Do-It-Yourself Engineering

Get started on DIY project number two: use cardboard to build a tower capable of supporting a 100-pound gravity load and a 10-pound lateral load simultaneously. This exercise closely replicates problems faced by real-world skyscraper designers. In this lesson, use vector math to analyze the forces exerted on each structural element of the building.

Now that you understand the forces your cardboard tower must withstand, conduct a series of compressive and tensile strength experiments to determine the size and shape of your structure's beams, columns, and braces. After completing your design, build the tower using ordinary wood glue and simple tools. Then pile on concrete blocks and marvel at the strength of your creation.

Design and build an 8-foot beam bridge capable of carrying a swarm of pedestrians across a small stream. First, consider three alternative concepts, with beams made of identical wood, but of different configurations. Then develop these designs, analyzing their stresses and failure modes before selecting the optimum, building it, and inviting your friends onto the span.

Elegant and efficient, the suspension bridge is your next DIY effort. Span the same small stream as in the previous project, but support the deck with suspension cables draped between two 5-foot-tall towers. Analyze the flow of forces through the structural system before designing each element. A 3D computer model helps you plan this impressive project.

It may sound suspiciously like a lead balloon, but a concrete boat can be made to float. Your engineering challenge is to create a concrete sailboat that can operate safely in 10-mph winds. Hydrostatics comes into play in designing a hull with sufficient buoyancy, and aerodynamics enters the picture in designing a sail that doesn't cause too much heeling in the wind.

Build your concrete sailboat. Consider the enhanced strength of a concrete shell that has been formed into a curved shape - a feature exploited in many buildings. Then apply basic aerodynamics and vector mechanics to determine how the wind propels a sailboat - sailing with the wind, into the wind, and at right angles to the wind. Try out these points of sail with your model.

Who has not tied a paper cup to a helium party balloon to make a primitive airship? In this lesson, design and build a far more advanced version: a radio-controlled blimp that you can remotely pilot around your house. Calculate the volume of helium required to lift your blimp and its control unit, borrowed from a toy tank. Use two motor-driven propellers for thrust and control.

Start your project on fixed-wing flight the way the Wright brothers did: by building a wind tunnel. Use it to test different wing shapes at varying angles of attack, exploring the phenomena of lift, drag, and stalling. Your goal is to design a wing appropriate for a low-speed model plane, powered only by a few strands of rubber and flying without remote control.

Dig deeper into aerodynamic science so you can choose an airfoil shape and appropriate wingspan, aspect ratio, fuselage length, and stabilizer dimensions for your model plane. Pay special attention to aerodynamic stability and such factors as the dihedral angle of the wings, noting these features on full-size aircraft. Then build the airframe, using wood, tissue paper, and metal wire.