How many times do I wrap the rails with fiberglass?
Standard glassing schedule is 2 layers on the deck and 1 layer on the bottom. Although you can laminate any number of layers you want to increase board strength.
You'll have 2 1/2 "laps" of fiberglass around the rail of the board. One from the bottom to the deck, one from the deck to the bottom, and 1/2 a lap on the deck to the midpoint of the rail.
Overlapping the fiberglass on the rails provides great strength and snap resistance as well as stiffens the board.
You can vary the length of the lap (how much fiberglass runs from the rail towards the stringer) to increase stiffness or reduce weight of the board..
The lap from the bottom to the deck is usually about 1 1/2" - 2" long... the deck to bottom lap is normally a bit shorter (around 1") on shortboards.