Originally Posted by
SplineDrive
Sans, running through the scaling math for beams, it looks like that for a given number of blades, solidity, and load factor, the spacing between the rotors can indeed be a constant proportion as gross weight is sized up. Loads, radius, airfoil thickness, blade stiffness, and tip deflection all change so that the blades are strained the same. I don't think that new materials are required as gross weights increase, though I can certainly imagine that specific pitch bearing joint technologies work well at certain size ranges and may practically constrain the hub design at some point.
I would expect that when actual photos of the SB>1 are released, the inter-rotor spacing is essentially the same as the X2 and S-97 as a percentage of the rotor diameter.
Calculations for static beams don't account for aeroelastic tuning concerns, effective airfoil shapes that must fully contain the structure, nor mast/hub sizing for the fixed end of your cantilever.