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Lu,
Agreed; this rotor will have to be 'beefed up' at the cost of some additional weigh.
helmut fire,
The situation is probably not all that bad.
The amount of undersling and the static pre-cone angle are selected to suit the mean coning angle of the rotor. A change in the active coning angle on both sketch A/ and on sketch C/ will cause the CG of the two blades to come out of alignment with their (virtual) teetering hinges. In other words, this is a problem for the conventional teetering rotor as well as 'idea C/'.
Assume a hypothetical 2-blade articulated rotor head, which is flying with a coning angle or +4 degrees on both blades. If blade #1 flaps up 3 degrees and blade #2 flaps down 3 degrees then blade #1 has a total angle of +7 degrees and blade #2 has a total angle of +1 degree, from the normal plane of the disk. This means that the 'centers' of blade #1 are closer to the disk's axis of rotation then are the 'centers' of blade #2. Hence, the need for lead-lag hinges. With an underslung teetering rotor, this problem of the blade 'centers' moving toward and away from the mast is much reduced.
The Hooke's Joint effect is not a major problem because the two blades are accelerating and decelerating in unison. Of course, a rotor with more than two blades will have a problem with the Hooke's Joint effect and must have a provision for lead-lag.
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