The Whirlwind Quilt Block goes by a bunch of other names - Modern Envelope, Twin Sisters, Water Wheel, etc, etc. The traditional Whirlwind quilt block uses only 2 colors but I saw one on Facebook that had 4 fabrics and wanted to figure it out for you (and me)! I'll show you 2 different ways to sew this block together and talk about another way that I've seen online.