A common project for physics or engineering high school classes is the construction of a strong and stable structure. Often, the project requires students to build a structure as light as possible or using as few materials as possible that can also hold a heavy load without collapsing. While different projects will allow different materials to be used for construction of the structure, the same basic principles can be applied to any structure to make it strong and stable. Using the properties of geometry, you can build a strong and stable structure for your school project.

Purchase balsa wood beams that are 1/8-inch by 1/8-inch. Balsa wood has the lowest weight to strength ratio, which means it can be used to build a strong structure with relatively few materials and little weight.

Make an equilateral triangle out of balsa wood beams to construct the base of the structure. Make 60-degree angle cuts at each end of the balsa wood beams. This will form the correct angles for an equilateral triangle. Glue the pieces together with a small dab of wood glue.

## Sciencing Video Vault

Sketch one side of your structure on a piece of poster paper. Make sure that the dimensions of the tower meet the height restrictions of your project. Begin by drawing the two primary support beams that run the height of the tower and connect to the base at a 70-degree angle.

Connect the two primary support beams with straight lines (which will become your secondary support beams) every 3 inches.

Sketch a brace beam from the top left corner to the bottom right corner of each quadrilateral formed by the intersection of your primary and secondary support beams. This will create two triangles that brace each secondary support beam. Triangles are the strongest shape in geometry, and have the best strength-to-weight ratio for your structure.

Lay balsa wood beams over the lines of your sketch and cut each beam to match the dimensions of your blueprint. Glue each juncture together with a small dab of wood glue.

Construct a total of three sides for your structure using the sketched blueprint.

Affix each side to your triangular base with a narrow bead of glue. Hold the sides to each other and to the base while the glue dries.

Test the integrity of your structure by applying a small amount of weight to the top. If you notice any shearing (bending or twisting of the structure), support the area with additional triangular support beams.

#### Tip

Cut your balsa wood beams with sawing motions rather than with pressure. Pressing a sharp edge into the balsa wood will compress the wood fibers and reduce the overall strength of the beam. Sawing motions will cut the wood cleanly.

If your structure is only slightly over the weight limit, sand your structure to remove some excess weight. Any joints where glue is visible will be particularly good to sand, as the glue is the heaviest component of your structure.