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Hull
Nigel Irens’s record breaking power trimarans’ ILAN concept served as the inspiration for the hull. It is characterized by a wave piercing slender central hull, flanked by two stabilizers. The application of this type of configuration is novel for surface effect ships. As the overhead lift fan relieves the hull from any lift providing features, it can be tailored for high speed acceleration and for handling higher sea states than is customary for planing hulls.
Fan
Jay Carter’s multi-patented high inertia, high mu capable lift fan defines the single most important feature of the HF. After pre-rotation, pulling collective releases the kinetic energy stored in the rotating tip weights of the fan to lift the craft clear from the drag of the water to allow a quick acceleration. Soon, the forward speed drives the fan in autorotation to provide the bulk of the lift until the speed up forces enough air in surface effect under the aerofoil to provide most of the lift. At that time, the fan is slowed down to minimize air drag. At any time, the fan is the main device for controlling the skimming height. In addition, it remains available for emergency braking or evasive maneuvering.
Aerofoil
Ground effect has been studied since WWII. The HF features a classic reverse delta Lippisch design with accompanying reflex airfoil. As the overhead lift fan is the main lifting device in the slower speed range, the surface effect is optimized for a much narrower high speed range. This keeps the aerofoil much smaller and much more stable in pitch.
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