Good Idea, Tyvek.
I see someone on line sells the 9' wide Tyvek for 3.50 per linear foot. That would be about $31.50 for 9 feet.
No seams! He says it is 1.85 ounces per sq. yd. so 3 yds x 3 yds = 9 yds. 9 x 1.85 = 16.65 ounces! and.... 9 x $3.50 = $31.50. Sounds very good. I carry a small scrap of Tyvek about 5x5 around in my pack for emergencies in the winter and it seems durable and I even put some grommets in the corners.
Thanks.....Jim
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Jim M