martin17773 said:
ghcoe, for the interested public, can you provide a quick idea of this added, solar panel supporting structure?
Yes. The simple way is to embed a 1"x2" or 2"x2" into the roof at attachment locations. I have not done this yet myself, but plan to in the future for not only solar panels, but also for a roof rack.
So for most people the idea would be to channel out the foam just slightly larger than the lumber being used. Ideally I would channel wide enough to have the side walls support the lumber, but not channel all the way to the roof edge. This would make for a cleaner roof edge when canvasing, but the channels could extend to the edges for simplicity. A hot wire setup would be ideal for this, but a circular saw set at the proper depth with a few passes would work as well.
Then take the lumber being used for embedding and screw some scrap 1x2's to one side of the lumber. These scraps will lay across the top of the roof to hold the embedded lumber flush with the roof line during glue up. I would do these at least one on each end and one in the middle of the embedded lumber. More if needed to keep the lumber completely flush across the roof line.
Now there is two ways to do the glue up. If you use Great Stuff, I would place the lumber into the channel and then spray into the channel on each side of the lumber to fill the voids. Some weight will need to be applied to the lumber because great stuff may try to push up on the lumber in the channel. Once dry unscrew the lumber pieces used to hold the embedded lumber flush and remove. Then take a razor knife to cut back the Great Stuff that has expanded out. Then you can sand smooth to the roof line. If there is still some voids use Dap Light Weight Spackle to fill and sand smooth.
If you choose to use caulking. Fill the bottom of the channel with liberal amount of caulking. Enough so that when you install the lumber you are embedding that the caulking will squish up the sides of the lumber a bit. Once the lumber is installed finish filling what might need to be filled on the sides of the embedded lumber. The idea with caulking is that you don't want it to come out above the roof line. You want it to be slightly below the level of the roof. Once the caulking is dry, it will take a long time, remove the lumber used to hold the embedded lumber flush. Then fill the slight void you left up with Dap Light Weight Spackle and then sand smooth. You are now ready to canvas.
The reason why we don't want caulking up to the surface is because it is difficult to sand. The Dap Light Weight Spackle has a similar sanding consistency to foam.
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