DEVELOPMENT OF THE inflatable liferaft as a piece of marine equipment is probably the outcome of the successful use of rubber dinghies during World War II. It was estimated that over 17,000 airmen owed their lives to these dinghies, known to many people as "the yellow thing the kids played with one summer." Today dinghies have not only changed considerably in design, but their name is also changed-to inflatable liferafts.

As far as the marine industry is concerned, inflatable liferafts came of age in May 1960 when the International Convention for the Safety of Life at Sea met in London to review safety regulations for merchant ships. With the experience gained by several maritime nations who had enforced carriage of inflatable liferafts on fishing vessels, the Conference agreed to their use on ships engaged on International voyages. The new International rules are still awaiting final ratification and full scale provisioning has not yet started. Since inflatable liferafts are relatively new it is proposed here to describe some of the operational features of their design.

Mr. Edwards' article on the background and design of inflatable liferafts represents the author's personal opinion only, and does not necessarily represent the official view of the U.S. Coast Guard. There are several areas in the construction standards for this type of equipment where differences of opinion presently exist. Mr. Edwards' article is presented because of its timeliness and interest.-ED.

FLOTATION

The prime purpose of a liferaft is to provide flotation to the survivors of an abandoned ship. Satisfactory flotation is dependent on many links in a chain of events which is described here in more or less logical order.

STOWAGE

To ensure that a liferaft functions when needed it must be stowed on the vessel correctly. The raft must be located where the crew can get to it even in a late stage of a casualty. The forecastle is usually considered

unsuitable and in a small vessel such as a trawler the best place for the raft is behind the wheelhouse. However, care should be taken to keep the raft away from excessive heat such as engineroom casings or funnel. It need hardly be said that rafts should be accessible; in one instance it was reported that a raft was located in the ship's store below decks! A liferaft is supplied either in a valise or a container. A valise stowed raft needs extra protection in the form of a wood or metal box fitted with collapsible sides, whereas a container stowed raft is suitable for installation without any additional protection. With new vessel construction a lot can be gained by providing lockers in the superstructure in which to stow the liferafts, the lockers having canvas shelves rather like pipecot berths.

PAINTER

As soon as a raft is installed the painter should be made fast to a strong point on the vessel. It is the painter which triggers off inflation and if this is let go when the raft is thrown overboard it will be lost.

Many raft stowages are fitted with a hydrostatic release but this will not inflate the raft and is only a refinement of the method of holding the raft on to the ship. With a hydrostatic release fitted, the restraining straps on the raft stowage will be undone automatically at a predetermined depth of water by the pressure, allowing the raft to float to the surface. In shallow water the valise will merely remain floating on the surface, tethered to the foundered ship and it will be necessary for a survivor to pull the painter to inflate the raft. Should the ship founder in more than 100 feet of water the buoyancy in the packed raft will be sufficient to put tension on the painter and trigger off inflation. Apart from the unlikely occurrence of a ship foundering in deep water before the crew can reach the rafts, there is one serious snag in making the design of a raft meet this condition, i.e.: after inflation of the raft has occurred the painter must break, or something must break, unless the raft is to be dragged under water with the ship. Now this means putting a limit on the maximum breaking strain of the painter system. Successful rescues by inflatable liferafts far outnumber the failures but it is interesting to note that among the failures painter breakages have been prominent. This fact has naturally caused concern among users and quite recently the Icelandic Government, which was the first to adopt inflatable liferafts on fishing vessels, has insisted that the strength of the painter system should be 2,200 pounds for rafts having carrying capacities of 9 men or more. The reasoning behind this approach is that the painter must be strong enough to hold the raft alongside a ship in the worst possible sea conditions-when the raft is needed the most. It is quite likely that an inflated raft, especially a large one, would break even a 2,200 pound painter before being pulled under by a sinking ship but there is no guarantee of this and so, quite rightly, automatic operation is taking second place to the more important aspect of not losing the raft from a ship still afloat in heavy seas.

INFLATION

Inflation of a raft is initiated by the pull on the painter, which, in addition to being attached to a strong point on the raft, is also connected to the valve of a gas cylinder. It is not necessary to open the valise or container in which the raft is stowed, since the internal pressure generated after opening the gas valve is more than sufficient to burst open the fastenings which are specially designed for this purpose.

TWENTY man liferaft.

The gas cylinder is filled with carbon dioxide and a small amount of nitrogen. At low temperature the pressure of carbon dioxide is very low and causes sluggish inflation and, in order to improve the inflation time, nitrogen is added. Unlike carbon dioxide, which liquifies and falls to a low pressure when cold, nitrogen remains a gas and its pressure remains relatively high and so helps the flow of the gas mixture into the raft. At normal or high temperatures the addition of nitrogen to the gas content does little or nothing to help, in fact it is a nuisance since its presence reduces the total weight of gas a cylinder can safely contain.

The volume to which the gas expands varies with the surrounding temperature and in order to achieve satisfactory inflation at very low temperatures it is necessary, in addition to adding nitrogen, to allow an extra amount of gas. This extra amount may be as much as one-third more than that required at normal temperatures. Obviously this extra gas has to go somewhere when the raft is inflated at normal temperature and for this reason relief valves are fitted. A small amount of extra gas can be absorbed by the raft as extra pressure, but with a one-third allowance this is not feasible since it would rise to over three times the working pressure at normal temperature, and to about six times at 150° F. If, on the other hand, only sufficient gas is contained in the cylinder

ABOUT THE AUTHOR

Mr. Edwards joined R.F.D., Inc., in June 1962 having served with R.F.D. Co., Ltd., of Godalming, England, for the past 10 years. He has been closely connected with liferaft design and operation over this period and has taken part in the development of inflatable liferafts to the stage where they were approved by the International Convention for the Safety of Life at Sea in 1960.

for normal temperature inflation, the raft will be badly underinflated at low temperature.

Relief valves can be described as a necessary evil since they are a potential source of leakage and it is usual to provide stoppers which can be used after any excess gas has been relieved. Pressure will vary in the raft between day and night temperatures but the difference is not enough to warrant the fitting of relief valves for this purpose alone.

BOARDING

This has been the subject of continuous research and development for several years. Many experienced seafaring men could see no real future for inflatable liferafts on passenger ships until some means of embarking passengers was found, other than making them jump into the sea or climb down a rope ladder. Inflatable rafts had proved themselves on trawlers and small vessels, but the methods of rescue which had proved so effective with physically fit and tough merchant seamen and fishermen could not be applied without modification to elderly passengers.

The challenge was met by R.F.D. and Schat Davits, two companies who put on a program of research and development which, after 3 years, produced a practical solution. Trials were carried out in shipyards, at docksides, in a wind tunnel, and on several occasions at sea. The trials culminated in a mock abandon ship drill for 42 volunteer passengers on board a 17,000-ton passenger liner in the Bay of Biscay. Three specially designed liferafts were inflated at deck level whilst suspended from a davit, boarded and then lowered to the water, one after the other.

This system of getting passengers into liferafts in the same way as lifeboats has been criticized on the grounds that it complicates the issue and makes liferafts subject to some of the disadvantages of lifeboats. However, on closer examination it can be appreciated that the rafts are still portable and can be carried from a disabled davit, or from an area of fire or dense smoke, or from one side of the ship to the other and launched from another davit, or in the extreme case the same rafts can still be thrown into the water and passengers made to board by ladder, by jumping, or by climbing in from the water.

This latter problem of boarding from the water has come in for more than its fair share of attention. As far as can be ascertained from survivors' reports the majority of rescues have been accomplished by survivors jumping into the raft direct from the ship, probably the low side where

there was a list. On one occasion the crew of a British Trawler had time to load blankets and other conveniences including a pack of playing cards, only to be rescued within 2 hours! Where reports indicated that survivors did board from the water only a few had any difficulty. Bearing in mind, however, that most of these rescues involved fit seamen and that rafts will be used increasingly for passengers, it is now common practice for rafts to be fitted with an inflatable step or ramp as a boarding aid. During tests on these devices it was found that a person with one arm completely disabled and wearing heavy clothes and a lifejacket could climb in unaided.

SHAPE

The basic liferaft design as far as shape and distribution of buoyancy is concerned must be touched upon although this is a subject on which not a little controversy has developed. The International Convention agreed on standard requirements which are 220 pounds buoyancy and 4 square feet for each person the liferaft is designed to carry. Some raft designs have this buoyancy distributed equally into two compartments one above the other, whilst other designs favour a bow and stern section of one tube. The basic difference in these two methods is that with the superimposed tube design, failure of one compartment still provides a fullsized raft, but in the case of the single tube raft only half of the floor area is usable. There are many other factors involved which make it diffiIcult to decide whether one method is best, and for the time being it must be assumed that both types of buoyancy division are basically satisfactory.

Differences in plan form also exist, some rafts being circular, as were the wartime dinghies, while others are boat shaped. A circular raft has the greatest beam for a given capacity of raft, a feature which cannot be disputed, and this makes the streaming of a sea anchor in heavy seas less important than is the case with the boat shaped raft.

MATERIALS

Many liferafts are still manufactured in rubber proofed cotton fabrics, although the use of synthetic textile and rubber is increasing. One of the synthetic textiles in common use is Nylon and this can now be woven in high tenacity yarns and has a superior strength weight ratio to cotton. It is also highly resistant to most forms of rotting. One of the well-known synthetic 'rubber' products is Chloraprene, or Neoprene, and

this is now used extensively for proofing fabrics used in liferaft construction. The advantage of Neoprene is resistance to ageing, weathering, and oil, although it does not have the same low temperature flexibility as natural rubber.

The fabric, even in two- or threeply construction, is relatively thin but it has remarkable strength-equivalent in tensile strength to mild steel. But the strength of a raft does not necessarily lie in the tensile of the fabric, but more in the low working pressure, about 2 pounds per square inch, which allows the tubes to "give" when subjected to impact. Only knife edged or pointed projections are liable to cause damage and neither the barnacle covered side of a listing ship nor a rocky shore should be cause for anxiety.

With the exception of the inflation cylinder and valves, metal and other hard materials are almost entirely eliminated from liferaft construction as damage can be caused to the fabric through corrosion or chafe.

PROTECTION

Protection is next, after Flotation, in the logical order of survival. Carley floats and other forms of buoyant apparatus provide flotation in that they keep a survivor from sinking, but flotation alone is not enough except for short periods in warm seas, and even then sharks are a problem. Exposure in very cold climates is fatal

after quite a short time and in hot areas some protection from the sun is also necessary. Even the early World War II dinghies had an apron under which the survivors could obtain shelter and there is still in existence a dinghy made in the late 1930's for Imperial Airways having a canopy held up by inflatable arch tubes in the same way as modern liferafts.

INSULATION

Liferafts today usually have a double-walled canopy separated by an air layer. The floor is also double and capable of being pumped up by hand. With these refinements a full complement of survivors can raise the temperature within a raft by body heat to as high as 70° F. even with an ambient temperature below the freezing point. This is good but it has brought along an attendant problem; that of carbon dioxide concentration, the product of exhalation. When the carbon dioxide content in the air becomes higher than 3 percent there is a danger of suffocation, and the only remedy is a supply of oxygen or fresh air. Unfortunately a high concentration of CO2 causes drowsiness and survivors in this state can easily succumb without realizing what is happening. It will be appreciated that ventilation is of the utmost importance in the design of a liferaft canopy, but in achieving good ventilation it must be borne in mind that the area of the ventilator must be sufficient to meet the needs of a full complement of survivors, it should not be possible to seal it off completely, but it must not allow water to enter the raft. last requirement of watertightness is not as easy as it sounds when it is remembered that water can come in the form of driving rain or spray or even breaking waves. One method commonly employed is to make the entrances provided for boarding of such design that they are impossible to seal off completely. It is also highly desirable that a lookout can keep watch at all times without disturbing the features of the entrance or ventilation systems.

SURVIVAL RATIONS

The

Under the general heading of Protection, mention could also be made of survival rations. Water is essential to survival and much more important than food. Two pints each day per person is reckoned to be the minimum requirement although on the first day water can be completely omitted. Doctors tell us that the digestion of food uses up water, and as every available drop of water is needed by the human body to prevent dehydration, the amount of food in

cluded in the survival pack is very limited and is in the form of hard bread or a biscuitlike substance. Condensed milk and rum fudge have also been included occasionally. Owing to the importance of water to survival, it is customary to embody in the canopy design a rain catchment area and collecting tube. Plastic bags stowed in the survival pack can be used to store water.

Provided there is a regular supply of water there is every chance that survival could continue for 2 months. During World War II three American airmen survived 70 days in an open rubber dinghy in the Pacific Ocean. In more recent times Dr. Bombard, a French doctor interested in the plight of shipwrecked mariners, crossed the Atlantic in a boat under sail, carrying a sealed ration pack which he did not open. The voyage lasted 65 days and he lived entirely from the sea.

Among the other survival items usually included are a first-aid kit, antiseasickness tablets, torch, knife, repair kit, and pyrotechnics.

LOCATION

Probably the first thing survivors think about is being rescued. It is extremely difficult to pick out a small raft on the sea even if it is being looked for. If it is not known that a raft is in the area the chance of being spotted is greatly diminished. Many a survivor has recounted the agonizing moments when a would-be rescuer has passed almost within shouting distance without noticing anything.

INFORMING RESCUE ORGANIZATIONS

It is most important to ensure that a distress message is sent before finally abandoning a ship. This may be stating the obvious but it may not be realized that once in the raft any communication with the outside world is very limited. Radio transmitters can be supplied for inflatable liferafts, but in these days of congested radio traffic a good, high, and well insulated aerial is needed in order to get a message through on the International Distress frequencies of 2182 and 500 k/cs, and this is not easy to achieve in a liferaft except in relatively calm seas. This situation will be a lot brighter when a wider use of Very High Frequencies is made but at the moment only the Services and aircraft are so equipped.

The most certain way of ensuring the commencement of a Search and Rescue operation is for every ship to make regular reports to her owners, AMVER or someone who will take action in the event of any failure to re

port. A great many searches have been initiated only by a ship being "reported missing" and obviously the greater the frequency of regular reports the shorter will be the time before search is started in case of trouble, and this will reduce the area of search.

EDITOR'S NOTE: The author recommends that the most certain way of ensuring the commencement of a Search and Rescue Operation is for every ship to make regular reports to her owners, the Coast Guard, or someone who will take action in the event of any failure to report. The Coast Guard does not have the facilities to provide a vessel-following service as envisioned by this statement. Even the AMVER System, which provides a dead-reckoning plot of reporting vessels, is not capable of keeping track of whether or not vessels are overdue. Vessel operators are encouraged to require their vessels to report to them periodically with an "All's Well"-type message in order to keep track of the safe progress of their own vessels. Such a system would give the operator an early indication of trouble and the Coast Guard could be so informed.

FINAL LOCATION

Once a search has begun the problem is narrowed down to the systematic coverage of an area which can be predicted fairly accurately from the vessel's last reported position, next port of call, speed, tidal information and wind force and direction. The role of V.H.F. radio equipment at this stage is to provide a signal on to which a search aircraft or ship can "home." An alternative, though not so effective, is the fitting in the raft

of a radar reflector. A good reflector will give a response on a search vessel's equipment over many miles providing the sea is not too rough. A raft without any equipment will give a radar response, but only up to 2 miles. Final location must of course be visual but this can be extended to many miles with careful use of the flare and smoke pyrotechnics and other equipment stowed in the raft. Pyrotechnics can be used in daylight although they are far more effective at night. A pyrotechnic radar reflective signal now available can eject 280,000 dipoles at 1,200 feet, giving a range of up to 12 miles for about 15 minutes.

The sun can be a help or a hindrance to location depending on its relative position to the raft and search vessel. The power of the sun can be used to good effect by reflecting its rays onto a search vessel by means of a heliograph. The colour of the raft, Indian orange and black, has been chosen after many trials to be the most conspicuous with the sun in front, behind or in twilight.

THREE CONDITIONS FOR SURVIVAL The three conditions to survival: Flotation, Protection, and Location are all involved in the design of an inflatable liferaft and its equipment. Many years of research have brought designs to their present advanced stage and it is gratifying to know that a good number of lives saved from marine casualties in recent years are due to inflatable liferafts.

Recently a vessel was loading pallets of flour, employing a long wire sling at No. 4. A supervisor was observing the loading operation; he saw nothing amiss-but like a batter in the box who scans the entire infield for a possible weakness-he was watching. He was also engaged in conversation with a man nearby, but his eyes seemed to follow the movement of the hook, going in the hold and coming out.

The winchdriver suddenly developed the lax and hazardous habit of dragging the empty slings on the return, across the deck, and over the side. The hatch tender (sad to relate) had his back to the entire operation.

Suddenly the dragging wire sling looped across the bulwark with the bights whipping underneath-with one catching on an oil vent.

Our man went into immediate action, and before he actually realized what he was doing, had shouted to the

winchdriver to "hold it!" He pointed to the snagged wire. Fortunately there was enough slack to enable everything to come to a halt before the wire set tight. Just a few feet away, with a surprised look on his face, stood the hatch tender.

What did our man prevent? We can think of several things. He prevented the possible maiming or death of the hatch tender, for vents do pull loose, and wires whip.

He prevented the possible pulling down of a boom.

He prevented, at the least, loss of time and money.

But best of all, he prevented an accident BEFORE it happened.

This quick action of his is known as automatic reflex action.

Many people have it, some never get it. Fortunate is the man who does. -"Stevedores' Guide"

There were 904 vessels of 1,000 gross tons and over in the active oceangoing U.S. merchant fleet on September 1, 1963, 11 less than the number active on August 1, 1963, according to the Maritime Administration. There were 15 Government-owned and 889 privately owned ships in active service. These figures did not include privately owned vessels temporarily inactive, or government-owned vessels employed in loading storage grain. They also exclude 26 vessels in the custody of the Departments of Defense, State, and Interior, and the Panama Canal Company.

There were two less active vessels and nine fewer inactive vessels in the privately owned fleet. One freighter, the American Contender, was delivered from construction. Three freighters, the Alcoa Pennant, Alcoa Pioneer, and Alcoa Pilgrim, and a tanker, Mermaid, were turned in to the Government on an exchange, and the three freighters, American Marketer, American Supplier, and Beloit Victory, were taken in exchange from the Government. Of the 89 privately owned inactive vessels, 12 freighters and 7 tankers were being repaired or reactivated. The others were laid up or temporarily idle.

The Maritime Administration's active fleet decreased by two while the inactive fleet decreased by two. Three freighters were sold for scrap, and three freighters were transferred to the private fleet. The total Government fleet was 1,833. The total U.S. merchant fleet was 2,811. Contracts were awarded for three new freighters and one tanker and for one tanker conversion. One new freighter was delivered. The number of large oceangoing ships under construction in U.S. shipyards increased by 4 to 56.

The St. Lawrence Seaway handled a record cargo of 4,196,000 tons during the month of June 1963. The previous high was 3,889,000 tons in October 1962. Figures released by authorities show a 14.7 percent increase during the April-June period over the same period last year. The increase reflected larger upbound shipments of iron ore.

The S.S. Pioneer Moon, one of nine fast cargoliners operated by the United States Lines in its express service to the Far East has established a new speed record recently on a run from Yokohama, Japan, to New York.

Captain James Knowlton, Master, reported that the 13,600-ton vessel had steamed the 9,726 nautical miles from Yokohama in 17 days, 14 hours and 48 minutes. Normally, the Company's cargoships operate on a 20day schedule from Japan to New York.

The Moon averaged 23.09 knots while steaming. The ship left Yokohama at 11 a.m. April 28th and arrived off Ambrose Lightship at 2:24 p.m. May 16th. She spent approximately 12 hours in the Canal Zone.

CAPTAIN EDWARD F. QUINN, Master of the Tug Margaret, recently received a letter of Commendation in recognition of the splendid seamanship shown in the rescue of 14 men from an oil rig, Mr. Louie, on October 3, 1961.

The presentation was made to Captain Quinn by the Maritime Administration at the Mobile Area Office.

The letter of Commendation reads as follows:

Captain Edward F. Quinn
Tug Margaret Walsh

It is my privilege to commend you for the perseverance, devotion to duty and splendid seamanship which you and the crew of the Tug Margaret Walsh displayed in the rescue of 14 men off the Oil Rig, Mr. Louie, on October 3, 1961.

As the Mr. Louie was being towed from the Bay of Campeche for drilling operation in the Louisiana coastal waters, high winds caught the vessel and damaged the structure's derrick, causing it to collapse and hang over the side. The tow was then broken, creating an imminent danger that the oil rig might become unbalanced and turn over. In response to a call for assistance, the Margaret Walsh was first to arrive on the scene. A tow line was secured to the oil rig but, due to extremely high winds and heavy seas, it broke. Fearing for the

July 25, 1963.

safety of the men aboard, and believing that they might be coming off in life rafts, you continued to stand by but 25 foot swells and 70 mile an hour winds prevented this type of evacuation. A careful survey of the situation revealed that the best possibility for removal of the men would be to back your vessel into a very small area on the leeward corner from which the men could be lowered aboard by the use of crane and nets. After completing this daring maneuver four times, all the men were safely removed from the rig.

I congratulate you and your crew upon the performance of a service which was in keeping with the highest traditions of the United States Merchant Marine and I have directed that a copy of this letter be made a part of your service record.

DONALD W. ALEXANDER,
Maritime Administrator.