I have made a recurve bow but would like to someday build a crossbow also. My questions are for any experts on the forum.

1. Why is it necessary for crossbows to have so much more pull weight than longbows, recurves, flat bows etc.? Example: 150 lbs. verses 50 lbs.

2. When I build the crossbow I intend to use laminations of wood and fiberglass, instead of spring steel as shown in Sir Ralph Payne-Gallwey's excellent work. " The Crossbow : Its Military And Sporting History, Construction and use". What I need from the pros is a chart showing the right combinations of wood, and fiberglass thickness to make a bow of 150 lbs. draw weight. If you have a draw weight chart for crossbows that would be great. Thankyou John