FOUR-MOTOR RC FOAMIE SCRATCHBUILT

This is a 100% foamboard (Dollar Tree plus some Hobby Lobby foamboard) airframe that I built in 2010 with one of the original Armin Wings and an underpowered twin motor powerplant setup. I've now re-equipped it with four 2830 1000KV motors with 9x4.7 propellers and it has nearly a 1:1 thrust to weight ratio.

This plane flies very much like a scale plane. The nearest approximation would be the Super Twin Otter, one of my favorite skydiving jump planes and legendary for its STOL and fast climb-to-altitude capabilities, however the Twin Otter is of course a twin motor.

I equipped this plane with ample ailerons, flaps, rudder, and an all-moving tailplane partly for pitch authority and partly as a foamboard engineering experiment. Low speed flight and short takeoffs and landings are impressive and easily controlled thanks to the large flaps placed in the inboard motor prop blast and the gyro installed on the aileron channel. The inboard part of the flaps are intentionally cut away to allow clean airflow to the horizontal and vertical stabilizers even with full flaps and at high angle of attack. This helps avoid "blanking" of the stabilizers in high alpha.

Flight times are 12 minutes with 3x2200mAh 3s packs in parallel, with aggressive maneuvering.

The wing structure includes a full-span carbon arrow shaft spar joined at the center with fiberglass RC helicopter blades as the struts. The struts actually bear the vast majority of the forces rather than the true wing roots. This provides a very strong, rigid arrangement with minimal parts and hardware.

There is probably no practical application to this design other than it being pretty cool and scale-like. Cargo drops are a possibility but not a priority, as I have a dedicated twin-motor Skyvan for this purpose.

Thank you to Airman 1958 for the motors, to Ruben for the excellent video, and to Trilucid and Alex Collings for the soundtrack!