A few years ago, I became interested in flying wings when I visited a local flying club and saw a few Crash Test Hobby Assassins, and Grim Reaper flying. They reminded me of when I was a kid and taken to the flying field for the first time. There were many impressive RC aircraft there that day, but the model that caught my eye was a glow engine delta wing. It was fast, agile, and looked relatively simple.
Like those old glow engine delta wings, the Assassin and Grim Reaper were fast, agile, and simple, with the added benefit of being almost indestructible. I purchased, built, flew and crashed, and flew again, a Grim Reaper XL and a Pinata. I started watching a lot of YouTube videos and found pilots with multi-engine RC aircraft performing wild spins by controlling each motor’s throttle independently. I also found videos of pilots building articulating motor mounts for single engine models which allow a RC plane to perform wild loops and spins. These planes look almost out of control and then settle back to level flight in an instant.
But, at that time, I could find nobody doing it with a flying wing. I imagined a flying wing with two brushless pusher motors that could flat spin and gain altitude…and loop and roll so tightly that the plane would be a blur and could then level off instantly. It seemed easy enough, and my FrSky Taranis could be programmed to do the mixes.
I knew that ultimately, the wing would be built out of EPP foam using the techniques I learned when building my Crash Test Hobby wings. But for proof-of-concept, I wanted something much simpler and cheaper. I decided to build a KFM wing from Dollar Tree foam board. For strength, I would embed 3mm carbon fiber spars. I would also use a pair of Sunny Sky 2212-1500kv motors and Hobby King Blue 30a ESC’s that I had laying around.
Preflight Motor Test
From the motor test video, you can see that hinge mechanism worked flawlessly. The final build was extremely light and with the two Sunny Sky x2212-1500’s and 8×5 HQ props, it generated over 3kg of thrust. It was VERY over powered. The flight was short. Unfortunately, the maiden flight video caught none of the actual flight, but did catch the mayhem, panic, and excitement. The crash was not a result of the plane, but of pilot error…my error. The launch was flawless. It gained altitude and maintained level flight. Trim and CG were perfect. I moved the aileron control to the right and the plane banked right and started to turn. I centered the stick and it leveled off, still climbing. I made a second right turn and gave a little down elevator to level the plane off. Next, I made my first mistake. I wanted a left turn to bring it around, but I gave it another right. PANIC…it was about to fly behind a large obstruction. PANIC…OK, I’ll just cut the throttle and let it come down. NOW I CAN’T SEE IT…PANIC…I gave it full throttle and it nosed at full speed into the ground.
It flew for about 23 seconds and control was perfect. From this plane, I learned that the motors I used were way overpowered. OK…I’ll build the next one a little larger. I also learned that I needed someone with a little more flight time and flight experience…someone who wouldn’t panic under pressure…to fly the next one. Lastly, I needed a field with a little more room…well, a lot more would be better. Even though I went home with the plane in pieces, I was excited at the outcome. My proof of concept worked…back home…to the drawing board.