Robert Biegler: Sketch of folding Dali foils on a canoe

Tilting the foil up around the hinge axis increases the angle of attack of the inner part of the foil. The steeper the hinge axis is inclined to the horizontal, the more the outer part of the foil will toe out as the foil is tilted up. Rotation by about 160 degrees folds the foil over the boat.