Swept Wing Stall Progression

ISEF Category: Engineering Technology: Statics and Dynamics

Subcategory: Aerospace and Aeronautical Engineering  ·  Difficulty: Intermediate  ·  Setup: Home Setup  ·  Time: 1 to 2 Months

The Hook

A wing can stop behaving smoothly before the whole wing stalls. That matters because a small change in stall pattern can change lift, drag, and control. You can see that change with tufts and slow-motion video. The wing itself becomes the signal.

What Is It?

This project asks how wing sweep changes where airflow breaks first. Forward-swept and aft-swept tips do not push air around the same way. One planform may keep flow attached longer near the tip, while another may lose it earlier. Think of airflow like water moving over a paddle. If part of the paddle shape changes, the water breaks away in a different place.

Tufts help you see that breakaway. Tufts are short strings taped to the wing. When flow stays attached, they lie flat and point in a steady direction. When flow starts to separate, they flutter, lift, or swirl. Slow-motion video lets you track where that change starts along the span of the wing, from root to tip.

Why This Is a Good Topic

This is a strong science fair topic because you can change one design variable, wing sweep, and measure a clear outcome, stall progression. You can connect it to aircraft stability, wing loading, and safer stall behavior. You can also build and test your own wing models without a university lab, then use video analysis to turn airflow into data.

Research Questions

• How does forward sweep versus aft sweep change the first spanwise location where tufts begin to flutter?
• What is the effect of wing sweep on the order in which the root and tip stall?
• Does sweep angle change how quickly separation spreads from one section of the wing to another?
• To what extent does wing sweep affect the speed at which tuft motion becomes unstable near the tip?
• Which planform produces the most uniform attached flow across the wing before stall?
• How does sweep direction change the difference in stall onset between the inboard and outboard tufts?

Basic Materials

• 1 m balsa wing structure or foam-core wing template
• Balsa strips or foam board for wing ribs and spars
• Lightweight covering film or paper skin
• Fine sewing thread or yarn tufts
• Low-tack tape
• Smartphone with slow-motion video
• Tripod or stable phone mount
• Measuring tape or ruler
• Digital angle gauge or protractor
• Permanent marker for tuft placement
• Notebook or spreadsheet for observations
• Safety glasses
• Closed-course vehicle setup or school-approved moving test rig.

Advanced Materials

• Wind tunnel access or school aero test rig
• Force balance or load cell for lift and drag estimates
• Smoke wand or flow visualization source approved for the facility
• High-speed camera or smartphone with manual frame control
• ImageJ for frame-by-frame tuft tracking
• Python for plotting tuft angle and stall onset maps
• 3D-printed wing ribs or precision cut templates
• Laser level or alignment jig for repeatable wing mounting
• Anemometer or pitot-based airspeed sensor
• Airfoil coordinate files for planform comparison.

Software & Tools

• ImageJ: Tracks tuft position, angle, and motion frame by frame in video clips.
• Python: Plots stall onset location, compares planforms, and runs statistical tests.
• Google Sheets: Organizes run data, conditions, and summary charts.
• Tracker: Marks motion in video and helps compare flow changes across trials.
• RStudio: Runs cleaner statistical analysis if you want stronger inference and graphs.

Experiment Steps

1. Define the exact planforms you will compare and keep airfoil shape, span, and surface finish as similar as possible.
2. Choose one airflow cue to measure, such as first tuft flutter, tip separation, or spanwise stall spread.
3. Plan a repeatable mounting method so wing angle, placement, and camera view stay consistent across runs.
4. Design a control set that checks whether any tuft motion comes from vibration, road turbulence, or mount flex instead of stall.
5. Build a video analysis plan that turns each run into a measured stall onset location or sequence.
6. Decide how you will compare the two planforms with graphs, repeated trials, and a simple statistical test.

Common Pitfalls

• Letting the wing twist under load, which changes the effective sweep and confuses the stall pattern.
• Placing tufts unevenly, which makes one side of the wing look more separated than the other.
• Using a camera angle that shifts between runs, which hides where spanwise stall really starts.
• Testing in unstable airflow, which mixes road turbulence with wing behavior and ruins comparison.
• Changing more than one wing feature at once, which makes it impossible to tell whether sweep or tip shape caused the result.

What Makes This Competitive

A stronger project goes beyond a simple before-and-after video. You can map the stall onset point along the span, compare repeated trials, and turn tuft motion into a real measurement. You can also test more than one sweep angle or compare sweep direction across multiple speeds. That gives you cleaner evidence about how planform shape changes separation, not just a dramatic clip.

Project Variations

• Compare the same sweep angles on a wing with a different airfoil section to see whether thickness changes stall order.
• Test three tip shapes, such as square, tapered, and rounded, while keeping sweep direction fixed.
• Analyze the same wing at multiple speeds to see whether sweep changes the speed threshold for tip separation.

Learn More

• NASA Glenn Research Center: Search the aerodynamics and wing stall pages for simple explanations, diagrams, and flight behavior basics.
• MIT OpenCourseWare: Search for undergraduate aerodynamics lecture notes and problem sets on wing lift and stall.
• USGS ScienceBase: Search for datasets and methods on fluid flow visualization and measurement workflows.
• NACA Reports: Search the NASA Technical Reports Server for classic wing sweep and stall papers.
• ImageJ Documentation: Use the official help pages for frame-by-frame video measurement and image analysis.
• PubMed: Search review articles on flow separation, boundary layers, and visualization methods if you want a broader methods background.