Introduction: Simple Sail Car
These lightweight racers are perfect for introducing students to some elementary physics concepts such as lift, inertia, and drag. Students can modify their design and method of propulsion to create the fastest car!
Step 1: Materials
Step 2: The Frame and Wheels
The frame can be any shape or size. I chose to make a lightweight frame in my example because it will have less inertia, which will make it easier to start moving quickly. It's also easy to build.
Like many of my other cars, the wheels are made by inserting a skewer into a straw, then fitting the wheels on the ends. The straw is taped and glued to the rectangular frame.
Step 3: Sail Supports
You can experiment with the position and size of the sail. Like the frame, I decided to keep it simple for the sake of demonstration.
Use craft cubes to support the vertical sticks.
Step 4: Designing the Sail
This is probably the most important part. I chose to make the sail by folding a piece of paper in half lengthwise, then folding a crease in the center to create a triangular shape. The pointed sail will help reduce drag by parting the air as it moves forward. It also has a large opening in the back that will easily catch the air.
This is by no means the most optimal design, but it is easy to make and effective.
Step 5: Safety, Tips and Troubleshooting
- Be watchful of accidental hyperventilation. If you see a student who is breathing in an out too rapidly, tell them to slow down and inform them that too much breathing can cause dizziness or fainting.
- Very minute obstructions can greatly affect the car's performance. If a car isn't working well, check for strands of hot glue, bent skewers (axels), or wheels that are pinching the straw.
- This is a fairly new project of mine, so please feel free to experiment and tell me how it goes.
Is it better to blow air through a straw to compress it? Or use a manual fan to rapidly blow gusts of wind at the car? Or simply blow air directly from your mouth?
I believe the answer is the latter. By blowing air directly from your mouth, you create a large stream of air. This air not only propels the car by pushing against the sail, but it also creates a tiny low pressure system. In other words, by simply blowing air from your mouth, you are removing air from that area, which causes the surrounding air to rush in and fill that space. The surrounding air that rushes around your air stream also contributes to propelling the car.
However you should allow your students to find out for themselves what works the best.