Well folks, all of your projects convinced me I should try my own 4-season tarp, so I'm waist deep in it now but concerned I may have botched it a bit. I know nothing about thread injection, but saw Mr. Littlefield's guide on stitches out on the DIY Gear Supply site, so was attempting to use his Flat Felled / French Seam hybrid for my ridgeline.
First stitch was easy enough, and the 2nd one went OK but not great...started to get out of whack a little. That 2nd stitch, and the difficulty of working with silnyl in large quantities set me up for troubles with the 3rd and final stitch. In short, there are places where the fabric isn't pulled tight between the 2nd and 3rd stitches.
My concern is that when the tarp is setup and stretched, in those places where the fabric is bunched a little, all the stress will be on that 3rd seam instead of the 2 seams working together as they would if the fabric was stretched tight between seams, and that will cause it to rip just enough to leak.
So what do you guys think? Are my concerns well-founded? Should I rip out those seams and try to do them over? I'm thinking maybe seam-sealer would plug the holes left by the old seam, if I did need to go that route?
I just want to make sure I'm doing it right so I don't find out in a downpour or heavy winds that my creation isn't all that sturdy or water-tight.