Sorry no piccies…..

Imagine a keel attached to the bottom of the front beam by a hinge which can only operate in the Port/stbd plane - directly under the mast

When the boat fly’s a hull, the keel will stay vertical (in the water) until the side of the keel fin touches the leaward hull. At this point the keel will start to provide righting moment as increased heeling will push the keel to windward.