I do recall some were plywood in the 60's, which he drew easy to build plans for originally. The first fleet was in the Chesapeake, then the class really took off!
By 1941, one of the bigger fleets was already on the west coast.
I'm not sure when the first glass hulls arrived, but here's some history I found. Penguins are still actively racing. Nice.
http://www.penguinclass.com/IPCDA_Handbook/IPCDA_history.pdf