There are many VHB tape variants, all have specific application objectives. I used 5952 based on the advice I got from 3M friends who worked in the Automotive Divison. It is a bit thicker, more adaptable to slightly irregular surfaces and slightly misaligned surfces (not quite parallel). It has a 91 psi tensile strength and very good shear strength.
Amazon.com: 3M VHB Heavy Duty Mounting Tape 5952, 1.5" width x 5yd length (1...
This is the recommended surface cleaner/adhesion promoter. Petroleum based solvents are inot appropriate, they interfere with the bonding process.
Amazon.com: 3M 111 Clear Tape Primer - Liquid Bottle - For Use With 3M VHB...
A very light sanding with 320 or 400 grit paper where the mounts attach is sufficient. Put the mounts on the oanel and put the panel in place. Blue tape around each mounting point, prep where the tape goes, don't forget the mount itself. Tape on the roof, roll with a J roller, remove backing film and place the panel. Press down firmly and let it sit over night. Remove the panel from the mounts and caulk all four sides of the mount/roof intersection with 3M 4000 UV adhesive/sealant caulk.
I used 12"x1.75"x3" aluminum angles at each corner. The angles were bent at 92° to account fot the curvatur of the roof and the width of the panels so the they sat flat on the roof and the flanges are parallel to the sides of the panels. The angle changes woth panel size. This gives me more than 6,500 pounds holding on each panel. I think a 6" long one in each corner would be sufficient.
I removed and repositioned one panel. It was an all day job, tape and caulk are very tough.
Do your energy balance math again. How much power do you use each day? What is the range between min and max? How much battery capacity do you have? Are you running an LP refrig or residential? Almost no one has sufficient battery or inverter capacity to run AC for any length of time so don't plan on it. For most with a residential refrig, typical use will be about 3200 watts per day +/- a lot depending on user. Without a residential closer to 1800 watts per day. Same +/- specs.
Back of the envelope numbers are 1600 watts of non tilting panels on the roof of your coach will get you about 3200 watts or more on 1/2 of the days of the year. A 1/4 of the year you will get an average of about 2,400. The rest of the year will average about 1600 watts per day. Where you are, what direction you are pointing, shade, clouds all make a difference. Solar panels mounted on a motorhome are not ideal. Tilting is dangerous, add more panels instead.
Leave room to get around on the roof for normal service and maint.
Panels in parallel are going to get you the maximum output especially relative to shade. Each panel should be fused. I used 8 and 10 ga UV rated solar panel cables for ech panel, run them down behind the refrig through the ref vent, through the floor to a fuse block then to solar charger. Output should be fused and switched to the batteries. At that end it should be fused as well.
Your panels can be 2-2 1/2 " off the roof (room for getting your hand underneath). Any shading due to AC covers is minimal at most during most of the year. When sun angles are so low that the AC cover's shade is an issue everything else will be worse.
I have 1200 watts now and will likely add 2 more 60 cell panels to get closer to 1900 watts and still have adequate access. They will add about 2 months to the time each year where we can be land line and generator independent. All bets are off if you get a week of rain.
If you don't have to do this now maybe us the coach for a year or so and learn how it works and you do in it. Good idea for almost everything.
Roger
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