I handed out the project description 2 weeks before attempting it in class together to allow for catapult construction at home. That may have been my 1st mistake (more on that later). A week before the project, students brought in their catapults for a show-and-tell of sorts. The idea was to test the catapults and make any necessary revisions. I had at least one group break their catapult on testing day.
On Day 2 we took our catapults and our calculations to the proving grounds. Originally I hoped to use my classroom but some of the catapults had more lift than I anticipated. When raised the 100 some odd centimeters to the table they hit the 10 ft ceiling.
Only one of the catapults was able to hit the paper plate target. Next time, I plan to go for a target distance rather than an actual target. I think there would be a lot more student success and a lot less frustration from all of us.