Let's Build Catapults!

I'm helping my husband teach a Physics class.  I know how to teach and he understands the physics--not my area.  We're going to start a unit on projectile motion with catapults.  You may want to make catapults, too!  They are a great means to teach some engineering.  Our lab next week is based on this projectile lab challenge.  We are focusing on both questions from the challenge and allowing our class to experiment with a variety of catapults using craft sticks, plastic spoons, rubber bands, protractors, marshmallows, rulers, and a glue gun.  This basic design has solid instructions.  This site has 15 more ideas for catapults.  Teach Engineering has a complete lesson for catapults with slideshows.  Make it a challenge!  BTW, the author of this catapult design created these for Cub Scouts.  Fun, right?