The nine year old boy in me wants one of these wooden catapults kits. They are historically accurate models using only wood, rope and leather. Pieces are joined by wooden dowels, not screws or nails. You only need white glue to assemble.
Would make a great project then you can spend the afternoon taking over castles.
Read more to find out where to get one of these.
You can get the Trebuchet Wood Kit from Flora and Henri for $43.