A ship is built much like a human being, only in the horizontal plane. Her keel fulfills exactly the same purpose as a backbone, being the basic piece to which all others ultimately are connected. The ship’s frames are her ribs, spaced out along the length of the keel to give the final structure her form. In human beings, the ribs join in front; in ships, they do not, but have their upper ends held in position by having transverse pieces running between them. These pieces are called “beams,” from the Saxon word for “tree,” and they also serve to support the deck planking. In time, the word “beam” also came to mean the width of a ship.
The use to which a ship is to put will determine the shape of her hull. If your ship is to be used in an express service, you will want one that is long and narrow, and will slice easily through the water as the famed “clipper ships” did. The length- to-beam ratio in such a ship might be nine or ten to one. Should you intend your ship to be used in hauling cargoes such as grain or coal, then you would want a hull that could contain a large volume; your length- to-beam ratio in this case would be down to perhaps five to one.
Thus, when someone spoke of a ship being broad-beamed, one thought of a rather ponderous vessel. And ashore, should one speak of another as being broad-beamed, one is saying. . . well, you know.
