This is a diagonally inclined daggerboard placed in the ama. It is asymmetric in design so it acts like an aeroplane wing providing lift as water flows over it. It works better and better the faster the boat goes. The fact that the Bruce foil is placed diagonally means that there is a compnent of thrust that acts horizontally and prevents leeway and a component that acts vertically and reduces drag on the ama by lifting it. When the boat is stationary it is just like a daggerboard and at speed it has the same vulnerability to damage as an ordinary daggerboard. The CATRI 24 uses Bruce foils as part of a clever stabilising system to make the CATRI an incredibly stable and safe design that is, as a consequence, extremely fast and yet nevertheless easy to sail. Of course it's not cheap.
