USS Alarm at New York Navy Yard, 1876.
An experimental armored ram of the U.S. Navy, USS Alarm was intended for harbor defense. Originally authorized during the Civil War and designed by Adm. David Dixon Porter, Alarm and the similar but larger ram Intrepid were meant to combine ramming capability (with a 32-foot ram for the purpose, nearly 20% of the ships' 170-foot length) with spar torpedo attack capacity. The short, nimble ships were an odd combination of gunboat, torpedo craft, ironclad, and ram. Their main weapons all faced forward. Accordingly the ships were designed for maneuverability, with a horizontal paddle-wheel drive that could swivel to either side of the hull to turn the vessel about on a dime -- much like today's jet-propelled tugs -- to keep the lethal prow facing target at all times.The two ships were caught up in the post-Civil War plundering of the existing navy by corrupt officials. They did not complete until 1874, but were among the most advanced ships in the U.S. fleet by that time. In 1864 the spar torpedo was state of the art, but the Whitehead self-propelled torpedo was developed during the 10 years the ships were under construction, first being marketed in 1868. So during construction the ships were adapted to release early Whiteheads from the iron spar at the tip of the ram (see illustration of the Intrepid below). At right, an illustration for an article on torpedo tactics, published in Harper's (1877), inaccurately shows the Alarm with torpedoes protruding in all directions underwater. Below right, a Civil War era spar torpedo. The Alarm's weapon differed somewhat, the explosive device being rigged to protrude from the point of the ram on a retractable, 35-foot spar; its charge was detonated by an electric trigger activated from inside the vessel rather than the simple pull-string trigger shown. 1877 was the year the Alarm ran extensive tests at the navy's torpedo school in Newport, R.I. This was also the year Whitehead torpedoes were first used in battle. Moreover, the first successful use of Whiteheads came only 6 months later, during the Russo-Turkish War.
Sadly, these two ships were not successful because of their slow speed. Heavily armored, they could only achieve 10 knots using the Mallory propeller. The Alarm had 4" armor (101.6 mm) over the bow portion of her iron double hull and a bullet-proof armored wheelhouse. Intrepid was built with a full waterline belt of 5" (127 mm) and, with 1,812-HP engines pushing her 1,150 tons, she too could achieve only 10 knots (the ship also had a 2-mast auxiliary sail rig to economize on coal consumption). At this rate, neither ship could attain one critical aspect of her stated goal: to stealthily attack the capital ships of any enemy. By 1885 both ships were laid up, out of commission, along the dockyard wall at the New York Navy Yard. In the last years of the budget squeeze, plans were floated to convert Intrepid to an unarmored China gunboat, and Alarm to a gunnery training ship. These proposed uses underlined the ships' uselessness as torpedo craft in the changed atmosphere of the nascent pre-dreadnought era: the new model was a much faster, lighter, more nimble torpedo boat. This new type was a torpedo attack specialist, unencumbered by the multiple conflicting purposes that hamstrung Intrepid and Alarm. Significantly, the new torpedo boats could outpace the standard warship speeds of the 1890s, 16-18 knots -- a pace that left lumbering ironclads designed in the 1860s bobbing distantly in the wake of their quarry.
Work proceeded at a snail's pace on both vessels' conversions. By 1886 Congress had come around to supporting an up-to-date navy and fostering technologically advanced shipyards and gun foundries in the U.S. With the funding now available for new construction, it proved less cumbersome to build appropriate ships from scratch than to convert these rusty, iron-hulled dinosaurs for new duties. Simply put, although never used beyond torpedo testing when they were fairly new, the ships were already hoplessly out of date and showing the results of 13 or more years' neglect. Although they had been carefully hoarded through the navy's period of scarcity and neglect, their utility was at an end. Intrepid was sold out of the service in 1892, while Alarm was struck off the Register in 1897 and sold for scrap early the following year.
Specifications for the Alarm:
Dimensions: 172' x 27'6" x 11' Displacement: ~800 tons. Armament: (1) 15" Dahlgren SB, (4) 9-pdr SB, (2) Hotchkiss MG. Single 35-foot iron spar at bow for delivering contact torpedoes or launching Whitehead torpedoes. 32' long reinforced iron ram at bow, with watertight gland at tip for deploying spar and torpedo. Construction: Iron double hull with watertight subdivision. Armor: 4" wrought iron belt armor distributed primarily on ram and forward hull. Bullet-proof wrought-iron plate on wheelhouse. Propulsion: (2) 2-cyl. compound engines developing 600 HP, geared to Fowler wheel. Steering/propulsion by Mallory Propeller system. Speed: 10+ kts. Crew: 66.
Metric Specifications:
Dimensions: 76m x 13.2m x 4.6m &nnbsp; Displacement: ~800 tons. Armament: (1) 381 mm Dahlgren SB, (4) 9-pdr SB, (2) Hotchkiss MG. Single 11-meter iron spar at bow for delivering contact torpedoes or launching Whitehead torpedoes. Reinforced iron ram, 9.75m long, at bow, with watertight gland at tip for deploying spar and torpedo. Construction: Iron double hull with watertight subdivision. Armor: 102 mm wrought iron belt armor concentrated on ram and forward hull. Bullet-proof wrought-iron plate on wheelhouse. Propulsion: (2) 2-cyl. compound engines developing 600 HP, geared to Fowler wheel. Steering/propulsion by Mallory Propeller system. Speed: 19.4 km/hr. Crew: 66.
Foreshortened closeup of the Alarm's intimidating ram, shot in 1896 when the ship had been 'in ordinary' for 11 years. The vessel was sold in February 1898.
Bow of the Intrepid in drydock. Her armor belt is plainly visible here, as are her wooden bulwarks. Note unusual, clinker-style plating pattern below the waterline, apparently unique to this class. The bow torpedo orifice is visible at the apex of the ram. Like the Alarm, this much larger (1120-ton) ship was designed for bows-on attack, primarily for spar torpedo use. She was later adapted to discharge a Whitehead 'fish' from the bow spar once within its limited (550-yd.) range. By the late 1880s Whiteheads had been so improved that the spar torpedo method had become a mere curiosity. With the invention of the torpedo tube -- launching the weapons with a burst of compressed air -- the U.S. torpedo rams were rendered obsolete, as was the unsatisfactory "frame" launching system used for TBs in many navies.
The Alarm's propulsion device: The Fowler wheel, which rotated on a vertical shaft. Gears at upper end of the shaft delivered power from the two compound steam engines. The entire assembly could swing out at sharp angles from the hull to pivot the ship on a remarkably tight radius, an arrangment patented as the "Mallory propeller." Ship was designed for bows-on attack, primarily for spar torpedo use, and later adapted to discharge a Whitehead 'fish' from the bow spar once within the torpedo's ½-km range.
Robert Whitehead and his many rivals and imitators used the tapered form shown until around 1906, when test tank trials proved that the now-familiar blunt-nosed shape actually caused less friction and made for a full knot's faster passage through the water. By 1912 the new shape was universally adopted. Also universally adopted from around 1890 were anti-torpedo nets, an elaborate defensive technology that gave a complacent sense of security to battleship advocates through 1914. Installed at great expense in all first-class navies, the nets proved almost completely useless in practice. SDI advocates take note! Camouflage paint, zigzagging targets and aggressively maneuvering destroyer screens, preventing torpedo vessels from taking careful aim, proved by far the best defense against the torpedo, perhaps the deadliest naval weapon of the Great War.