RV curved roof mounting...

Terry
Terry Registered Users Posts: 3 ✭
in Caravan, Recreational Vehicle, and Marine Power Systems #1
My new RV has a curved roof, and I have 320w panels with "Z" type mounting feet with 3 holes for roof mounting. They recommend using "shims" on curved roofs. I assume all hardware should be stainless, so what would you use for shims to compensate for the curve?
Thanks
4.8kw Grid Tied Array
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640w camper array
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  • littleharbor2
    littleharbor2 Solar Expert Posts: 2,113 ✭✭✭✭✭
    #2
    I'd use aluminum to shim between the panel frame (aluminum) and the Z bracket. I see no reason to have to use stainless shims.

    2.1 Kw Suntech 175 mono, Classic 200, Trace SW 4024 ( 15 years old  but brand new out of sealed factory box Jan. 2015), Bogart Tri-metric,  460 Ah. 24 volt LiFePo4 battery bank. Plenty of Baja Sea of Cortez sunshine.

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  • BB.
    BB. Super Moderators, Administrators Posts: 33,626 admin
    #3
    Be aware that stainless steel bolts and nuts can be an issue... Depending on the grade of SS, Stainless on Stainless threads tend gailing and binding (and lock, you will twist/snap the bolt before the threads give-way). Better to use Stainless and Brass, or Brass on Brass... If still using stainless sets, use anti-seize compound on the threads.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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  • littleharbor2
    littleharbor2 Solar Expert Posts: 2,113 ✭✭✭✭✭
    #4
    Not to say that doesn't happen but from my experience I've found very few stainless bolts that have seized , probably less than 1% of the many thousands of bolts on old arrays I have dismantled. When they do, you definitely will end up snapping  or having to muscle them to get them apart.

    2.1 Kw Suntech 175 mono, Classic 200, Trace SW 4024 ( 15 years old  but brand new out of sealed factory box Jan. 2015), Bogart Tri-metric,  460 Ah. 24 volt LiFePo4 battery bank. Plenty of Baja Sea of Cortez sunshine.

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  • Terry
    Terry Registered Users Posts: 3 ✭
    edited December 2019 #5
    Thank you for the reply's.
    littleharbor2: That makes sense. But exactly what would these shims, apparently designed to apply a tilt to match the roof curve, and maintain a solid connection look like? Are there washers that gradually become thicker across their diameter?
    BB: The panel mounting hardware is supplied with the Z Feet, but nothing that looks like a "shim".
    4.8kw Grid Tied Array
    840w Battery Backup array
    640w camper array
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  • mike95490
    mike95490 Solar Expert Posts: 9,583 ✭✭✭✭✭
    #6
    leveling washers:


    Commonly called beveled washers, these are tapered to fit inside an I-beam's flange to provide a parallel bearing surface.

    18-8 stainless steel washers have good chemical resistance and may be mildly magnetic.

    Hot-dipped galvanized iron washers are corrosion resistant in wet environments.

    Aluminum washers are lightweight and corrosion resistant in wet environments.


    https://www.mcmaster.com/standard-washers


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  • littleharbor2
    littleharbor2 Solar Expert Posts: 2,113 ✭✭✭✭✭
    #7
    Terry said:
    Thank you for the reply's.
    littleharbor2: That makes sense. But exactly what would these shims, apparently designed to apply a tilt to match the roof curve, and maintain a solid connection look like? Are there washers that gradually become thicker across their diameter?
    BB: The panel mounting hardware is supplied with the Z Feet, but nothing that looks like a "shim".
    We may be thinking differently as to the application of the mounting hardware. I'm visualizing straddling the curved surface with the panel and mounting the z brackets along the two edges that would be parallel to the roof. The shims would just make the z brackets a little taller, keeping the frame from actually hitting the roof surface at the peak of the roof. That was your issue, I thought.  If the direction your panel is mounted at would put the long sides of the panel doing the straddling I would add an extra bracket of some type on either side of the panel where it spans the peak. 

    2.1 Kw Suntech 175 mono, Classic 200, Trace SW 4024 ( 15 years old  but brand new out of sealed factory box Jan. 2015), Bogart Tri-metric,  460 Ah. 24 volt LiFePo4 battery bank. Plenty of Baja Sea of Cortez sunshine.

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  • Estragon
    Estragon Registered Users Posts: 4,496 ✭✭✭✭✭
    #8
    I've used scrap bits of composite decking as shims.  It's UV stable, doesn't corrode or rot, and is pretty easy to work with common woodworking tools.  
    Off-grid.  
    Main daytime system ~4kw panels into 2xMNClassic150 370ah 48v bank 2xOutback 3548 inverter 120v + 240v autotransformer
    Night system ~1kw panels into 1xMNClassic150 700ah 12v bank morningstar 300w inverter
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