I host a science club for our homeschool group twice a month. Last week, the kids had a lot of fun building boats out of straws, clay, and aluminum foil.
Then, they competed to see whose boat could hold the most weight (as measured in washers and pennies).
After the initial test, we discussed why some boats were more successful than others and I gave the teams another chance to improve upon their boats.
Everyone declared it to be a lot of fun!