Ketch mizzen sheet. So on a ketch, the dual purpose of the mizzen sail is to both propel and balance the vessel, while on a yawl, the smaller mizzen mainly serves the purpose of trim or balance. Yawls tend to have mainsails almost as large as those of comparable sloops. A ketch may be distinguished from a cutter or a sloop by virtue of having two masts rather than one, though a ketch with two foresails is sometimes called a "cutter-rigged ketch". Both the ketch and the yawl differ from the two-masted schooner, whose aft mainmast is taller than the foremast.
Bomb vessel Bomb vessel A bomb vessel, bomb ship, bomb ketch, or simply bomb was a type of wooden sailing naval ship. Its primary armament was not cannons (long guns or carronades)—although bomb vessels carried a few cannons for self-defence—but mortars mounted forward near the bow and elevated to a high angle, and projecting their fire in a ballistic arc. Explosive shells (also called "bombs" at the time) or carcasses were employed rather than solid shot. Bomb vessels were specialized ships designed for bombarding (hence the name) fixed positions on land. In the 20th century, this naval gunfire support role was carried