After searching for a functional, mostly 3D-printed rubber band-powered ornithopter and coming up short, I decided to design and build my own. This project was a fun and exciting challenge that allowed for quick iterations and a lot of learning along the way. The final design is light, flies well, and is crash-resistant due to its low weight and kinetic energy.

Design Overview:
Wingspan: 40cm
Weight: Approximately 8 grams, including the rubber band

Materials:

• 3D-printed parts (weigh around 5.5 grams in total)
• Brass tube (4mm outer diameter, 3mm inner diameter) or any similar metal tube that fits the wire
• Steel wire (0.8–1mm in diameter)
• Tissue paper (for the wings) or alternatives like plastic (thin trash bags work too)
• Rubber band (basic office rubber bands or, ideally, sport-modeling rubber bands for better performance)

Printing and Assembly:
I printed the parts using a 0.3mm nozzle, but other nozzle sizes should work if your printer is accurate enough. Just make sure that the printed parts alone weigh around 5.5 grams to ensure optimal flight performance. After printing, assemble the components using the brass tube and steel wire. The tissue paper or plastic material is used for the wings.
Unlike in a video provided i used a simple crankshaft with just two 90 degree bends, the flapping motion making part should be around 7mm.

Even with simple office rubber bands, the ornithopter flies impressively well and even glides smoothly when not powered. It's so light that crashes don’t cause any real damage—an added bonus when testing new iterations or tweaking the design.

Assembly Video:
For detailed assembly instructions, refer to this video, which I used as a guide when putting everything together: YouTube - Rubber Band Ornithopter Build.

Next Steps:
I’m currently using basic office rubber bands, but I’m planning to upgrade to sport-model rubber bands for even better flight performance. With these, I expect longer flights and more powerful wing flapping. Feel free to experiment with different types of rubber bands and materials for the wings to see what works best!

I hope you find this project as fun and exciting as I did. Happy building, and I’d love to hear about any improvements or modifications you make!