Day 4: Wind Tunnel
Welcome to the Wind Tunnel Lab.
There's a clear plastic tube standing over a fan at the front of the room. The fan blows air straight up. Objects you drop into the tube either float, climb, spin, fall, or wobble out of control. Today you figure out why — by building things, testing them, and changing one variable at a time.
The setup is simple — but how you use it matters.
- A 20-inch Lasko fan sits on the ground, blowing air straight up.
- A clear plastic tube — 18 inches wide, 4 feet tall — is held by one of your teammates above the fan.
- Your partner raises and lowers the tube to control the gap between the fan and the bottom of the tube. That gap is where you place your flying object.
- Partner holds the tube up, opening a gap above the fan.
- You place your object in the gap, in the air column above the fan.
- Partner lowers the tube — the air column tightens around the object and lifts it into the tube.
- Together, you adjust the tube's height to find the sweet spot where the object floats stable.
The tube's height above the fan is one of the variables you'll experiment with all day. Higher tube = more open air, weaker column inside the tube. Lower tube = tighter, more focused airflow. Different objects want different gap heights.
- Lift — the air pushing up on your object
- Gravity — pulling everything down
- Drag — how much the object catches the air (more surface = more drag)
- Balance — whether the object's mass is centered or tipped
You won't memorize these. You'll feel them. Every test you run is one of these four forces winning or losing — plus the gap height your partner is controlling.
Before you build anything complicated, test simple things first. Get a feel for how the tunnel responds.
- Paper (printer, tissue, kraft)
- Cardstock and lightweight cardboard
- Foam sheets
- Coffee filters
- Plastic wrap, cellophane, plastic shopping bags
- Tissue paper, kraft paper
- Drinking straws
- String, tape, glue
- Paperclips, washers, pennies (for adding weight)
- Pipe cleaners
- Scissors, ruler
- Small scale for measuring mass
Pick up a coffee filter, a piece of tissue paper, a flat sheet of printer paper, and a small paperclip. One at a time, place each one in the gap between the fan and the tube while your partner lowers the tube to catch it. Watch carefully.
On your 📋 Wind Tunnel Field Notebook, predict before each test, then record what happened:
- Did it float, climb, sink, or shoot out the top?
- Did it stay stable or wobble?
- Where in the tube did it settle (if anywhere)?
- What gap height worked best — partner holding the tube high, low, or in between?
Take two identical pieces of printer paper. Crumple one into a tight ball. Leave the other flat.
Test both — separately — in the same gap. Same material, same mass. Different result.
Record both results. Then ask your group: What does this tell you about what actually matters in this tunnel — weight or shape?
Now design something on purpose. The goal: control what your object does in the tunnel — not just guess and hope.
Pick a design to start with. A few ideas — but don't feel limited:
- Mini parachute — coffee filter or plastic bag + string + a small weight
- Paper cone — flat sheet rolled into a cone
- Spinning paper helicopter — cut a paper strip with two angled "blades"
- Foam shape — cut a small piece from a foam sheet
- Tissue paper ghost — light fabric-like shape that catches air
- Anything weird — combine materials in a way no one else has tried
Before you test, on your 📋 Wind Tunnel Field Notebook:
- Measure your object's mass on the scale (grams).
- Sketch it. Label dimensions.
- Predict what will happen in the tunnel — float, spin, climb, fall?
Place your object in the gap. Have your partner adjust the tube height until you find the sweet spot where the object floats stable. Time how long it stays floating before it falls out the bottom or shoots out the top. Note where in the tube it settles.
Record on your Field Notebook:
- Time in the tunnel (seconds)
- Behavior — stable, wobbly, spinning, climbing, falling
- Gap height that worked best
- Did your prediction match what actually happened?
Pick one thing to change for version 2:
- Mass — add a paperclip, washer, or penny
- Surface area — make it bigger or smaller
- Shape — cone vs. flat vs. curved
- Symmetry — balanced vs. lopsided
- Material — paper vs. foam vs. plastic
- Gap height — same object, but ask your partner to hold the tube higher or lower than before
Test version 2. Record the same data. Compare to version 1. Did your change help, hurt, or do nothing?
Run a version 3 if you have time. Different variable each time.
Pick a goal. Build something that does it. Everything you've learned in the last hour should show up in this design.
- 🕐 The Hoverer — design an object that stays floating in the tube as long as possible. Goal: 10+ seconds without falling out the bottom or shooting out the top.
- 📈 The Climber — design an object that climbs to the very top of the tube and stays there.
- 🌀 The Spinner — design an object that spins as fast as possible while staying inside the tube.
- 🎯 The Stabilizer — design an object that floats perfectly still — no wobble, no drift. Hardest challenge of the four.
Use what you discovered in Section 3. Sketch it before you build. Measure it before you test. Time it when you run it.
Record your best run on your Field Notebook — challenge picked, design sketch, mass, behavior, time in tunnel. This is the evidence you'll share at the end.
You didn't read this in a textbook. You found it by testing. Here's what the patterns you saw actually have names for:
- Terminal velocity — when lift and gravity balance perfectly and the object stops accelerating. That's why your best designs hovered instead of climbing or falling.
- Drag coefficient — how much an object resists moving through air. A crumpled paper has low drag. A flat sheet has high drag. Same mass, totally different behavior in the tunnel.
- Mass-to-surface-area ratio — heavy small things drop fast. Light big things float. The ratio between these two numbers is what every aerospace engineer is optimizing.
- Stability — symmetric, balanced objects are stable. Lopsided ones wobble or flip. Your Stabilizer designs prove this.
- Turbulence — air doesn't flow smoothly past every shape. When it doesn't, you get wobbling, spinning, or chaotic motion. That's turbulence.
- Which of these did your best design rely on most?
- If you had one more hour, what variable would you test next?
- Where in real life have you seen something like terminal velocity? (Hint: skydivers, parachutes, feathers, helicopter seeds from trees.)
Wind tunnels are how every airplane, race car, and rocket gets designed. There's one nearby called — iFly — that's a giant vertical tunnel humans actually float inside. Skydivers train there before they jump out of planes.
- Aerospace engineer — designs aircraft, drones, rockets, satellites. Uses wind tunnels at every step. Boeing, SpaceX, NASA, Lockheed.
- Automotive aerodynamicist — shapes cars to cut drag and add downforce. F1 teams have billion-dollar wind tunnels. Every Tesla and electric vehicle is shaped this way.
- Parachute designer — military, skydiving, space landings. Your coffee filter parachute is the toy version of what they do.
- Wind turbine engineer — designs the blades on every wind farm. Tunnel testing is how they figure out blade angles and lengths.
- Sports equipment engineer — designs cycling helmets, Olympic ski suits, golf balls. Every dimple on a golf ball is in a wind tunnel result.
- iFly instructor / professional skydiver — full-time job teaching people to fly in vertical wind tunnels. No 4-year degree required — certification-based.
Closer than you think: aerospace engineering programs exist at Cal State Long Beach, UC Irvine, USC, and Cal Poly. UC Irvine's program is 20 minutes from PAL. Community college transfer paths exist — Orange Coast College and Cypress College both have engineering tracks that feed into 4-year aerospace programs.
Before you leave, share one word that describes today. Just one.
Nice flying. You designed, tested, measured, and iterated — and every variable you changed taught you something the textbook can't. The next plane you see overhead got its shape from somebody asking the same questions you asked today.