PVC pipe is one of those ordinary construction materials that is cheap to buy, readily available and easy to work with. You can cut it, paint it, drill it and glue it easily.
Goat’s Foot Lever. Two claws hook around metal lugs that stick out from the side of the stock. By pulling on the lever, the claws slide along the posts and pull the string along with it. This way he ca shoot a bolt once every 12 seconds.
Spanning Lever (Gaffle or "Goat's-Foot" Lever) Date: late 15th or first half of the 16th century Culture: Western European, probably Spanish Medium: Steel Dimensions: L., extended 19 5/8 in. (49.8 cm); W. 2 13/16 in. (7.2 cm); Wt. 25 oz. (713 g)
Fig. 43. - How the Goat's-Foot Lever was Applied to Bend a Small Crossbow.
Fig. 44. - The Mechanism of the Goat's-Foot Lever. Half Full Size
reinforced PVC crossbow with laminated stock
How to make a Crossbow - PVC Crossbow - All
50 lbs PVC Crossbow
This has the easiest design for a trigger and seems to be a really good design for a crossbow.