SEA KINDLINESS AND SHIP DESIGN

BY

'CAPTAIN K. MACDONALD, .0.B.E, AND E. V. TELFER, D.Sc., Ph.D4, Vice President

A Paper read before the North East Coast Institution of Engineers and Shipbuilders in Newcastle upon Tyne on 2the 18th March: 1938.(Excerpt from theInstitution . Transactions, Vol. LIV)

NEWCASTLE UPONTYNE PUBLISHED BY THE NORTH EAST COASTINSTITUTION OF ENGINEERS AND SHIPBUILDERS BOLBEC.HALL.

LONDON E. & F. N. SPON; LIMITED, 57, HAYMARKET,S.W.I. 1938. THE INSTITUTION IS NOT RESPONSIBLE FOR THE STATEMENTS MADE, NOR FOR THE OPINIONS EXPRESSED, IN THIS PAPER, DISCUSSION, AND AUTHOR'S REPLY

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Printed by J. G. Hammond & Co., Ltd., Moor Street Birmirohatn, and London. SEA-KINDLINESS AND SHIP DESIGN BY CAPTAIN K. MACDONALD, 0.B.E., and E. V. TELFER, D.Sc., Ph.D., Vice-President SYNOPSIS.-/t is suggested that modern progress in ship design has been principally directed to improved smooth-water performance and not suffi- ciently to improved behaviour under adverse weather conditions.Such behaviour as is good is known as "sea-kindliness," a quality not to be confused with seaworthiness. Rolling considerations are used to introduce the subject of sea-kindliness. Sailing ships and steamers are compared and light versus concentrated cargoes are discussed.Various design aspects are mentioned.Next, pitching is considered in relation to cargo distribution and to external form. Particular attention is given to the modern fashion display in stem design, and a preference registered for the old-fashioned clipper stern as having scientific justification.Fine versus full cruiser sterns are discussed. Course- keeping as effected by rudder and stern design, for loaded and ballast conditions, receives some attention, and the adoption of the topgallant forecastles in shelter-deckers and trysails aft is considered in this connection. Adequate engine power to face normally heavy, but not dangerous, weather is next introduced for discussion as it is felt that this aspect of the problem has been seriously overlooked in the modern economy ship.Propeller design is also touched upon. The behaviour and control of ships in really dangerous weather is next studied and reference is made to recent Board of Trade enquiries into the loss of various merchant vessels.The importance of heaving-to is empha- sized and its technique is outlined, various alternative methods being dis- cussed.The difference between sail and steam is again emphasized and a plea is made that the training of officers should compulsorily include training in small steam or sail vessels.Finally, the possible use of model experiments in assisting the better understanding of sea-kindliness and possibly the better interpolation of freeboard between various types of deck erections, concludes the paper.

HE following notes are intended to serve as an introduction to -the general subject of the sea-kindliness of ships and its useful discussion before this Institution. Much has been written on the so-called economy ship, and of the immense amount of model experiment that has largely made such economy 228 SEA-KINDLINESS AND SHIP DESIGN possible.Little, however, has been heard of the nautical handling of these vessels, or for that matter of that of their less efficient predecessors. It is quite certain that efficient handling and loading in adverse weather conditions are of an importance at least equal to that of the economy of an economy ship.It is further certain that some ships lend themselves better to efficient handling than others.This fact suggests that ease of handling can be inherently a ship quality which, together with other features of good behaviour, constitute various acceptable aspects of sea-kindliness.In what follows, discussion will first be directed to those aspects of sea-kindliness that appear to depend upon ship design as distinct from those which essentially involve the skill of the navigator. It is, incidently, to be suspected that many of the intrinsic design qualities may be entirely negatived by poor seamanship.This fact must be anticipated in design work, and every endeavour made to reduce the possible relative importance of the human factor, while of course still allowing this factor full scope in the better handling of the ship.Design and navigational skill call for separate and also joint discussion, and the particular joint authorship of the present paper has been undertaken in the hope that extreme diversity of outlook may in itself assist in producing a discussion sufficiently stimulating to excuse any lack of novelty from which the paper, as such, may suffer. 2 Sea-kindliness must not be confused with sea-worthiness. A ship is regarded as seaworthy when her hull and machinery are sufficiently sound, structurally and mechanically, to admit of any projected voyage being undertaken and completed with dispatch, and with complete safety to both ship machinery and cargo. A seaworthy vessel need not, of course, be sea-kindly, although it may easily happen that the deficiency in sea-kindliness is so marked in adverse weather as to result in the vessel's sustaining such structural or mechanical damage that she is rendered unseaworthy.Sea-kindliness is thus a very desirable adjunct to seaworthiness, and for some voyages may even be regarded as a very necessary adjunct.This aspect of the problem is best illustrated by a consideration of transverse stability in relation to seaworthiness and sea-kindliness.Sufficient stabilityin amount and angular extent is apparently essential for seaworthiness.The use of "apparently " here requires justification and qualification since it is well known that too much initial stabilityas is usually possessed by a vessel carrying ore can result in very excessive rolling and thereby exposethe vessel to a greater likelihood of heavy-weather damage than would be the case with a vessel rolling slower and less violently in response, notonly to less initial stability, but probably actually negative initial stability. It is generally considered by sea-going people of experience that a sailing ship is more sea-kindly and seaworthy in heavy seas than a power- driven vessel of the same size, since the sails very effectively prevent heavy rolling, and consequently also prevent the shipping of dangerous SEA-KINDLINESS AND SHIP DESIGN 229

athwartship seas.Accepting that this is so for the moment, it is interest- ing to contemplate how essentially different the sailing vessel is from the steamer in this respect.The former, because of the relatively high centre of gravity, must be designed for a high vertical position of meta- centre.The beam can therefore be expected to be large and the rise of floor pronounced, particularly where beam is restricted or excessive beam is to be avoided. A sailing ship carrying ore has a greater metacentric height than a steamer having the same homogeneous-cargo metacentric height.Despite this, due to the steadying influence of the sails and the more circular frame sections in the vicinity of the waterline, rolling is not severe.Where the beam wind does not accompany the beam sea the sailing ship will, of course, suffer excessive rolling, and it is probable that vessels were usually dismasted under such conditions.In some modern power-driven vessels there is a tendency to design for rounder sections and greater beams.Such forms, although low in wetted surface, must necessarily have large metacentric heights and thus suffer from excessive rolling.Sufficient experience must have now been obtained with these vessels to compare their smooth-water and heavy-weather performance, and it is hoped that such data will be available in the discussion of this paper.Large-beam vessels, which maintain their full amidship beam down to the ballast draughts, suffer extremely from excessive metacentric heights.Their rolling is excessive and it is not improbable that such vessels become unmanageable more frequently than do vessels of more moderate beam. At the other end of the scale, the low-beamed ship, while good for ore cargoes, becomes under suspicion for, say, timber cargoes.The majority of timber cargo vessels trade for at least the latter part of each loaded voyage with either a negative or a very small metacentric height.Such vessels generally develop a list to leeward and then behave in a remarkably sea-kindly manner, and lost deck cargoes represent a relatively small percentage of the total carried.Evidently here also, as in the sailing ship, the wind steadying effect and the long easy roll are factors that contribute to seakindliness.A well lashed and secured deck cargo represents a very material increase in reserve buoyancy and stability at large angles.Provided that the greater vulnerability of the hull at large angles is adequately protected against, the intrinsic safety arising from excellent sea-kindliness in association with ample angular stabilityis fully recognized in the latest international freeboard regulations where increased draught is allowed vessels carrying timber.The design principle here involved is evidently that sea-kindliness at small angles is relied upon to ensure seaworthiness at large angles.This principle appears to be of real importance. 3 In the previous section the subject of sea-kindliness has been introduced and illustrated chiefly by reference to rolling.The next feature of behaviour involving seakindliness is that of pitching.Under suitable sea and swell conditions all vessels pitch, but obviously the manner and 230 SEA-KINDLINESS AND SHIP DESIGN amount of pitching must differ between ship and ship.The worst kind of pitching is that when a vessel heaves and pitches into an on-coming sea. The easiest type of pitching is that of a vessel whose stem is rising in anticipation of the crest of the on-coming swell.The phasing of a vessel's pitching between these limits is essentially a matter of relative swell and wave frequency and pitching frequency. This latter is not always capable of control except possibly in the case of an ore carrier. Here, although it is possible to reduce the pitching period by concentrating weights amid- ships, thereby making the vessel more lively and only likely to synchronize with relatively short less dangerous seas, yet such concentration if extreme may seriously increase sagging stressesalways the more dangerous and thus an attempt to improve seakindliness may act adversely on the ultimate seaworthiness. Pitching is something that generally is perforce tolerated by the navi- gator.He may occasionally change course or speed to avoid the repetition of dangerous synchronism, but it is doubtful whether this art is seriously practised in merchant ships.From the design standpoint, very little is really known of the effect of out-of-water form on pitching behaviour.Some flare forward is usually regarded as essential for dryness in short steep seas, but against heavy seas it appears to avail but little.A well flared forecastle on a shelter deck is, however, rarely itself swept by heavy seas.In association with a middle body having even a moderate tumble-home at the shelter deck (say 12 inches in 56 feet beam) it is curious how seas appear generally to be shipped abreast the foremast at a point where the forward flare changes into the amidship tumble- home.Such seas are very troublesome from the standpoint of easy access to the saloon house, and recent experience has shown that the accommodation should be arranged to avoid side doors. The after lines do not appear to have the importance of the forward lines.The change from the cylindrical stern to the cruiser stern can be said to have passed without great objection.Cruiser sterns do not poop any more, and actually probably less, frequently than cylindrical sterns, and the really fine-lined cruiser stern is not likely to offer any advantage over a very much fuller and flared out cruiser stern correctly designed in avoiding flat-bottomed sections.This point was brought out in the discussion of Mr. R. C. Thompson's paper on the modernized motorships Silverpine and Silverlarch.*It would be of interest to learn whether the subsequent service performance of these ships has shown any definite lesson on fine versus full sterns.The fine stern may result in a less vertical pitch aft than forward, which may just manage always to keep the screw submerged ;but this is not necessarily good, since a propeller just submerged is known to be definitely less effective than one three-quarters submerged.The fuller stern on the other hand receives greater fore and aft pressures from following seas where synchronous pitching is unlikely, and is thus likely to be better in a following sea than the fine stern.This opinion is generally held by seagoing people.

*Trans. N.E.C. Inst.Vol. LH. 1936, SEA-KINDLINESS AND SHIP DESIGN 231

In sailing ships the centuries of development produced an out-of-water form fine forward and full aft, the most obvious feature being that of the clipper stem.This stem has recently shown some general evidence of revival.In some cargo vessels recently built by Messrs. J. Readhead & Sons for Messrs. Andrew Weir, the load waterline entrance angle was kept constant to the forecastle head.This, in association withthe usual flared frame sections, produces a very pleasing clipper-stem outline with some claim to scientific as well as msthetic design.This considera- tion ensures that the vessel pitches in with no greater waterline angle than that which the usual smooth water model experiment shows is good for the service speed and free from likelihood of growth at such higher speeds as locally result from the passage of ocean waves.Such a stem design is not likely to result in appreciable, if any, increase in resistance during pitching.A few North Atlantic ore-trade service results are already available for these vessels ; and despite heavy weather and the nature of the cargo, excellent voyages have been made.The maximum propeller apparent slip in the heaviest weather westward has so far only amounted to 11 per cent., a fact which suggests considerable promise that one important commercial and propulsive aspect of sea-kindliness has lent itself to development.

4 The subject of stem design also very intimately concerns the man- ceuvring, ease of handling, and course-keeping qualities of ships. Whatever virtues can be ascribed to the modern heavily raked stem, these must be entirely negatived by the poor course-keeping ability of vessels fitted with such stems.Already the craze appears to be easing off and a return made to moderate rakes or the clipper stem. Excessive rake probably more adversely affects the ballast performance than the loaded.Good ballast speeds call for long fine entrances, a feature which is entirely destroyed by excessive rake. However essential a topgallant forecastle may be from a dryness standpoint, it is probably a definite disadvantage in heavy beam and bow weather.Whatever the remaining distribution of deck erections, it is quite certain that the forecastle or its vicinity is the chief cause of a vessel's being unable to turn into the wind and thus falling off her course. Actually, from sister ships fitted with normal and sunk forecastles respectively, it appears that height is not the vital factor :flare seems to have a greater determining importance on the effective height of the deflected wind than forecastle height alone. The control of effective height naturally directs attention to forecastle streamlining.That of the Normandie will be immediately recalled as a bold and pleasing combination of two old ideasthe clipper stem and the turtle deck stringer.This latter is an old idea applied to railway train roofs and these have the effect of reducing side pressure on the rails.Further, in our fast stream-lined trains the engine nose is given a negative sheer or inverted scow form. This nose will have a low 232 SEA-KINDLINESS AND SHIP DESIGN resistance for all wind directions forward of the beam, and some similar device is really required for ships.Actually, of course, the idea nautically is old ; the turtle forecastle was a feature of the early torpedo boats, modern motor launches and many old and new coasters.The idea does not yet seem to have been applied to large merchant ships, but it appears clearly preferable to the modern topgallant forecastle on shelter deckers. Intimately associated with forecastle and stem shape is rudder area and shape. Adequate rudder area does not yet concern the classification societies, but its minimum value is just as important as the now introduced minimum speed for scantlings.An analysis of available data for mechanically propelled vesselssuggests that rudder area given by A =LD /100 (1 V 12-VL), A being rudder area in square feet, L length of vessel on load waterline in feet, D load draught in feet, and V speed in knots, represents existing practice very well.If the rudder has fixed stream-lining in front of it, half the fin area may be subtracted from the formula area while fully maintaining a vessel's steering and course- keeping qualities.Ballast steering considerations raise the question whether a rudder should be rectangular or of increasing fore-and-aft width towards the keel.This device, while attractive, never seems to have persisted.It is probable that excessive rudder bias in the loaded condition may be the explanation of its general disuse despite occasional signs of revival.Ballast course-keeping, particularly against a lee shore, is obviously of the greatest importance. Heavy rake of stem, pronounced forecastle extent of flare, and to a certain extent excessive trim by stern (although this increases rudder area)all tend to make a ballast ship fall off the wind.This problem has, of course, long been acute with the trawler and drifter, and the device there adopted since the inception of the types, that of fitting a trysail abaft the mainmast, should again receive serious consideration in the modern merchant vessel.The use of such a sail for easing permanent helm and thus directly and indirectly assisting propulsion, also in somewhat reducing heavy rolling, is too important to be neglected.Whether such a sail take the ordinary form or some modern wing form consisting of a light steel structure capable of simple adjustment, is worth detailed investigation. The modern form could be made the more effective and controllable.It would require no arduous control in heavy weather but would revive a lost art in modern seamanship and produce sea- and wind-kindlier ships.

5. When a vessel is proceeding against boisterous weather but not of aseverity necessarily dangerous, the problems of adequate engine power and efficient propeller design assume a definite importance in sea-kindliness and economic performance.The weather in question does not call for any heaving to, and may be approximately defined as that which causes the propeller apparent slip to increase to about 30 per cent.Under these conditions, to reduce power simply results SEA-KINDLINESS AND SHIP DESIGN 233 in a distressingly and disproportionately heavy loss of speed, whereas above a certain power no additional speed seems possible or desirable of attainment.To fix one's views on this point, an examination of the records of a range of vessels suggests that a ship should at least be capable of averaging a steam indicated horse-power of 16A/A where p is the load displacement in tons, in order to face ordinary heavy weather with safety and efficiency.It must not be assumed from this that the expression gives the maximum power required.As the formula power refers to 30 per cent. slip, the fine-weather(say 5 per cent. slip) power which must at least be averaged by the machineryusing average fuel to the boilers, will need to be some 10 per cent. higher. To allow for trial conditions (of power development) the formula power should be increased by a total of 30 per cent. in order to get the maximum trial power required. The power so attained should be adopted as aminimum in preference to any less figure obtained by adding the usual weather and appendage percentages to the power deduced from model experiments. Recent model propeller experiments in the ballast condition show quite extraordinary differences in freedom from flow breakdown at heavy thrusts. The principal lesson of these tests is the clear advantage of low pitch ratios (and large diameters), and the complete treachery of high pitch ratios (and small diameters). A vessel whose propeller suffers from thrust breakdownwhich isquite different, of course, from propeller cavitationbecomes extremely difficult to handle.The propeller revolutions become erratic and despite heavy _slip,theslip stream velocity Js reduced and this in association withslipstream aeration reduced the forces induced by rudder action and thus the ship steering also becomes erratic.

6 The final stages of sea-kindliness to be considered are those intimately concerned with seaworthiness.These refer to really dangerous weather when all the skill of the navigator is called upon to ensure primarily the safety of his vessel and secondarily her progress in the voyage direction. That this aspect of the problem is still border-line so far as the limits of our knowledge, is evidenced by the recent Board of Trade enquiries intothefounderingofthesteamersBlairgowrie,Millpool and Usworth.The evidence at the enquiries showed that theloss of the vessels was due to the weight of seas shipped on board involving the failure of structure and equipment. The avoidance of the shipping of heavy seas is largely within the skill of the navigator in a well-found ship.Such skill requires years of training ;and those who have been trained in sail hold the view that a loaded sailing ship is a more seaworthy craft than a corresponding power-driven vessel of the same or larger size.This may be due to sail training, of necessity being spent in high- latitude voyages where heavy weather is more consistently met with, thus presenting many more opportunities for ship nursing than are available to those trained in the modern power-driven vessels. Heaving-to 234 SEA-KINDLINESS AND SHIP DESIGN was a much more frequent process in sail than in steam since damage to, or loss of, masts, sails or spars was obviously to be avoided at all costs.. At the present day it can almost be said with truth thatmany serving officers have never had a spray of salt water over them, and it is not idly suggested that modern training should now compulsorily include part time in small craft, either steam or sail, in seas where boisterous weather prevails.Along with this training, scientific training in applied aerodynamics should be given.This will eventually produce a set of men who will be able to produce more sea-kindly ships than those at present available.Sea-going people are not trained in recording their experiences, but this defect is slowly being removed by better preliminary education, the development of marine meteorology and direct official encouragement. 7 The technique of heaving-to is of interest.A loaded sailing ship hove-to, with her yards sharply braced-up, generally lies about fiveor six points off the wind and drifts slowly to leeward with littleor no headway. The absence of heavy rolling prevents the shipping of dangerous athwartship seas ;and the absence of headway and the ship heading several points off wind and sea, prevents violent pitching and avoids shipping heavy seas forward. For steamers, it is sometimes assumed that the vessel should be kept as near as possible head on to wind and sea. To maintain this direction in a heavy gale requires considerable engine speed to ensure rudder action. Being forced head on to the seas results in excessive pitching and the shipping of dangerous seas forward. To avoid this, only sufficient engine speed should be used to control the head falling off and to come up between two and four points off the wind.Sails aft in this condition would be a help since engine power could then be further reduced and excessive helm action prevented.Seamen, however, hold varied views regarding the best method of heaving-to in heavy weather. Some contend that with engines stopped the propeller drag will cause the stern to heave up to wind and sea.Others contend that with engines stopped a vessel will take up a dangerous position broadside on to the wind and sea. These varied views are probably both correct and depend upon the vessel and in any case, to keep a disabled steamer, unprovided with sails, out of the trough of the sea is a serious task.One method adopted frequently by an experienced shipmaster consisted of trailing the vessel's cables shackled together, with the anchors previously removed, below the vessel.This kept the vessel's bow up to wind and sea. Another case may arise with steering gear disabled but the propelling machinery intact. In this case the following measures are suggested. Secure the rudder hard over to starboard against the stops, put the engines dead slow ahead and heave to on the starboard tack in the northern hemisphere and vice versa in the southern.The ship will come up until she is, say, two points off the wind, when the wind resistance will stop further headway. She will falloff, with headway, come SEA-KINDLINESS AND SHIP DESIGN 235 up again and repeat the whole process time and again.Great care must be taken only to obtain steerage way to get within two points off the wind, as otherwise there will be a danger of getting the wind on the other bow. To avoid this,stopping of engines may be necessary. With heavy stern trim in the ballast condition, say off a lee shore, keeping the engines going full speed astern should enable the stern to be kept within four points off the wind when the steering gear is disabled or the wind is too strong to turn into when going ahead. Steering gear trouble is very frequently due to forced running in heavy weather.All small or moderately powered vessels running before a heavy gale should always heave to in good time since in the high latitudes six hours generally suffice to see the worst of the storm pass, after which the vessel can safely proceed in the wake of the storm.

8 The remarkably useful work accomplished by the model experiment in the improvement of the propulsive performance of ships suggests that outstanding problems of sea-kindliness and seaworthiness may also be investigated by such means.It would be of value to have the opinion of experimenters whether alternative methods of heaving-to could not be satisfactorily investigated in the experiment tank.For example, as each ship appears to have generally its own behaviour characteristics,itshould be possibletoanticipate many of these by tank testing instead of waiting for the actual ship to show that her behaviour was misunderstood. Another important set of tests would be to investigate the quantity of water shipped on board with forward wells of different location and extent, and with different freeboards.This may prove of extreme value in connection with freeboard interpolation. The effect of steadying sails should admit of simple investigation, since the installation of a sufficiently powerful fan should not be impossible on the modern tank carriage.Steering tests are already well known, but it would be a useful extension of existing data to test the whole range of possible helm orders ahead and astern and check that the vessel's response is normal, or if unusual discover the reason for the change and if possible to modify where necessary so as to ensure normal response, thus avoiding possibility of error when the vessel is in charge of a pilot. Existing work on the wind resistance of deck erections should be continued and heroic measures adopted.Should any of these show a marked reduction in resistance the possibility of its being made a practical feature of ship construction should receive the sympathetic consideration of the industry. 9.Conclusion The Authors are fully aware of the shortcomings of the present paper. They feel, however, that these shortcomings should not prevent a discussion taking place worthy of the importance of the subject.The views of all 236 SEA-KINDLINESS AND SHIP DESIGN interested parties, and particularly navigating officers, are invited. The opportunity thus presented for the consideration of relevant problems, either solved or unsolved, is one valued by the Authors, and it is their hope to have added usefully to the better introduction and appreciation of the subject of the way of the ship.

(Discussion to be published latersee " Dpages) DISCUSSION ON SEA KINDLINESS AND SHIP DESIGN* TEE CHAIRMAN what round midship sections and great (MR. H.G. WILLIAMS0.B.E., beam, and suggest that these will suffer Fellow) from excessive rolling due to great meta- The officers who control the navigation centric heights.Will that not depenkon and the machinery of ships together with whether the maximum beam isat,or the owners who manage them commercially above,orbelowthewaterline ? I constitute the final court which passesremember a freak type of ship built on the judgment on the work of the shipbuilderTees in the 1890's in which the designer and manufacturing engineer, and the titleexhibited a most greedy desire for saving of the paper indicates that we may heardeck-beam length and consequently also to-night something of the principles and deck-beam depths.These ships had their of the evidence on which that court founds greatest beam just about the upper turn its judgments. of the bilge, and had a big tumble-home from there to each deck.These ships MR. C. WALDIE CAIRNS, Fellow : were "as stiff as a rock" when empty, As the Authors state, a vessel may bebut as they had raised quarter decks and so lacking in sea-kindliness that she may"part-awning deck" forming bridge and sustain structural or mechanical damage. forecastle in one, they listed like sailing This may arise from a resulting tendencyyachts when filled with light grain, lying to ship heavy water which may smash upover as the wind blew them. A skipper deck fittings or boats, or it may bring hertaking one of them to the Baltic and intoperilby thedisplacing of hatchtrying to load her with timber got the coverings, while conditions on deck makesurprise of his life:a few tons of wood theirreplacementandsecuringvery on one side or the other on deck put her dangerous. on her beam ends.She was probably an ideal ship for ore. Even under less acutely perilous con- ditions a ship lacking some of the features Intheirreferencestopitching,the Of sea-kindliness may be so dangerous to Authors have not mentioned pounding.. work that it is hard to ensure that every-Perhaps there is just a doubt whether they thing necessary shall be done at the right wouldacceptrelativefreedomfrom time.I have in mind an old steamer built pounding in ballast trim in heavy weather in the 1880'sof fine form, about 260 ft.x as one feature of sea-kindliness, but as 36 ft.beam x 19 ft. 10 in.draught,with this is a matter which can be modified by bar keel, but no bilge keels.That vessel design, I think there is good reason for in ballast condition was reputed to rollso bringing it within the scope of a paper violently at times in the North Sea thatsuch as this.We perhaps hear less of the chief officer and hands busy on the damage under fore-ends of vessels from this forecastle head had to move on theircause than we used to, in spite of increase hands and knees.Then another somewhat of average speeds of cargo ships ;fore- smaller ship of similar form was suchaends of bottoms are now muchmore rapid roller that she would roll into andstrongly constructed than thirty yearsago, scoop up an oncoming beam sea with herand a little has been done to obviate flat weather bulwarks.Both these ships weresurfaces near the forefoot.In spite of much improved by bilge keels, in spite ofthat, a modern ship often takesa blow thevery" easy " bilgesavailableforunderthefore-endwhich makes her fitting them. vibrate from end to end, andsome in- Another effectarising from excessivecreased fining may still be advisable for rolling is difficulty in keeping steam, whereships intended to keep going when in one is dependent on men with shovels toballast, in heavy weather.These blows, put the coal where it is wanted in theand the vibration resulting, probably have furnaces, and to slice and rake and clean their effect in increasing the actualstresses fires. arising amidships in heavy weather. The Authors, refer to vessels withsomeF The Authors comment on the effect of a topgallant forecastle in causing a ship Paper by Captain IC. Macdonald, 0.B.E., and to fall away in a head wind.I have Dr. E. V. Teller; Vice President.(See p. 227 ante.) gathered many reports on this matter from Dl 1.2, DISCUSSIONSEA-KINDLINESS AND SHIP DESIGN ships With and without forecastles.In include a spell in small craft, either sail or ships of the 1890's with forecastle and not steam.It would be difficult to find the much power, I have heard complaints ofsailing craft, unless like the German and falling away, and in one or two of thosesome other foreign nations we equip and ships I believe a trysail was sometimes run special seagoing sail or auxiliary power used and found helpful ;but from moreships, and then one risks a large number modern ships, with more power, and withof hopeful lads in one bottom.(ft will a considerable mass of deck-houses forbe remembered that the Danes lost many crew's entrances,steering-enginehouse, youths and a fine sailing ship some years lavatories and lockers on after end of ago.)Small steam or motor craft are shelter deck, there has been no complaint plentiful and are becoming more so.(I from theshipswithforecastlesfrom sometimes wonder why some of the young masters who have handled ships both with men with a little capital who hanker after and without forecastles, and all agree that adventure do not try owning and running the topgallant forecastleisa valuable motorcoastersiftheyreally want protection to No. I hatch, especially where adventure without havingit" Cook's- side extension houses are continued tilltoured " for them).Still, I think good abreast of or abaft of hatch corners. shipmasters could train good steamship Admittedly a balance of beam wind load masters in steamers, and make sure that is highly desirable ;the less helm onethe youngsters got a hold of most of what has to use in keeping a ship on her course, matters by using a little good sense in the the more economically she will be propelled, training. either in moderate or extreme winds. The But I have often advocated that the turtle-backforecastlewould no doubttraining of every young naval architect help both in cutting down head resistanceought toinclude a few winter North in a head gale, and reducing tendency forAtlantic voyages.I would not condemn head to fall away to leeward in beamhim to the smallest ships for that run, winds.I can remember many fast old because on the one hand I would not like paddle passenger cross-channel boats so him to be so helpless as to be unable to built.If adopted in its full features, theobserve what was happening, and on tha windlass would have to go underneath other, it is possible that the larger ships no doubt good for the windlass, but pro-may strain somewhat more in North ducing somewhat "blind"working.IAtlantic seas. wonder, too, whether there would be any I certainly have it on very good authority difficultyabouthandlingfendersand that in the North Atlantic in fairly heavy moorings from a turtle-back. head seas,the 400-foot ship has the Regarding entrances to housesI thinkcurious fault of flooding over the stern. most saloon houses are now entered atThis is not pooping with a following sea, after end, but I have been surprised to but presumably dipping her stern unduly find recent steamers with entrances towith a head seaanother lack of sea.=, accommodationalongsidetheengine kindliness ? casings from an outside alleyway.This is the part of ship with lowest freeboard, CAPT.H. STONEHOUSE (Hull) : and appears to get the worst of the weather The Authors of this Paper should be with wind and sea approximately abeam. complimentedonchoosingasubject The Authors' references to clipper stemswhich is a very difficult one to which to rather puzzled me at first, but I find they give a really constructive answer.How- refer by that term rather to what we usedever, taking sea-kindliness, I would first to call " Pyman's teapot spout" ratherof all say, that ships are like children than to the graceful clipper stem headwhile they may be sisters, they have quite such asoriginally supported a bowsprit different actions in many cases in a sea-way, and a figurehead.It had its disadvantagesand so many attributes to this can arise when a ship had to be swung in a crowded from different causes, namely basin, however beautiful it looked with Nature of cargo. ship underway.In looking up references Distribution of weight. to overhaul my definition of a clipper stem Handling of vessel in a sea-way. I happened on a quotation from Hovgaard which backs up the Authors' contention Explained as follows : about poor course-keeping qualities of the heavilyrakedstem.Hovgaardasserts Coal, of all bulk shipments, is one that the square forefoot is an aid to the of the best to my mind for sea-kindlinessi rudder when ship is moving at high speed. if stowed as explained below in No. 2. The Authors suggest that the training 2.In colliers where there is little sub- ofships'officersshouldcompulsorily division, to get the most out of sea- kindliness, the coal cargo should be * Engineering, Vol.48 1889, p. 128. loaded by filling the centre holds full, DISCUSSIONSEA-KINDLINESS AND SHIP DESIGN D 113

and the balance tapered off in the end mentiononefactorwhichsometimes holds to suit draught.This positionseems to be overlooked by shipbuilders, I would point out, however, would causethat is, the respective heights of forecastle the technical and commercial managers and bridge.I have been in three vessels to disagree, as an equal distribution ofwhere it has been impossible to see over the coalismore essential to quick the forecastle from the navigation bridge, despatch.Practicallythe same thingand navigating had therefore to be done applies to homogeneous cargoes. from the flying bridge, which only afforded 3. This is a purely practical proposition very meagre weather protection. and can only be really dealt with by a I agree entirely with Captain Stonehouse master with some experienceofthe in his remarks about stopping the engines actions of his vessel in a sea-way.I altogether as a means of heaving-to in personally had experience of a 5,000-tonheavy weather. steamer broken down inthe North As regards sea-kindliness in general, I Atlantic in the month of December, with feel that most present-day ships would be tail-end shaft broken, and for twenty-sea-kindly if loaded to the best advantage, three days this vessel drifted 1,000 milesand in this connection I think that the ship- under a fore and main trysail, and while builder would assist greatly by supplying some heavy water occasionally came on thenavigatorwithfullerinformation board, the vessel did not labour.This regarding stability, trim, etc., than has been experience leads me to say that a vessel hitherto customary. can be manceuvred into a position to make her sea-kindly. MR.R.C. THOMPSON,Memberof Ship Designwas, I think, given in the Council : Paper as seaworthiness.This raises the With regard to the Authors' reference question of the forecastle head which, Ito the motor shipsSilverpineandSilver- will say quite definitely, I consider to be a larchand the alteration to the sterns of great asset when a vesselis ploughing these ships which is described in my paper into a head sea ; but there should be aof 1936,* I am very pleased that Captain big flair on the forecastle head, so that when Fletcher is present at the meeting and has the vessel takes a sea the first incentive tobeen able to describe his experience with lift will be given, instead of the vessel one of these ships since the alterations were dipping right into the sea and awaiting the made.Ithinkitcan now bestated sea getting well aft before making an definitelythat afine-lined cruiser stern attempt of lifting the ship. properly designed, tends to a reduction in As far as the forecastle head is concened pitching and assists a vessel to maintain her as being a drawback to the vessel keeping speed in heavy following seas without risk of"pooping ". It should be borne in bow to wind, I am of the opinion thatmind, however, that the shape of the stern this is negatived in most modern vesselsis not by any means all important, as far by the erections at the after end. as the amount of pitching and also as far as the liability to "pooping" is concerned, CAPT.0. FLETCHER(Newcastle-on- as the shape of the fore-end and position Tyne): of longitudinal centre of buoyancy are also I have been master of theSilverpine,one of the two vessels mentioned in the Paper, important features. for the past two years. The Authors have I have received a letter from the captain said that it would be of interest to learn of theSilverlarchdescribing his experience whether the subsequent service performance of typhoon conditions off the Philippine of these ships has shown any definiteislands with his vessel in ballast conditions lesson on fineversusfull sterns.Speaking as follows : for theSilverpine, Iwould say that her " I regret to inform you that we ran performance compares most favourably into the region of a very severe typhoon with that of the fuller cruiser-stern type of on passage from Hongkonglloilo. ship. Even when running before very heavy Western Ocean weather,Ihave Commencing as a strong breeze on .experienced no trouble whatsoever, and at 9th inst., around 6.0 a.m., weather got no time has the vessel shown any tendency gradually worse, freshening into a whole to poop.In the case of theSilverpine, I gale with squalls of hurricane force on have found that the Authors' suggestion 10th inst.Exchanging frequent weather that the fine stern may result in a less reports with the Observatory at Manilla vertical pitch aft than forward is correct. it was found that the typhoon was almost With regard to the Authors' remarks stationary.Under the circumstances I dealing with topgallant forecastles, I am decided to carry on on the Southerly of the opinion that the only disadvantage course we were steering, not wishing occurs when a ship is in either the light or to be caught when the typhoon corn- ballastconditions. Inconnection with topgallantforecastles,Iwould liketo Loc. cit. D114 DISCUSSIONSEA-KINDLINESS AND SHIP DESIGN

menced moving as they invariably take of ships with square or box-form sections, a North or North West direction and the square shape produces a damping effect this naturally would have put the vesselon rolling, similar to bilge keel effect. in the track of the storm.The vessel As far as tramp vessels are concerned was behaving very well indeed with athe question of stability is a very difficult high confused sea on port quarter and aone from the designer's point of view very heavy swell on port beam, she had because the vessel may be required to carry to be kept up considerably to clear theiron ore one voyage and a timber cargo Scarborough Reef. with a large quantity of timber on deck Passing the line of bearing of typhoon the next voyage, so that all the designer with centre a matter of forty milescan do is to aim at a happy mean.The distant, weather improved slightly forsame problem arises when one starts to about one hour when wind backed to discuss the question whether a shelter-deck West and weather got worse than ever. ship should also have a topgallant fore- Barometer continued tofall and at castle.I think it can definitely be stated 2.0 p.m. wind reached hurricane force,that in ballast such a vessel would be better and vessel by this time was unmanage-without a forecastle, and when fully loaded able, having little room she was driftingwould be better with a forecastle.Bearing fast onto a lee shore.Tanks with thein mind that modern tramp vessels often exception of No. 3, which was filled with have to make long ballast voyages, I think water prior to leaving Hongkong, hadsuch a vessel would be better without a all been prepared for the loading offorecastle, but with a well raked stem and general cargo, so that all hands were putas much flareas possibletoprevent to preparing Nos. 1 and 4 deep tanks shipping heavy head seas when loaded. ready for flooding and I must say that On p. 233 the Authors give a figure for everyone, realising the seriousness oftheminimum power.I suggest that this figure position, worked with a will under greatneeds considerable qualification to take difficulties as by this time it was impos-into account the different types of super- sibletostand on one's feet without structure which may be fitted.1 suggest grasping something firm and holdingthe vessel with a square four-tier bridge on for grim death. withlarge head-wind resistance would At 3.30 p.m. I commenced pumping requirea minimum power appreciably up Nos. 1 and 4 deep tanks and at5.15 higher than the vessel with carefully shaped p.m. the vessel feeling thebenefit ofdeck erections of modest proportions.The the additional weight, I was able todifference between the former and the latter coax her into a position so thatit wasmight fairly be stated as being about possible to heave her to, when she rode10%, in so far as minimum power require- ments are concerned.I do not, however, a very steep mountainous seasplendidly. suggest there will be a difference of 10% At 1.30 this morning weather hadin the average service performance of such moderated slightly,vessel was turnedvessels, this probably being in the nature round and dredging in slowly.Cabraof 3 to 4%. Island light was sighted at 3.30 a.m. I would like to endorse the Authors' Vessel was then put to full speed andremarks on the subject of the training of voyage continued." sea-going people inproperly recording as Ithink thisletterrepresents further theirexperiences.Untilsuchtime evidence of the advisability of classification this can be properly done, it is very difficult societies and owners taking more interest to form correct conclusions from reports in the ballast capacity ofships.In this received. case No. 3 deep tank carrying1,000 tons On thesubjectofheaving-to,the of water was full and yet it was necessary Authors' remarks are very interesting, but to put considerably more ballast intothe I suggest that the aim of designers should ship to keep the vessel manageablein the be to produce vessels that are sufficiently particularlysevereweatherconditions sea-kindly and seaworthy for completely experienced. heaving-to to be unnecessary.1 suggest that in the case of a well designed 10,000- There are several different aspects to be should be borne in mind on the subject of the relation- ton vessel, fully loaded, all that ship between beam and draught andthe necessary in very badweather conditions, would be to ease down and possibly change question of circularversusbox-shaped This introduces rather forms.Ido not thinkthatstability course somewhat. measured in terms of metacentric height a complicated problem becauseit is now in the vertical position as a straight-generally agreed that in moderately bad forward calculation, is as important as is weatheritisadvisabletokeepthe of machineryrunning at thehighest often thought. The moment of inertia good the cross section plays an important part possiblepowertomaintaina performancewiththe modern in that it affects the periodictime of rolling service In other and also I am of the opinion that inthe case relatively low-powered vessel. DISCUSSIONSEA-KINDLINESS AND SHIP DESIGN DI I 5

words, the captainis now faced with vessel proceeding via the Cape of Good instructions to increase power in moderately Hope to Australia, and while running the bad weather and then if the weather gets casting down three of the propeller blades too bad he must ease down, and as it iswere thrown and had it not been for the only if this process is properly carried out sails the vessel carried (she was brig rigged), that the best service results will be achieved, Jam afraid we would have fared very badly ; it will be seen that the navigating officersas it was, with the assistance of the sails can play a very important part in achieving the vessel covered over 1,2J0 mites with thebestserviceresultson a modern one blade. economy steamer. On the subject or steering tests, I would MR. A. G. AKESTER, Member : liketo ask exactlywhatis"normal At the outset, I am not altogether sure response" on a modern vessel ?It would thatIlikethisterm " sea-kindliness." be interesting to have this laid down bothSeaworthiness on the other hand is an all- with the vessel going ahead and astern. embracing term and has many ramifica- In my experience the response is not the tions, and the Authors admit that in some same in the case of vessels with semi- circumstances atleast,itincludes sea- balanced and ordinary rudders, particu- kindliness. larly when manoeuvring in port, and further- Happily the distinction made more itdoes not appear that modernbetween the two qualities helps us to vessels with well designed lines, behave in understand better the aims of the Paper. the same way as the old-fashioned type of Before leaving this question, however, I ship built 10 years ago. wonder whether the Authors are right in putting such a rigid interpretation upon seaworthiness as they do in the beginning MR. H. W. WILLCOX, Member : of section 2.It is indeed a high standard At the time I was at sea I do not thinkif a ship has to do her work under all shipbuilders ever thought of or considered conditions "with complete safety to both sea-kindliness. I sailed in a Tyne-builtship, machinery and cargo," leaving out vesseltradingbetween Londonand of the picture for the moment the question Australia.She was a flush-deck vessel,of safety of life.I believe the Marine brig rigged and instead of being fitted with Insurance Act says a ship is deemed to be ordinary hatches to the holds, she had twoseaworthy when she is reasonably fit in all hatches athwartship to each hold.The accommodation was below deck, and therespects to encounter the ordinary perils berths in the Tropics were so hot that theof the seas of the adventure insured. Devil himself could not have slept in them. The fact that voyage and cargo are At certain periods of the weather theintroduced asfactors of seaworthiness waves would synchronize with the rolling would indicate that seaworthiness is not of the ship, so much so that she would roll measured by an absolute standard, but the hatches partly under water. On one that it expresses a relationship between the occasion I was working at the winches state of the ship and the perils it has to meet and had the connecting rod and bearings in any situation. on the main hatch adjusting same, when Reverting once more to sea-kindliness, it without any warning the vessel gave a is certain that marine insurance companies sudden lurch which sent the gear over- and classification societies generally would board, and I nearly followed.The angle be only too pleased if ships had this quality of roll was so great that the boatswain to the maximum degree.One of the most ran up one side of the engine-room casing prolific forms of damage met with in regard and coming down the other side broke his to underwriting and survey work is that leg.The coals ran out of the bunkersdue to heavy weather. The Authors stress into the stokehold, and the coolie firementhe importance of "efficient handling and were up to their shoulders in coal. loading in adverse weather conditions," After Ileft the vessel, she was trading and rightly so. between New Zealand and the Mediter- The ship's schedule is also of importance, ranean and disappeared on one of these and it is sometimes this lack of time margin voyages withall hands, presumably in necessitating the ship "ploughing through the Gulf of Lyons.I personally am of theit" which leads to trouble. opinion the vessel turned turtle. The Authors compare the sea-kindliness I am in agreement with the Authorsof sailing ships with that of power-driven regarding propellers, namely, low pitch vessels and give the advantage to the sailing ratios and large diameters ; but I do not ship.Indirect confirmation of this may agree that a propeller just submerged isperhaps be taken from the fact that some definitelylesseffective than one three- fifty odd years ago the rudder heads of iron quarters submerged. sailing vessels were generally frominch to The use of sail, I agree, is too important 1 inch less in diameter than those of steam to be neglected. I was an engineer in avessels of corresponding size. D116 DISCUSSIONSEA-KINDLINESS AND SHIP DESIGN

On p. 229 the Authors refer to the list steam steering gear in which he described that timber carriers generally take withthe gear anditseffectiveness ;a high impunity towards the end of a loadedadmiral in the discussion said it was quite voyage ;Ithinkitisa requirement, unnecessary to have these things (steering however, that on leaving a port after agears) and that on his ships the helmsman deck cargo of wood goods has been loaded,had printed orders not to use his helm at a ship must not have a list. all, but to steer entirely by the sails.Of On p. 232 the Authors suggest that classi- course he made no allowance for the fact fication societies might introduce in theirthat the steam steering gear was introduced rules a minimum value of rudder area.and proposed for steamships, which in This could be done, no doubt, for the those days, though they were assisted by a ordinary rectangular rudder :in fact such sail, still needed more steering power from a formula is put forward as representing the helm than a purely sailing ship. existing practice ;but on trying this in A lot of my experience is obtained on several instances (principally large tankers), trial trips, where the men are unaccustomed the actual areas are found to be about to the ship, and I find the worst things done 5 per cent, less than those obtained by the with the best sort of steering gear ; thus use of the formula. the easier the steering gear works, the worse The reference to steering gear in the Paper the steering is as a rule.There can, of has raised during the discussion the some- course, be a great difference between one what controversial question of secondary helmsman and another.The man who has means of steering, and whether this should learnt his steering on a sailing ship had to be by hand gear or by arrangement ofbe very careful in his use of the helm and blocks and tackle.The Report of thehad to watch hissails carefully when Steering Gear Committee recommended moving it.Such helmsmen on steam ships that hand gear of the right and left-handedhandle the steering wheel with restraint, screw and nut type should not be fittedand wait for the ship to respond to a move- on ships exceeding 3,500 tons gross.Some ment of the wheel.The bad helmsman steering-gear makers have developed awho may have to operate a small easily hand gear of the worm-geared friction-turned handwheel, keeps spinning it back clutch type, which has given good resultsand forward, not even giving the steering in service. engine time to keep up with his movements, As regards the arrangement of blocksmuch less waiting till the ship feels the and tackle, it is perhaps only fair to sayeffect of the rudder movement. that with the gear stowed ready for an We have found this difference in men emergency, as it is now required to be, andbrought out very strongly lately with a new the crew more accustomed to its use, there type of steering gear which, instead of is a better chance than formerly of this having a helm indicator pointer geared to type of auxiliary gear proving effective,the handwheel, has no such pointer, but especially if the winch be given some forman indicator worked by the rudder, so that of protection. what the helmsman seesistheactual While the question of steering gear inrudder movement and not just the position relation to a ship is,of course, of thewhich the rudder will move if he givesit utmost importance,itshould be borne time.Some men steer perfectly with this in mind that of something like 10,000 ship gear straight away and prefer it tothe casualties reported in the public press in normal type, but others find it very difficult a year, less than of 1% are in any way to handle at first, because when they move related to steering gears.On the otherthe wheel and the indicator pointer does hand, casualties due to fires on boardnot move immediately, with and as far as ships are more like ten times this number,the wheel, they think nothing has happened, and as we know only too well, occur even and turn the wheel further ; the indicator on some of the largest vessels. pointer then comes over at the speed of the rudder movement, and goes far further MR. W. SPENCER PAULIN, Associatethan necessary, so that a frantic movement Member : in the other direction results.Fortunately I was very much interested in the remarks unless the man is very stupid, he soon gets as to how the steering of a vessel is affectedthe hang of the thing, especially after a by thestructureof theship and the little explanation. difference between the steering of a sailing There have recently been modifications in ship and a steamer. My knowledge ofthe attitude of the Board of Trade and the steering of a sailing ship is almost classificationsocieties to emergency negligible, but from what I have gathered steering gears.They are limiting the use there seems to be quite a different technique of hand emergency steering gears to small in steering the two types of vessel.In theships, and preferring an emergency arrange- sailing ship very much less use is made ofment of wire rope connecting the tiller to a the helm ; the sails themselves are used topower winch.The reason for this is that assist steering.In fact I read a paper somethey state that hand emergency gear is too time ago written by the inventor of theslow in operation to keep the head of a DISCUSSIONSEA-KINDLINESS AND SHIP DESIGN D117 ship to the sea in heavy weather, claiming This latter method, it would appear, is that frequent rudder movements of 200 to ideally suited to the collier and particularly each side are necessary and that it must be the self-trimming collier. possibleto make a movement of this In reducing the metacentric height, one magnitude in a few seconds.I would like must bear in mind that thereis some to know whether the Authors agree with minimum value which the ship must have this view.Personally I do not, since there in order to provide sufficient dynamical are hundreds of small craft with only hand stability. steering gears, and even the smallest take Again, the transverse stability of a vessel, over a minute to go from mid- to hard-over. and hence the rolling, must depend to a Small ships of this type would be muchlarge extent on the nature of the cargo and livelier in heavy weather than a large ship in the vessel which may be dealing with and require much more helm to keep it to cargoes of very different densities, as in the the seas, yet these smallcraftweathercase of the tramp steamer, it is impossible storms very successfully. to obtain suitable metacentric height in all In my view the main thing is to get the conditions.This leads to a question I ship under control as quickly as possible should like to ask the Authors.If rolling when the main steering gear breaks down, has an adverse effect on the manceuv ing and in this respect the hand emergency capabilities of the ship, would it be advisable gear is very much superior to the gear to fit some automatic means of stabilization advocated by the Board of Trade andsuch as the anti-rolling tank, gyroscopes, classification societies. or the Denny-Brown ship stabilizer, which It would be as well at this point to make itappears to have been very successful on the clear that there are two main types of hand Isle of Sark?I know that the argument emergency steering gear, the right and left against such equipment is that the weight hand screw gear and the worm-geared is considerable, being about 14 per cent. friction-clutch type of gear.The screw of the displacement for an anti-rolling tank, gear is not a sound proposition except which may amount to about 2 per cent, of for very small ships, as the full shock of the deadweight. On theother hand, a blow on the rudder from a heavy sea is however, if the fitting of such equipment taken solidly by thegearwithout anyimproved the sea qualities of the vessel, resilience. This has led to these gearsthis should compensate for the loss in breaking up under very severe conditions. deadweight. Suchbreakdownshavecausedhand It is suggested in the Paper that heavy emergency steering gears tobe viewed rake of stem makes for a full entrance and with suspicion.The friction-clutch typehence bad steering properties.I would of gear is quite a different proposition.Itsuggest that the modern tendency to have is mechanically sounder, and is providedthe longitudinal centre of buoyancy well with a friction drive which will slip underforward of0also tends to give a full extreme forces, relieving all partsfrom entrance. undue mechanical strain. While on this question of steering,I It is this second type of hand gear that I should like to ask the Authors' opinions advocate for larger ships than are at presenton deadwood aft, and also if they have any allowed to have hand emergency gear, data with regard to the steering qualities the present maximum being ships with of Maier-form vessels and vessels with 9 in. diameter rudder stocks. bulbous bows. Iwould very much appreciatethe Authors' views on these points as there is a lack of available data from men who CAPT .W. E. SOMMERVILLE, Newcastle: have had actual experience of emergency As aseaman,theexpression" sea- steering in bad weather. kindliness " strikes me as being particularly The method quoted on p. 234 for keeping apt.It describes just that quality which a ship with damaged steering gear up tomany a seaman has at times desired that the weather by locking the rudder hard overhis ship should possess above all. and steering at such a speed that the turning It is a peculiar point that two ships effort of the weather and rudder balancemuch the same in form may not possess isvery interesting.How woulditbe this particular quality in anything like the possible to put the rudder hard over ifsame degree, and it would be interesting the breakdown was such that no means ofto have the results of some comparisons steering was left ? in design between actual ships of known good and bad behaviour.I have happy MR. W. MUCKLE, Associate Member: recollections of some ships of very ordinary With regard to heavy rollinginthe design which were noticeably sea-kindly, ballast condition, there are two methods and inthem, perhaps withoutspecial that have been adopted in order to reduce considerationforimprovementinthe the metacentric height quality, a very successful balance in design The fitting of boilers on deck. seems to have been attained. The fitting of topsides ballast tanks. The chief functions of cargo ships are to D118 DISCUSSIGNSEA-KINDLINESS AND SHIP DESIGN

Carry cargo, to carry it expeditiously, and be a danger to the Ship's safety at full speed- to fulfil the Bill of Lading promise to In this age of speed there is at times some, deliverit in the same good order and thing to be said for the snail which arrives, condition as that in which it was when late perhaps, but with shell and contents, shipped.The more sea-kindly the ship, intact. the more likely is she to comply successfully I doubt whether it is as generally realized with the second and third of these require- 'amongst seamen asitshould be that ments. In my own experience in connection synchronism occurs with the sea on other with the ordering of new ships, such as it points than on the broadside.At least, was, although much was discussed on onehearssynchronismmentionedin subjects such as form in relation to speed association with rolling more often than and economy, machinery, boilers, capacity, with pitching. tonnage, ratios to deadweight, and so on, Rolling means added resistance to ahead I never heard the subject of behaviourmotion and addedfuelconsumption. in heavy weather mentioned. Its Comparatively smallalterationsinthe prominence in passenger shipsiseasily course do not, however, usually add greatly understood, but it seems doubtful whether to the distance, and in addition to rendering sea-kindliness receives due consideration in the condition less dangerous, an alteration design elsewhere. in the course may sometimes bring a net The loading and distribution of weight gain in ahead movement. form the most important considerations I have always been interested to learn in an existing ship, and while matters of thetruehistoryof tumble-home. It cost and loading and discharging facilities seems that one early reason for its existence frequently rule the matter of weight dis-was in connection with scantling.There, tribution,cases do occur where some does not appear to be muCh in its favour latitude is allowed in the manner of stowing from the point of view of sea-kindliness. the cargo.To enable the ship's officersOne group of ships I know were given a to work to the best advantage, it is necessary tumble-home of 14 in.in 50 ft.beam. that comprehensive information regarding The reason for not dispensing with it alto- spaces, measurements, trim and stability gether was, so far as I could gather, similar should be provided.Information which to the reason why a certain thrifty ship- would permit those on board to find for master always turned his " siller " on seeing themselves thestabilitycurvefor any the new moon :"If there's anything in condition of loading, especially in the caseit, ye have it." of deck cargoes, would be very helpful. Little appears to have been done in the I agree with the Authors' remarks inway of passing on to seamen, in concise Section 2 in comparing the behaviour ofform, useful information on some of the sailing ships and steamers.One has to,conclusions reached by experiments on experienceonly once asailingship's shore. On subjects, for instance, such as behaviour when the wind has dropped afterstrength,strains,rolling and pitching a heavy gale and while a high beam sea issomething on the same lines as the business still running, to appreciate the steadyinghintstomasters compiled bycertain effect of sails. societies and issued to the masters by the Pitchingisone of the most trying owners.This would be helpful in handling conditions to deal with in handling athe ship and would help to direct the steamer, and I have on occasion in such aseaman's attention more closely on these case, when in ballast, stopped the engines points. and allowed the ship to lie with wind and Some types of ships tend to ship more sea broad on the side,Rolling is then water thanothers. My experience in veryheavy,but muchpreferableto ships with a short well forward was not subjecting the ship to the heavy strain and very satisfactory.On one voyage the severe pounding caused by forcing her ship was nearly lost through the continual up to the sea. hammering of heavy seas on the well Close attentionto theeffectof an deck during a succession of heavy gales occasional change of course or speed isin the North Atlantic, to such an extent an essential part of good seamanship, and that the deck was set down 24 in. and a ifas the Authors seem to fear, thisis, large quantity of water got into the hold. something of a lost art, the loss is regrettable. The No. 1 hatch was well lashed with rope The principalbenefit of sea-kindliness,and fortunately held intact. The conditions apart from comfort, is that less heavywere perhaps exceptional, but the experience water is shipped, and ships are hove to gave me a decided dislike for the type. more often because of shipping heavy seas Dr.. Teller'sillustration of the effect than because of excessive straining.Some-,of a well flared bow on the wind is inter- times in the loaded condition it is possible esting.Any feature that tends to force to maintain the course at reduced speedthe ship's head off the wind is not likely to when the only alternative is to heave-to. be welcome to seamen, especially with a Sometimes itis wise to reduce speed,light ship on a lee shore.It seems at although the sea may not be so bad as topresent as if the cruiser stern has come to DISCUSSIONSEA-KINDLINESS AND SHIP DESIGN D119 stay. My only objection to this feature isapplying somewhat similar measures to from an aesthetic point of view.It issteamers should be worth investigating. interesting also that the clipper bow is Ships' officers of today have to cover being re-introduced. A clipper bow and a a much wider field in their studies than cruiser stern on the same ship, if time should formerly, and present-day circumstances prove these to be the most successfulend may cause them to pay, in general, less forms, would look odd to old hands, butattention to the study of wind and sea no doubt we could get usedtothe effects on ships. My personal opinion is combination. that anything in training or experience It has been suggested that the tendency which would re-direct closer attention on the is towards increasing power to an extent subject,includingperhaps someearly that would render heaving-to unnecessary. experience in a harder school, would be all I presume this applies only to large vessels. to the good. Medium-sized and small ships at present There is much to be said for the idea may at any time meet with weather which of an interchange in experience between would necessitate heaving-to or reducing designers and seamen.Looking back speed. over some twenty-three years spent in There seems to be no best method of sail and steam, I feel that any time in the heaving-to applicable to all ships.Ships, earlier stages that could have been spent weather and other conditions vary so much, in the designer's office and the shipyard and what may be the best method onwould have been a great asset later on. one occasion may not be the best onFor the designer, I would suggest that part another, even with the same ship. According of his sea-going experience should be spent to design and trim mainly, ships take upin the less pretentious type of tramp ship. different positions relative to wind and Not from any unkindly desire to deprive sea with the engines stopped.It would behim of the comforts of the large liner, but interesting to know whether tank experi- because the smaller ships suffer more from ments on this subject could be carried out, the effects of sea-irizkindliness. and the results passed on to those who handle the ships at sea. MR. F. GREEN, Associate Member : When a ship is hove-to or heading up The Authors, inreferring to ballast to the sea and a breakdown occurs, nearlycourse-keeping, have suggested the fitting always she will fall off before control canof a trysail abaft the mainmast to ease be regained. The first thing to do in a case permanent helm and keep the ship from falling off the wind.I knew of one ship of this sort usually is to reduce speed orwhich used to cross the Atlantic up to stoptheengines. Ihave on several occasions and throughdifferent causes about 1924, making use of such a sail with lain broadside to the sea with engines good effect.The classificationsocieties stopped and with success, though this appear to have cut out the rule for steamers actionwould probablybeinadvisable to carry sails since about 1916, and it under certain conditionswith an orewould he interesting to learn whether any cargo, for example.The principal con-steamers make use of such sails nowadays siderations are sea-kindliness and run of MR. JOHN REID, Member, also took the sea.If the ship is properly preparedpart in the discussion. for bad weather and sea-kindly, and the sea is running true, she would probably THE CHAIRMAN lie very well like this.There is, however, (MR. H.G.WILLIAMS, 0 .B.E. always the danger of a sea exceptional in Fellow): height, form, or direction, causing damage, We have had an interesting and compre- though this risk would probably exist tohensive discussion, and in winding it up some extent whatever the direction of theI confine myself to emphasising a few of ship's head.In a great number of casesthe points which have been touched upon. of damage, itisthe unusual sea that In Section 2, the Authors have grappled causes it.A collation of experiences ofwith what is always a most difficult ques- ships lying with engines stopped in heavytion, the exact definition of a word, in this weather would be of value. Some seamencase," sea-kindliness." They sayitis would be aghast at the idea of heaving-tonot to be confused with "seaworthiness," stern or quarter on to the sea, but it hasbut I feel that that injunctionis not made been done withsuccess manytimes.more easy to observe by the illustrations Perhaps, too,it has been tried withoutthey give of the distinction between the success. meanings of the two words. A vessel that At least one steamer trading today is so unmanageable by a qualified navigator has had her steering qualities, and possibly as to suffer disabling structural or mecha- her sea-kindliness, considerably improvednical damage is, in my opinion, unsea- by the provision of sails.Many sailingworthy on account of its unmanageability. ships in the past rode out heavy gales with Moreover, I think that the proposition nothing but a tarpaulin stretched acrossthatsufficientstabilityisessentialfor the mizzen rigging.The possibility ofseaworthiness does not require any quali- DI20 DISCUSS/ONSEA-KINDLINESS AND SHIP DESIGN

fication.The truth of the proposition isyouth that the French naval constructors inherent in the word "sufficient."It is, believedthat a ram bow reduced the of course, also true that the transverseangle of pitching and that this was the metacentric height in the upright condition reason for the somewhat exaggerated ram can be too high for seaworthiness ;but Ibow of the French warships of that time. think that negative metacentric height inI have no doubt that the ram bow would the upright condition can never be desirable. have on pitching a somewhat similar effect An ordinary ship approximately wall-sided to that which bilge keels, or rather a bilge in the neighbourhood of the waterline,keel on one side of the ship only, would having a negative metacentric height in the have on rolling ;but whether that on the upright condition, will have a position ofwhole would be a good and useful effect stability at some inclination at each side is another question.It might cause the of the upright, and I cannot believe that aoccasional shipping of seas heavier than ship would be less liable to heavy-weatherthe average over the bows. damage if her stable position were inclined then if it were upright. Asregardssteering,dealtwithin A ship should have at least sufficient Section 4,Ithink the rake of stem and positive metacentric height in the upright cut-up of the fore-foot, as in the so-called condition to prevent her heeling more than Maier form, and corresponding differences a few degrees when the helm is put over.aft have to be considered together.They I have been in a great liner when in awill have a joint effect on the initial and perfectly smooth sea puttingthe helm subsequentlyvaryingpositionsof the over caused the transfer of an excellent centre of lateral resistance of the ship lunch from the tablesto the deck.I when yawing and will thus determine how forget what was said about the ship on that fartheshipwillpossess the opposed occasion, but I do not think that eitherqualities of quick response to helm and " unseakindly " or " unseaworthy " was steadiness on a course.The worst con- the most hard-worked epithet. dition is when there is too much longi- On the general question of the definition tudinal surface forward, which will make of the words, I should have thought that the ship liable to violent yawing under sea-kindliness "was the more appropriate small helm angles. description of those qualities which cannot The formula given on p. 232 for rudder be, or have not yet been reduced to numeri- area looks good in so far as it gives the cal expression, and " seaworthiness " togreater rudder area to the ship of higher those that have. speed ; but much depends on the shape The only point I am disposed to criticize and position of the rudder and the yawing in Section 3is the statement on p. 230qualities of the hull. that the continuous submergence of the The remark on p. 233 as to the advantage screwis not necessarilya good thing.of low pitch ratio and large diameter of Whether or not the screw is more or less propeller is in line with general opinion so efficient when partly or wholly submergedfar as it recommends the use of the largest I think it is better that it should remaindiameter and lowest pitch ratio consistent in one or the other condition than that withsmooth-waterefficiency.Do the its state should alternate between complete Authors advocate the use of such extremely and incomplete submergence fromthe low pitch ratios for screws of ordinary point of view of constancy of enginesegmental blade sectionas are generally revolutions and avoidance of racing. supposed to involve substantialloss of I remember that we were told in ourefficiency in smooth-water trial ccnditions?

VOTE OF THANKS On the motion of the CHAIRMAN (Mr. H. G. Williams) a vote of thanks was accorded to the Authors for their Paper.

CORRESPONDENCE MR. J. P. ALLAN, Associate Member : ago, a director of a prominent shipyard Dr. Telfer preferred to delay his answerwhich specialized in this type of craft spent to the question whether the cutting away some six months in the Antarctic, investi- of the dead wood aft had any good influence gating the methods and performances of or not until he had made investigations the whalers, and on his return he was most into the matter. My own experience ofemphatic that the deadwood aft should whale catchers in which vessels' turningbe cut away as much as possible and that qualities are most desired,isthat thethe stern which, previous to his southern opening of the stern frame and the openingstrip, had been fined and fined untilit in the extension at the foot of the sternresembled a dessert spoon, could be filled frame are very necessary.Someyears out and given less rake, or rather, as there DISCUSSIONSEA-KINDLINESS AND SHIP DESIGN D 121 was little or no straight, it may be betterloss of steerage way and it had become described as less curvature. dangerous to continue running before such With reference to the Thompson type a sea, I decided to heave to.Having no of stern, it has occurred to me that theseprevious knowledge of how this ship would fine-lined cruiser sterns owe their dryness, best heave to, I decided first to give her a a feature which is being remarked by all trial with engines stopped.With engines captains who have sailed in these vessels, stopped she lay dead broadside on to the partly to the fact that they have no drag sea,lurching and flinging from side to as the stern rises or the crest drops.Some side to a dangerous extent.In this position cruiser sterns, particularly those of small she did not ship seas, the seas appearing craft with large propellers, to increase the to break, just short of the ship, over the waterline length at all, are necessarily very eddies left to windward of the drifting hull flat-bottomed, and itis my opinion that but I dreaded to think what would happen this flatness causes a time lag owing to a if one of these seas did land on the decks certain amount of suction.This delay as she rolled to windward.(See sketch.) combined with an unfortunate wave-crest I then decided to heave to bow on to the timing would account for " pooping " in wind and sea, and I put the engines dead the full cruiser sterns and conversely the slowahead,graduallyincreasing the good riding qualities of the fine cruiser revolutionsuntilthevesselhadjust sterns. sufficient steerage way to head the sea. The formula given for rudder area of When within about four points of the mechanically propelled vesselsisslightly wind a very heavy sea was shipped amid- more involved thanthe usual rule-of- ships which dingedin the side ofthe thumb formula of a year or two ago, and funnel.I then brought her right head on is a step in the right direction, but I thinkto the sea and she undoubtedly lay best that one very important variant is omitted, in this direction.When she dived in to that is, beam, for while I have no doubtthe trough of the sea it often appeared

that the area derived would suitthe doubtful whether she would be ablelto average merchantman of to-day, some oflift in time to ride the next on-coming sea the more beamy vessels would require a but she always did so, being helped, in my larger surface or at least a wider blade so opinion,by theadditionalfreeboard as to operate in the most effective stream. provided by the raised forecastle. Regarding the raised forecastle on this CAPT. J. T. BAKER (Leith) : shelterdeckship,itsadvantages when Some particulars of the behaviour ofsteaming into a heavy head sea, in my thes.s.Cairnross (425 ft.by 55 ft.by opinion, more than outweigh any hin- 25 ft. 6 ins. dr. 2 dks. and sh. dk. -75 block drance it had in bringing a ship round into coefficient) in very heavy weather may bethe wind, its area being too small in com- of interest.On one occasion, when inparison with the bulk of the ship for it command of thisvessel,1 was running to have any noticeable effect.ln this ship before a westerly gale, in mid-Atlantic, theeffectinboth respects should be with the ship in a loaded condition. The relatively great as the forecastle is super- vessel started shipping too heavy seas so imposed on a shelter-deck having the sheer 1 reduced the engine speed, which caused appropriate for absence of forecastle ; this her to ship less. arose from the decision to fit a forecastle As the gale was increasing in force the being taken late in the design stage. improvement thus gained was soon lost, Regarding the effect of oil distributed and she again started pooping and tumbling from bow pipes when running before a gale, seas on board from aft right along the my experience is that a small trickle of oil length of the ship, in spite of the use of oil has no appreciable effect and that it would from the forward pipes. have to be used in considerable quantity Having reached the stage where further to prevent the seas breaking on the ship's reduction of speed was not possible without quarters. D122 DISCUSSIONSEA-KINDLINESS AND SHIP DESIGN

'Mg. R. BEAL, Associate Member : considerablepracticalimportance. In I agree that efficient handling in adverseNorway we have had a large number of weather is as important as the economy of ships employed in the ore and timber trades. an "economy ship "and with a reasonablyIn the first case the difficulty is to get a good shipisalmost synonymous withsufficient amount of sea-kindliness, and sea-kindliness.In rough weather we know in the second, it is a question of not getting that even a change of helmsman can maketoo much of that quality. The Norwegian a big difference and that from comparative Veritas have in the circumstances found it comfort and freedom from shipping heavydesirable tolet the shipowners have a water, the reverse can obtain; due -to iipamphlet with advice regarding the hand- change at the wheel. ling of the ships, which can be passed on to My experience of the modem economythe captains. ship of the type with which I am best Ships, including cargo and ballast, must acquainted shows little difference in sea- as a matter of course be handled in a proper kindliness to its less efficient predecessors,manner if damage to the hull or cargo is except that reports say that it rolls ratherto be avoided.Our classification certifi- quicker.While beam has increased acates for iron and steel ships have therefore little, such increase is not excessive andthe following clause printed on them : when compared with draught it is some- " The regulationsarebased on the thing of the order of 2.25 now to 2.15 assumption that the ships are handled previously in ships of length from 255 ft in an ordinary seamanlike manner, to 310 ft.The present ships in this length particularly as regards the stowage range are more easily handled and are just of heavy cargo, the distribution of as manageable in bad weather. We find ballast and bunker coal, and the touch- less trouble with fore-end riveting nowadays ing of ground.Suitable strengthening and reports are that pounding is not so must be provided where the circum- heavy. stances make it necessary that a con- The Authors raise an important point siderable portion of the cargo or the regarding powering for satisfactory pro- ballast must be concentrated on a gress in heavy weather.I have looked up smaller areaofthe bottom or on a various ships with which I am concerned short length of the vessel, or where and find that 16 A/is a good figure in the bottom of the sea must necessarily each case and the ships make quite good be touched now and again.Itis voyages in bad weather. likewise supposed that the cargo, coal The section of the Paper on heaving-to and ballast are distributed in such a isveryinteresting.All the masters I manner that the vessel moves easily sailed under hove to with the wind and sea in a seaway.If the speedofthe ship almost ahead and the engine speed reduced is as far as possible to be kept up in tosuit conditions.They all spoke of heavy weather, then the hull is to be other methods, but apparently did not specially strengthened." care to try them.There was one ship For wooden ships the clausespecifies with a broken rudder reported in the press much more complex regulations, which last winter where the master had hove to have been in force for some 70 years, and stern on to weather and had kept the ship,which have been particularly useful for quiet and comfortable in that position for all the soft wood ships. some considerable time. The pamphlet mentioned deals with the The Authors mention excessive trim by various factors that affect the vessels' sea- the stern in the ballast condition as tendingkindliness, and which are under the control to make a ballast ship fall off the wind andof the master. The proper distribution of I should be glad if they would indicateheavy cargo is now with the modem long what trim they consider excessive. Many and broad vessels of greater importance of the best coasting colliers to-day trimthan previously in the existenceofiron and 6 ft. by the stern in ballast.They have steel ships.In the time of wooden vessels, good, if not complete, propeller immersion, it was particularly necessary to provide for they " pull " well in heavy weather, andsea-kindliness in order that the strength make excellent ballast passages. of the hull, spars, and rigging, might be - The Authors are to be congratulated sufficient. upon producing a paper on what is at It is unfortunately impossible to lay down present a vague subject and the views of specificregulations for the amount of navigating officers will be of great value. sea-kindlinessdesirable. This problern I am sure some of them will agree that many must be entirely left to the judgment of a good" sea boat" in some hands becomesthe captain, who alone is in a position to a bad one in others, and in that respectdeal with it.Ifimprovements as regards the Authors' suggestion on training issea-kindliness are to be effected, it must be valuable. through the better qualifications of ship masters. DR.. J. BRUHN (Oslo): There are some methods whereby sea- The question of sea-kindlinessin ofkindliness can be improved, but which are DISCUSSIONSEA-KINDLINESS AND SHIP DESIGN D123 notrecommended by classification do not think I can do better than give a surveyors.It happens that captains with comparison between rounded-form models their vessels in ballast fill the wells withand sharp-bilged models by means of water to get increased draught.This may resultsobtained by tanktests.These be quite justifiable with a leeward shore models weretested atTeddington, near.Most vessels will, when in ballast, Wageningen and Hamburg, the models have sufficient stability to stand up with being towed at the designed speed in still this amount of water on deck, and if they water.During the runs, the models were have not, the thing will regulate itself by inclined to 100 and allowed to roll until the vessel discharging the water over thethe roll became extinct.The period of side.Sometimes a poop or after hold isroll was noted and a graph made of the filled with water, but there is in that case a declining angles. greater chance of the vessel sustaining damage. Table 1 shows the comparison between two models ofequallength,midship The ordinary load-line rules are really area,draught and displacement. The only anarbitrarystatutoryregulation breadth of the sharp-bilged model (.99 putting a limit to the amount of cargo midship coefficient) is taken as unity.The the vessel ought to take.It is always for breadth of the rounded-form model being the master to see that there is a sufficient 10% greater than the other model at the amount of freeboardtoprovidethe load waterline is designated 1-10.The necessarystabilityandsea-kindliness, midship areas are the same in both models under all the circumstances to which the therefore the lower waterlines are reduced vessel may be exposed on the contemplated in width in the rounded form, producing voyage. a greater fall-in of bilge.These models Itis particularly desirable that sailingwere tried with and without bilge keels, vessels have the necessary sea-kindlinesSthe depth of keels on both models being The great number of losses of large sailing equal and equivalent to 12" on ship. vessels a generation ago was due to dismast- ing owing to want of sea-kindliness. TABLE1 It has been suggested that vessels ought to be in possession of sufficient strength to Sharp Rounded. make heaving-to unnecessary. bilge form That seems Moulded breadth .. 1.001.10 hardly reasonable:it would mean that vessels would ordinarilycarry an un- Midship section coefficient 99 .90, necessary amount of structural material. Prismatic coefficient . 78, 78 Period of roll (no bilge keels fitted) ...... 100% 77% Period of roll (bilge keels MR. N. H. BURGESS, Member : fitted) .. 104% 80% Reliable records of rolling and pitching'Time required to reduce roll in conjunction with a reliable description from 10° to 2° (no bilge of the prevailing sea conditions are unfortu- keels fitted) .. 100%46% nately very difficult to obtain.It is quite Time required to reduce roll common to get from different persons quite from 100 to 2° (bilge keels different stories when giving their descrip- fitted) ... 70% 42% tion of a certain vessel's behaviour at sea among waves, and further it is extremely difficult to compare one particular design In the above comparison, it will be noted of hull with that of another on account ofthat while the overall damping effect of thepresenceofsomanyvariables, the rounded-form model isgreater, the particularly the weather variable. bilge keels were actually more effective on the sharp-bilge model, evidently due to The only reliable method, in my opinion, the greaterleverage from the axis of when comparing two different designs of rotation.The rounded-form model with hull is for the shipowner to appoint onea beam of 1-10 had necessarily a con- of the captains of the fleet to make severalsiderable fall-in of bilge in order that the voyages in each type of vessel and to makemidship areas of the two models should be observations by the aid of a Sperry Rolling equal.It will also be noted that the period Indicator. Unfortunately,theseinstru- of roll for the rounded form of model is ments are very costly and the supply is23% shorter. than that of the sharp-bilged very limited, and up to the present, very Jmodel. few shipowners have considered it necessary Table 2, like Table 1, shows the compari- to install such a device. son between two models of equal length, In order, therefore, to give the Authors midship section area, draught. and dis- some useful information about the rolling placement.The breadth of the rounded, and pitching obtained on recently builtform model in this comparison, however, vessels of more or less rounded form, I.is 1-06. D124 DISCUSSIONSEA-KINDLINESS AND SHIP DESIGN

TABLE 2 In this comparison, the periods of roll Sharp Rounded areapproximatelythe same for both bilge form models and as in the case of the fuller Moulded breadth .. 1.001.06 models in Table 3, the damping properties Midship section coefficient 99 935 of rounded form are more effective than Prismatic coefficient .. 78 78 inthe sharp-bilge vessel, but to a lesser Period of roll (bilge keels degree.It should also be noted that the i fitted) .. 100% 93% rounded form has 21" keels as against Time required to reduce roll 12" in the other. from la' to 2' (bilge keels With regard to pitching, here again we fitted) ..100% 67% have difficulty in obtaining reliable informa- tion, but it is generally acknowledged by the masters of the vessels having rounded In the above comparison it should bemidship section and fuller end lines that noted that the bilge keels on the rounded they are excellent sea boats in a head sea, form were the equivalent of 21 inches formaintaining a good speed and shipping the ship, whereas on thesharp-bilged very little water.This would appear to model it was impossible to fit anything be confirmed by tank tests carried out at over 12". Hamburg on the models shown in Table 3. The period of roll is 7% shorter in the These models were for a proposed 15,000- rounded-form model and the time required ton tanker. The models were self-propelled, to reduce roll from 10° to 2' is 33% less. head on to waves, equivalent in size to Table 3 shows the comparison between 590 ft. by 13 ft.The results which were twomodels of equal length,breadth, somewhat surprising showed a loss of speed draught and displacement, the differences in a sea-way of 3.17 knots for the rounded beingin midship section and prismaticform and 3. 67 knots for the sharp-bilge coefficients. modelwithfinerends.Actually,the TABLE 3 difference in speed of the two models in a Sharp Rounded sea-way was84 of a knot due tothe bilge form rounded form model being .34 of a knot Moulded breadth .. ..1.00 1.00 faster in smooth water, both models, of Midship coefficient .. 985 .935 course, being run at the same power.It Prismatic coefficient 73 .77 was also shown that the sharp-bilged model Period of roll (bilge keels pitched to a greater angle. fitted) .. ..100% 102% I trust that I will not be accused of adver- Time required to reduce roll tising when I mention that the rounded from 10° to 2° (bilge keels form of miciship section developed by the fitted) ...... 100% 70% late Sir Joseph W. Isherwood, Bt., has since itsrecent use for slow-speed merchant In this comparison, as would be expected, ships, been adopted in quite a number of the period of roll is approximately the same new vessels totalling a deadweight carrying for both models, but the time required to capacity of some 400,000 tons, 90% of reduce roll from 10° to 2° for the rounded which vessels have the comparative breadth form model is again about 30% less.In of 1-05 to 1.06, this having been found to comparingthedampingpropertiesof givebestall-roundresultsafter much both models, it should be noted that the tank testing. moment of inertia of load water-plane in the rounded form model is slightly greater than that of the sharp-bilge model ;also, CAPTAIN C. V.GROVES, Associate : that the rounded form has 21" bilge keels The Authors state that a topgallant fore- as against 12" in the other, fife latter beingcastle is the chief cause of the inability of a the greategraepth that could be fitted. vessel to come up to the wind in heavy Table 4 shows the comparison between weather, and this is undoubtedly true. They two finer models of equal length, draughtmake some interesting remarks concerning and displacement and approximately theheaving-to and most masters of vessels of same beam, the principal differences being 10 or 11 knots will agree that to endeavour midship section and prismatic coefficients. to keep the head of such a vessel within 2 to 4 points of the wind and sea is hopeless. TABLE 4 The result is she lies with the wind some- Sharp Rounded where near the beam for the greater part bilge form of the time, taking occasional sheers into

Moulded breadth .. ... l'00 1.015 the wind and sea and so shipping heavy Midship coefficient .. 985 .945 water forward.The speed of the ship Prismatic coefficient ..... 695 725 through the water at that time may be Period of roll (bilge keels 2 knots and that of the sea itself 12 knots, fitted) .. 100% 98-5% so that a heavy volume of water strikes the Time required to reduce roll forward deck erections at 14 knots carrying from 10° to 2' (bilge keels destruction in itswake. May notthis fitted) .. 100% 85% practice of endeavouring to keep a low- DISCUSSION7,SEA-KINDLINESS AND SHIP DESIGN D125

powered vessel's head to wind and seaprobably due totheexcessbuoyancy often be the reason why one hears of bridge obtained in a sea-way from the long over- fronts being set back bodily ? hang.The value of reserve buoyancy was In tempestuous weather with plenty of impressed on me many years ago when sea room there is everything to recommend analterationinfreeboardregulations the gradual stopping of the engines andenabled a small coasting vesselabout allowing the vessel to fall off slowly into 220 ft. long to get just 14,- in. more draught. the trough of the sea.Careful nursingOn meeting the master subsequently he of her will be necessary until the desiredtold me "she used to be a good little sea position is attained, and there may be aboat, now she's like a half-tide rock ! " few anxious moments, but if it is correctly Of course, it is sine qua non that a vessel timed the manceuvre will be successfulmust be buoyant,but what struck me and the vessel will take up a position beamwas that the small increase in draught had on to the sea with the wind anywhere from made so great a change in the vessel's 2 points forward of, to 2 points abaft, the behaviour. beam. She will then drift bodily to leeward No doubt the suggestions about forms leavingacomparative" smooth"to of bows and sterns and dispositionof windward and heavy sprayis probably superstructures would all help to correct all that will be taken aboard, for little orthe special defects observed ;but there no resistance is offered to the elements. remains a mystery about the sea-kindliness. If at the same time a little oil is allowed to Right back from sailing-ship days we have escape from scuppers on the weather side, heard of ostensible sister ships going to it will be an advantage. sea, and one turning out a success in every Those who have had experience of both way, the other more or less a failure. They sail and steam will heartily endorse the seemed to develop a character of their own, Authors' statement that a sailing ship isand some even degenerated to the rank a more seaworthy vessel than a power-of murderers, throwing men off the yards, driven vessel of equal or larger size.With-killing them with broken spars, or washing out entering into the years-old controversy them overboard. This may have been under- of sail versus steam training, it may be saidstandable in the old days when ships were that the requirements for modem condi-built more by rule of thumb ;and the tions would be met by training in quitemaster shipwright in fairing might produce small power craft. fuller or finer forms, and a little difference Reference is made to the pooping ofin position of masts or in the sails might vessels, and when such has occurred itbe accountable for much ;but we still will generally be found that the shape ofhear of ordinary tramp steamers built the stern, whether elliptical or cruiser, has from the same scrieve, one turning out an little to do with it, the predominant cause unfortunate and unlikable vessel, and the being the maintaining of too much speedother reasonably profitable and sea-kindly. when running and thus causing the seas1 think this mystery is beyond the naval to break. architect's province, and must be referred to the seafarers for solution.Apart from MR. L. HARVEY, Member : the proper loading and handling of the The term "sea-kindliness as defined invessel, it appears to me that in obtaining the Paper will, I think, be easily understood the right amount and disposition of reserve andappreciatedby seafarers,while buoyancy lies the secret of sea-kindliness. difficult of appreciation by naval architects and engineers.To a seaman a " sea-MR. J. L. KENT: kindly " vesselis what he would call a With reference to paragraph 3, a vessel " good sea boat" ;she would be perfectlymay pitch periodically into the crest of an seaworthy, but might have a flexibilityon-coming sea,because of a want of bordering (in the eyes of the naval archi-isochronism in the pitching and dipping tect) on weakness and generally a smallof the ship with the period of encounter margin of initial stability.An eminentlybetween ship and waves.Thisis due seaworthy vessel, on the other hand, mightprincipally to the change in ship resistance be so rigid and have so much margin ofto pitching with angle of pitch or extent stability as to be far from a sea-kindlyof dip, and the result is that the ship will vessel. occasionally pitch into a wave crest even No doubt the cut-away forefoot and in perfectly regular seas.This can be large expanse of fore-end above water inshown by model experiment and is illus- a vessel of Maier form type will tend totrated in my paper read before the Insti- cause her head to fall away, especially in tution of Naval Architects in 1926. ballasttrim,but 1 understand that in As regards the shape of the bow best loaded condition against heavy seas thissuited to sea-kindliness with a view to form of bow is easily driven, and reallykeeping the fore deck free from water, sea-kindly.I believe that it is under such experiments have been made at the William conditions that the value of this form ofFronde Laboratory on a number of models fore-end is most noticeable and thisis with this object ic mind.The buoyancy D126 DISCUSSIONSEA-KINDLINESS AND SHIP DESIGN of the ship forward should increase rapidly I speak from experience of the steadying as the vessel pitches and diminish rapidlyeffect of sails.Two steamers whichI as it ascends, sohull forms with forwardcommanded were fitted with fore and main sections of V shape, or narrow with wide trysails, and I always used them with great V tops to them, always gave the best advantage, particularly in a heavy beam performance in rough water when tested sea, or even when the sea was well on the for sea-kindliness. bowcoming west across the Indian Ocean A second hint on design learned from in the S.W. monsoon, often of gale force, these experiments was to ensure that bow and also in the North Atlantic.Even the lines from about quarter beam to ship'schief engineer, who at first scoffed at my side had their rounded portions stepped sails, had to admit how useful they were, back aft,sothat as the bow pitched as it made the ship much steadier in the downwards the water found an easy outlet heavy sea-way. under the bilge turn and did not pile up One seldom hears of a sea anchor being the ship's side and come aboard towards resorted to to-day, but an emergency one amidships. is easily made with, say, an awning or a One other point worth notice in this good spare tarpaulin, and with this and the connection was that slow cargo ships with storm trysail aft, and oil dropping from full bow lines create a wide bow breakereach quarter, a disabled steamer would forward, and the higher this bow breakerride out anything comfortably. the greater must be the freeboard forward Loading is undoubtedly one of the most to avoid shipping seas when pitching.Itimportant factors in making a ship kindly is, therefore, advantageous to cut awayin a heavy sea-way, the weight being the forefoot of such vessels in the manner distributed in height to give just sufficient of the Maier-form bows. metacentric height to ensure stability and The Authors' remarks onheaving-to thus give an easy roll.Much can be done are of interest to me as I have watched this in this way with a general cargo but little manceuvre several times at sea, and in onecan be done with coal or bulk cargo, instanceitwas attempted under veryexcept to raise the weight as much as difficultseaconditions without successpossible to give easy rolling.With ore being achieved.I agree with the Authors cargoes no ship is what may be calledlively that much could be done by model experi- in a sea-way, and, of course, heavy rolling ment to improve the seakindliness of ships, cannot be prevented.This is where the although from the experimentsirkthis use of sails would again come in. direction which we have already carried Steamers with a good flare are naturally out,a considerable amount of careis much drier when going into a head sea, needed in the technique of such work toand I consider that every vessel should ensure reliable data being secured. have as much flare given as possible, when building, otherwise No. 1 hatch CAPT.W. LIGHTOLLER (Blundellsands): generally catchesitprettybadly, as a I agree with many of the statementsvessel with even moderately straight bows made in the Paper. plunging into a heavy head sea takes very With many years in command of bothheavy water in over the forecastle head. sail and steam, I consider the experience I believe most sailors of experience, where gained in sail training invaluable in thesea room permits, will keep away a couple later handling of a steamer inheavy of points or so, and so bring the sea more weather. A sailing ship has to be nursedon the bow and make better weather ofit. in heavy weatherher peculiarities studied With a shelter-deck steamer I prefer to and that experience is naturally broughthave the topgallant forecastle, although to bear when in steam.Most maritimeperhaps as stated, it is more difficult to nations recognize the value of training inkeep her head to wind when laying to, but sail,which we neglect,but should be thisis compensated for by the vessel's foremost in.Failing sail training, a certain being so much drier. amount of sea service in small steamers We have two steamers, Lancaster Castle would give what Icall a " sea sense."and Lowther Castle, built by Sir James Much damage can be and is frequently Laing & Co., Ltd., of Sunderland, on done by careless driving into a heavy head their lines, with fine cruiser sterns and sea.Few steamers are to-day providedraked stem, and from reports, their per- with sails or the means of fitting them formance in bad weather is all that can be a storm trysail aft is a very greathelp in desired.ConsequentlyI do not agree keeping the ship head to wind, and Iwith the statement in the Paper of the consider that every tramp steamer wouldpoor course-keeping abilityof a vessel be better fitted with one, particularly those with a raked stem, as these steamers prove with the old-fashioned type of chain-and-the contrary ;also their speed in ballast rod steering gear.This would not onlytrim is very good :in fact, the results have help to keep her head well up to wind and been quite up to our expectations and sea when laying to, but proveinvaluable better. in case of an accident to the steering gear. At one time I should probably have DISCUSSIONSEA KINDLINESS AND SHIP DESIGN D127 agreed that the full stern would be betterkeeps a more moderate pressure of the than a fine stern in a following sea, butship's shell and internal bulkheads and our experience with thetwo steamersdoes not affect capacity so much ; but for above mentioned has proved the contrary, ordinary 9,000-ton ships a good scheme and I now consider the fine cruiser sternis a deck ballast tank well forward under by far the best in a following sea, and notthe saloon house which isin turn the so liable to poop.With the fine lines aftfloor of the wheel house. You then can there is much less drag. get sea-kindliness in ballast, help to get a The statementthat a propeller justgood immersion forward and provide a submerged is known to be definitely lessgood look out over the bow, while it may effectivethanonethree-quarterssub- be possible to get the tank off the tonnage. merged, is news to me, and one I cannot Boilers and Machinery.The same credit.I am not a propeller expert, but speaker alluded to the lifting up of boilers. my experience is that better speed is made This is an old proposition to which the with the propeller fully submerged, and in standard objection used to be priming of a long ballast trip the more it is under the boilers.Evidently this does not take water, the betteralso to avoid excessiveplace asInotice that the people who racing. specialize inthis get a good succession of orders.These vessels are bound to MR. R. MAcGREGOR, Member : carry well and be easy in ballast. Timber carrying.I remember a series As a scheme I find it possesses many of of seven vesselsbuiltin Antwerp for the sea-kindly merits which I think would Continental owners.These vessels were arise from using electric propulsion as 210 ft. x 30 ft. 6 in. x 14 ft. They all carried fitted in motor tankers, Brunswick, etc., about 1,300 tons deadweight.The firstbut utilizingthe extreme after end of two had about9 in.tumble-homeat shelter 'tween decks to house the four upper deck and 9 in.rise of floor, and generating units, instead of keeping them carried 375 standards of wood.The next below.These units could be of 500 b.h.p. three were built with vertical sides andeach, and turning at about 600 r.p.m., this type carried 405 standards.The last something like those used on the Diesel two had vertical sides, no rise of floor, a rail cars.The only space required below somewhat cramped tunnel, also a framewould be what is needed to house the space, and less engine- and boiler-room electric motors on main shaft.The deck length.These latest vessels carried 425would be stiffened in the same way as is standards with the same running costs,done by the firm at Fredriksstad, using and were the best behaved ships at sea. the side of the oil-fuel tanks with girders The cutting out of tumble-home gave them between them.I found that this type of the necessary beam to stand upright when vessel,if compared on deadweight,is previously the vessels had to loll over tocheaper than theheavydirect-coupled get the breadth on the waterline.The Diesel-engined ship owing to the reduction ballast tanks also were much bigger withoutin weight of machinery.No auxiliary the rise of floor, which also improvedgenerator is needed as one of the main timber carrying. engines at reduced power replacesthis, Side tanks.One speaker at the meeting while the efficiency of small Diesel engines raised the question of side tanks.I had a is just as good as large units. The fear patent for colliers of thistyPe, which of being held up for long periods by broken carried the side coamings of their broad shafts disappears. self-trimming hatches right down to the Form.I quite agree with the modern shellasfore-and-aft bulkheads for the idea of increasing the beam and fining the full length of hold at about 3 ft. from ship'sends; but I cannot think that the heavily moulded-breadth line at bottom. Ordinary rounded midship section is good practice. It floors were fitted and a portable steel ceiling looks too like the 'midship section of H.M.S. ;. fitted between thekeelsonriderplates. Revenge of 75 ft. beam and about 31 ft. The engines were right aft.Capacity was draught, which was built on the Tyne.This sufficient for cargo of Welsh coal as then class of battleship was built to suit the then used by the Admiralty, instead of oil fuel existing dock entrance at Portsmouth and as used to-day. had no bilgekeels.The Revenge left Two vessels of this type were built, one Jarrow about 1893 and in 1894 she nearly in Antwerp and the other in Sunderlandrolled herself under with her crew of 800 They proved goodfleetcolliers,being in the Bay of Biscay.The angle of roll specially fitted for this work, with double was given as over 40°. All these Revenge derricks and double winches at each masttype of vessels were altered by fitting them and were very sea-kindly in ballast.The with bilge keels and the dock gates were reduced capacity puts this out of courtaltered, so that we now find the vertical for ordinary vessels. They need theside and quick bilge on the modern battle- 1 nveting to be good and plentiful in wayship as a result of experience gained with of deep-side tanks.The cantilever tank the other type.It seems to me that good partially produces the same effect and beam, full 'midship section and fine ends D128 DISCUSSIONSEA-KINDLINESS AND SHIP DESIGN will give much better results on the samehas to perform in taking a ship over the ocean safely and comfortably.I fear that displacement. often many of us are prone to forget that About the position of centre of buoyancy, much of the credit for successful per- I have seen extremes in this.One vesselformance is due to the personnel, officers with a knife bow and full stern was aand crew. We constantlybuild better very poor ship.The centre of buoyancyships and, if they are less seaworthy, it was 1 per cent, of length abaft midships.is due to poor personnel.Whether the Another was a vessel with centre of buoy- former better seamanship could be revived ancy 2 per cent. forward of midships asby the Authors' proposition to train men a result of a mistake.Her block co-in sailing ships or small craft is a much efficient was 0.81 and she turned out todebated question.The seamanship ques- be extremely economical.The old oiltions in connection with big ships are very tankers with coal firing had to have adifferent from those in small ships or in similar position to avoid trimming bysailing ships, and this brings up the refer- the head.I think 1 per cent. forward ofence of the Authors to steadying sails on midships for ordinary speeds will be founda modern ship.The ships are too big to to give satisfaction. make any practicable sails of any use. Sailing Ships.Lastly, I may say that As to the example in Section 2, after I had to do with sailing ships in my earlystating that sea-kindliness may be regarded days, as they were still being built when Ias a necessary adjunct to seaworthiness, went to work inFrance.They werethere is given the illustration of the ore ship, allowed a bounty, but this was later appliedand the statement is made that too much to steamships in their stead. initial stability is usually possessed by a vessel carrying ore, which can result in I can only say that it is a blessing thatexcessive rolling and greater likelihood of they are no longer built and I think thegreater weather damage. Do the Authors modern mariner isfar better employedhave in mind in this example an ordinary in adapting himself to the power-drivencargo ship loaded with ore ?If so, the vessel and all that goes with it instead ofonly thing to expect would be serious thinking about the sailing ship.I oncedamage and perhaps loss of the ship in saw a sailing ship skipper take a brand new heavy weather.Or have they in mind a trawler and flatten her nose against theproperly designed ore carrier,in which dock wall through having no notion ofthe initial stability is not excessive, although handling a steamer.Another thing thatit may be higher than for ordinary cargo stands out in my mind was seeing a sailing ships ? ship arrive from Australia and being lost I am also not in entire accord with the with all hands within 200 yards of Victoria statement on the middle of p. 230, that from Pier, at Hull, owing to having no powerthe design standpoint very little is really aboard.I saw four sister vessels built inknown of the effect of out-of-water form on one yard, of which two were lostin goingpitching behaviour, and the further state- from the North of France to the Tynementthatsomeflareforward,while for a coal cargo ; the ballast for the shiftregarded as essential for dryness in short was totallyinsufficient,but a naturalsteep seas, is not effective and avails but inclination was to gamble on fine weatherlittle against heavy seas.Accepting that and avoid the cost of filling and emptyingpracticable changes in the shapes of ships the ballastwhich was usually gravel or have very little effect on the pitching motion, sand.One also remembers thetragicI think it may be said in general that flare losses of German, Belgian and Danish at and immediately above the designed load school sailing ships ;so let us be thankfulwaterline forward is objectionable from the that we have nothing of the kind afloatstandpoint of wave-making, the tendency to-day, and let us keep our sailors as drybeing to turn over or break the bow wave as ever we can. also that full-endedwaterlines forward at and above the designed load line are REAR-ADMIRAL GEORGE H. ROCKconducive to forms that are essentially dry. (C.C.), U.S.N. (retd.),Honorary The question of seaworthiness as affected Fellow : by pitching seems to be more a matter of I find it difficult to understand exactlythe water or spray taken on board than of whatismeantby "sea-kindliness." safety as far as I understand the Authors, The sea is kind to a ship properly designed, or indeed as far as concerns opinionin properly handled, and may be consideredgeneral. A good flare forward may keep by one thinking of sea-kindliness asunkindsome spray off forward and a goodclean to a ship thatis not properly designedside may keep spray off the ship farther for the work or is not properly handledby aft, but this would hardly be a matter of moment toaseaman.Obviously we the personnel. is a In this connection the Authors dowell must humour the passengers, but this to stress the function that aship's crewdifferentmatter. A bigshipmeeting DISCUSSIONSEA-KINDLINESS AND SHIP DESIGN D129

short waves will merely plough throughship properly designed to meet any condi- them.Itis only in a long-period swell tion of sea and weather, and that they that the ship's bow can rise and fallto prefer a ship with a more moderate design accommodate itself.With a small ship ofthat will under normal weather conditions short period, things are different. be more comfortable for the passenger I appreciate that the Paper is written personnel on board, and then look to the more forthe comments of navigating handling of the ship, in seriously adverse officers, and although I am making many weather conditions,to ensure sufficient comments, I am not of that class ;;but the safety.If I am correct in my inference, impression I got from the Paper was thatI do not agree with the attitude of the the Authors oppose the results at sea on a Authors.

AUTHOR'S REPLY Reply to Mr. C. Waldie Cairns.Mr. papers by Dr. Kempf before this Institution Cairns's remarks are a valuable amplifica- and the Institution of Naval Architects tion of the paper. We agree particularly in 1934 that a curious breakdown in thrust with his views on training of navigators is found when the propeller is just sub- and naval architects :ship construction merged.The propeller thrusts much better would benefit. at smaller (say three quarters) immersion Freedom from pounding should certainly than when just submerged.The break- be regarded as a feature of sea-kindliness. down was found on all screws tested ; and Despite some progress in avoiding pounding personally we believethe phenomenon at low speeds, the evil still persists in the does exist on both model and full scale. 13-to16-knot high-speedcargo-vessel class of otherwise most modern design. Replyto Mr. A. G.Akester.Mr. It appears to occur with undue concentra- Akester's remarks on sea-kindliness are tion of weight amidships in the ballast of interest.We submit, however, that condition, when the pitching period is least only a definition based upon complete and when the vessel simultaneously heaves safety can possess the absoluteness essential and pitches in.Inspection of pounding for legal discussion. damage shows that the damage extends His reference to sailing-ship rudderheads further aft the greater the speed-length isintriguing. We suggest that a more ratio.By reducing the speed the centreprobable explanation is the fact that the of pounding attack will move forward steamer rudder works in the propeller slip- to the sharper bottom sections and will be stream and for the same ship speed will be reduced in intensity.Synchronism between subject to at least twice the rudder pressure the ship's heaving periods and the wave of the sailing ship. We are obliged for his period of approach is made more remote checking our rudder-area formula.The by speed reduction, and also by changing fact that actual areas checked appear about course toavoid on-coming seas being 5 per cent, less than the formula, suggests directly ahead.Research on this subject that Mr. Akester has not included half the is urgently necessary. fin area in front of the rudders in making Reply to Capt. H. Stonehouse.Capt. the comparison. Stonehouse's comments are helpful.It is agreedthat deck erectionsaft help to Reply to Mr. W. Mackie.Mr. Muckle produce a balanced wind profile, but why raisesa number of interestingpoints. should not wind balance be obtained as a With regard to automatic stabilization, matter of simple routine and be as positivewhile at the moment this is still probably as, say, trim ?A sail aft gives a wide too complex for general commercial adop- range of control and should berein- tion, yet with the simplification that pro- troduced. gress is bound to bring, the cargo ship of the future will profit by such controlled sea- Reply toCapt.0.Fletcher.Itwas kindliness. fortunate that Captain Fletcher should have been able to attend the reading of the Reply to Capt. W. E. Sommerville. Cap- Paper and givehisexperience of the tain Sommerville's remarks add to the value Silverpine.Hisconfirmationthatthe of the discussion.We agree with most of centre of pitching is further aft with thehis views, particularly that ship's officers fine stern is particularly useful. shouldbesuppliedwithfullstability information to enable their vessel to be Replyto Mr. H.W. Willcox.Mr. correctly stowed and loaded with safety. Wilcox remembers the bad old days when ships were even less sea-kindly than they Reply to Mr. H. G.Williams. Mr. are now.With regard to propeller immer- Williams does not accept that a negative sion, Mr. Willcox will find by reference to metacentric height produces sea-kindlines Dl 30 DISCUSSIONSEA-KINDLINESS AND SHIP DESIGN because, although a vessel will take up some Reply to Dr. J. Bruhn.Dr. Bruhn' s stable inclinationat either side of thecontribution to the discussion is particu- upright, there would appear to be no virtue larly appreciated since the control of sea- intheinclinationitself against heavy- kindliness by loading and by handling is weather damageThis is true :but it isclearly regarded as an essential of sea- the long easy rolling which apparently is worthiness.Vessels that have to maintain the virtue. aspeedschedulearerarelyhove-to. We havedealtwithpropellersub- Such vessels must be specially strengthened mergence in reply to Mr. Willcox. We doand it would not appear unreasonable not say that continuous submergence is to grant a concession in freeboard which not necessarily a good thing. We wouldwill allow the load draught to be increased presume that a steady condition isthe by an amount which will compensate for better.We do not recommend segmentalthe extra material carried and will allow sections at all for low-pitch-ratio screws.the vessel at least to carry the same dead- Low pitch ratios demand low-drag sections weight. A useful case in pointis the for acceptable efficiency at low loads. adoption of steel hatches.It is suggested The old French ram bow iscurious, that the introduction of safer hatches would and we are surprised that French con- begreatlyencouragedif afreeboard structorsbelieved the bowreduced reductionequivalenttotheadditional pitching.Hovgaard does not share this hatchweightcouldbeinternationally view, and we agree that it is more likely conceded. to be wetter than the clipper bow.Mr. Williams states that steering will be worst Reply toCapt. C. A. Groves.Capt. with too much longitudinal surface forward, Grovessuggeststhatintempestuous since then the vessel will yaw violentlyweather there is everything to recommend under small helm angles.This view is stopping engines and allowing the vessel to opposed to that by Hovgaard quoted byfall off into the trough of the sea and Mr. Cairns and is not supported by our own gradually take up a beam-on position. experiences.It isthe cut-away forefootIt is suggested that this would only be a safe that produces directional instability at lowprocedure with a vessel in ballast or with a helm angles. loaded ship of small metacentric height, good freeboard and high erections, offering Reply to Mr. J.P. Allan. We agreesubstantial wind pressure to supply the with Mr. Allan that the removal of the dead- analogous steadying effect of sails in a wood aft is better than its removal from sailing ship. forward as a means of ensuring ease of turning combined with good stability of Reply to Mr. L. Harvey.Mr. Harvey's route. We do not follow Mr. Allen in referencetoanadditional14 inches his suggestion to include a beam term in the more loaded draught in a 220-foot coaster rudder area formula, since in single-screw converting her from a good little sea boat vesselstherudderforcesareentirely to a half-tide rock is important.Many controlled by the propeller slip-stream. seagoing people have expressed similar views.If they are right the correct deter- Reply toCapt.J.T.Baker.Capt. mination of minimum freeboard should Baker's description of the Cairnross in heavy be a simple matter of experiment rather following weather is particularly interesting.than of doubtful interpolation from inter- He, in common with most masters, con-national regulations. siders that a raised forecastle is essential The apparent differences of sister ships on a shelter-deck vessel. are probably due to different circumstances, Reply to Mr. R. Beal. We are gladdifferent handling and different loadings. to have Mr. Beat's confirmation of ourThe differences when correctly analysed proposedminimumpowerforspeed never amount to very much. schedule work in heavy weather.This confirmation isthe more valuable since Reply to Mr. J. L. Kent.Mr. Kent it refers to a lower displacement range thanemphasizes the advantage of forward flare constituted the greater part of our ownin producing sea-kindly types and outlines data. how this should best be provided.The To decide when trim is excessive depends advantage of easy bilge shoulders forward on the merits of each case.No propeller is not so obvious, and it is good to have should work with less than 60 per cent.Mr. Kent's observations on this point, immersion.This should be secured byparticularly as to avoiding water piling trimming if impossible by bodily sinkage. up the ship side in this locality.We are not Any further propeller immersion isbest sure that we altogether agree with Mr. got by bodily sinkage.In fine weatherKent in cutting away the forefoot.While much greater trims could not be regardedthis reduces the bow wave height at the as excessive, particularly where high power stem, it also slides the crest aft where the is available to produce speeds which profit freeboard is less and seas can be shipped from the finer entrances produced by trim. more easily. DISCUSSIONSEA-KINDLINESS AND SHIP DESIGN b131

. Reply to Capt. W. Light°Iler.,Captain ReplytOMr. N. H.Burgess.Mr: Lightoller's remarks amplify and confirm Burgess's remarks on the rolling of Arcform many of the points dealt with in our Paper.ships are very interesting.There is a vast Hisreferencetothe Lancaster Castlefield for research intotherollingof and Lowther Castle are interesting.He ships and tests can take many forms. also emphasizes that the fine cruiser stern Those quoted are fairlystandard, and is by far the best in a following sea.Un- whileclearlyshowing the more rapid fortunately these vessels have many otherextinction of the Arcform rolling, yet such new features in addition to fine stems, tests are not necessarily as representative and it is extremely difficult to admit that of sea conditions as they could easily the whole virtue lies in any one feature. be arranged to be.For example, ships do not as a rule take a large lurch and then Reply to Mr. R. C. Thompson.Mr. steady up in a certain number of rolls Thompson is thanked for following up ourit is the incessant, steady, rolling, day in invitationto enlarge upon theservice and day out, that is so objectionable and performance of the Silverpine and Silver-has any appreciable influence on ship larch.With most of his remarks we can speed port to port. A motor driven out- agree, but what we would really like to of-balance weight in a model can be made see would be a comparison between the to impart a constant rolling moment to a modern fine cruiser stern and the equally self-propelled model :and the form that modernfullcruiserstern.Theissue rolls the least and requires the smallest between these alternatives is by no means power increment to maintain the desired obviously in favour of the fine stern. speed should easily be determined. Chiefly Our suggested minimum power should the behaviour under synchronism would be taken asreferringto the ordinarywould be the most vitaldistinguishing arrangement of deck-houses.If any reduc- feature between various forms of model tion of wind resistance can be really estab- researchalongsuchlineswouldbe lished; the power saving say at force 6 extremely valuable ;it would be truly an should be deducted from the formula value. investigatiOn into sea-kindliness. We have yet to learn, however, that what masquerades under the name of deck- Reply to Read-Admiral G. H. Rock. house stream-liningeffectsany serious Admiral Rock's remarks provide a welcome reduction in power in merchant ships. naval angle to the discussion.He doubts We agree with Mr. Thompson that inwhether steadying sails would be of much low-powered vessels the power should be use on a modern ship.The vast majority increased in the moderate weathers and of modern merchant ships, however, cannot only in damageable weather should be be considered too large for sail control, power be eased.Whether heaving-to can since the presence of a forecastle can upset always be avoided even with the finest the wind balance and a sail need have no designs is a moot point.It is certain,greater area than the forecastle profile. however,thatimprovedsea-kindliness Our reference to ore carriage was exclu- will mean less time lost in heaving-to. sively to ordinary cargo vessels.Special ore carriers are, of course, excellent from We agree with Mr. Thompson's remarks a sea-kindliness standpoint, but the greater on steering tests. A full reply can hardlyvolume of the world ore trade is carried be given in the present discussion. in ordinary cargo vessels. Reply to Mr. W. Spencer Paulin.With Admiral Rock lays himself open to most of Mr. Paulin's views we agree. attack from our Institution Reading Com:, We can confirm that the easier steering is mittee when he disputes that little is known made for the helmsman the greater is the of theeffect of out-of-water form on chance of poor steering.His remarks on pitching behaviour.His further remarks rudderindicatorsareinteresting.Forsuggest that a paper from him on this deep-sea work a device whichtripsat subject would be highly informative. . 10 degrees would be a useful incentive to We agree that a ship should be properly good steering. designed to meet any condition of sea or weather, but cannot agree that in seriously We agree with Mr. Paulin's criticism ofadverse weather condition the personnel the latest regulations concerningemergency shouldbe absolved from nursing the steering.The hand-wheel type ofgear vessel., coupled with relieving tackles has been found serviceable on ships up to 470 feet Reply to Mr. F. Green.Mr.Green's in length.It is considered retrograde to reference to a steadying sail aft encouraged limit hand gear to ships with rudder headsus to re-examine the classification-society of below 9 in. diameter.If the steeringattitude to the matter.It is of interest engine is out of action thereare surelyto note that Lloyd's current yacht rules many sailor ways of lashing the rudderstill state that "Full power single-screw hard-over, provided that the vessel is, ofmotor-yachts are to be provided with a course, first stopped for the purpose. mast and steadying sail."For ordinary D132 DISCUSSIONSEA-KINDLINESS AND SHIP DESIGN vessels up to 1896 Lloyd's requiredall in the 'tween decks.It would have no vessels to have sails in sufficient number. net-tonnage gain in shelter-deckers.His In 1897 this rule was changed to read that Diesel-electric proposal is good and should all vessels having sails, should keep them prove a useful design. We do not share in good condition.This latter rule wasMr. Macgregor's pleasure at seeing sails entirely deleted in 1922.In our opiniondisappear :thereisa future forthe the re-introduction of the steadying sail as ascientific sail. definiterequirementin connection with General steering-gear regulations should be seriously The Authors are pleased to have pro- reconsidered. duced such a useful discussion, and are ReplytoMr. R. MacGregor.Mr. grateful to all the contributors for placing MacGregor raises many interesting points, their views and experience on record. some of which may be open to argument.They trust that others will take up the His suggested 'tween deck tank is good,subject of sea-kindliness and that our although it would be preferable to arrange Transactions may again be the vehicle of it abreast the engine and boiler casingprofessional opinion in this matter.