Jamison and his neighbor friend decided they wanted to make trebuchets for their fifth-grade classroom science project. What a great idea! That meant I would get to help.

After a bit of searching online, we found some plans for a simple, tabletop trebuchet on hilaroad.com/projects. The plans are perfect for a first build with limited equipment and skills. They are quite detailed and show almost everything you need to know.

A few helpful hints we learned the hard way:

• The pictures suggest the main pivot is a hollow tube. We started with 1/4-inch copper pipe but discovered the pipe was larger than 1/4 inch in diameter (the dimension is the inner diameter?) and it bent too easily. We had better luck with a 1/4-inch diameter, 6-inch long, hex-cap, machine screw.
• The holes for suspending the counterweight should be fairly close to the top of the sides. The lower they are, the deeper the slot needs to be to clear the arm. We’d put ours a little higher next time around.
• The notch at the end of the throwing arm needs to be sanded smooth to consistently release the sling. Make sure the metal hook on the loose end of the sling slides easily in and out of the notch.
• The narrow strips of duct tape, recommended by the plans to shape the duct tape into a pouch, kept our marbles from easily exiting. We had much better luck without them.

Maybe one more thing: your current trebuchet is never big enough. We’re already looking forward to designing and building a larger trebuchet to launch dirt clods into the green space behind our backyard.