Bird Wings: Drag & Lift

Every year, there is a robotics game that involves launching “Drones” (Paper Airplanes) or shooting objects through the air. Suddenly, robotics students become Aerospace Engineers. We have to learn what birds know instinctively: Lift vs. Drag.

The War of Air Resistance

When an object moves through air, the air fights back. This is Drag.

• Form Drag: Being a brick. A flat plate has high drag. A teardrop has low drag.
• Friction Drag: The air sticking to the surface.

Birds (and planes) are streamlined to cut through the air. In FTC, we launch paper airplanes.

• If you launch it flat, it has high Lift but huge Drag. It goes up, stalls, and crashes.
• If you launch it like a dart, it has low Drag but no Lift. It hits the ground.

Tuning the “Flaps” (Trim)

Planes use flaps (Ailerons/Elevators) to change the shape of the wing. When we build a paper drone launcher:

1. Launch Velocity: We use rubber bands to accelerate the plane to 30mph.
2. Launch Angle: 45 degrees is theoretically best for a vacuum, but in air, 30 degrees is usually better.
3. Trim: We slightly bend the back of the paper wings UP.
   • This forces the tail down.
   • Which forces the nose UP.
   • This creates Angle of Attack, generating Lift.

The Knuckleball Effect

When we shoot round balls (like Wiffle balls), aerodynamics gets weird. If the ball spins Backwards (Backspin), it creates Lift (The Magnus Effect).

• Air moves faster over the top.
• Pressure drops.
• The ball floats upwards against gravity.

This allows us to shoot a ball flat across the entire field (30 feet) in a straight line, rather than arcing it like a cannonball. We manipulate the air to fight gravity for us.