A spar torpedo is a weapon consisting of a bomb placed at the end of a long pole, or spar, and attached to a boat. The weapon is used by running the end of the spar into the enemy ship. Spar torpedoes were often equipped with a barbed spear at the end, so it would stick to wooden hulls. A fuze could then be used to detonate it.
The extremely close range required to use spar torpedoes was a major limitation. The perfection of the self propelled torpedo rendered the spar torpedo obsolete. It was used in the second half of the 19th century.
The most famous use of a spar torpedo was on the Confederate submarine Hunley, which managed to sink the Union screw sloop USS Housatonic in 1864, although the Hunley was lost.
On October 27, 1864, Lieutenant Cushing employed a spar torpedo to sink the Confederate armor-clad ram Albemarle. Because the Confederate navy was tiny, the sinking of the Albemarle was the Union navy's only successful sinking of a Confederate vessel by torpedo. Lieutenant Cushing employed a spar torpedo designed by John Lay.
Spar torpedoes were also used on small wooden launches in the late 19th century, although they were not very useful weapons. The locomotive torpedo (what we think of today as a torpedo) replaced the spar torpedo as a weapon for submarines and small boats in the 1870s.