No rudders, just plain vertical stabilizers. Yaw control is via
asymmetric thrust across the 9 motors - kinda like the DC-10 in Sioux City. Yaw signal from the "pilot's" RC box throttles up left engines and throttles down right engines to yaw right and vice versa, by way of the programming of the digital flight controllers on each of the 9 part-planes.
Differential elevator across all 9 aircraft for roll control - the elevators act as "trim tabs" to change the wings' angle of attack on the left and right sides. Some lateral roll stability built-in by angling the hinge connections between the wingtips - if one individual aircraft tries to nose up or down, the hinge geometry tends to push it back to nose-level and in line with the others.
If you watch the whole video, at the end there is a link to an "explainer" video that discusses the controls and construction.
Some airplanes are fondly described as "a large group of spare parts flying in close formation."
This is the ultimate poster child for that concept.
I'm kinda interested in the airfoil - which
seems to be just the proverbial "barn board," except with an additional wrapping or layer around the leading edge to provide a little camber ------===