VHB solar mount preparation in the face of Tropi-Cool paint

[chrisstratton]

I'm considering mounting 100W solar panels using VHB tape to the fibreglass roof of my shuttlebus. We also want to paint the roof. Will's method is to stick the panels to the stand-offs, then mount the standoffs to the roof, and that makes sense as things should align well.

IF I paint the roof first, what might constitute good prep for the "feet" of the panel stand-offs? Could I use an angle grinder with abrasive/flexible pads?

Also - Will has suggested tying the panels together with paracord, which seem sensible, in the event of a possible adhesion failure (I'm sure we'd hear the first one banging around like a kite with rabies, then pull to the side of the road). Does anyone have a photo of doing this "securing panels with cord" as I'm considering what might be a reasonable way to do this.

It is looking like VHB 5952 1.1mm tape, plus "111" adhesion promoter for prep? Yes/No/Maybe

Finally, I saw someone suggest putting extra panel mounts on the leading edge (nearest the front of the bus) to mitigate the stronger wind turbulence there. Any thoughts on this? Also -

 

[chrisstratton]

I would not use tropi cool on your roof, it is silicone based and nothing will stick to it. This is discussed in depth on RV forums and is considered the cheap way out. A better product would be a 2 part liquid EPDM rubber. I used this product on my last RV and it worked great - /www.epdmcoatings.com/liquid-roof.php

Thank you for the suggestion. I'll consider it. BTW - I don't think VHB tape will stick to EPDM either? Do you have a link to the RV discussions?

 

[HRTKD]

Thank you for the suggestion. I'll consider it. BTW - I don't think VHB tape will stick to EPDM either? Do you have a link to the RV discussions?

You wouldn't want to put VHB on EPDM anyhow. The panel would lift the EPDM off the subsurface. The glue holding the EPDM down is (usually) good enough to hold down the EPDM, but not much else.

If the fiberglass roof is in good shape, I wouldn't touch it. VHB on fiberglass is OK. I'm not a fan of it, but it should work. My preference is to have every panel mount bracket firmly attached to the roof's trusses or rails with a fastener. In the case of using VHB tape, every panel needs to have a metal safety cord attached to it with the other end securely attached to the roof. Paracord is not acceptable in my opinion.

 

[chrisstratton]

Thanks. I have been wondering about a ss cable, as it seems likely the pars cord will age given time and exposure. And, I think all panels, VHB or not, should be secured with a safety/secondary cable.

 

[chrisstratton]

Interesting about not painting the roof? Why not?

 

[HRTKD]

A good fiberglass roof shouldn't need it. The paint adds more weight, (slightly) changing your center of gravity. It's a pittance compared to all the solar panels that are going up there, but still.

To properly paint a roof, you need to remove all objects on the roof first, remove any residual sealants, then paint, then reinstall the objects and reseal. That's a buttload of work.