The main foil is a stainless steel wing in the shape of a chevron, positioned slightly ahead of the boat’s center of gravity, that spans the tunnel created by the catamaran hulls.
It is parallel with -- but not protruding below -- the bottom of the hulls, meaning that the wing is always in the water and that there may be some protection for it in case of accidental grounding.
As soon as the boat begins to move forward, water passing over and under the shape of the wing generates lift, identical to the idea behind an airplane wing. A low-pressure area is generated on the top of the wing, and a high-pressure area is formed on the bottom of the wing.
As speed increases, lift increases, forcing the boat upwards and decreasing drag – again, just like an airplane wing. The relatively small wetted surface offered by a catamaran hull is made even smaller as lift continues.
Tunnel Affect. There is no doubt that air trapped and compressed in the tunnel at higher speeds will also add to the lift potential before passing through the end of the tunnels at the transom.
Two More Foils. In addition to the main foil, there are also two “trim” foils aft in the tunnel walls ahead of the transom. These act to lift the transom and help the boat run at a steady fore-and-aft attitude at low and medium speeds. In effect, the foils automatically and continuously trim the boat.
Trim foils also play a part in helping the boat reach planing speed more quickly. Unlike the main foil, they will eventually rise above the surface of the water at high speeds, and drag will be further reduced.
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