IFMU,
What is the drag penalty for those two masts sticking up, with not only double the profile drag, but also interference between them? That's one thing that seems unequal.
The rotors on both craft are identical.
Four blades each, etc., etc. The induced, profile and parasitic drags should be equal.
As far as the 15% benefit with respect to disk area, how much of that is undone by the fact that the lift vectors of the synchrocopter waste some of their effort against each other, since they are inclined outwards?
The upper blades, which are facing outward, are the retreating blades. They produce little thrust compared to the advancing blades during cruise.
I believe that this offers an advantage over the Coaxial. A problem with the Coaxial is that on one side of the craft the low thrust retreating blades are located underneath the high thrust of the advancing blades. In addition, the Coaxial's lower retreating blades span the full length of the upper blades. This is source of strong rotor-to-rotor vibration.
I think that it has something to do with symmetry.
I have read that the original ABC had big vibration problems. It had two 3-bladed rotors.
Yes. It's top speed was limited by excessive vibration. These pages are on the subject of rotor induced vibration on ABC, 3 and 4 blade rotors.
OTHER: Aerodynamics - Vibration - Rotor Induced - Analysis of Coaxial
DESIGN: UniCopter ~ Rotor - Disk - Lateral Dissymmetry of Lift and Drag? - (3-blades)
DESIGN: UniCopter ~ Rotor - Disk - Lateral Dissymmetry of Lift (Drag?) - 4-blade Rotors
Dave