Past and Present Coast Guard Vessels for the Arctic: Encyclopedia Arctica 9: Transportation and Communications

Captain Edward H. Thiele, USCG

With the advent of U.S. Revenue Cutter Service (Coast Guard) operations in the Arctic it was apparent that ^ a ^ special type ^ of ^ craft would be necessary to cope with the problems of extreme cold weather, ice and operations in remote sparsely inhabited areas. Because of the lack of experience in this type of operation, the logical solution was arrived at by investigating the types of ships then in existence and plying these remote areas.

At that time whaling and sealing in the polar regions were in full swing, and through bitter experience a type of vessel had been developed that would with– stand the rigors of arctic navigation within the limits of the facilities available. It was common practice, especially with whalers, to make cruises into the Arctic of several years duration, freezing in during the winter months — sometimes purposely, other times unavoidably. As a result of this type ^ of ^ operation, the hull form, construction and means of propulsion were governed by the probability of becoming ice-bound and being caught in heavy squeezes.

The U.S. Navy had acquired two special type craft, which had originally been constructed as arctic sealers, for use as relief vessels in connection with the ill-fated Greeley expedition. After the successful completion of several missions to the Arctic under the Navy, these two vessels, the Bear and Thetis , were transferred to the "Revenue Cutter Service" in 1885 for patrolling Alaskan territorial waters.

The construction of these two vessels was modern and in accordance with the best practices of the period, and proved to be highly successful for the duty in tended. The hulls were built in Dundee, Scotland, by A. Stevenson and Sons, about 1874, and the boilers and machinery in Greenock, Scotland, by the Greenock Boiler and Iron Works. Details, showing the inboard profile and midship section, are shown in Figs. 1 and 2. The vessels were similar. The characteristics of the Bear were as follows:

By the 1870's it was recognized that power was essential to work in northern waters, but the possibilities of losing or damaging the propeller or rudder, if caught in the ice, were ever present. With no assistance available and no communications, the only solution in case of underwater damage was to rely on sail. No ship would dare enter the A rotic without two sets of sails (one spare).

The Bear was operated by the Coast Guard in arctic waters from 1885 to 1926. In 1927 the Coast Guard built the Cutter Northland (Figs. 3,4) to replace her. The Bear had proven satisfactory for routine Coast Guard duties during her many years service in the Bering Sea, and so, naturally, many of her characteristics were incorp– orated in the Northland . The principal characteristics of the Northland were:

Although the Northland had some of the same general characteristics as her predecessors, the Bear and the Thetis , many improvements were embodied in her design. The massive wooden hull of the earlier ships was replaced with steel. Special attention was given to providing hull strength to withstand the crushing forces of ice and to limit flooding in case of hull damage. The waterline plating of the hull varied from 1-1/4” thickness at the bow to 1” thickness at the sten. Other strakes of plating varied in thickness from the maximum of 1-1/4” to a minimum of 1/2”. It was expected that this plating would be sufficiently heavy to resist the abrasive and tearing action of ice which this vessel might normally be expected to encounter. The vessel was of riveted construction and was subdivided by nine transverse watertight bulkheads. In addition to the function of limiting flooding, these transverse bulk– heads were designed as strength members and contributed towards the vessel's ability to withstand crushing.

The Northland was built with a typical (European type) cut-away bow that had been successfully in arctic operations by other nations. Although the Northland could break light ice, she was not built primarily as an ice-breaker. She was built with sufficient strength to withstand the contacts with ice accompanying navigation in fields of broken ice; and with sufficient endurance to permit operating away from a base for long periods of time, and to give the crew a reasonably good chance of sur– viving until the thaw, should the vessel become entrapped.

Although great strides had been made in the design of machinery and materials, navigators were still reluctant to take a ship into arctic ice without sails as an auxiliary means of propulsion. As a result, the Northland was rigged as a barkentine ship to satisfy the old line experienced arctic skippers. In the process of changing from wood to steel ships the propulsion machinery was given intensive thought and study. The advantage of diesel economy was recognized, but a means of providing rapid maneuverability and protection for the propeller and main engines was desired. After weighing all factors it was decided to adopt diesel electric drive, and as a result one of the first successful installations of this type was made. As an added precaution to protect the propeller and the main motor, an electromagnetic coupling was installed in the line shafting between the main motor and the propeller. This feature was later eliminated when it was found that the coupling would throw out in a sea-way when the propeller broke water.

The reliability of the main power plant was of utmost importance. The refore two main generators were employed, supplying current to a single double-armature motor. In this manner it was possible to provide two independent sources of power to a single propeller, thus increasing the reliability of the motive power. We note that in all modern arctic vessels this principle of multi units has been adopted.

Although aviation was still somewhat in its infancy in 1926, the specifications for the Northland included a boom for hoisting a seaplane to the after deck. A sea– plane was not operated from this vessel to any great extent until World War II, when the Northland was used on patrol duty off Greenland, nearly twenty years after she was built.

The Northland proved herself a worthy successor to the Bear , and was used in arctic operations from 1927 until 1946. The Northland was designed for extended cruises into the Arctic and for work in broken ice fields, but it was never intended that she should be able to break or force leads into heavy ice. The Coast Guard subsequently built several other vessels with ice operating features, including the Calumet Class (1934-1935), and six vessels of the Escanaba Class built during the period from 1931 to 1935. Much was learned from the ice operation of these vessels in regard to the desirability of various types of propulsion machinery, the design precautions necessary to insure proper operation of the machinery in ice, and the the structural effects of ice operations upon the hull.

Coast Guard experience in the Arctic indicated the desirability of having vessels designed not only for operating in ice, but also capable of breaking ice. A study of the entire problem was instituted in 1937, including a review of all of the date obtainable on the characteristics andperformance of all of the ice-breakers ever built. A representative was sent to Europe to inspect and gather information on ice– breakers built for the Soviet Union, Sweden, Denmark and Holland. Investigations were made to find the most effective hull form for breaking ice, and to develop the proper relation between displacement, hull strength and horsepower. Also, all available in– formation on actual operating experience was reviewed. The results of this study were incorporated into the design of a group of 110’ harbor cutters built in 1939. These small vessels were eminently successful as ice-breakers, so many of their characteristics were included in a group of 180’ buoy tenders built in 1941, and in the Storis , a 230’ vessel built in 1941 for operating off Greenland.

The culmination of this series of vessels was the Wind Class (Figs. 5-6), the first of which was completed in 1944. Some features of the early Northland appear in the Northwind and her smaller prototypes. All of this series of ice-breakers are powered by multiple-engine direct current diesel electric plants. This type plant offers economy in space and fuel consumption, flexibility of operation, and dependability. It also makes possible the use of pilot house control to permit fast and accurate maneuverability while working in ice, thereby minimizimg the possibility of damage. The magnetic clutch used on the Northland was not used on these later ice-breakers, but main motors of a light weight high capacity type have been used in order to reduce the rotating mass attached to the propeller.

The general characteristics of the Wind Class vessels are as follows:

The use of double bottoms and wing tanks for fuel has been incorporated in the larger recently-built ice-breakers. This provides protection from hull rupture and also makes it possible to utilize every available bit of space for the great quantity of fuel necessary for long periods of operation away from a base at full– power operation, and for surviving long periods of immobilization if entrapped in ice.

The most outstanding feature of thw Wind Class is the hull form. Hulls of the same relative type had proven fundamentally sound by experience gained with the 110’ Harbor Cutters and the 180’ Buoy Tenders. This hull is characterized by a cut– away bow, and bow sections having a great amount of slope. These sloped sections cause the buttocks to provide an angle of attack the same as the cut-away bow, and make it easier for the vessel to ride upon the ice. The design also causes the breaking force to be distributed over the entire forebody of the ship, and not concentrated at the forefoot, as would be the case with more conventional lines. Since a vessel must sometimes be backed into ice, the hull lines aft are very similar to the fore part of the ship. The after propellers are kept as low as possible and in close to the hull for protection, and the rudder stock is protected by a heavy cast fin, so constructed as to give a breaking angle aft similar to the bow. There must be a very definite re– lationship between the transverse strength of the vessel and the angle of flare of the midship section, so that, in case the vessel is caught between ice floes, it will be lifted before it is crushed.

The hull of the Wind Class is of all-welded construction, as was the case with the smaller prototypes. Due to the use of extremely heavy plating and structure, some unusual welding problems developed. The shell plating is of high tensile steel, varying in thickness from 1-1/4” at the keel to 1-5/8;” at the ice belt. This plating is backed up with truss type transverse frames spaced on 16” centers, capable of giving a uniform panel strength throughout the hull. The transverse strength is obtained by making the decks and bulkheads strength members.

These vessels are designed to operate in temperatures as low as minus 50 degrees F. The entire hull and superstructure above the waterline is insulated with 5 inches of cork, and provision is made for isolating the central portion of the ship as winter quarters in case of a freeze-in. Also, some provision had to be made for the removal of ice forming topside. Such ice may be removed by chipping or by thawing with warm water. A large supply of warm water is provided for this purpose by utilizing the cooling water discharged from the main and auxiliary engine heat exchangers.

Experience has shown that, in successful ice-breaking and ice-working operations, a means must be provided for freeing the ship if it becomes wedged into the ice. On smaller vessels it is customary to roll the vessel by swinging the rudder, but in the case of the larger ships other means must be provided. The Wind Class ships are constructed with heeling and trimming tanks. The heeling system permits the shifting of 240 tons of water ballast from one side of the ship to the other in an 80-second cycle, thus inducing a rolling motion of about 8° form the vertical and preventing the skin of the hull from freezing in if the vessel is stopped by the ice. The trimming system permits the shifting of water ballast (120 tons) between the fore and after peak tanks, thus giving a change of trim of approximately 5 feet.

The underwater appendages of an ice-breaker are very susceptible to damage by ice, and propellers are a problem that require particular attention. Single screw vessels provide the most protection, because of the position of the propeller on the centerline behind a skeg, but the amount of power that can be absorbed is limited. Of necessity, the diameter must be kept small to permit broken ice to pass over the blade tips. On small vessels a single propeller is used in all cases, but on larger vessels the power is distributed between two or more propellers. At present there are two distinct types of ice-breakers in general use. The "European Type" consists of a cutaway crusher bow, with all power being applied to propellers aft. The "American Type" consists of a cutaway crusher bow, but with a propeller forward as well as propeller or propellers aft. The latter type was developed on the Great Lakes during the nineteenth century. Both the "European" and "American" type vessels have distinct advantages, depending on the operation to be undertaken. The "European Type" is best suited when working alone in extremely heavy ice such as is encountered off the East Greenland Coast. Forcing leads through heavy ice floes is known as "ice working." The "American Type" is far superior for straight "ice breaking" and for convoying other vessels through ice where the ice-breaker must work without benefit of leads. This, of course, can only be done in ice which is not beyond the breaking capacity of the ice– breaker. In the case of the Wind Class vessels the two types have been combined, in that the bow propeller can be installed or left off as operational requirements dictate.

Propellers of the Wind Class vessels are solid nickel steel construction. The after propellers are designed to give the ma ^ x ^ c imum thrust while the vessel is in the ^ ✓ ^ stalled position. The forward propeller is used as a low efficient pump for dredging ahead of the vessel or for creating a wake along the skin of the hull to wash broken ice clear. No a ttempt is made to protect the bow propeller except by placing the tips of the blades as far below the water li ^ n ^ c e as possible and keeping it well clear of the ^ ✓ ^ ice-hull contact points. Provision is made for the removal of the bow propeller and capping the bow tube when it is anticipated that the vessel will be sent into the high Arctic where ice-breaking is impossible and where only ice working can be expected.

Power for the three propellers is furnished by six 2,000 h.p. diesel engines. The power from these engines may be divided between the after shafts, giving 5,000 shaft horsepower on each after screw, or it may be divided between the three shafts, giving 3,300 shaft horsepower each. Quick maneuverability is considered an essential in ice; therefore, all modern arctic vessels are provided with pilot house control of the main engines.

It has been found from experience with Coast Guard ice-breakers that assisting other vessels through ice frequently terminates in a towing job. Accordingly, the ice– breakers of the Wind Class are provided with very rugged towing equipment. A 40-ton automatic electric towing machine is provided with 300 fathoms of 2-inch steel towing hawser. These vessels tow in open water in the customary manner, utilizing a long hawser, but when towing in ice, an ice-breaker, when suddenly stopped by a hummock or pressure ridge, is likely to be run down by the vessel being towed. To avoid such difficulty the Wind Class vessels have a notch in the stern, so that the towed vessel can be hauled in tight to prevent overriding and to keep the vessel in the clear water directly astern. This arrangement offers an additional advantage, in that the extra thrust from the vessel coupled astern may be used to assist in breaking ice.

Regardless of the size or strength of vessels built for arctic operations, it is always the best and safest policy to pick leads where the ice is easiest to negotiate. Planes used for reconnaissance are of inestimable value in this respect, and, therefore all arctic vessels of a size permitting stowage are equipped for this type of equipment. The Wind Class vessels are now provided with helicopter landing platforms. These rotary wing planes are ideally adapted for ice reconnaissance and require no pen water for take-off or landing.

Looking into the future of arctic operations and ships to accomplish this mission, the experience being gained in the development of stronger hulls and more powerful machinery indicates that eventually a type of craft will be devised that will be able to negotiate most of the water-borne obstacles imposed by nature. To this end the Coast Guard is committed in it responsibilities established by law as the protectors of life and property at sea.