I’ve been reading for a long time that the DJI Phantom is “less stable” with 9" props than it is with 8" props. Today, I finally managed to get a set of 9" x 4.7" Gemfan carbon-fiber props onto my Phantom, which I attached securely by using a M6 lock nut and a M8 washer. I used a metric prop reamer to ream out the hole in the prop to 8mm, which took a long time. Carbon fiber props are hard to ream by hand, and a drill press is probably a more appropriate tool for doing such things. See the next post for video of it flying with this setup.

Although the props are balanced and attached securely, the motor assemblies with props attached are probably not even close to being balanced. Reaming out the prop hole to 8mm is great, but the motor’s shaft isn’t quite 8mm, which leaves some room for slop. Furthermore, the M8 washers also fit a bit loosely, which leaves more room for slop. It’s probably better to ream the props out to 5/16", which is 7.9375mm—a size that should fit snugly on the DJI motors. I’ll bet a 5/16" washer would probably work better, as well, but I haven’t tried one, yet.