keder welt for tarp

That sounds like a good approach! And the HD poly should hold up for a long time. But if it does ever wear out, you could just remove the keder and put it on the next one. That keder welt is seriously tough! You could remove the stitches (especially if they're a little longer) or even just cut it off and stitch it on to the next tarp. What type of sewing machine are you using? 

Re home sewing machine, if it's early 1970s or older, definitely up the task (metal parts, motor quality, etc.) If it's newer, it depends on the machine. In general though: #14 or #16 needle depending on the fabric, longer stitch and slower stitch. If you run a "not up to the task" machine too fast over thickness (ex seams folded over) it can throw off the timing. Only an industrial machine should be run fast over thick fabrics. You can use a heavier duty thread as well, but for this purpose it doesn't need to be seriously heavy. For a tarp, there are a variety of fabrics that will work nicely and that most reasonable-quality home sewing machines can handle. Another tip is to avoid folding hems twice, to reduce the thickness. You can buy (for reasonable prices) fabric samples from Sailrite.com and from SeattleFabrics.com   I know there are other vendors as well, these are the two I'm most familiar with. Hope that helps! 

Curious to see how this works out - can you post finished results once the tarp is done? Also interested to know what you use for fabric (and if it can be sewn with home sewing machine)