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Mr. K. S. Harrison
Chief Counsel and Member
DIST. (SDL NO. 82)
A: a b c d e w(2); f g h i j k l m n o p q r s t u v(1)
Lieutenant A. J. Arnett, USCG, Editor
Common sense advice to the less experienced on conducting a vessel through rough weather passage was the order of the day nottoo-long-ago at a meeting of The Honorable Company of Master Mariners in London. The advice is universal and most apropos this winter season. It is our pleasure to pass it along to an even wider audience.
Captain G. Lindsey
THE INDULGENCE of senior shipmasters is craved in placing before less experienced members of the profession the following considerations concerning deep sea ship management in heavy weather. The ordinary practice of seamanship should cover everything stated, but it will be agreed that the ever increasing repair yard costs makes the school of experience an extravagant method of instruction which much be supplemented in every way possible. For there can be little doubt but that a considerable amount of weather damage sustained in way of hatches, ground tackle, rudders, and setting down of decks, etc., apart from the more serious strains through pounding, racing, and laboring, could be reduced with a better appreciation of the problems involved, especially in regard to engine speed and steering in adverse conditions. There may be some who consider that it is sufficient to enter port with varying degrees of damage, relying on suitable log book entries to absolve the ship from blame in the matter, but such recourse can bring little satisfaction either to the master, the owners, or underwriters involved.
Having for some 20 years commanded passenger and cargo liners, general traders, bulk carriers, and tankers the writer has gained a fairly wide experience in this matter. It is of course well known that no two ships are exactly alike, even sister ships vary in their behaviour at sea, and lines and engine power make so much difference. In the low powered bluff bowed ore carrier, damage in heavy weather by excessive speed is not perhaps so likely, for engine revolutions will at least to some extent automatically drop when driving against head winds and seas, and
nursing such ships may then consist of little more than keeping the most comfortable course compatible with the direction it is intended should be made good. But in every trade faster ships are now the order of the day, the 10 to 12 knotter being rapidly linked with the past. And it would appear that it is just when the vessel's capacity exceeds this low minimum that the trouble begins, for damage by excessive speed can so easily be sustained unless a constant weather eye is lifted and timely action taken.
In passenger liners and other vessels where the maintaining of timed schedules is essential it may be found necessary at times to continue at speeds which would otherwise be undesirable, and in any case such ships are generally strengthened for the purpose. But in the great majority of general traders, bulk carriers, tankers, and tramps, the master will surely best serve his owner's interests by carefully nursing his ship through heavy seas, reducing speed as necessary to insure that damage is kept to an absolute minimum. By "reducing speed” is not meant just a token adjustment to comply with the “reduced speed for heavy weather" entry in the log book, but a realistic reduction to suit the circumstances. It will often be found that a reduction of perhaps up to a quarter of the maximum revolutions will ease the strain considerably with little loss of speed in the prevailing conditions. Greater reductions should however be accepted without hesitation if conditions so warrant, the resultant saving in fuel, apart from any other factor compensating to a considerable extent for mileage losses. Many vessels employed on charter work will have speed clauses in their agreements with
which their masters will be anxious to comply, but even here every advantage should be taken of fine weather to maintain satisfactory overall speeds, easing engine revolutions when occasion demands. To assess and allow properly for the changing situation requires the master's constant attention and it need hardly be stated that when speed is reduced, the keenest watch must be kept for any improvement in conditions which can justify increased revolutions. The operative word is “nursing” (to tend, foster, and preserve) calling for unfailing vigilance, in shepherding the vessel through heavy weather.
As already stated to achieve satisfactory overall speeds it is manifestly necessary to take every possible advantage of fine weather conditions. Draught, trim, and condition of ship's bottom are the factors governing speed in fine weather, the master haying a varying amount of control over the former two. In the loaded condition most vessels get along best on a more or less even keel, they should never be trimmed much by the stern, and some vessels will even make better speed when trimmed a little by the head than too much otherwise. When light, the propeller should of course be sufficiently deep in the water to get a good "grip," possibly just completely submerged, whilst the draught forward should be as light as can be without allowing pounding to take place. Those keen enough will carefully study the "slip" figure from passage to passage, for by so doing a fair idea may be obtained of speed efficiency in relation to weather, engine revolutions, and condition of ship's bottom. True slip incidentally is the difference between distance by engine (pitch X revs), and the cor
Towering waves temporarily submerge the catwalk connecting the midship house with the aft quarters of this Texaco tanker. On the latest tankers in the Texaco fleet, the catwalk has been replaced with a patented underdeck tunnel, which protects both seamen and equipment from rough seas.
error of the log, which must be carefully ascertained over known distances and conditions, must always be applied to make the pitch calculations of any real value. Generally speaking a vessel with a clean bottom should in fine weather suffer a slip of not more than 6 percent. It follows that slip must be positive, and a “negative slip" can only be described as anomalous.
Apart from speed control in nursing the vessel, it will be appreciated that excessive pitching, lurching, and rolling can often be eased by comparatively small alterations of course. Το prevent isochronism a vessel's period of pitch or roll (in itself dependent on weight distribution, draught, etc.) must be kept out of step with the wave cycle, and it is obviously here that small alterations of course or speed can somctimes be so beneficial. Possibly only after a period of trial and error, but well worth the effort just the same.
Stability, another factor affecting the ship's behaviour at sea, is one over which the master today has decreas
suitable metacentric heights will pay dividends. A tender ship is always preferable to one with excessive righting moment, the writer having served for many years in ships carrying full citrus cargoes with large quantities on deck, where the GM is unavoidably reduced to an almost minus figure. Whilst this makes for heavy slow rolling such ships are nevertheless comfortable and do not suffer any straining. On the other hand in tankers and bulk ore carriers the metacentric height is more or less fixed, whether in the light or loaded condition, and is always high. In this connection mention should be made of the advantages to be gained from some bulk carriers, wing tanks enabling these compartments, with their comparatively high center of gravity, to be used in preference to the DB's. Again in tankers slack tanks should be avoided where possible, apart from other reasons, to decrease metacentric height.
Draught and trim, especially in the ballast condition, and trim particularly as apart from actual draught,
rough seas. Whilst it is appreciated that such disposition cannot often be completely achieved in general traders, there would appear to be no reason why tankers and bulk carriers cannot at all times be satisfactorily ballasted in this respect. Tankers must approach their loading berths with minimum ballast to assist quick turn around, but draught and trim in such vessels is easily adjustable at sea, and no effort should be spared in so doing at any time to suit varying weather conditions. For whilst on the one hand there is no point in trapesing cargoes of water around the oceans, neither should the ship be allowed to suffer through insufficient, or incorrectly distributed, steadying weight. In really fine weather conditions, such as are experienced a good deal in many tanker trades, the writer has found that the effort of reducing the quantity of ballast to an absolute minimum has been rewarded by quite exceptional speed averages. The whole matter of ballasting forms an important factor in ship nursing, and whilst many smaller vessels get around perfectly well without permanent ballast arrangements of any kind, other than their DB tanks, masters should surely take every advantage of such facilities as are placed at their disposal.
The increasing popularity of the bridge aft design, in the construction of all types of vessel, has highlighted another problem in ship management at sea, that of vibration. Excessive vibration is the cause of much damage on board ship, and although not directly connected with heavy weather this trouble can be much accentuated by it. In the bridge aft vessel the navigational instruments are particularly vulnerable to damage by vibration, for it would be difficult to imag
but alterations to trim and ballast, often quite limited, can sometimes help in this direction. The more distressing vibrational disturbances on board ship originate around the propeller cavity, and generally decrease with deeper draft. Vibration is, of course, another problem devolving from isochronism, and apart from basic ship design, the positioning of mechanical auxiliaries, layout of piping, method of securing, etc., have all to be considered in attempts to abate this nuisance.
To prevent unnecessary wear and tear on the rudder, its carrier, engine, and bearings, in heavy seaways, the helmsman should be warned against the practice of applying continual and
adjustment will also need some increase to prevent "hunting." Makers of automatic steering equipment boldly refer to their equipment as "Brains Units," but their admittedly clever devices have yet to be "taught" to carry helm, and until this can be achieved an experienced helmsman will best nurse the vessel through really adverse sea conditions. That experienced helmsmen are difficult to find these days is appreciated, but they can be taught. Here it might be mentioned that on altering course at any time when proceeding at full speed it is obviously undesirable to put the helm “hard over" unless the alteration of course desired is urgent.
ine a more unsatisfactory position than high up on a ship's bridge placed almost directly over the stern area, for the siting of this delicate equipment. Yet there, of course, it has to be, and even so it is still common practice to bolt radar sets, gyro compasses, etc., directly to decks and bulkheads without any form of cushioning whatsoever. As a result equipment in this type of vessel often needs servicing, and whilst the problem of vibration is now the subject of serious study in ship design, this point might well be given more immediate consideration, and attention. Action by the master to lessen vibration would seem to be confined to avoiding critical speeds and racing of the main engines,
excessive helm in the fruitless task of keeping the vessel exactly on her course. The aim must always be to find and carry the right amount of helm to keep the vessel reasonably close to the direction intended, thereby relieving the rudder of the intolerable strain of constant movement. Automatic steering gear, with rudder angle adjustment and yaw controls, is now rapidly becoming standard equipment. But these controls must be properly understood and adjusted to suit varying weather conditions. The right amount of adjustment can perhaps best be ascertained by studying the rudder indicator, and whilst in rough weather greater yaw must be permitted, the rudder angle
Susceptibility to deck weather damage must be linked to a considerable degree with freeboard, the loaded tanker and deadweight ore carrier being particularly vulnerable in this respect. A few years ago due chiefly to the multiplicity of watertight compartments, new rules were introduced allowing deeper loading in this type of vessel, the minimum freeboard being reduced by some 18 inches in the case of a 15,000-ton deadweight ore carrier commanded by the writer at that time. With such little freeboard the decks of this vessel were continually awash even in moderate weather, heavy seas being constantly shipped and, due to the open bulwarks, as quickly thrown off again. The vessel rolled with a period of not more than 6 seconds, so that no water remained on board for long, and experience showed that this deeper loading did not lessen the safety factor provided that the vessel was properly nursed as occasion demanded. In such vessels, with long open sweeps of deck, great care must be taken to prevent heavy seas landing on board with gathering momentum, carrying away fittings, etc. Deckhouse bulkheads, apron plating, etc. are particularly vulnerable in this type of ship, and the breakwaters sometimes provided are most helpful. Masters of vessels whose employment includes the carriage of fragile deck cargoes soon appreciate the need to avoid shipping heavy water and do not hesitate to heave to completely when occasion demands, for it is the accepted thing to deliver such cargoes damage-free. Admittedly these vessels, mostly of the shelter deck type have high freeboards, and with care and attention can normally be kept reasonably dry. Here it might be suggested that masters employed by companies operating ships of various design and speed should bear in mind the very different propensities of the vessels to which they may be appointed.
Every experienced seaman will know that it is essential for anchors to be hove absolutely tight home and properly secured when proceeding to sea to prevent anchor fiukes, shipside plating in way of same, and hawse and spurling pipes sustaining fractures and other damage through movement at sea. Frequent inspection of ground tackle should be carried out in heavy weather to insure that all is well in this respect. Flooded forecastle spaces causing considerable store damage result from failure to place weather boards in position and tonnage openings in shelter deck vessels are especially vulnerable. Need it be mentioned that ports especially in the lower accommodation must be the subject of regular overhaul both as to packing and greasing of lug screws, whilst timely warning before alteration of course into a beam sea sent down particularly to the galleys and pantries can avoid personnel accidents involving heavy claims. All common practice of seamen of course, but sometimes overlooked.
There is talk these days of the crewless vessel ploughing the oceans by remote control when the electronic device will take the place of seamanship and the shipmaster's profession lost in the mist of antiquity but until that time does come along surely it is
Swedish freighter Orion labors in heavy seas 430 miles northwest of Achill Head, Ireland, after radioing an urgent message on October 13, 1965, that she had three cracks in her decks. T'he U.S. Coast Guard Cutter Northwind stood by the freighter and her 30 crewmen for more than 12 hours until the seas abated.
Four days later the Orion again radioed for assistance when she was in heavy seas 680 miles northeast of Cape Race, Newfoundland. The Cutter Northwind, a 269-foot icebreaker, again stood by the freighter and escorted it to the safety of the sheltered waters of the Gulf of St. Lawrence. The freighter was en route Toledo, Ohio, from Leppaluoto, Finland, with a cargo of wood pulp.