Ships husbandry or ship husbandry is all aspects of maintenance, cleaning, and general upkeep of the

hull Hull may refer to: Structures * Chassis, of an armored fighting vehicle * Fuselage, of an aircraft * Hull (botany), the outer covering of seeds * Hull (watercraft), the body or frame of a ship * Submarine hull Mathematics * Affine hull, in affi ...

rigging Rigging comprises the system of ropes, cables and chains, which support a sailing ship or sail boat's masts—''standing rigging'', including shrouds and stays—and which adjust the position of the vessel's sails and spars to which they ar ...

, and equipment of a ship. It may also be used to refer to aspects of maintenance which are not specifically covered by the technical departments. The term is used in both naval and merchant shipping, but ''naval vessel husbandry'' may also be used for specific reference to naval vessels.

Etymology

Ships husbandry diving

Underwater ships husbandry can be financially advantageous when it eliminates the need for

dry-dock A dry dock (sometimes drydock or dry-dock) is a narrow basin or vessel that can be flooded to allow a load to be floated in, then drained to allow that load to come to rest on a dry platform. Dry docks are used for the construction, maintenance, ...

repairs or extends the interval between dry-dockings, and reduces the time a ship is required to stay in dry-dock. Underwater ship husbandry includes the following operations, usually done by commercial divers, though some can be done by ROVs or robotic machinery: * Underwater hull cleaning to remove fouling organisms which increase drag, and therefore reduce top speed and increase fuel consumption. Such cleaning may be of the entire hull or parts thereof, particularly

propellers A propeller (colloquially often called a screw if on a ship or an airscrew if on an aircraft) is a device with a rotating hub and radiating blades that are set at a pitch to form a helical spiral which, when rotated, exerts linear thrust upon ...

shafts ''Shafts'' was an English feminist magazine produced by Margaret Sibthorp from 1892 until 1899. Initially published weekly and priced at one penny, its themes included votes for women, women's education, and radical attitudes towards vivisection, ...

and thrusters. The underwater hull may be inspected prior to cleaning, and the amount of cleaning done may depend on the inspection results. Hull cleaning may be done by divers using hand held or self-propelled mechanical brushing equipment, water jets or scrapers. *

Non-destructive testing Nondestructive testing (NDT) is any of a wide group of analysis techniques used in science and technology industry to evaluate the properties of a material, component or system without causing damage. The terms nondestructive examination (NDE), n ...

and inspection including

fouling survey Fouling is the accumulation of unwanted material on solid surfaces. The fouling materials can consist of either living organisms (biofouling) or a non-living substance (inorganic or organic). Fouling is usually distinguished from other surf ...

s, inspection of known or suspected damage to structure, equipment or coatings, and inspection of repairs. Several methods may be used, including visual inspection, video recording and magnetic particle testing. * Underwater painting is done to repair paintwork after repairs, or where small areas of paint have been damaged or have worn out. Suitable paints are applied by the diver using brush or roller. *

Fiberglass Fiberglass ( American English) or fibreglass (Commonwealth English) is a common type of fiber-reinforced plastic using glass fiber. The fibers may be randomly arranged, flattened into a sheet called a chopped strand mat, or woven into glass cl ...

repair, can be hull repair or propeller shaft protective coating repair. Repair of fibreglass shaft coating is generally done in a dry habitat mounted over the shaft, allowing access through the open bottom for the divers. The shaft is first cleaned before wrapping with a new layer of sheathing. *

Underwater welding Hyperbaric welding is the process of welding at elevated pressures, normally underwater. Hyperbaric welding can either take place ''wet'' in the water itself or ''dry'' inside a specially constructed positive pressure enclosure and hence a ...

is either done in a submerged dry habitat or wet. Better quality welds can be achieved in dry conditions as the cooling rate is reduced and there is less problem with hydrogen embrittlement. Weld surfaces are prepared by cleaning with scrapers, chipping hammers or hand-held brushes, and pneumatic or hydraulic grinding tools. * Minor repairs to the rubber coating of sonar domes can be done by divers. This entails removal of damaged rubber, preparation of the surface and application of a rubber patch using a suitable adhesive.

Environmental impact

Several of the operations classified as ship husbandry will release some quantity of harmful material into the water, particularly hull cleaning operations which will release antifouling toxins. Underwater ship husbandry can cause an adverse environmental effect as significant amounts of copper and zinc are released by underwater hull scrubbing. Alien

biofouling Biofouling or biological fouling is the accumulation of microorganisms, plants, algae, or small animals where it is not wanted on surfaces such as ship and submarine hulls, devices such as water inlets, pipework, grates, ponds, and rivers tha ...

organisms may also be released during this process.

Diving under the hull

The underside of the hull is an overhead environment with no direct vertical access to the surface. As such it constitutes an entrapment hazard, particularly under large vessels where it may be too dark due to low natural light or turbid water to see the way to the side of the hull. The bottom of the largest ships is mostly flat and featureless, exacerbating the problem. Only

surface-supplied diving Surface-supplied diving is diving using equipment supplied with breathing gas using a diver's umbilical from the surface, either from the shore or from a diving support vessel, sometimes indirectly via a diving bell. This is different from sc ...

is authorised for this work in most jurisdictions, as this not only secures the diver's breathing gas supply, but also provides a guideline to the exit point. The use of mechanised bottom scrubbing devices which are steered along the hull surface by a diver and scrub it with rotary brushes has been linked with high release of environmental toxins. There is also a hazard of crushing if the clearance is small and the tide range is large.

References

{{Underwater diving, prodiv Shipbuilding