Flexible solar panels on hardshell RTTs

[spressomon]

The relatively high surface energy of anodized aluminum and gel coat fiberglass makes for a great match using VHB. I used solid back 80/20 profile...to get as much surface bonding as possible. However, its all about the strength-to-stress ratio whether using solid back or slotted <80/20> profiles, relative to any bonding materials.

I did find this, this morning while perusing 3M VHB searches (see attached).

And, plenty of information here: https://www.3m.com/3M/en_US/vhb-tapes-us/

 

[spressomon]

My project.

 

[jellis]

Very cool! Do you have any closeup pics of the panel attachments on the camper? I've got a home-made pop-up on an M101A that I'd like to add some panels on.

 

[spressomon]

This photo was during initial mock-up & install a couple years ago. You can see the 80/20 base on the rear roof. The rear, after complete install, is the same configuration as the front PV panel system as shown. I wanted a mounting system that could be changed/adapted as needed/wanted downstream rather than bonding the SS vertical supports directly to the trailer's roof.

 

[e9999]

nice. And you used the double width 80/20 too so even more real estate to adhere. And good that you have a flat roof for that. No adjustable tilt yet, looks like. Why did you put in slides?

 

[spressomon]

Tilt is too complex for this set-up and not needed. 800w rated (4 - 200w panels) makes quick work charging the 500Ah LFP charged during non-shoulder months. If/when, I have a 170w Merlin to augment.

 

[e9999]

ah, double stacking. Clever!

 

[jellis]

This is wicked brilliant to use t-slot as the base, glad I asked for details I'm totally going this route!

Edit to add: Also the slider is so clever, why wouldn't you do that?!?

 

[spressomon]

^ it all depends on how much solar you need relative to roof real estate. Ideally I'd like to have another 400w for late & early shoulder months and/or less sun % days. I have room on the roof to add two long & narrow panels that would bring another 180w rated to the party.

 

[87warrior]

I had 3M VHB tape fail on me after 3 years.

This is how I installed the panel.

The flexible panel adhered over the inoperable sunroof on my 100 series. The tape failed on I70 coming into Limon, CO at 75mph into a 35mph head wind. The corner of the panel that was leading into the headwind came up and folded 1/2 of the panel over. It separated quickly and I damn near needed a clean pair of shorts when it let go and started slapping the roof. The 3M separated from the painted sheet metal, not the panel.

Obviously this was installed by myself, a DIY'er with a can do attitude. I cleaned both the panel and roof surface/sunroof glass with alcohol then covered the bottom of the panel with 1" wide VHB strips. I was surprised at how easily the VHB pulled up from the painted roof. It took a lot more effort to pull it off the sunroof glass and was almost impossible to remove from the Eternabond tape I have sealing the sunroof. I've since moved to a rigid panel that is bolted to the roof rack...

☝️The big crease in the middle of the panel is from me folding it over at the truck stop so it would stick to itself (and not to my luggage) when I tossed it in the back. The front passenger corner is where it lifted from the vehicle.

 

[jellis]

Wow, super scary!!!! Glad nothing and no one got hurt!!!

I suspect the direct application of the panel to the metal allowed the temp got too hot and degraded the tape. Spacing it a bit off the surface has the side benefit of increasing your panel efficiency.

Alternatively, maybe your clear-coat finally degraded and that's why it let go from the roof. I know mine is going bad quickly in that exact location.

 

[spressomon]

@87warrior what was the 3M VHB tape # you used?

FWIW, for the best performance with an application such as your's/our's/mine you need to seal the perimeter of the PV panel to the substrate (roof) to prevent water penetration, which over time, could degrade the adhesion 3M VHB tape.

 

[87warrior]

@jellis - It wasn't a warm day when it let go. I was headed to CO for snow skiing. However, it did sit through of couple of Midwest summers.
A bit of air gap would have probably helped with the panels efficiency (and possibly VHB adhesion), but it kept my battery topped off so I never gave it much thought.

@spressomon - I cannot locate my receipt for the VHB to verify the tape product #. All I can remember is it was about 1" wide and relatively thin, obviously not helpful information...
I did not seal the edges of the panel. What sort of product would you recommend to seal the edges from water ingress?

Edit: I checked the specs on 3M's site and believe the tape I used was #5925.

 

[e9999]

S, why do you think that exposure to some water can be so detrimental? That does not seem obvious.

 

[spressomon]

VHB is an adhesive not a sealant. Having said that I do understand 3M states VHB creates a waterproof seal. I can't locate the source where I learned about sealing the perimeter of the substrates when using VHB on mobile applications (methinks it was a marine site) but have not had an issue with any project using VHB tape for mobile applications since I started this practice. Whereas I have had VHB tape compromised when I didn't apply a sealant around the perimeter of the substrates. I have used 3M 5200 on the Escape project for sealing.

As with most things, selecting the proper adhesive/sealant for the intended purpose, substrate type & surface energy, temperature extremes, etc., is critical as is substrate preparation, cleaning, priming (if necessary), minimum 50F application temp, etc. VHB does have a shelf life too...

Edit: Sheesh, so much contradictory information out there on VHB. Here they say it is a sealant too:

@87warrior I wonder if the .6mm thin 5925 was too thin? The Merlin panel I have has enough texture to maybe require a thicker tape. FWIW, I used VHB 4959 to attach the 80/20 profiles to the fiberglass Escape roof (used 3M 5200 to seal the perimeter). Generally, 3M recommends using the thinnest tape for a given application so thicker isn't always better. But for substrates with undulations I think the 49XX series is more conformable.

 

[Tesota]

Before applying the VHB how clean was the surface? I've had panels on both my hood and a James Baround RTT for years without any issues whatsoever. They may as well have been bolted in place:

Panels on the hood after switching RTTs (if I had to do this over again, wouldn't bother with them though):