Second, the created down force results in less side slipping of the runners. The result is that the boat will accelerate faster and have a higher top end simply because the sail can be sheeted in harder without the boat tipping or sliding.
Exit foils nicely balance out the boat to give a lot of performance over a large wind range.
The process outlined below is a method of building foils completely from scratch. Using a table saw, cut two pieces 3.6 inch wide, 1.75 inch thick and 30 inch long. Once the glue has dried, you can sand the foam to the desired final shape. Once the rear edge hardens, remove the plastic wrap and lightly sand. Once the top and bottom laminates are hardened, the ends need to be sealed.