I make a huge PVC frame and covered it with 2 large cheap tarps last winter. It tore itself apart in the wind and damaged my gelcoat in several places. The marina had to remove it for fear of it toppling the boat (and the other "dominoes" nearby). I did a thorough write-up on it and many other people chimed-in with their designs. See the thread here:
http://www.sailnet.com/forums/gear-maintenance/50405-completed-inexpensive-pvc-frame-cover.html
Regards,
Brad
http://www.sailnet.com/forums/gear-maintenance/50405-completed-inexpensive-pvc-frame-cover.html
Regards,
Brad