Paisley777 said:
I too have an E150 with fiberglass top. I am looking to get the panels soon.
My questions is - why not just attach to the top? Clearly have to carefully seal the bolts, but other than that, why take the chance with adhesive?
While many fiberglass roofs do have some wood inside which can hold a screw pretty well, fiberglass itself is not so great a medium for retaining a screw.
My roof has some OSB strips sandwiched in between fiberglass which hold a screw OK.
To even come close to successfully getting a screw to hold OK in fiberglass, One MUST predrill the hole, and the drill bit diameter needs to be only a smidge smaller than the diameter of the screw used, minus the threads. Even predrilled with precision, the screw's holding power is not all that great. Ideally for both a water intrusion and for increased strength.......after the sheet metal or wood screw cuts its own threads in the predrilled hole in the fiberglass, it would be backed out and polyester sanding/finishing resin applied with a Q tip to reseal the broken frayed fiberglass, then the screw redriven in before resin gels. This will greatly strengthen the bite the screw has in the fiberglass. And the screw will still be able to be backed out at a later date after the resin gels, but one couls also apply and remove some carwax to the Stainless steel screw to ensure it can be backed out later easily, but honestly nothing really bonds all that well to stainless steel.
I have drilled and tapped my fiberglass roof for 1/4-20 machine threads, and when tapping, one must go slow and make sure the fiberglass cuttings are properly ejected by backing off and blowing them away and it is all too easy to strip the hole if one is not precise on the anglem, and goes very slow.
This was not for a solar panel install, but adding a 3rd brakelight which does not get really any stress on it as it is also glued, and only 1Cm high, if that.
I've also tapped thicker fiberglass rope saturated with epoxy and found the hold strength impressive, when the force was straight back but lateral stresses one could break the fiberglass by hand and rip the screw out if attempted.
I wound up using those threads and glassed in threaded brass inserts too, for maximum strength.
http://www.amazon.com/dp/B00207NF6W..._m=ATVPDKIKX0DER&pf_rd_r=1ZZS3BZ736GAZMYZYGVZ
These screws are pulling my fiberglass roof down to the metal over the windshield. The original conversion van company tried to get screws into this area and mostly failed, allowing the roof to flex way too much in this area, always breaking any sealant used, allowing in water and rust.
I roughed up the threads on those brass inserts and laid more epoxy saturated fiberglass rope around them. I never tried to get them to thread into fiberglass which is what one would have to do if intending to use them on a solar panel install on a fiberglass roof.
I went a bit overboard with the homemade fiberglass rope and epoxy as the rust had eaten so much steel that it no doubt compromised strength. now this area is ridiculously strong and no more issues with sealant cracking or water intrusion.
So Getting a screw to bite and hold in fiberglas is hardly impossible, but to do it right, requires some skills, and not just someone with a impact driver and self drilling Stainless steel screws, though this approach can work too, if performed skillfully and the fiberglass is at least 3/16 inches thick.
