First Year Engineering Design
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Rubber Band-Powered Aircraft Design
For my Cornerstone of Engineering course, I designed and built a small rubber band-powered aircraft. The aircraft’s wing ribs were 3D-printed using an ultralight plastic, while the main structure was constructed from carbon fiber tubing, achieving the goal of minimizing weight. This project required iterative design and prototyping within constraints including time, weight, and the challenges of printing with a difficult filament.
Design Process & Challenges
The first step was researching airfoil profiles suitable for low-speed, low-thrust gliders. Since the aircraft’s propulsion was limited, I selected a glider airfoil that maximized lift while minimizing parasitic drag. However, the first iteration of the design encountered structural issues during assembly. Initially, I planned to space 3D-printed wing ribs every 20mm, covering them with heat-shrink film to form a smooth aerodynamic surface. Unfortunately, the ribs weakened and deformed when the heat was applied, revealing a key lesson: while 3D printing filament requires high temperatures to melt, it weakens at much lower temperatures.
To solve this, I redesigned the wing structure for the second iteration. Instead of using individual ribs with heat-shrink film, I extruded the ribs into 200mm-long sections, allowing them to act as both the structural support and outer skin. The final wing assembly consisted of four of these sections, with printer paper bridging the gaps for additional surface continuity.
Construction & Testing
Several small but critical components were also 3D-printed using PLA filament. These included:
Wing spar connectors that attached the carbon fiber wing spar to the wooden fuselage dowel.
A propeller adapter (provided by the professor) mounted to the front of the aircraft.
A rear adapter that secured the stationary rudder and elevator, while also serving as a mounting point for the rubber band motor.
Adjustable trailing edge fixtures to fine-tune the wing’s angle of attack. I printed 12 different versions at varying heights to determine the optimal angle—balancing maximum lift while avoiding stalling, which occurs when airflow separates from the wing surface, causing a loss of lift.
Additionally, a rudder piece was laser-cut, as the project required at least one laser-cut component. The rudder’s dimensions were fine-tuned through sanding to improve aerodynamics.
Final Results & Lessons Learned
The final aircraft was visually well-designed, but in test flights, the rubber band-driven propeller lacked sufficient thrust for the wings to generate adequate lift. Even with a strong hand launch, the plane failed to stay aloft. Due to project constraints, further iterations were not possible, but the experience provided valuable insights into aerodynamics, structural integrity, material selection, and iterative design.
While the aircraft did not achieve sustained flight, the project was a successful exercise in engineering problem-solving, demonstrating the challenges of lightweight construction, aerodynamic performance, and rapid prototyping.