A steam brig is a two-masted sailing ship with auxiliary steam power. [1] The key advantage was that the ship could sail up-wind and it could use the steam power to move relative to the wind for an advantageous sailing angle. [1]
In practice, the disadvantages combined rather than the advantages. The type had great wind-resistance, leading to an increased use of fuel up-wind compared to a pure steam ship. At the same time, the requirement to store coal reduced the cargo space over that of a sailing ship. It thus combined the slow speed, high maintenance and poor righting (ability to resist capsize and wind) of a sailing ship with the small cargo space and fuel expense of a steam ship.
The ship was typically abbrievated as StBrig - steam brig. [2]
A prominent early example was the steam brig New York, built at Newcastle Street, Norfolk, Va., in 1821. [3] [4]
A British example was the Sunniside, an 1830s cargo vessel. [1]