OCEANOGRAPHIC VESSELS AND THEIR FACILITIES

Vessels

For purposes of oceanographic research, a very sturdy, seaworthy vessel capable of working under practically all weather conditions and of withstanding any storm is required. Vessels engaged in marine investigations can be broadly classified as either oceanic or coastal types, depending largely upon their size and cruising radius, but the two categories are not sharply defined, since large vessels may be used for near-shore investigations and relatively small vessels sometimes extend their operations far out to sea. In the following discussion, vessels and equipment used in coastal surveying and in the study of fisheries problems will not be described, although vessels engaged primarily in such work are sometimes employed in oceanographic investigations. Practically any vessel, small or large, can be used for certain types of investigations, but rarely is any single craft, unless specially designed, suitable for all kinds of oceanographic work. One of the chief requirements of oceanographic vessels operated by private or small organizations is economy of operation. This generally means a relatively small craft with low maintenance cost which can be handled by a small crew. Vessels owned or operated by national agencies, such as the Meteor (Germany), Discovery II (Great Britain), and Willebrord Snellius (Netherlands), are generally fairly large, but in most cases they serve a dual purpose. For example, the Meteor was used as a naval training ship and as a survey vessel, and the Snellius was especially built for surveying work in the Netherlands East Indies.

The following features are desirable in vessels that are to be used in oceanographic research:

1. Sturdiness and seaworthiness, large cruising radius, and accommodations for laboratory work and the storage of collections.

2. Low freeboard in order to make possible the handling of instruments near the sea surface and to reduce the wind drift when hove to at stations.

3. Sails to increase the cruising radius, to provide a safety factor in case of engine breakdown, and to improve the working conditions on board by reducing the roll and vibration when under way. Riding sails to steady the vessel when hove to at stations and to reduce the leeway by keeping the vessel headed into the wind.

4. Sufficient clear deck space for the installation of winches and for handling bulky equipment such as trawls and dredges.

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In table 57 are listed certain representative vessels that have been extensively used in oceanographic investigations. Those owned by national agencies are large, over 200 feet long, and carry large crews, while, on the other hand, vessels owned and operated by institutions are generally between 100 and 150 feet long and carry crews of less than twenty. During the nineteenth century the practice of utilizing only large craft in oceanographic work made it impossible for private organizations to engage in independent and systematic investigations. However, Björn Helland-Hansen, of the Geophysical Institute in Norway, convinced that small vessels could be used effectively, had the Armauer Hansen built to conform to his ideas. This small vessel, only 76 feet long, has carried out both intensive and extensive work in the North Atlantic and has ably confirmed Helland-Hansen's thesis. Following his lead, other private institutions have purchased or built small vessels that can be economically operated.

Winches

Winches used in oceanographic investigations vary so widely in construction that it is impossible to describe any standard designs. The type and design of winches depend not only upon the character of the work contemplated but also upon the size of the vessel, the space available for the installation, the length of wire rope to be carried, and the power for operating the winch. Details of construction and installation of the winches on the vessels listed in table 57 may be found in the references cited.

Winches may be classified under three headings, depending almost entirely upon the strength of the wire rope they carry.

Sounding winches are relatively light. They carry single or multistrand wire of small diameter and are designed for sounding and for obtaining bottom samples with light gear. Sometimes they can be used for other types of oceanographic work. An electric powered deep-sea sounding winch is described by Parker (1932).

Hydrographic winches are moderately stout. They carry somewhat heavier wire than the sounding winches and are designed for handling water-sampling devices, thermometers, and plankton nets. Since the introduction of sonic sounding methods, winches especially designed for taking wire soundings are not so common, and hence hydrographic

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winches may be used when it is necessary to take wire soundings or bottom samples.

Heavy winches are strongly built to carry the largest and strongest cables. They are used for dredging, trawling, anchoring in deep water, and for any other work requiring heavy equipment or the ability to withstand a great strain.

The construction of winches depends not only upon the size of wire rope handled, but also upon its length, since those carrying small amounts need not be so large or so strong as those that must handle several thousand meters of wire rope. For investigations in the open sea, winches should carry at least 5000 m of cable, and for studies in the deeps, more than 10,000 m may be required. Winches carrying only a few hundred meters of wire rope can be cheaply built and, if necessary, operated by hand. However, heavy winches and those carrying large amounts of wire are always power driven. Winches may be operated by steam, as on the Discovery II, by gasoline or diesel motors coupled directly to the winch, by the main engine through some suitable mechanism, or by electric motors. Because of its economy of operation and its flexibility, steam is in many ways the most desirable source of power for winches, but it is practical only on steam-driven vessels. Oceanographic winches are now most commonly operated by electric motors. It is essential that all winches, particularly those used in handling water-sampling devices and nets, have a considerable range in speed of lowering and hauling in. They must also be capable of being controlled quickly and accurately so that instruments can be lowered to a predetermined depth and raised to a convenient level above the water for examination or removal from the wire. The maximum rate of haul on the hydrographic winch should be about 200 m/min. If electric motors are used to operate winches, speed control is obtained by the use of rheostats. In certain installations, reduction in speed also reduces the horsepower of the motor, but such designs should be avoided, because heavy loads must be hauled in slowly.

Electric motors mounted on deck must be waterproof, and the winches themselves must be so constructed that they can be readily lubricated and protected from corrosion by salt water. Winches carrying large amounts of wire rope must have drums with extremely staunch flanges; otherwise, the packing of the wire may break the flanges away from the core when the winch is hauling in under tension.

Spreaders of some type are necessary to lay the wire smoothly and evenly on winch drums that carry large amounts of wire rope. If no provision is made for such spreaders, the wire may accumulate unevenly on the drum, causing the strands to break down and, what is more serious, causing the wire to slip down between the underlying coils in such a way that when payed out again it may be badly snarled. Spreaders may be

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operated by hand, but are generally an integral part of the winch and are mechanically operated.

The hydrographic and sounding winches are customarily placed on deck near the rail, where they can be conveniently operated and where the wire rope will clear obstructions on deck and on the hull. The heavy winch, which is more bulky, must be installed in such a way that it can be strongly supported, can withstand heavy loads, and will not affect the stability of the vessel. On smaller craft it is commonly installed amidships below deck or, sometimes, half sunk below the deck level. The axis of rotation of the heavy winch is generally athwartships.

Wire Ropes and Accessory Fittings

Wire ropes used in oceanographic work must have the following properties:

1. They must be of strong material so that rope of relatively small diameter can be used, thus reducing the bulk of the winch.

2. They must be flexible and not liable to kink or unravel.

3. They must be made of a metal that is resistant to corrosion, and thus long-lived, and free from materials that will contaminate water samples and plankton catches.

Such requirements are best answered by multistrand ropes of stainless steel, but this alloy is expensive, and in practice tinned or galvanized steel ropes are satisfactory. Phosphor-bronze and aluminum-bronze ropes are also used, as they are noncorroding, but they are only about one half as strong as steel and their life is limited because they crystallize with use and lose their strength. Many wire ropes have hemp cores, but these are not so satisfactory as ropes with wire cores, because the hemp may shrink and break when submerged, and it is also liable to rot unless specially treated. High-grade manila rope is about one tenth as strong as steel rope of comparable diameter.

The strength of steel depends upon its composition and treatment and varies from about 50,000 to 400,000 lb/in². Steels employed in wire ropes are usually of relatively high tensile strength, the tensile strength of the rope increasing with decreasing diameter of the individual wires. The greater strength of a rope made up of smaller but more numerous wires is offset, however, by the greater surface offered for corrosion and by the greater likelihood of the individual wires breaking after a certain amount of wear.

Single-strand wire of the type known as piano or music wire is used for deep-sea sounding and for running taut-wire traverses (p. 342). This wire is of extremely high tensile strength, but is stiff and liable to break if kinked. If no bottom sample is required when sounding at great depths and in taut-wire traverses, the wire is usually cut away, as it is not worth the time required to reel it in again. Piano wire of

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0.8 mm diameter (No. 21, B & S gauge) has a breaking strength of about 240 lb. Stranded wire, which is used on shallow-water sounding machines (for depths of less than about 1000 m), consists of seven tightly twisted double-galvanized wires of 0.5 mm diameter (No. 24, B & S gauge). This seven-strand wire has a breaking strength of over 500 lb, is quite flexible, and can be used for handling many types of light oceanographic gear.

The wire ropes used on the hydrographic and heavy winches are generally of either the 7 × 7 or the 7 × 19 types. A 7 × 7 wire rope consists of six strands, each composed of seven individual wires that are wound around a central core strand which itself contains seven wires. A 7 × 19 wire rope is similarly constructed, but each of the seven strands contains nineteen individual wires. The 7 × 19 ropes are slightly heavier than the 7 × 7 type, and the ropes of smaller diameter are considerably stronger, but the small size of the individual wires is a disadvantage. Ropes of the 7 × 7 type with diameters between about one eighth inch and one quarter inch are sufficiently flexible for oceanographic use, but, to obtain the desired flexibility in larger ropes, it is necessary to employ 7 × 19 rope on the heavy winch. In table 58 are given the characteristics of 7 × 7 galvanized steel ropes of the type known as aircraft cord.

For most purposes it is considered that the working load of wire rope should not be more than one fifth of the breaking strength—that is, a safety factor of five. In marine investigations it is sometimes impossible to maintain such a high factor of safety, but, if the anticipated strain is known, the diameter of the wire should be such that the maximum load is never more than half the breaking strength. There is not only the danger of losing valuable equipment, but also the hazard to those on deck if the wire should break near the water surface. Steel has a greater elasticity than bronze, and the safety factor must be somewhat greater when bronze ropes are employed.

When great lengths of wire rope are paid out, the weight of the rope in the water may approach the breaking strength and exceed the safety factor of five, even when there is no gear suspended from the rope. Ropes of the type listed in table 58 exceed the safety factor of five when more than 4000 m of wire are suspended in the water. When taking water samples and temperatures or other observations with light gear where there are no sudden strains upon the rope, the safety factor may be reduced and the work extended to great depths. However, in trawling, dredging, and taking cores of the bottom sediments, and when anchoring in deep water, the equipment must be such that it can withstand a heavy working load in addition to the weight of the wire rope. The increased working strength necessary for observations in deep water is gained by using tapered wire ropes, which are of the smallest diameter

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at the free end and increase by stages toward the inboard end. When working with apparatus on the bottom where there is danger of fouling, a weak link should be introduced between the wire rope and the equipment. This link will part if the load approaches the breaking strength of the rope and will either release the whole instrument or transfer the strain to some other part of the device in such a way that it will pull free.

Many preparations are on the market to be used for the preservation of wire ropes. Whether or not any of these are suitable depends upon the manner in which the wire rope is to be used, as those which flake off will contaminate plankton samples and other collections. Relatively frequent application of used crankcase oil is a satisfactory method for preserving steel ropes. The oil is applied before the rope is first placed in the water, and thereafter at intervals, particularly when the rope will not be in service for a long period.

The wire rope used on the hydrographic winch must be smooth and free from kinks or stray broken wires that will prevent the passage of messengers or weights. Where a break or other damage necessitates a join, wire rope may be repaired with a long splice, which does not materially increase the diameter of the wire or decrease the breaking strength. Kinks that form in the wire should never be pulled out, but should be eliminated by untwisting the wire, straightening the strands, and realigning them.

Sheaves are aIways necessary for leading the wire rope outboard. They should be free-running and of such diameter that the wire passing over them will not be cramped or strained. Unless the circumstances

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make such size impractical, the diameters of the sheaves should be at least thirty times, preferably fifty times, the diameter of the rope. All sheaves must have guards to prevent the wire from slipping between the wheel and the frame.

An essential part of the equipment for each winch is a meter wheel (fig. 83) for measuring the amount of rope payed out. A meter wheel is a sheave with a wheel of appropriate circumference fitted with a device that records the number of revolutions. The device is so designed that the difference between two readings of the dials gives directly in meters, fathoms, or feet the amount of wire that is run out or hauled in. For soundings and for obtaining temperatures and water samples the meter wheel must be carefully constructed and checked from time to time for wear. The effective diameter of the wheel is its own diameter plus the diameter of the wire rope. The meter wheel may be mounted on the boom or davit that leads the wire outboard, or it may be built into the spreader on the winch. The latter arrangement is a convenient one because the winch operator can then see the recorder at all times. If the meter wheel itself is in such a location that the dial is not readily seen, recorders operated by a flexible speedometer cord may be mounted in a more convenient place. To avoid slippage of the wire rope over the meter wheel, the angle of contact should be at least 90 degrees.

The wire rope is led outboard from the winch through sheaves and finally from a boom or davit extending out over the side of the vessel on the windward side. The lead from the heavy winch must be approximately amidships because, when dredging, the vessel must be maneuvered under sail or power, which is possible only if the wire rope is suspended from a sheave near the middle of the vessel. To avoid striking the side of the vessel the outboard leads should be arranged so that the wire, when hanging vertical, is several feet away from the hull, and to facilitate the handling of gear it is usually necessary to have a working platform extending out from the hull and large enough to accommodate two men. If the wire rope on the heavy winch is used for deep-sea anchoring,

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sheaves must be arranged so that the rope can be led forward and over the bow.

Sudden strains on the wire rope that may be caused by the rolling of the vessel or by fouling equipment on the bottom are a hazard to both the apparatus and the wire. These strains may be equalized somewhat by the use of accumulators, which are usually coil springs mounted with one end secure and the other end attached to the sheave through which the wire rope passes. Accumulators can usually be calibrated so that the extension or compression of the spring may be used to measure the strain on the wire rope. Some types are secured to the outer end of the boom or davit with the meter wheel or a plain sheave attached to the free end, or they may be an integral part of the davit or winch. The strain on the accumulator may be used in deep soundings to determine when the weight strikes the bottom, and in dredging and trawling it should be watched so that sudden strains may be eased by slacking off on the winch. Special devices known as dynamometers may be used to measure the strain on the wire rope.

Shipboard Laboratories

The location of laboratories on shipboard, the amount of space devoted to them, and the facilities installed depend upon the size and nature of the vessel and the types of investigations to be made. The laboratories may be classified as deck laboratories and analytical laboratories. The deck laboratory opens on the deck and is used for storing certain oceanographic equipment. There the reversing thermometers are read, water samples are drawn from the sampling device, and certain preliminary steps are taken in the preservation or preparation of water and plankton samples. The deck laboratory should contain racks in which the water-sampling bottles may be placed as soon as they are removed from the wire rope. These racks should be so arranged that the temperatures can be read and the water samples can be taken out without removing the bottles. Space should be provided for the glass bottles in which the water samples are transported, for certain chemical reagents, and for the solutions required for the preservation of biological material. A bench where records and labels can be prepared is also a great convenience. A large sink with running fresh and salt water is very useful, and the deck should be watertight and provided with drains because water is spilled in filling the glass bottles. Deck laboratories are a great asset on oceanographic vessels, particularly in bad weather and at night, as much more satisfactory work can be done under shelter where there is good illumination.

The analytical laboratories are usually located below decks where there is the most space and where the motion of the vessel is at a minimum.

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Vibration transmitted through the vessel from the engines and motors is often more troublesome in the laboratory than the roll or pitch of the vessel, and consequently the engines should be mounted, when practicable, on flexible springs or on cork or rubber. The equipment used in the laboratories will generally be identical with that used on shore, but the benches, storage space, and methods of securing apparatus to the benches must be adapted to work at sea under any conditions. Work benches are usually of such a height that the worker can be seated on a stool or seat that is fixed in place and so arranged that he can brace himself with his legs, thus leaving his hands free. In some cases provisions are made for a bench mounted on gimbals, but the advantages of a relatively level surface are often outweighed by its unsteadiness. All apparatus must have suitable storage compartments in which there is no danger of the apparatus falling out or smashing together in a high sea. Burettes and other instruments, while in use, must be secured to the bench or to permanent burette stands.

The analytical laboratory should be provided with running fresh water and a source of distilled water. The latter may be carried in large bottles or, preferably, in specially installed tin-lined tanks. On a long cruise it may be necessary to provide distilling apparatus. When living organisms are to be investigated, a source of cooled sea water or a cold box is necessary. A cold box is also desirable for preserving water or sediment samples for bacteriological examination.

Laboratory work on shipboard is usually kept to a minimum because of the undesirable working conditions that arise from the cramped space, the motion of the vessel, vibration, and the time required for merely collecting the samples. However, there are certain chemical tests that must be made immediately after the samples are collected, and generally these must be made on board. The methods of analysis are referred to in chapter VI. On longer cruises it may be necessary to do more of the work on board, but in such cases the analyses may be done when the weather conditions are favorable or when the vessel is in port or at anchor. Biological work on board the vessel is limited in character, since most specimens can be preserved for later examination ashore and because vibration and motion of the vessel make the use of microscopes virtually impossible.

Samples of water, organisms, or sediments that are to be examined ashore are usually not stored in the laboratory but must be kept in a place not subject to wide ranges in temperature or to extreme temperatures. High temperatures lead to the disintegration of the rubber washers used on most bottles and thus permit evaporation, which will ruin the specimens. Fluctuating temperatures may loosen the stoppers and lead to evaporation, or may even break the bottles. Freezing temperatures must also be avoided, owing to the danger of breakage.