¡What is the difference between the Jetfoil and conventional hydrofoils?
Conventional hydrofoils are called semi-submerged foil type. When the hull of conventional hydrofoil lists by wave, wind, etc. The listed side foil immerses more than the other side foil. That comes to immersion area difference, which results in lift force difference. The listed hull is consequently turned upright by this lift force difference without specific control system or equipment. Hence the hull is always affected with wave due to the fluctuation of immersion area of foil. So, the precise attitude control can not be obtained.
On the other hand the Jetfoil is called fully submerged foil type hydrofoils. Although the hull of the Jetfoil lists, the fully submerged foil area does not change, i.e. lifts at both sides do not change. So, the attitude control of the hull done by a flap movement is indispensable for the Jetfoil and that is controlled by the Automatic Control System (ACS).
Eventually, it can not be avoidable for the conventional hydrofoil to have rolling and pitching in the waves, but, for the Jetfoil it is possible to have steady FOILBORNE without rolling and pitching in the waves.
Conventional hydrofoil ( semi submerged foil type )
Kawasaki Jetfoil ( fully submerged foil type )
Forward foil Forward and aft strut