Your best bet would be to look at the kind of holes in the sails to figure out the material they're made of.
What material can a hole be made of :?
Have you been watching Abbott and Costello again?
I'll just go with canvas I guess then. The holes look like a result of some standard shot mixed with grapeshot.
What's the guy's name on first base? What's the guy's name on second base. I'm not asking you who's on second. Who's on first. I don't know. THIRD BASE!
Anyway . . . . lol Canvas it is.