What is stronger than campfire coffee and wider than the sky?Its a bond shared by Sisters on the Fly, a group of nearly 1,500 women ranging in age from 25 to more than 90.They are sassy women who love to decorate vintage trailers and go on cross-country road trips pulling their handiwork behind them.They share a love for fly-fishing, playing poker for pennies, cooking food in cast iron skillets, and telling tall tales around the campfire.Local author Irene Rawlings started to write a book about the sisters then fell in love with the group and became a member herself.I'm Sister No. 1322," Rawlings told 7NEWS. "It's been so much fun. It's like Girl Scouts for grown-ups."Rawlings said the Sisters are rescuing vintage trailers from fields, farms and ranches.We find them in junkyards and on the Internet, she said.The Airstream, Scotty and Shasta trailers hearken back to the golden age of trailer travel when Americans simply hitched up a trailer to the back of their jalopy, and went cruising across the country with the comforts of home in tow.Rawlings has completed her book, "Sisters on the Fly: Caravans, Campfires and Tales from the Road."She and Sister No. 1, Maurrie Sussman, who founded Sisters on the Fly with her real life sister, Becky Clarke, in 1999, will sign books and talk about the love of trailers and cross country sojourns.Several of the Sisters will have trailers on display Wednesday in front of the Tattered Cover bookstore on East Colfax Avenue.Guests are welcome to check out the décor inside and out.For more information on Wednesday's book signing for "Sisters On The Fly", visit www.tatteredcover.com.