Aluminum angle iron and VHB tape to mount a solar panel to an Econoline roof?

FarmerFrederico

Adventurer
Question is in the title. I'd like to avoid mechanical fastening if possible. My only other consideration is to use a gutter mount rack.

Thanks for any input you can provide!
 

broncobowsher

Adventurer
I can see that working. Real VHB is really good stuff. To the point the weakest part is the strength of the paint sticking to the vans roof.
 

Bbasso

Expedition goofball
I think the mechanical attachment points might be easier to repair then the tape, that stuff sticks and stays stuck.
 

FarmerFrederico

Adventurer
I originally was thinking about an inexpensive way to get some stuff up on top of the van with the idea that I'd get a pop-top in the future, but the pop-top will be a long way off now - if ever...maybe to improve my ability to change stuff in the future and make things as modular and trouble free for myself or a future owner, I should just get a gutter mount rack. Will cost more right now but probably pay for itself in flexibility down the road, don't you guys think?
 

luthj

Engineer In Residence
If your paint is in good shape VHB tape works very well. Another option is sikaflex 252 to bond the brackets. I have successfully used sika 252 on several rooftop applications. For extra security a sheetmetal screw can be used during application of the bracket. Cover the head with sealant. You need to size the bracket and bond area for the load you are supporting. Ideally you would locate the brackets above a roof support beam or near the edges of the roof where the metal is stiffest.

For very heavy loads (or just really secure mounting) Set a rivnut into the roof. Then bond AND bolt the bracket to the roof. It will never leak, and is very strong. Do not over tighten the bolt as the sikaflex needs to have a certain minimum thickness for optimum bond strength.

IMG_20160530_123633 by J Luth, on Flickr

IMG_20160530_123624 by J Luth, on Flickr
 

FarmerFrederico

Adventurer
Even though I think I'm making up my mind for a gutter mount rack for optimum flexibility for myself and a future owner down the road, this thread could help someone else. For what it's worth - my intention was to consider the aluminum angle iron and VHB tape for 1-2 panels with dimensions roughly 40"x40" and to mount this at the leading edge of the roof, very close to the windshield on a lifted E350. Would forces from wind at 80mph be something to consider with that placement?
 

luthj

Engineer In Residence
Assuming you size the VHB patches correctly, and that the panels are no more than a couple of inches from the roof, you don't have anything to worry about. The windshield actually pushes the air up and away from the roof, so at speed there isn't much of a "wedge" affect on the panels leading edge. You do not want the panels to extend past the roofs leading edge and over the windshield, as this can create much larger aerodynamic forces, and may substantially impact fuel economy.
 
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huskyhauler

Adventurer
Assuming you size the VHB patches correctly, and that the panels are no more than a couple of inches from the roof, you don't have anything to worry about. The windshield actually pushes the air up and away from the roof, so at speed there isn't much of a "wedge" affect on the panels leading edge. You do not want the panels to extend past the roofs leading edge and over the windshield, as this can create much larger aerodynamic forces, and may even impact fuel economy.

Some of the air will be pushed up and over, but it won't be a dead zone by any means. I had a yakima roof rack mounted 3.5 inches from the windshield of my commuter car and it caught A LOT of wind. It created so much drag my average MPG dropped from 32 to 28 in a four-banger and the wind noise it generated was really, really really loud.

The solar panel would have to be nearly flush mounted with some sort of air dam between it and the windshield to truly deflect air up and over the unit. Anything otherwise would cause it to split the air above and below it.

Take a look at this wind tunnel test of a van. https://youtu.be/oMsg8KorxJA The only true dead zones are just behind the vehicle, or in pickups, in the bed of the truck by the cab with the tailgate down, or in the whole of the bed with the tailgate up. Even then, they aren't true dead zones as the air still swirls, just not as fast as the air flowing over those pockets, or dead zones.

Even though I think I'm making up my mind for a gutter mount rack for optimum flexibility for myself and a future owner down the road, this thread could help someone else. For what it's worth - my intention was to consider the aluminum angle iron and VHB tape for 1-2 panels with dimensions roughly 40"x40" and to mount this at the leading edge of the roof, very close to the windshield on a lifted E350. Would forces from wind at 80mph be something to consider with that placement?

Personally, that would cause me a lot of anxiety. I would be worried about hitting a pothole at speed or large gust of wind at speed.

Also, if you are looking for a non-permanent solution this isn't much better than simply bolting it to the roof. The tape will be very difficult to remove without peeling your paint off. For non-permanent I would go with a gutter rack. Plus, with the rack you can always mount for stuff up there, or use the rack as a tie down point for an awning or a windscreen sidewall or similar.
 
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