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The design of this airplane started in spring of 2024. Using the software XFLR5, a friend of mine created a flying wing with enough space in the body for all the electronics. The airplane needed to be small enough to manufacture using the machines available to us. At the same time, a larger wing span allows for more lift at lower speeds, which makes the plane easier to fly.
The final design has a wing span of 128 cm, and should not weigh more than 550 g, including all electronics.
The first approach to producing the airplane started with a 3D printed mold. The design of the molds was quite laborious, since most CAD software is not designed to work with the compound curved surfaces of the flying wing. Using Onshape, the mold was designed to be clamped shut using aluminum maker beam profiles.
Expanding PU-foam can be poured into the mold and left to cure. Using packaging foil as a mold release, a test wing was poured. The wing exited the mold with very few defects. However, as it continued to cure, it deformed over the next week until it was unusable.
Since it was difficult to pour foam into a mold and achieve good results, we resorted to a different approach. Using a CNC foam cutter service available at the TU Delft, the airplane was cut to shape in four separate parts which can be glued together. The material is pink XPS foam, which is similar to styrofoam but has better mechanical properties.
The final airframe
The final airframe
The CNC'd wing sections were glued together in preparation for the fiberglass layup. Above, you can see how the 2 oz fiberglass is draped over the foam wing. In the middle of the wing, a laser cut wooden bracket allows us to mount the motor to the airplane. We also used the motor mount to hold the airplane up during the fiberglass layup. This way, we could coat the entire airplane in fiberglass and epoxy and let it cure without having to lay the airplane on one side. The control surfaces and servo mounting holes are cut from the fibreglassed wing, to have them nicely integrate into the airframe.
The finished airframe weighs 141 g without electronics and wingtips. After trimming the leftover fiberglass from the trailing edge, we glued wingtips to the plane. The total weight including electronics is around 400 grams.
Electronics setup
Electronics setup
Since the aircraft is a flying wing, we need Delta mixing of our radio control signals. Otherwise, the stick movements would be incorrectly matched to the control surfaces of the airplane. And since we are not the best pilots, some electronic stabilization would also be a nice to have!
On the picture, you can see the complete wiring diagram of the electronics on the airplane. The Xfly pulsar gyro can be used for flight stabilisation, but it also functions as the delta mixer in the setup. The battery is a 1100 mAh 18550 3S Li-ion pack, but any 2s - 4s battery could be used.
Test flight
Test flight
The day has finally arrived. On March 16th, 2025, I set out to a test flight of the flying wing. There was a 15 km/h wind, which made launching very easy! The airplane took off with just a little throw in to the wind, and was stable while still being controllable.
And here is a video of a nice low flyby:
Low_flyby.mp4Page updated
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