What is a Bilge Keel?
What is a Bilge Keel?
A bilge keel is a device added to the hull of a ship to aid against rolling in heavy seas. It usually consists of a flat, steel plate welded to the hull at the area where the sides of the hull turn to form the bottom. The bilge keel provides a surface of the hull to resist or act against the water to prevent rolling. By attaching to the hull at an angle to the bottom of the ship, the bilge keel does not add to the depth or the draft of the ship. In some military ships such as a battleship, the device was used as an integral component of the ship's torpedo defense system.
Unlike many anti-roll devices that can be fitted to a ship's hull, the bilge keel does not require any control devices, added pieces or mechanical abilities. The steel strip is simply welded or riveted into place along the hull. While commonly used in various lengths and widths, the average bilge keel is fitted to the hull and runs approximately the full distance from stem to stern. It protrudes out from the turn of the hull to a distance parallel to the sides of the ship. This eliminates any interference with the docking of the ship caused by a protruding keel strip.
In some rare instances, a ship might be fitted with two or more bilge keel strips, however, this is very rare. The downside of installing the strips to the side of a ship is the increased resistance that the bilge keel places on the forward motion of the vessel. The advantage over other types of anti-roll devices such as fins is the absence of interior infringement by the bilge keel resulting in no decrease in cargo space. A fin requires the placement of control and operational components inside of the hull, resulting in a loss of available cargo space.
Some sail-powered ships use a bilge keel to combat roll instead of a longer keel fin. This allows the ship to fight roll while not increasing the draft of the vessel by lengthening the keel fin. Some vessels designed to operate in both deep water, such as a large lake or ocean as well as shallow water such as a river or channel, use this type of keel in place of a deep-running hull. By using the strip affixed to a shallow bottom, a day cruiser or personal yacht can ride smooth in rolling seas and still navigate the shallow waters required to dock in some locations.
What is a Gun Deck?
A gun deck is a level of a warship, usually a wooden-hulled vessel, which is primarily used to carry guns for broadside firing. Large warships often had several different gun decks, while very small warships entirely lacked this type of dedicated deck. Space was at a premium on wooden warships, and gun decks served other functions when a ship was not actively engaging enemy forces. During combat, conditions on these decks were very dangerous, as crewmen were at risk from both enemy action and their own weaponry.
The great warships of the age of sail relied on large banks of guns mounted so as to fire primarily from ports in the sides of vessels that were opened when engaging the enemy but kept closed under normal circumstances. The guns were typically mounted on one, two, or three dedicated gun decks. Such decks were usually dominated by rows of cannon along either side of a ship. Supplies could be stored in the middle of these decks, and sailors would sleep in these spaces.
Smaller warships, such as frigates, did sometimes feature one or two decks dedicated to guns. Parts of these decks were sometimes sectioned off for other uses, such as cabin space for the captain, when they were not needed for the mounting of naval guns. In some cases, smaller ships mounted all of their guns on the upper deck and on raised decks both fore and aft. The first covered deck on such ships was still sometimes referred to as a gun deck, however.
When wooden ships engaged the enemy, all non-essential items on a gun deck were secured, and ammunition, bandages, and damage control gear made ready. Naval guns were tremendously loud, could misfire, and produced clouds of hazardous smoke, all of which served to make life on a gun deck very dangerous for a ship’s crew. Enemy shot could penetrate the wooden hulls of most ships and had the potential to set off explosions or to send clouds of deadly wooden shrapnel tearing through the confined space of a gun deck, making the lives of gunners even more dangerous.
The advent of metal-hulled warships led to the disappearance of gun decks. Metal warships could withstand tremendous amounts of damage, and very large guns were needed to engage them effectively. These guns were best mounted in turrets on top of the main decks of ships and replaced the rows of broadside guns mounted on gun decks.
Discussion about this post