Are there different types of peel ply ? It's my understanding that peel ply is used in in a wet layup to soak up excess resin and can easily be pulled away as witnessed here in one of Bob's videos at the 6:40 time mark... http://www.youtube.com/watch?v=wVQZy9AVxpY&feature=player_embedded#!
If the peel ply is being used as a hinge, how does it remain secure in the sandwich layup ?