Boomilever

The inspiration:

Our boomilever project is inspired by the Science Olympiad boomilever contest. For the Science Olympiad event, contestants design and build a truss cantilever, or "boomilever", out of balsa wood or basswood, according to certain specifications (for example, the length of the structure must be between 40 cm and 45 cm). One end of the structure is hung from a wall hook. The other end has a hook from which a weight is suspended. The contestant is judged by the ratio of the maximum weight their boomilever can support to the weight of the boomilever itself.

The project:

We modified the Science Olympiad rules so that students could build and test their boomilevers at home. They were supplied basswood sticks and glue, and a 2 lb bag of sand to serve as the weight that their boomilever had to support. Students uploaded pictures or videos showing themselves testing their boomilevers, and calculated the total length of basswood used in their designs - the less material used, the better.

Boomilever design:

Long skinny structures like the basswood sticks used to make boomilevers behave differently under different kinds of forces. They are relatively strong under tension, that is, when they are stretched. They are weaker under compression, and tend to buckle. (You can observe buckling in a straw: hold the two ends and push inwards.) 

When a weight is hung from the end of the boomilever, the lower, horizontal sticks are compressed, while the upper, slanting sticks are under tension. The sticks that are under tension can be safely left alone, but the sticks that are under compression must be stiffened in some way.