
 
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