Ballast is dense material used as a

weight In science and engineering, the weight of an object is a quantity associated with the gravitational force exerted on the object by other objects in its environment, although there is some variation and debate as to the exact definition. Some sta ...

to provide stability to a vehicle or structure. Ballast, other than

cargo In transportation, cargo refers to goods transported by land, water or air, while freight refers to its conveyance. In economics, freight refers to goods transported at a freight rate for commercial gain. The term cargo is also used in cas ...

, may be placed in a vehicle, often a

ship A ship is a large watercraft, vessel that travels the world's oceans and other Waterway, navigable waterways, carrying cargo or passengers, or in support of specialized missions, such as defense, research and fishing. Ships are generally disti ...

or the gondola of a

balloon A balloon is a flexible membrane bag that can be inflated with a gas, such as helium, hydrogen, nitrous oxide, oxygen, or air. For special purposes, balloons can be filled with smoke, liquid water, granular media (e.g. sand, flour or rice), ...

airship An airship, dirigible balloon or dirigible is a type of aerostat (lighter-than-air) aircraft that can navigate through the air flying powered aircraft, under its own power. Aerostats use buoyancy from a lifting gas that is less dense than the ...

, to provide stability. A compartment within a boat, ship,

submarine A submarine (often shortened to sub) is a watercraft capable of independent operation underwater. (It differs from a submersible, which has more limited underwater capability.) The term "submarine" is also sometimes used historically or infor ...

, or other floating structure that holds water is called a

ballast tank A ballast tank is a Compartment (ship), compartment within a boat, ship or other floating structure that holds water, which is used as ballast to provide hydrostatic stability for a vessel, to reduce or control buoyancy, as in a submarine, to co ...

. Water should be moved in and out from the ballast tank to balance the ship. In a vessel that travels on the water, the ballast will be kept below the water level, to counteract the effects of weight above the water level. The ballast may be redistributed in the vessel or disposed of altogether to change its effects on the movement of the vessel.

History

The basic concept behind the ballast tank can be seen in many forms of aquatic life, such as the blowfish or members of the argonaut group of

octopus An octopus (: octopuses or octopodes) is a soft-bodied, eight-limbed mollusc of the order Octopoda (, ). The order consists of some 300 species and is grouped within the class Cephalopoda with squids, cuttlefish, and nautiloids. Like oth ...

. The concept has been invented and reinvented many times by humans to serve a variety of purposes. In the fifteenth and sixteenth century, the ballast "did not consist entirely of leakage, but of urine, vomit, and various foul food leavings that lazy sailors discharged into the ballast contrary to orders, in the belief that the pumps would take care of it." In the nineteenth century, cargo boats returning from Europe to North America would carry quarried stone as ballast, contributing to the architectural heritage of some east coast cities (for example

Montreal Montreal is the List of towns in Quebec, largest city in the Provinces and territories of Canada, province of Quebec, the List of the largest municipalities in Canada by population, second-largest in Canada, and the List of North American cit ...

), where this stone was used in building. During World War 2 ships returning from Great Britain to the United States used rubble as ballast. The ballast would be dumped in New York and used for construction projects such as FDR Drive and an outcrop colloquially named Bristol Basin since it was made from rubble from bombed-out

Bristol Bristol () is a City status in the United Kingdom, cathedral city, unitary authority area and ceremonial county in South West England, the most populous city in the region. Built around the River Avon, Bristol, River Avon, it is bordered by t ...

Uses

Ballast takes many forms, for example: * Sailing ballast, or ship's ballast, used to lower the centre of gravity of a ship to increase stability **

Ballast tank A ballast tank is a Compartment (ship), compartment within a boat, ship or other floating structure that holds water, which is used as ballast to provide hydrostatic stability for a vessel, to reduce or control buoyancy, as in a submarine, to co ...

, a device used on ships and submarines and other submersibles to control buoyancy and stability * Ballast (car racing), metallic plates used to bring auto racing vehicles up to the minimum mandated weight * in

underwater diving Underwater diving, as a human activity, is the practice of descending below the water's surface to interact with the environment. It is also often referred to as diving (disambiguation), diving, an ambiguous term with several possible meani ...

, a diver weighting system comprises blocks of heavy material, usually lead, used to compensate for excess buoyancy of the diver and their equipment. * in

gliding Gliding is a recreational activity and competitive air sports, air sport in which pilots fly glider aircraft, unpowered aircraft known as Glider (sailplane), gliders or sailplanes using naturally occurring currents of rising air in the atmospher ...

, weights added to maximise the average speed in cross-country competition, especially when thermal convection is strong * in a balloon, as part of a buoyancy compensator '' Sailing ballast'' is used in

sailboats A sailboat or sailing boat is a boat propelled partly or entirely by sails and is smaller than a sailing ship. Distinctions in what constitutes a sailing boat and ship vary by region and maritime culture. Types Although sailboat terminology ...

to provide righting moment to resist the overturning moment generated by lateral forces on the

sail A sail is a tensile structure, which is made from fabric or other membrane materials, that uses wind power to propel sailing craft, including sailing ships, sailboats, windsurfers, ice boats, and even sail-powered land vehicles. Sails may b ...

. Insufficiently ballasted boats will tend to tip, or heel, excessively in high winds. Too much heel may result in the boat capsizing. If a sailing vessel should need to voyage without cargo then ballast of little or no value would be loaded to keep the vessel upright. Some or all of this ballast would then be discarded when cargo was loaded. '' Ballast weight'' is also added to a race car to alter its performance. In most racing series, cars have a minimum allowable weight. Often, the actual weight of the car is lower, so ballast is used to bring it up to the minimum. The advantage is that the ballast can be positioned to affect the car's handling by changing its load distribution. This is near-universal in Formula 1. It is also common in other racing series that ballast may only be located in certain positions on the car. In some racing series, for example the

British Touring Car Championship The British Touring Car Championship (BTCC), officially known as the Kwik Fit British Touring Car Championship for sponsorship reasons, is a touring car racing series held each year in the United Kingdom, currently organised and administered by ...

, ballast is used as a handicap, the leading drivers at the end of one race being given more ballast for the next race. Ballast may also be carried aboard an aircraft. For example, in

it may be used to increase speed or adjust the aircraft's center of gravity, or in a balloon as a buoyancy compensator.

References

Sources

* {{cite book , title=Railway Maintenance Equipment: The Men and Machines that Keep the Railroads Running , last=Solomon , first=Brian , publisher=MBI Publishing Company , year=2001 , isbn=0-7603-0975-2 Mechanisms (engineering) Weights