If you’ve flown Blade helis, you would know that they often use 2mm round CF tubes for their tail boom. To keep the tail rotor aligned to the main shaft, each end of the boom is keyed. In the shape of a D.
The tail boom is one I often fracture or break. Horizon Hobby does not sell replacement CF booms by itself. One has to buy the entire tail assembly for about $15. Many of us hobbyist simply purchase 1 meter CF tubes or rod, and cut to length. This is much more economical and keeps more money in our pocket.
Since learning to fly 3D with the Nano CP X, I have fractured more booms than I care to share. And I am sick of needing to carefully file the D shape, making sure not to remove too much material from each side. On top of that, one have to ensure that the flat part is on the same plane on each end of the fabricated tail boom to ensure the tail rotor lines up with the main shaft. It was a nightly ritual that I am done with.
I know some people have solve the issue of broken tail boom by using a 2mm round solid rod. Then they wrap the tail wires on the outside. I personally don’t like the wires wrapped on the outside. During crashes, the enamel coating can be rubbed off and the resulting short will burn out your tail FET. Using solutions like CAT5 wiring just seems to be heavy and clunky on the Nano.
Personally, I wished the Nano CP X uses the 2mm square boom that the v911 uses. It has more meat to it and there is no need to make the key at each ends of the boom to keep the boom from getting out of plum with the main shaft. Plus, it’s easy to purchase replacement boom for the v911 heli on the cheap that is already in a good length. In fact, when the v911 first came out, I purchase a bunch at $0.50 each but have not fractured the tail boom of the v911 yet. It’s the only heli I own that I can say that about.
Noticing that the Turnigy FBL100 and HiSky FBL100 heli both uses 2mm square boom, I purchased a spare FBL100 frame. Cut the rear portion and epoxied it onto the Nano CP X frame. It was actually very easy to do and line up since the flat surface mates to each other securely with epoxy.