What Fabric Is This

It's likely to be 2oz PU coated nylon – but with a CRISP coating. [PU fabrics bave two possible coatings – soft and crisp).

If the fabric looks like it has a grid on it then it will be RipStop

Polyester doesn't tend to rustle/crackle. Spinnaker cloth feels much thinner than paper.

Remember that spinnaker cloth is many times the price of PU , will be RipStop and it's unlikely to be anywhere outside of specialist stores.

this stuff is super thin and very light. However, if it is PU, is this useful in outdoor (tarp) situations?

Yes,

I use crispy PU for tarps and groundsheets. It's excellent for tarps and pasasble for groundsheets.

If it's spinnaker then it will stretch a little if strongly encouraged. Nylon doesn't tend to stretch or tear.

Either way, it's likely to be 2oz or under per square yard.

If you are buying it to experiment with then consider that it might be worth paying $2-3 yard just to have a play.

It's not worth getting hooked on "is it or isn't it spinnaker". Instead consider is it light enough for what you want, is it strong enough and is it waterproof enough. Think about function.

well I bought it last night from wal-mart for $1/yd. Thanks for the help mike!

I always feel funny trying to blow or suck air through fabric at Walmart.