Isn’t the HeliFerry an airplane?
For sure, the HeliFerry planes on air. But to create the air cushion, the HF must remain close to the waves as much as a ship requires the water to float on. Surface effect ships use an air cushion to help create lift. The HeliFerry is an extreme surface effect ship in that almost all of the lift is provided by the air cushion, at least at cruising speed.
The HeliFerry does not look much like a ship.
Form follows function. Most ships are designed to remain in the water and travel at speeds of a dozen of knots while keeping the waves from hitting the deck. These considerations generate the typical form of a ship we have become accustomed with since our first picture books in kindergarten. High speed boats, on the other end, morph into very “spacey” forms. The form of HF fits its unique functions: skimming over the water surface to attain high speeds safely.
Isn’t a large overhead lift fan for a ship pretty weird?
Several ship types such as hovercrafts and surface effect ships already feature powerful fans that pump air into a central cavity spared in the hull. These fans remain mostly hidden in the hull surface. However, the larger the fans, the more efficient they are at pumping air. The large fan used in the HF is extremely long and thus so efficient in “pumping air” that the HF can forgo the enclosed air box, freeing the hull shape for cargo and wave piercing capability.
Doesn’t the HF rotate around its axis during rotor pre-rotation?
This all depends on the technology used. If there is a rotational reaction, the inertia of the craft and the high sideway drag would limit this effect. Then, there are several ways to counter that rotation, depending on the configuration: the air propulsion fans could blast against the fully cocked vertical stabs; or a small rudder with modest forward speed would be sufficient; or the air propulsion fans could be pitched differently left and right and provide counter yaw much like the tail rotor in helicopters; …
What happens when the rotor hits a bird?
Large rotors have been used for almost a century of flying and helicopters or wind mills have not shown to be especially vulnerable to bird hits. Of course, birds have been known to be sucked into the engine or, on rare occasion, crash into the cockpit. Both are unlikely in the HF because the intake to the turbine is already designed to keep out water spray and the cockpit window is designed to withstand serious pounding of waves.