Flexible panels and VHB? Regrets and tips appreciated

Just starting with my AluCab Khaya build, considering flexible panels particularly SunPower. I am attracted by the flush fit and the, perhaps perception, of being less likely to be damaged.

the roof of the Khaya is diamond plate would this make for a less than ideal adhesive surface?
 

Happy Joe

Apprentice Geezer
I worked quite a bit with black VHB (before retirement) the nubs is the diamond plate will likely give conformance (non stick) issues. when doing very wide sections of VHB.

Definitely degrease both the substrate/diamond plate, before applying the VHB and the back of the panel before applying it to the bonded VHB and apply to a slightly warm area .
We used air pressure assisted set of rubber rollers for widths of around 18 inches and typical lengths of around 48" to achieve the recommended bonding pressure).

Definitely make sure you apply enough pressure to make full contact with the VHB (If I remember correctly the spec was around 14 or 15 psi but go to the 3-M site and look it up).
If doing separate (relatively narrow ; 3/4 to 1" of VHB you can probably press the strips in to contact between the nubs of the diamond plate by hand which might work but you will likely not get good contact with the flexible panels between the raised nubs; I would measure the height of the nubs and verify that the VHB is at least as thick or thicker , (VHB) comes in several thicknesses, as I recall. then use, many, squares of VHB applied between the nubs in the diamond plate.
If the nubs in the diamond plate are much higher than the VHB is thick I'm not sure what you will do (you might want to call up 3-M and ask).
. ..definitely use caution applying a flexible panel to to the VHB to keep from damaging it when you press with the force required to bond it to the VHB that is stuck to the diamond plate.

..Hope it helps...

Enjoy!
 
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CoyoteThistle

Adventurer
I went with the flexible panels for the same reasons you listed plus the lighter weight. My results are mixed. A Suaoki panel off amazon went bad in under a year (the clear film on the outside of the panel degraded and started pealing and the efficiency of the panel approached zero). Other panel I got from Windy Nation (also on Amazon but they are local for me) is still going strong. No experience with SunPower though.

One thing to consider is that the efficiency of panels go down as they get hot. Don't know if adhering directly to an aluminum roof would tend to make the panel hotter?
 

Rando

Explorer
I have had two sets of semi-flex panels die. The first was an aluminum backed one that I had VHB'd to the top of my pop-top landcruiser. It died after a year or two with no apparent cause. That was a royal pain to remove. Second time I learned my lesson and didn't VHB tape the panels down, but VHB taped some 1" Al bar with studs to the roof of my FWC, then bolted two 120W panels to the studs through their grommets. Both panels lost half their cells in a hail storm. It was super easy to remove the panels, but I have been unable to find new panels with the same grommet spacing. So now I am back to a 160W rigid panel mounted to yakima tracks.

My advice - don't VHB panels to your roof.
 

shade

Well-known member
Everything I've read about flexibles indicates they don't last long compared to rigid panels. A lack of ventilation to the rear hurts efficiency, too. I've seen them mounted on hoods, which is probably the worst location for heat & impact damage.

3M Very High Bond tape is great stuff. Installed correctly, I think it may pull paint loose before releasing.

Flexies do look nice installed this way, though. For the OP's Khaya (congrats on that fine purchase, btw), I'd use a large residential panel in the 300W-400W range. Those are much more durable and efficient, and the roof of that camper is long enough for crossbars to be installed front & rear without shading the panel, if that's a concern. That's how I'm installing solar on my GFC.
 
Everything I've read about flexibles indicates they don't last long compared to rigid panels. A lack of ventilation to the rear hurts efficiency, too. I've seen them mounted on hoods, which is probably the worst location for heat & impact damage.

3M Very High Bond tape is great stuff. Installed correctly, I think it may pull paint loose before releasing.

Flexies do look nice installed this way, though. For the OP's Khaya (congrats on that fine purchase, btw), I'd use a large residential panel in the 300W-400W range. Those are much more durable and efficient, and the roof of that camper is long enough for crossbars to be installed front & rear without shading the panel, if that's a concern. That's how I'm installing solar on my GFC.
Thanks, I’m in Phoenix probably best to have some airspace lest they melt and slide off.

BTW, any recommendations of panel sourcing? Amazon doesn’t have much for brands other than Renogy. I pawed around the sticky but it’s a bit dated.
 

luthj

Engineer In Residence
I would still consider putting a bead of sikaflex or dicor urethane around the leading and side edges of the panel. Just as a belt and suspenders approach.
 

Pinnacle Campers

Chateau spotter
I was thinking about this the other day, wondering if you could put a thin layer of insulation between the panel and the roof leaving the perimeter to vhb/glue, etc.
Impact products (DIYvan) carries this thin layer of 3M thinsulate or use a closed cell foam, Landau, mincell, even a layer of foil bubble wrap to de couple the panel from the conductor.
 

luthj

Engineer In Residence
Insulating will reduce heat transfer to the roof/cab, It will make the panel hotter though. Flexible panels can have heat stress issues, so I am not sure if its a good idea. Though it may not have an impact.
 

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