In July of 2012 Erik Johnson posted a description of his company's protected-propellers frame prototype. The production model went on sale today. http://safeflightcopters.com/
I have ordered one.
Anyone flown theirs yet? Mine should arrive in a few days; was going to paint it a light gunmetal color. I got 4 rctimer motors and the Qbrain esc. Looking forward to flying it.
I was thinking all black, with a low lux camera, and some nav lights and bright forward facing lights.. sort of like my profile picture .. which is a TBS discovery frame that unfortunately crashed into a tree...oops.
So I finally got around to putting one of my two Safe Flight Copters together so I thought I'd give a short report.
It's a very innovative design and there are not many options out there for copter frames with prop guards but I'm afraid I had very poor luck with this frame. The problems I found were:
1. the installation and shrinking of the nylon netting above the propellers is time consuming.
2. the frame is very brittle. Any small crash and the frame cracks. I even cracked some of the seals picking it up.
3. unstable flying especially if there's any kind of wind. Rough maneuvers especially on the pitch axis could cause the copter would flip over. I suspect an aerodynamic effect caused by the large surface area of the prop guards. I can't 100% guarantee that that's the cause, I was also using a new type of motor that I'd never used before (EnRoute 800kv) paired with a HobbyWing 4-in-1 ESC but I strongly suspect it was the frame. The flips would come especially when flying forward at speed (not even a very high speed) and then flattening out so I suspect that wind would catch under the frame and flip it over.
I managed to get a somewhat stable vehicle (although still far from acceptable) by setting the Rate Roll/Pitch P gains really high (I used 0.25 which is much higher than the arducopter default of 0.15 which is already high for most vehicles).
I was unable to do an autotune on the frame and from reviewing with Leonard we saw lots of little zig-zags in the rotation rate. We estimate these were at about 12hz and we think they're caused by flexing in the frame.
So overall not a happy report I'm afraid! I see the frames are no longer for sale but I did very much like the innovative approach of the designers so I hope they try again with a different design.
I wanted to add one extra bit of commentary, I think that one thing that can be learned from this experience is that even though it's a copter, at some point, aerodynamic effects do matter. A lot of surface area far out from the center of gravity has a bad effect on the stability of the copter.
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