A topmast is a part of the mast structure of larger sailing ships that required higher mast heights due to the amount of sail they carried. The topmast section is the second mast above the deck, and is attached to the lower mast. For ships requiring even more height, a topgallant mast section was added above the topmast, and above that might be a topgallant royal mast.
Until steel, aluminum, fiberglass and other composite materials were used in ship construction, sailing ships were made of wood. Sails were raised or hoisted, using rope made of hemp or other natural fibers, into position on large vertical wooden masts. These masts were formed from the longest straight trees that could be found in the areas where ships were built. In many cases, the bark was stripped from the tree and the entire mast was soaked in the sea for long periods to make it bug-resistant.
As the ships became bigger and faster, more sail was needed to propel them. Additional masts could be added to the ship design, but even more performance could be gained by adding sail area vertically with higher masts. The lower mast had reached practical limits due to the size of available trees, so another section was added called the topmast. Rigging was added to pull more sail vertically using the higher mast. The two mast sections were held together with rope or metal bands and bolts.
Higher masts created the problem of greater loads on the ship's masts and framework. Sails filled with wind create a very high force that has to be safety managed by the masts and rigging. Additional ropes to keep the masts in place and to hold the sails were added. Rigging used to support the masts, and transfer sail forces to the boat structure, is called standing rigging. The ropes, pulleys and other devices that move sails are referred to as running rigging.
Standing rigging that holds the masts upright and supports the loads of sails and wind are called stays. A forestay normally is any stay that points forward toward the bow or front of the ship, regardless of whether it is attached to another mast or the main deck. Backstays are attached toward the stern or rear of the ship from where they are attached on the mast. Halyards move the sails up and down, and sheets control the position of the sails. Each mast on the ship has its own name as well, with the largest normally called the mainmast. Therefore, a topmast used in this mast was called the main topmast.
At the top of each mast section was a cap, which protected the wooden mast from rainwater that can rot the wood. A crosstree was added a short distance below the mast top, which was used to connect the upper ends of stays and sail hardware. Depending on the mast height, a crow's nest might be added, which was a small platform used by crew members to look for other ships, weather, or schools of fish for fishing vessels. Each mast section had its own set of sails, and crews were normally assigned positions to be taken whenever sails were raised or lowered.
Sailing ships were the primary way to transport goods between cities and countries until steam engines were invented. Gaining the best ship speed was a constant concern, as well as cargo capacity of the ship. As the ships became larger and more complex, the sailing industry developed a terminology, or naming system, for the rigging and ship structures. Young sailors were required to quickly learn all the ship rigging names and functions to avoid chaos when handling sails. Many of those historic names continue to be used on sailing vessels of all sizes into the 21st century.