I made a cardboard tube sword (with dowel and foam core) to crush my nephew in our swordfights

Dowel running the length of it right down through the handle. Used string to compress the foam. Fed it into the tube and unwound so the foam expanded to wedge it in there so the tube can be replaced.

Next time I babysit I'm going to dominate the swordfighting... Once he admits defeat he can keep the sword