Baltimore (tug)
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Baltimore in 1989
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| History | |
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| Builder: | Skinner Shipbuilding Company |
| Launched: | 1906 |
| General characteristics | |
| Displacement: | 81 tons (gross), 55 tons (net) |
| Length: | 84.5 ft (25.8 m) |
| Installed power: | Compound reciprocating steam engine |
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Baltimore (tug)
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| Location | Baltimore Museum of Industry, Baltimore, Maryland |
| Coordinates | 39°16′28″N 76°36′1″W / 39.27444°N 76.60028°WCoordinates: 39°16′28″N 76°36′1″W / 39.27444°N 76.60028°W |
| Built | 1906 |
| Architect | Skinner Shipbuilding |
| NRHP Reference # | 93001613 |
| Significant dates | |
| Added to NRHP | 4 November 1993 |
| Designated NHL | 4 November 1993 |
Baltimore is a preserved steam-powered tugboat, built in 1906 by the Skinner Shipbuilding Company of Baltimore, Maryland. She is formerly the oldest operating steam tugboat in the United States, but at present does not hold an operating license issued by the US Coast Guard, so is unable to leave her dock at the Baltimore Museum of Industry on Key Highway, Baltimore. Her hull is not capable of operating on open water. Baltimore was built and operated as a harbor inspection tug, capable of acting as a municipal tugboat for city barges, as well as an official welcoming vessel and VIP launch, an auxiliary fireboat, and as a light icebreaker.
She was declared a National Historic Landmark in 1993, and is part of the Baltimore Museum of Industry. The Baltimore and Chesapeake Steamboat Co., a nonprofit organization, was established to maintain the tugboat.
Baltimore is equipped with a compound reciprocating steam engine, fed by a Scotch marine boiler. Hull construction is rivetted iron, with a wooden deckhouse. The 84.5 feet (25.8 m) wrought iron hull has proven to be more durable than steel or wood. Displacement measures 81 gross tons and 55 net tons. The hull form is typical for its time, with an upright stem, moderate sheer and elliptical stern. Bulwarks are vertical about the stern rather than inwardly-sloped as in more modern designs.
The boiler was a replacement for the original, fitted in 1922, but is similar to the original. The cylindrical boiler measures 9.5 feet (2.9 m) by 10.25 feet (3.12 m), with two Morrison furnaces connecting to a combustion chamber at the rear. The fire tubes pass from the back to the front of the boiler. Exhaust passes through an annular steam dryer/superheater on its way to the smokestack. Originally designed to burn coal, the boiler was converted to oil in 1957. The boiler has since been converted back to coal and the original coal bunkers restored by the Baltimore Museum of Industry as part of their conservation and restoration work. Steam pressure as designed was 150 psi (1,000 kPa), however it is limited to 115 psi (790 kPa) by the boiler rating.
The tug is powered by a compound double-acting, vertical-inverted steam reciprocating engine, a common type for tugboats. A 12 inches (30 cm) high-pressure cylinder operates at 150 psi (1,000 kPa) (now 115 psi (790 kPa)), while a 25 inches (64 cm) low-pressure cylinder takes the high-pressure cylinder's exhaust at 17psi. Both cylinders have a stroke of 22 inches (56 cm), offset by 90 degrees to keep the engine from being stuck on center. A manual jacking gear acts as a further measure to prevent sticking on center. Stephenson valve gear permits reversing, aided by a steam reversing engine or ram to adjust eccentric rods. The propeller has a diameter of 6.75 feet (2.06 m) with a pitch of 8.66 feet (2.64 m).
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