Great Balance Dock
From Wikipedia, the free encyclopedia
 The Great Balance Dock with the Russian frigate General Admiral aboard in 1858 | |
 United States | |
|---|---|
| Name | Great Balance Dock |
| Owner | New York Balance Dock Company |
| Builder | William H. Webb, New York |
| Launched | September 30, 1854 |
| General characteristics | |
| Length | 325 ft (99 m) |
| Beam | 99 ft (30 m) |
| Capacity | 8,000 tons |
The Great Balance Dock was a floating drydock in New York City. It was the largest such facility in the world when constructed in 1854, and consequently, many of the most important ships of its time were serviced there.
The underwater portions of ship's hulls require periodic maintenance. This includes removing marine growth from the hull, and repairing rudders. For the wooden ships of the nineteenth century, hull maintenance included caulking between hull planks, and nailing thin copper sheets to the bottom to discourage marine growth and wood-boring marine worms.[1] Propeller-driven vessels required work on the propellers themselves and the associated bearings, shafts, and stuffing boxes. Hulls damaged in storms, collisions, groundings, or by the action of worms or rot also needed work below their waterlines.[2]
It has always been difficult to access the underwater portions of a ship's hull. From earliest times this was achieved by careening. To careen a ship, it was grounded on a steep beach at high tide. As the tide ebbed, the hull would be exposed so that work could be done. Careening has numerous disadvantages not the least of which is that work is interrupted after only a few hours by the return of the tide. Graving docks are an ancient alternative to careening. A basin was dug into the shoreline, lined with stone, and sealed with water-tight gates. Ships would float into the dock with the gates open. Once the gates were closed, the water in the dock could be pumped out, setting the ship on the dry bottom of the dock. Graving docks are costly, difficult to build, and require significant amounts of shoreline real estate. As ships reached 300 feet (91 m) and longer in the mid-nineteenth century, the investment required to build such a dock became prohibitive.
In 1840 John S. Gilbert patented a new form of floating drydock.[3] The New York Balance Dock Company was incorporated on April 18, 1848, to build such docks.[4] In 1853, the company commissioned William H. Webb to build the Great Balance Dock at what was estimated to be a cost of $150,000.[5] She was launched at his Williamsburg, Brooklyn shipyard on September 30, 1854. The dock's pumping machinery was installed by Mott & Ayres after she was launched.[6] She was sufficiently large to handle the largest ships in existence at the time.
The Great Balance Dock was built of wood planking and timbers. She was 325 feet (99 m) long, 99 feet (30 m) in breadth, and 38.5 feet (11.7 m) in height. The dock contained 12 water-tight compartments, which could be flooded to lower the dock sufficiently for a vessel to enter it, and could be pumped out to lift a vessel free of the water. Each compartment had its own pump. The pumps were driven by two steam engines, each of which produced about 300 horsepower. The pumps could move 3,500,000 US gallons (13,000,000 L) per hour, so ships could be lifted quickly.[7] The dock had a lifting capacity of 8,000 tons.[8]
The name of the dock was descriptive. In order to maintain a horizontal orientation as ships were hauled out, different amounts of water were maintained in her 12 tanks to balance the uneven load of the captive ship.
