RedCruiser – DIY Depron airplane for FPV

Few months ago I’ve wrote about my first handmade Depron airplane. It was cool design. Super simple, with KFm-2 airfoil, durable and easy to fly. But it had few serious flaws:

  • motor mounted in front of fuselage is great for flight characteristics, but propellers breaks all the time. Even with prop savers,
  • big fuselage is not the same as fuselage with a lot of space inside.

Depron KFm-2 airplane with pusher propeller

That’s why, I have build a second Depron airplane. This time with pusher propeller mounted on a tower behind wing. Wing is almost the same design as in my first airplane. It is still an KFm-2 (Kline-Folgeman, modified) airfoil, 150mm chord, 12mm thick. But is a little shorter: 1200mm instead of 1250mm. The main difference is inside wing. Instead of carbon fiber spars I’ve used two carbon fiber 6mm pipes. That gives plenty of stiffness. Wing almost does not bend in flight, even during hard maneuvers. And generates more than enough lift to give nice, slow flying experience without danger of heavy stall. You really have to want to stall it. And event when it stalls, it recovers nicely: drops a nose, dives for a second or two, and you have lift again. No need to work with rudder, just let it dive and gain speed and then level. 

Turnigy D2826-6 2200KV

Power plant is  Turnigy D2826-6 2200KV motor, Turnigy 2700mAh 20-30C 3S battery and APC 7×4″ APC propeller. That combined with almost 900g of weight lasts for at least 20 minutes of slow level flight or around 10 minutes of heavy acrobatics. There is not enough thrust for 3D flying, but thrust-to-weight ratio is only slightly below 1 and that is enough for rolls, flips, inverted flight or short candle.

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Radio link is “classical” FrSky X9D Plus Taranis with x8R receiver. You can see antennas mounted on a wing on a picture below. Previously I was using Turnigy TGY-i6 (FlySky FS-i6) with FS-iA6 receiver, but changes to Taranis 2 weeks ago and it was worth the money. FlySky FS-i6 is a good radio with decent range, but Taranis is just better.

FPV gear on Depron airplane

Not like previous airplane, this one was build with FPV in mind. Currently FPV gear consists of:

  • RunCam PZ0420h camera. This is popular Sony Super HAD 600TVL branded by RunCam in plastic case. I will write few words about it in a near future. On a picture above you can still see FPV 1/4 CMOS HD Color Camera Module 600TVL 120 Degree Wide Angle I was using previously,
  • Boscam TS351 5.8GHz 200mW video transmitter with whip antenna. I had no chance to test real range of this setup due to really bad weather and RC radio issues, but at 500m I had crystal clear picture using 11dBi patch receiver antenna, so I suspect ranges of 1-2km are fully doable,
  • There is still not OSD, but that will change when new minimOSD micro will arrive from China and I will setup Flip32 with Cleanflight. That should happen in 2-3 weeks.
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Here are two videos. First is from maiden flight, and second is a compilation of some aerobatics.

Final conclusion: it’s really cool airplane. Maybe it is not the fastest one, but flies pretty well. And it’s easy to rebuild after crash: a lot of polymer wood glue, some tape and you can fix almost everything. Not that it is breaking a lot. The only real crash I had with this plane was my fault. And even when something breaks in flight, there is a pretty good chance you will be able to land it. It glides good enough to land without motor, and event fly for some time if there was enough altitude. Once I was even flying it without one aileron. Pushrod broke, left aileron was not moving and I flew 2 batteries in 15m/s wind. The only symptom was slow roll speed.

2 thoughts to “RedCruiser – DIY Depron airplane for FPV”

  1. This plane looks cool. I was just curious about how you mount the motor. Is that sufficient enough for the motor torque not to break the motor holder?

    1. Motor mount is 4 layers of 6mm depron in total. Plus some carbon fiber spars inside. Pretty tough. And motor is mounted to plywood, and plywood to depron

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