Would the effectiveness of a two part segemented wing lie somewhere between a fully twisted wing and a twisted flap wing, esp. figuring wind shear? Or would the exposed edges of each segment create more drag than the advantages of rotating the top section would give you, even if the top section was above the layer of most shear?
It's not the exposed edges that are the problem, it's the step change in lift across the joint. This results in shedding a vortex into the wake, which increases induced drag.
Vorticity is shed continuously along the span. It's not just shed at the tips, which is part of the problem with the "high pressure on one side flows around the tip to the low pressure on the other side" explanation for the tip vortices. It's true that most of the vorticity is shed at the tips, but not all of it, and a lot of vorticity can be shed elsewhere. The strength of the vortices shed along the span is proportional to the slope in the spanwise lift distribution. So where you have a sudden change in the lift, meaning a steep slope to the spanwise lift distribution, you get strong vortices shed into the wake.
You can see this in action if you watch airliners on approach to landing in humid conditions. Water vapor condenses in the low pressure of the cores of the trailing vortices. Vortices can be seen trailing from the ends of the flaps as well as from the wing tips. In fact, the vortices from the flaps are typically more visible than the vortices at the wing tips, and often only the flap vortices can be seen. There is, of course, a big drop-off in the lift between the flap and the outboard part of the wing, and the strength of the vortex shed at the end of the flap can be calculated from that drop-off.
The split panels of the HarborWing rig would be effective in reducing the loads due to gusts and shear. However, they are not the least draggy way of adapting the wing to shear. They have the advantage that they can react quickly and passively, so it's a practical solution rather than the most efficient solution. For best performance, you'd want the lift distribution to vary smoothly, and twist does that. But twist generally has to be applied by explicit control, and is usually a slow process.
That's not to say that twist and discrete panels are mutually exclusive. For example, the flaps in each panel could be twisted so as to smooth out the variation in lift across the panel joint. Although they are separate, the panels can be operated so they are lined up and act like a single continuous wing. This might be the steady state trimmed position of the panels. The panels would still react individually to rapid gusts, and there would be a vortex shed at the joint at that time. But the vortex wouldn't be as strong and it would go away when the panels came back into alignment as the gust died. So there would be a modest drag penalty for the dynamic variation in the wind but not for the mean wind shear. The cost of the increased efficiency would be the added hardware and complexity of having flap actuators at both the top and bottom to twist the flap, instead of a single actuator per flap.
It all depends on the mission and how the dynamic response stacks up against the need for performance. HarborWing are getting a lot of experience in the real-world aspects of operating a rigid wing rig at sea. It's not surprising their rig is evolving to emphasize those aspects, while C-class rigs have evolved in the direction of performance.
