Engineering Wonders of the World
Volume I

FLOATING DOCKS. 411 Most floating docks, as will be gathered from our illustrations, are in general appear- ance not unlike a huge box Method of without ends or top. A brief working a . Floating- Dock. exPlanatl0n as to the method of working will enable our readers the better to understand these interest- ing structures. The bottom consists of a tank and these are used as necessary for supporting the vessel. To undock a ship after the bottom has been “ sighted ” or the repairs completed, the dock is again sunk by refilling the pontoons with water, and the ship is hauled out from between the walls. The simplest form of floating dock is that which is technically known as the “ box ” Fig. 3.—THE GENOA OUTRIGGER DOCK. This type resembles the depositing in being movable, but is not designed to deposit vessels. or pontoon, or several pontoons securely fastened together ; and it is by filling these pontoons with water that the dock is sunk sufficiently to enable the ship which requires docking to be floated over the pontoons. The vessel is then hauled in between the walls of the dock by capstans fitted on the tops of the walls. By means of powerful pumping machinery (either steam or electrically driven), which is usually located in the dock walls, the water is removed from the pontoons ; and as they are emptied the dock rises gradually until the ship is lifted clear of the water. While on the dock the ship rests on keel blocks. Mechanical side shores and bilge blocks are also provided in most modern floating docks, Types of Floating Docks. type. The two sides and bottom of a box dock are one solid structure, with no joints whatever, and consequently have great strength. Numer- ous examples of this type, of moderate size and lifting capa- city , have for many years performed excellent service. It has, however, one drawback : un- less the dock can itself be placed in another dry dock, it is impossible to clean or effect repairs to the under-water portions. This objection has not proved in practice such a sei ious one as might be supposed. The accum- ulation of marine growths, so detrimental to a ship on account of reducing her speed th rough the water, tends rather to preserve the iron or