riff_raff,
I wonder if most people really appreciate how difficult it is to design a lightweight hub structure and pitch bearing mechanism capable of handling the huge moment forces produced by a rigid rotor. It was likely a difficult design problem at the small scale X2 demonstrator. One can only imagine how hard the problem will be to solve with the exponentially larger moments imposed by a larger diameter rigid rotor.
This is one of a number of advantages that the
Interleaving-ABC configuration offers.
For the same disk-loading as the
Coaxial-ABC the Interleaving-ABC, and the
Intermeshing-ABC, will have physically smaller disks and therefor blades with shorter spans.
Dave