Tropicool vs VHB - rooftop solar panels

[shaymcquaid]

Originally Posted by Bon Voyage

If I were you I’d rethink the tropicool. I have it on my bus and it holds dirt badly so it’ll always dirty looking after any rain etc.. and yes nothing sticks to it. I put a sunroof in which is a piece of clear plastic and sealed it down over the tropicool - it leaks so when it rains because the silicone doesn’t stick. now I have to pull the plastic off scrape the silicone and tropicool off then paint white and reinstall the sunroof. It also leaks at my plumbing vent through the ceiling. One of 2 or 3 big mistakes I made on mine was that tropicool. Just paint it white instead, it’s cheaper and easier

THIS.
I too regret Tropicool. Its sucks. Just don't.

[baipin]

Like someone else said, Tropicool has silicone in it, which will prevent all sorts of materials from adhering to it. The problem with chemical vs mechanical adhesion (VHB vs bolts, respectively) isn't even the tensile or shear strength of either medium. In the case of chemical adhesives, it's the sheer amount of engineering that has to go into figuring out of one surface will affix to the other surface, sufficiently, with VHB. That requires a lot of knowledge about the chemistry involved, the ability to properly clean each surface, and so forth. There's just waaaay too much going on there for an average person to do with any modicum of safety and the ability to say "that is a properly engineered connection". The result of failing that is killing people driving behind you. Not a good risk to take when you could just use bolts that are guaranteed to hold any number of materials down, with known torque, shear, and tensile values that make the strength of your connections objectively verifiable to the average person.

[BeNimble]

Sailors know that 3M 5200, a polyurethane glue, is a permanent glue that just does not come off. It is like spray foam but super dense.

Using 5200 you can glue steel rails to a steel bus roof and they will not come off, that is the downside here, never going to get them off if you change things later.

They key is maximize surface area, like how buses are riveted with millions of rivets to maximum adhesion, and how you glue wood by spreading the glue over the entire area, not just a dab here and there.

And with any adhesive, you need clean surfaces, a surface with silicone on it, nothing is going to stick.

You don't want wind getting under solar panels, yet you need air gap to let them cool, so it takes some thought, this applies to bolting as well.

[LargeMargeInBaja]

'My brackets attach to the bus with adhesive tape'.
Nope.
Your tape attaches to the paint.
The vehicle or the Brooklyn Bridge or anything else under the paint is irrelevant.
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Your expensive essential photovoltaic panels need mechanical connections such as stout bolts through stout girders secured by stout bolts through the vehicle cross-members.
'Stout bolts through the vehicle cross-members' is different than 'screws into sheet-metal'.
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Some flexible photovoltaic panel-sheets are engineered to attach with adhesive.
Unfortunately, sunlight cooks their efficiency.
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A stand-off of an inch or three allows air circulation, and is said to increase efficiency.
This's the way I engineered my panels, and they are well-into more than a decade of bashing up rough logger tracks, trundling through rivers, and a lot of substantial breezy weather.
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My bolts will last for years.
What is the shelf-life of tape (I have an image of crumbling painter 'mask' tape after a few days in direct sun on a hot roof)?