Best adhesive to mount solar panels with?

jkam

nomadic man
I used 3M VHB on the bottom of the brackets on my aluminum skinned roof.
Then I covered over the bracket with a piece of Eternabond.
I've driven down the freeway at 75 mph for hours with them tilted and still no problems.
No holes drilled, been up there 8 years now without issue.
 

llamalander

Active member
While you said you wanted to minimize penetrations & you actually did the math you need, you might still consider running a leash from your panels to the roof and bolting it in well. Should your panels come up, they won't make it past the back of your vehicle and you will be sure to notice. Lets you trust your theory and still sleep well.
 

Peter_n_Margaret

Adventurer
The body of our rig (in the avatar) is built (16 years ago) from FRP sandwich panel and is completely held together with Sikaflex 252. There are no mechanical fixings. All the interior is also FRP sandwich panel held together with Sikaflex 252 and Sikaflex 11FC.

2 years ago, it ran down a steep hill and into a creek because the hand brake was not properly applied. It weighs a bit over 6T.
The front (Dana 60) axle and axle housing was snapped like a carrot near the diff. The chassis was bent. The Warn 16.5Ti winch was destroyed. The windscreen, bumper bar and most of the front end sheet metal was replaced.

Not a single glue joint in the FRP sandwich body failed.
Cheers,
Peter
OKA196 motorhome
 

ckent42

New member
I talked to my PE coworker about it, and he recommended not relying solely on adhesives for mounting the panels. He brought up the Big Dig tunnel Ceiling collapse in 2006, which was due to creep induced by constant loading on the structural epoxies holding everything together, and how that incident caused building code books to remove adhesive as a structural connection until around 2014?ish. He also brought up something I hadn't considered, which is uplift on the panels due to suction from passing trucks, which can induce loads has high as 30 psf, which on a 3'x6' panel is an additional 500 pounds of uplift. Finally, after all that, the most convincing thing he told me was that should the panels fall off and injure or kill someone, I will be found criminally negligent. His recommendation was at the very least to have a few thru-bolts or sheet metal screws in addition to the adhesive, or to forgo the adhesive completely and just rely on mechanical fasteners. I know that anecdotally lots of people have relied on adhesives to hold down their panels, but I'd rather add a few extra holes and be sure that nothing it going to go flying off my roof.

While you said you wanted to minimize penetrations & you actually did the math you need, you might still consider running a leash from your panels to the roof and bolting it in well. Should your panels come up, they won't make it past the back of your vehicle and you will be sure to notice. Lets you trust your theory and still sleep well.
That's an idea I was considering as well, and something that should probably be done no matter the mounting situation. It's a simple, cheap and effective failsafe, even if it does complicate the install a little bit.
 

grizzlyj

Tea pot tester
I know some Euro vans with solar panels just "glued" on had the panels come off with the paint, glue/Sika etc whatever intact.
 

ckent42

New member
The guy is PE and JD ? Thats devotion to the game !

Hahaha I think you just become intimately familiar with all the legality that comes with the responsibility of stamping drawings and calculations. That was just his opinion, and that might not be the correct legal term. But I'm sure that should the panels fly off and hurt someone, I would legally be responsible, since I'm the one who installed them.

Can't tack weld to the aluminum?
I'm sure someone could, but I've never welded in my life, and I would be worried about burning through the sheet, or having such a crappy weld that it would break sooner rather than later. Also, welding is the most permanent option.
 

Hoooogan

Member
Get the 30# extreme duty VHB tape. Make sure the surface is clean enough to eat off. 3M also makes a primer, should you feel it necessary. Scuffing the surfaces can also help bonding. None of which is absolutely necessary, other than cleaning. The adhesive is pressure sensitive, so more pressure makes a stronger bond.

There are trailer companies that bond the outer aluminum skin to the frame using VHB tape and found it performs better than rivets or bolts.
 

Neil

Observer
I know some Euro vans with solar panels just "glued" on had the panels come off with the paint, glue / Sika etc whatever intact.
Ours are stuck on with Sika 512 only, no screws on a painted roof on 50 mm angle brackets

Two have been there 7 years and are still rock solid. The third got damaged after 5 years and had to be replaced . Getting the old Brackets off cleanly after 5 years of sun and weather took the best part of 2 days and lots of Tourettes.

I personally would avoid putting unnecessary screw holes in the roof is they can be avoided.

I have visited several of the Cabin makers in Germany and they have all use just Sika or similar

Neil
 

grizzlyj

Tea pot tester
Ours are stuck on with Sika 512 only, no screws on a painted roof on 50 mm angle brackets

Two have been there 7 years and are still rock solid. The third got damaged after 5 years and had to be replaced . Getting the old Brackets off cleanly after 5 years of sun and weather took the best part of 2 days and lots of Tourettes.

I personally would avoid putting unnecessary screw holes in the roof is they can be avoided.

I have visited several of the Cabin makers in Germany and they have all use just Sika or similar

Neil
Hi Neil
Did you think I meant all panels just glued on are imminently about to fly off?!?
I did see some pics of I think a Fiat panel van where the brackets that did hold the solar panels on had come off. The adhesive holding the bracket to the paint was solid and intact (so correctly prepared by the installer) but the manufacturers paint had come off the metal roof. There are a few posts on camper forums where solar panels have blown off. I'm not saying it's a totally unsafe thing to do, but maybe Sika won't say it's fine to rely only on whichever of their products because it depends on what you're gluing to?
 

gdlals

Member
I wouldn't use an adhesive to mount solar panels personally. Where the panels are mounted on the roof, whether turbulence can build in the gap between the roof and the panel will all create forces in multiple directions, not a single shear direction where adhesives excel.
 
Ours are stuck on with Sika 512 only, no screws on a painted roof on 50 mm angle brackets

Two have been there 7 years and are still rock solid. The third got damaged after 5 years and had to be replaced . Getting the old Brackets off cleanly after 5 years of sun and weather took the best part of 2 days and lots of Tourettes.

I personally would avoid putting unnecessary screw holes in the roof is they can be avoided.

I have visited several of the Cabin makers in Germany and they have all use just Sika or similar

Neil
My Sika equivalent glue has strength of 3 MPa. So a 5cm X 10cm area has a 1.5 tonne breaking strength. Each of my 4 brackets has adhesive strength to lift my entire camper. The roof or brackets will fail a lot sooner than the adhesive.

Sent from my SM-T860 using Tapatalk
 

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