So I found myself rummaging through the bargain bin in walmart and picked up about 10 yards ripstop. It is some nice light stuff. I'd say around 1.5oz weight.

I did a little water test. I simply poured some water onto the fabric and created a little pouch. After squeezing the pouch pretty hard the water began to bead through. I am guessing this is not silnylon?

Would this work for a tarp? It seems to not allow water through without force...

Regardless I can find some use for it. Perhaps a gathered end hammock..