The usefulness of naval craft at the lower end of the scale of size and power has been one of the striking lessons of the war. For many years the thought of the naval designer had been directed only toward the production of larger and more powerful types of vessels, whether submarines, destroyers or capital ships. The idea that any surface fighting craft smaller in size than a destroyer could have a place in a well-balanced naval establishment was given up years ago by all first-rate naval powers. The reasoning which led to the abandonment of small craft similar to the former torpedo-boat was correct, from the point of view of the use that could be foreseen for such vessels at that time.
However, the role played by the submarine, even in the early stages of the European war, brought about new conditions. The destroyer and cruiser forces of the Allied powers were found inadequate for effectively patrolling the waters of the war zone and for combating the activities of the submarine. Pleasure craft and small commercial vessels of all descriptions were converted by Great Britain to this use, so far as possible, by mounting guns of such caliber as could be carried and as were available. Early in 1915, the British Government placed a contract with an American company for 550 motor boats, for the purpose of augmenting the patrol forces of the British Navy. These boats had the following characteristics:
Length, 80 feet.
Beam, 12 feet 2 inches.
Draft, 4 feet 6 inches.
Speed, 18 knots.
Machinery, two 220 H. P. gasoline engines, built by Standard Motor Construction Company.
The capacity for building engines which was developed in the United States by reason of this contract proved of great value to the navy later on in obtaining similar engines for the 110-foot submarine chasers.
In 1916, the Navy Department began an investigation of the probable resources of the United States in the way of pleasure craft and other small power-driven vessels which would be available for conversion into patrol boats should the necessity arise. A campaign was also started to interest prospective owners of pleasure craft in designing their boats so that they could readily be converted to patrol uses. Naval architects and their clients were encouraged to submit their designs to the Bureau of Construction and Repair of the Navy Department, for criticism before building. In this way some interest was aroused in the subject, but the results, so far as obtaining suitable vessels was concerned, were slight.
The investigation which was made revealed that a surprisingly small number of the so-called power-driven craft would be of real service. The one outstanding disability of most yachts is that they are not seaworthy to the extent demanded of naval vessels. This is due to the fact that the average yacht owner is not interested primarily in a boat which can go to sea in any weather. He is in a position to choose his time in cruising from port to port. Furthermore, seaworthiness under all weather conditions entails the sacrifice of certain characteristics and arrangements of construction which are of more importance to him, such as deck structures, comfortable quarters, easy motion, and appearance.
The second and perhaps equally great disability of many such vessels is that their power plants are usually not reliable for continuous running. This was found particularly true of the gasoline engine installations. The reliable marine gasoline motor of large power and light weight has not yet arrived. The tendency of all yachtsmen is to want a little more speed than the other fellow's boat can make. This has resulted in an endeavor on the part of the engine builders to strive for lighter weight and more revolutions than good engineering, from the point of view of endurance, would dictate. The result is that the large majority of gasoline-driven pleasure craft have engines which are good only for comparatively short endurance. There are, of course, exceptional boats that have been designed on the principle of observing such a balance of characteristics as to make for seaworthiness and reliability of power plant.
The conclusions reached from the pre-war study of this subject have been fully borne out by experience with these craft in actual service. Some of the stauncher vessels were sent to the other side, but in general it may be said that the converted yachts which have proved suitable for naval service have been very few in number. Many of the smaller craft have, however, been found useful and necessary for patrol work in harbors and in partly enclosed waters on the Atlantic coast.
When it became apparent that our existing resources of this type of vessel would fall far short of the requirements in case the United States was drawn into the war, the Bureau of Construction and Repair took up the design of a vessel specially adapted for this service. On account of the shortage of steel construction capacity, all of which was needed for building destroyers and merchant vessels, it was decided that the boats would have to be built of wood. As wood construction presented a special design problem, the services of an eminent yacht architect, Mr. A. Loring Swasey, who later rendered invaluable service as superintending constructor for the United States Navy in the New York district, were obtained for this duty in the Bureau of Construction and Repair.
The most important characteristic for this type of craft was considered to be seaworthiness. This characteristic cannot be given to very small boats. On the other hand, in wood construction the limit of size beyond which the hull weight becomes excessive is soon reached. The best compromise was found to be a boat110 feet in length over all. This length made it possible to incorporate in the design all of the essential service requirements, and to make for a thoroughly seaworthy boat.
Considerable pressure was brought to bear from various quarters to build boats of smaller size, on the grounds that such boats could be produced in larger quantities in a given time. While this would have been true, it would have been equally sound to have manufactured air rifles for the army instead of Springfields. Before definitely rejecting the design of the 80-footers, which were built in the United States for England, the opinion of the British Admiralty on these boats was obtained. The comment of the British Admiralty, confirmed our opinion that the 80-footers were not sufficiently seaworthy for general service.
There was practically no choice as to the machinery installation. Steam engines were out of the question, because of the lack of capacity for building light weight propelling machinery in quantity. One make was briefly considered, but the production would at the best have been a matter of tens instead of hundreds of units in the time available. Even as to gasoline engines it was found that there was no choice, as the question of quantity production entered into the problem. It was found that only the Standard Motor Construction Company had both an acceptable engine as to design and suitable capacity for producing the numbers needed. Even at that the production of engines proved later on to be the limiting factor in turning out completed boats.
A triple-screw arrangement was adopted using three 6-cylinder 220 H. P. engines. While speed was not considered the most important characteristic of the boats, an endeavor was made to obtain a maximum speed of 17 knots. Due to the addition of many features which increased the displacement of the chasers beyond the design calculations this speed has not been reached in service, although on trials at the designed displacement the boats came up to expectations in this respect.
The requirement that the boat should be able to go to sea and to stay at sea in any kind of weather was considered the high spot in the design. As to this quality every expectation has been fulfilled. The 110-foot chasers are quick rollers, their period being about five seconds, but this is a characteristic which is fundamental to seaworthiness in a small vessel; otherwise, green seas over the bows become the rule instead of the rare occurrence. Many interesting reports have been received of these small vessels sticking to their convoys when larger escorting vessels were scattered and battered by heavy weather.
The design of the gasoline storage and supply system was given much attention. Any gasoline boat is a potential volcano. No matter how carefully the system may be designed and built—gasoline fuel is a hazard because carelessness is a common human failing. Fortunately, the serious accidents in service have been few. Such accidents as there have been can be traced to failures to observe the precautions that are necessary in dealing with this dangerous fuel. As this article may be read by someone who has been living on a gasoline-driven boat so long without accident that he has forgotten that eternal caution is the price of safety, the most serious accident which has occurred on a chaser will be briefly recited:
Several months ago a 110-foot chaser was fueling at sea astern of a tanker. In order to accelerate the flow of gasoline the commanding officer ordered the manhole covers of the tanks removed, thus permitting the fumes to vent directly into the boat. This was the first mistake. Then also the radio operator was directed to stand by to receive or to send messages. This was the second mistake. While taking on gasoline the commanding officer should have forgotten that he had a radio outfit on board. The operator received a call and went below to take the message. On completion of the message he opened the motor-generator switch. An explosion followed which killed several men and injured others.
The two principles which underlie all precautionary measures with respect to gasoline are: First, to prevent the accumulation of gasoline fumes inside of the boat; and second, to avoid sparks and open flames in localities where gasoline fumes are likely to be present. The first principle requires the venting of tanks into the open atmosphere, the closing of all doors, hatches and airports while taking on gasoline to prevent vapors given off by the vents and filling pipes from creeping along decks and penetrating through such openings into the boat: keeping the bilges clean and free from gasoline; and inspecting the piping system and tanks frequently to detect leaks. The danger from sparks and open flames in the vicinity of gasoline vapors is obvious. All of these matters are fully covered by regulations and instructions. It seems like an elaboration of the obvious to invite attention to these precautions. If these precautions were always observed a gasoline installation would be practically as safe as a steam installation, but it is human to become careless.
The armament originally contemplated for the chasers consisted of one 6-pounder and two machine-guns. After the design had been practically completed this was changed to two 3-inch and two machine-guns. Later on a depth bomb projector was substituted for the after gun. There was some question as to whether the armament of the chasers would be effective against submarines. A demonstration of the adequacy of the 3-inch gun was afforded at Durazzo where the chasers sank an Austrian submarine by gunfire. The depth bomb, however, proved to be the most effective weapon of the chasers, as there was seldom an opportunity to use the gun against submarines. It was assumed that a submarine would not consider it worth while to engage in a gun duel with a chaser, as the risk would have been out of proportion to the result which the submarine would accomplish in destroying so small a vessel as a chaser.
The principal characteristics of the 110-foot submarine chasers as finally adopted are as follows:
Length, 110 feet.
Beam, 15 feet 4¾ inches.
Draft aft, 6 feet 3 inches for displacement of 75 tons.
Mean draft, 5 feet 3 inches for displacement of 75 tons.
Freeboard forward, 9 feet 9 inches.
Freeboard aft, 4 feet 1 inch.
Propelling machinery:
Three 6-cylinder standard marine gas engines.
Bore, 10 inches; stroke, 11 inches.
B. H. P., 220; R. P. M., 460; weight, 6300 pounds each.
One 2-cylinder 4½-inch x 5½-inch Auxiliary engine driving a 4½-K. W. dynamo and pumps.
Speed at displacement of 66.5 tons:
One engine at 370 R. P. M., 9.4 knots.
Two engines at 460 R. P. M., 14.25 knots.
Three engines at 460 R. P. M., 16.85 knots.
Cruising radius at 10 knots, 999 miles.
Fuel capacity, 2400 gallons of gasoline.
Fresh water capacity, 945 gallons.
Armament:
One 3-inch 23-caliber gull.
Two machine-guns.
One depth charge projector.
Complement :
Two officers.
Twenty-four men.
Contracts were placed for the construction of 355 chasers toward the end of March, 1917, shortly before the United States declared war on Germany. This number included 135 ordered to be built at navy yards. The program called for delivery of all of the boats by January 1, 1918. While a number of the boats were not completed until after this date, due principally to the difficulties encountered by the Standard Motor Construction Company in making engine deliveries, the program was completed so close to schedule time that it is believed to be unique in this respect as compared to other war programs of equal magnitude.
The construction of so large a number of boats in less than a year was possible only by the closest co-operation between the bureaus of the Navy Department, the builders, and the inspectors—the last mentioned in many cases having to assume the functions of management at the building yards in order to expedite the work.
There is always an element of chance in venturing on a very large duplication program without building a pattern boat to correct omissions and conflicts in the plans. It is impossible to reduce to drawings in advance of construction every detail of a ship design of an entirely original type, especially when time is the essence of the undertaking. In the case of the 110-foot chasers the risk had to be taken of proceeding at full construction capacity without awaiting the completion of one boat. However, the next best substitute for building a complete pattern boat was adopted by pushing one of the chasers at the New York Navy Yard ahead of the rest.
The New York Navy Yard was given an order to proceed with the construction of 60 chasers on March 19, 1917. The first boat was launched on May 7, 1917. On May 9, 1917, the gun firing trials were held on this boa—50 days after the order to proceed with the work was received by the yard. This was a remarkable piece of work, as the yard had to purchase practically all of the materials for the job, many plans had to be made and details of construction had to be perfected.
The design of the gun foundations was of particular importance, as it was necessary on the one hand to avoid excessive weight and on the other hand to provide an adequate structure for properly distributing the recoil stresses to the hull of the boat. There was no past experience to draw on, as the installation of a 3-inch gun on a wooden boat of light construction was a new departure. The first boat was so rapidly completed at the New York yard that no delays in the program resulted from postponing the final design of the gun foundations until after the gun trials on this boat.
In the summer and fall of 1917, extensive experiments were conducted by the Bureau of Steam Engineering on listening devices for detecting the presence of submarines. The 110-foot chasers were largely used for making these experiments. The boats as now equipped have two types of listening apparatus, although one is in a measure a development of the other. Eventually it is probable that a single device will be perfected which will accomplish what the two separate devices now accomplish. One is the K-tube which is lowered over the side or trailed astern. A submarine under way can be heard, under favorable conditions, at a distance of about 30 miles with this type. In the K-tube electrical and acoustical principles are combined to produce a wonderfully ingenious instrument of remarkable sensitiveness.
The second is the SC-tube, or in the case of some of the boats, the MB-tube. These latter devices are purely acoustical in their functioning principle. The SC- (or MB-) tubes are fitted in duplicate through the bottom of the boat and are raised and lowered through permanent hull castings. The reason for the two types of apparatus is that each has its special use. The K-tube is at its best when trailing over the stern or alongside with the boat drifting. In its present state of development it cannot be installed as a permanent fitting to the hull. It must also be taken in when the boat is under way. It is the instrument for detecting the approach of a distant submarine. While the SC- and MB-tubes are good only for about three miles, they have the great advantage that they are fitted to the hull. These tubes can be placed in service instantly the boat stops and no delay is involved in housing them on getting under way. The story of the development of listening devices is one of the most interesting pages of the history of the war. While some of the best scientists and engineers in the country were engaged on this work and accomplished remarkable results, it is probable that the surface of this field of investigation has only just been scratched.
In order to provide favorable conditions for hearing distant propeller sounds, it is necessary that local sounds on the listening vessel be suppressed to the maximum. During the early tests on destroyers and other steam-driven craft, it appeared that the difficulty of stopping all local noises, such as pumps, generators, blowers, etc., would set a limit on the efficiency of listening devices. In the case of the 110-foot submarine chasers none of these handicaps exist. The engines and auxiliary set can be stopped in a moment, the lighting system and blowers under these conditions taking their power from the storage battery. This leaves no running machinery except the blowers. These can be stopped for such periods of time as necessary without discomfort. A mounting was eventually developed for the forward blower which insulates the sound from the listening device so that it can be kept running continuously.
From several points of view, the 110-foot submarine chasers are the ideal type of craft for hunting submarines. As mentioned above, the suppression of local sounds offers no difficulties, thus permitting the use of the listening devices at maximum efficiency. The boats can be stopped from full speed ahead in less than two boat lengths. The turning circle is very small and the maneuvering facilities are therefore ideal for this work. In this connection it may be mentioned that the destroyers were often considerably handicapped in making depth bomb attacks on submarines because of their large turning circles.
The tactics used by the 110-foot chasers in hunting submarines were as follows: Three chasers worked together, running in line abreast at about 400-yard intervals. On signal, all of the vessels stop, lower the listening tubes and take a bearing of the submarine sound. The two wing boats transmit the bearings by wireless telephone to the center boat, which is the flag boat, the center boat having in the meantime also taken a bearing of the submarine. A three-arm plotting board is used for plotting the position of the sound, this being at the intersection of the three bearings. The boats then proceed at a directed speed to the position of the submarine as plotted. On arrival at this position, the boats stop, lower their tubes, and take another bearing. This procedure is continued until the chasers reach a position within a few hundred yards of the submarine. By this time the group commander can make a fairly close estimate of the speed and course of the submarine. The depth bomb attack is begun by dropping a pattern which will include all of the area in which the submarine is likely to be at the time—the formation of the boats being shifted accordingly. After each pattern, the chasers again listen in to determine whether the submarine is still under way. If the water is shallow the submarine will probably lie motionless on the bottom. A trailing device is in use on the chasers which is supposed to indicate when it is dragged across the submarine.
Chaser tactics in hunting submarines would no doubt have been developed to a high degree of efficiency had the war continued. To meet the contingency of a submarine coming to the surface to attack by gunfire instead of making an attempt to escape under water, the plan was being worked on at one base of using a destroyer as a killer, to accompany a certain number of chasers, acting as the hunters only, with the idea that should the submarine come to the surface, the destroyer's gun power would be available to deal with the situation.
As the need for patrol craft was particularly urgent on the coast of France, the first 50 vessels to be completed were turned over to the French Government. These boats crossed the Atlantic in winter weather and to a considerable extent under their own power. They were towed part of the way, as their fuel capacity was not sufficient to carry them across. Later on, special arrangements were made on several tankers for fueling the chasers on the way across. This proved to be more satisfactory than towing.
One of the chasers in the first group taken over by the French became separated from the convoy, due to an engine breakdown. After repair's had been made, the 'chaser failed to catch up with the convoy and had further machinery trouble. The supply of lubricating oil then ran out. Olive oil and butter were used as a substitute, so far as available. Finally, the gasoline supply became exhausted with the chaser still hundreds of miles from port. The commanding officer then made a sail from blankets, sheets, and pieces of canvas and finally reached port after being on his own for almost a month. After this, all of the chasers were equipped with a sail.
Just how the chasers managed to stow all of the gear which was added from time to time is a mystery. However, the problem of stowage room was of smaller concern to the designers than the constantly increasing weight of the boats. Nothing grows so fast as the displacement of a small boat. The designed normal load displacement of the chasers was 54 tons. This has grown to approximately 84 tons for full load condition. The increase in displacement started with the change from a 6-pounder to a 3-inch gun, then the addition of an extra 3-inch gun, the change to the depth bomb armament, the addition of listening apparatus, direction indicators, towing gear, etc., and the end is not yet. No doubt most of the added weight is useful and increases the efficiency of the boats even at the expense of speed which has necessarily suffered.
It requires some stretch of the imagination, however, to justify some of the weights added unofficially by the personnel. One commanding officer took great pride in pointing out a large hot water heater which he had rigged in the bathroom—it must have weighed more than a hundred pounds and consumed a shocking lot of K. W.'s from the already overloaded storage battery. If this enthusiast had known how grudgingly weight was allowed for such important features as an added eighth of an inch of thickness for the planking, how prayerfully the question was considered of reducing the rudder stock from 5 inches to 4½ inches to save a few hundred pounds, when there would have been so much more comfort to the designer in the 5-inch stock, he would have hesitated to point with pride to his hot water heater.
The first submarine chasers to reach France gave such good satisfaction that 50 additional boats were ordered in January, 1918, and in March, 1918, 42 more were ordered for our navy.
Chasers were built by the contractors and navy yards tabulated on next page.
THE EAGLE CLASS
Toward the latter part of 1917, further consideration was given to the possibility of building steel boats of smaller size than destroyers, but having a greater cruising radius than the 110-foot submarine chasers. The greatest disability of the submarine chasers was their short cruising radius and their large consumption of gasoline, which was difficult to obtain in the war zone. The 110-foot chasers have a cruising radius of about 900 miles at a speed of 10 knots under full load displacement of 84 tons. This radius is perhaps sufficient for off-shore work in hunting submarines, but is not enough to permit their use as escort vessels to any great distance.
In considering the possibilities of building steel patrol boats, it was again necessary to eliminate the established shipbuilding facilities as possible sources of construction. The interest of the Ford Motor Company was awakened in this project and after a general estimate of the situation had been made, a design was prepared by the Bureau of Construction and Repair of what are now called the eagle class of boats. The construction of the boat was simplified in every possible way, having in mind that the Ford Motor Company were not shipbuilders and needed every consideration in the way of simplified construction to facilitate the work.
The boats have the following general characteristics:
Length, 200 feet.
Beam, 25 feet 6 inches.
Draft, 7 feet 3 inches.
Normal load displacement, 500 tons.
Single screw, turbine driven.
Normal shaft H. P., 2000.
Overload shaft H. P., 2500.
Speed, 18.3 knots.
Cruising radius, 3500 miles.
Armament: Two 4-inch 50-caliber.
One 3-inch 50-caliber anti-aircraft.
One depth bomb projector.
The Ford Motor Company was directed in January, 1918, to proceed with the construction of 100 of these boats, to which number 12 more were added later on for the Italian Government. Since the signing of the armistice this number has been reduced to 60. A shipbuilding plant was erected at River Rouge on the outskirts of Detroit for fabricating and assembling the hulls. The machinery and fittings were largely built at the Ford Motor Company's plant, Highland Park, Detroit. The contract called for the delivery of 100 boats by December 1, 1918. While only seven of the boats left the plant before the close of navigation, the performance of the Ford Motor Company in completing even this number is creditable when one considers that this company had had no previous experience in shipbuilding and made practically no call on the shipbuilding industry for assistance. This latter policy is considered by some to have been a mistake, as the work could have been very materially accelerated had the contractor employed a sufficient number of men skilled in the various shipbuilding trades to act as instructors for his men. Great credit is due Mr. Charles C. West, the superintending constructor for the navy, and to Commander Carlos Bean, U. S. N., inspector of machinery, for the assistance which they rendered the Ford Motor Company in this project.
The Ford Motor Company attempted many novel methods of shipbuilding, some of which proved successful, such as building the boats on trucks which were moved along as the construction progressed and which finally transferred the hulls to a hydraulic dock which lowered them into the water. One of the innovations was the building of a complete pattern ship for the purpose of perfecting the working plans and for making the templates, forms and patterns which were used to duplicate the various parts of the 112 vessels.
The construction of this pattern ship under the direction of the superintending constructor for the navy, Mr. West, who is a skilful and experienced shipbuilder, made it possible for a company with no previous shipbuilding experience to build successfully seven ships of 500 tons displacement in nine months.
It is not generally realized that the eagle boats are vessels of considerable size. They are much larger than the early torpedo-boats and are in fact larger than the destroyers built in 1902 and 1903. The destroyer McDonough, commissioned in 1903, had a displacement of only 400 tons.
The eagle boats are designed to have a cruising radius of 3500 miles. On trial, the first boat made a speed of 18.3 knots. These boats will prove a very valuable addition to the navy, as they are adapted to the kind of duty performed by gunboats. This is more than can be said of the 110-foot chasers. While these latter vessels were a successful temporary expedient, they are a heavy liability as a permanent addition to the navy, because of the rapid deterioration of any vessel built of wood.
The question of what types and numbers of vessels to build for the navy is largely a matter of cost. In the case of capital ships, cost must be relegated to a secondary place if the navy is to keep step with the most recent construction of other powers, as such ships are usually built as an answer to the designs of other navies with a constant endeavor to improve on the previous design.
In the case of a definite problem, such as presented itself in this war, namely, combating submarines, it is interesting to speculate whether the 110-foot submarine chasers, the 200-foot eagle boats, or the destroyers, were the best investment for the particular problem which had to be solved. The following is a comparison of the approximate cost in 1918, and the man power required to operate these three types of vessels:
Assuming that a periscope can be seen as far from the bridge of a chaser or an eagle boat as from the bridge of a destroyer, and this is believed to be a correct assumption, the ratio of sea area covered by the three types of vessels is about 1:1.2 and 2.3, based on the speed of each type. Applying this ratio to the cost it will be noted that per dollar of investment a 110-foot submarine chaser covers approximately 10 times as much area as a destroyer and that an eagle boat covers about twice as much area as a destroyer. The man power for operation is also in favor of the smaller vessels.
Any discussion of the relative value of destroyers versus smaller ships, such as the 110-foot chasers or eagle boats for escort and patrol duty, may perhaps now be considered academic, because the submarine will probably never again play the role that it did in the Great War. As units of a fleet in action it is doubtful whether any surface craft smaller than a destroyer is a good investment. However, off-shore patrols will always have to be maintained in case of war with a sea power.
Our experience with the 110-foot chasers has demonstrated that patrol vessels capable of going to sea and staying at sea in any kind of weather can be provided at a cost far below the price of destroyers, both as to original cost and as to man power required for operation. It has also been demonstrated that it is not possible to augment the destroyer force quickly, whereas it is possible to build large numbers of smaller craft suitable for patrol work in a short space of time. One year from the declaration of war three hundred and fifty 110-foot chasers had been added to the navy list, whereas only seven new destroyers had been commissioned.