RV curved roof mounting...

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
840w Battery Backup array
640w camper array
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  • littleharbor2
    littleharbor2 Solar Expert Posts: 2,095 ✭✭✭✭✭
    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.

  • BB.
    BB. Super Moderators, Administrators Posts: 33,599 admin
    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
  • littleharbor2
    littleharbor2 Solar Expert Posts: 2,095 ✭✭✭✭✭
    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.

  • 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
  • mike95490
    mike95490 Solar Expert Posts: 9,583 ✭✭✭✭✭
    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


    Powerfab top of pole PV mount | Listeroid 6/1 w/st5 gen head | XW6048 inverter/chgr | Iota 48V/15A charger | Morningstar 60A MPPT | 48V, 800A NiFe Battery (in series)| 15, Evergreen 205w "12V" PV array on pole | Midnight ePanel | Grundfos 10 SO5-9 with 3 wire Franklin Electric motor (1/2hp 240V 1ph ) on a timer for 3 hr noontime run - Runs off PV ||
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  • littleharbor2
    littleharbor2 Solar Expert Posts: 2,095 ✭✭✭✭✭
    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.

  • Estragon
    Estragon Registered Users Posts: 4,496 ✭✭✭✭✭
    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