A cathedral hull is a hull shape used in modern boats, usually power-driven. It can be thought of as a kind of vestigial trimaran in which the center hull has two smaller side hulls which are so close to the main hull that there is no longer any open space. A cathedral hull is a vee-bottomed boat with sponsons which extend almost as far forward as the main hull. The airspace between the hulls may be very small or nonexistent—a good example would be the classic "Boston Whaler 13" which is nearly a flat-bottomed scow at the stern.