Preparation of the Keel

In the first of these photos is the Keel laid on a 16 foot long plank. We will be working on the plank until all the frames are fastened to the keel and the gunwales. Gunwales are the boards that are at the upper edge of the sides of the boat.

In the second photo Schuyler is using a smoothing plane to plane the ends of the keel to a 3/8 in wide tip to meet up with the Stem and Stern posts.

In the plans the instructions refer to this keel as a hog and then refers to the keel as the centre rubbing strip. From my limited boatbuilding experience would not the keel actually be a structural part of the vessel rather than a protective strip on the bottom?