Sea kindliness and ship design

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 the

_Institution

. Transactions, Vol. LIV)

NEWCASTLE UPON TYNE

PUBLISHED BY THE NORTH EAST COAST INSTITUTION OF ENGINEERS AND SHIPBUILDERS BOLBEC. HALL.

LONDON

E. & F. N. SPON; LIMITED, 57, HAYMARKET,S.W.I. 1938.

STATEMENTS MADE, NOR FOR THE OPINIONS EXPRESSED, IN THIS PAPER, DISCUSSION, AND AUTHOR'S REPLY

MADE AND PRINTED IN GREAT BRITAIN

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

-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 stability

in 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 expose

the vessel to a

greater likelihood of heavy-weather damage than would be the case with

a vessel rolling slower and less violently in response, not only 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 sailinterest-ing 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 stability

is

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

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.

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 with

the 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

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 vessels

suggests 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

a

severity 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

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 machinery

using 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 a

minimum

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 is

quite different, of course,

from propeller cavitationbecomes extremely difficult to handle.

The

propeller revolutions become erratic and despite heavy _slip,

the slip

stream velocity Js reduced and this in association with

slip stream

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

into the foundering

of

the steamers Blairgowrie,

Millpool and

Usworth.

The evidence at the enquiries showed that the loss 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

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 that

many 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 five or

six points off the wind and drifts slowly to leeward with little or 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

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, it

should be possible

to

anticipate 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

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 ON SEA KINDLINESS AND SHIP

DESIGN*

TEE CHAIRMAN

(MR. H. G. WILLIAMS

Fellow)

The officers who control the navigation and the machinery of ships together with

the owners who manage them commercially

constitute the final court which passes judgment on the work of the shipbuilder and manufacturing engineer, and the title of the paper indicates that we may hear to-night something of the principles and

of the evidence on which that court founds its judgments.

MR. C. WALDIE CAIRNS, Fellow : As the Authors state, a vessel may be so lacking in sea-kindliness that she may sustain structural or mechanical damage. This may arise from a resulting tendency to ship heavy water which may smash up deck fittings or boats, or it may bring her

into peril

by the

displacing of hatch coverings, while conditions on deck make

their replacement and securing very dangerous.

Even under less acutely perilous

con-ditions a ship lacking some of the features

Of sea-kindliness may be so dangerous to work that it is hard to ensure that every-thing necessary shall be done at the right

time. I have in mind an old steamer built

in the 1880'sof fine form, about 260 ft.x 36 ft. beam x 19 ft. 10 in. draught, with

bar keel, but no bilge keels. That vessel

in ballast condition was reputed to roll so

violently at times in the North Sea that the chief officer and hands busy on the

forecastle head had to move on their

hands and knees. Then another somewhat

smaller ship of similar form was sucha

rapid roller that she would roll into and scoop up an oncoming beam sea with her

weather bulwarks. Both these ships were much improved by bilge keels, in spite of

the very " easy " bilges available for

fitting them.

Another effect arising from excessive

rolling is difficulty in keeping steam, where

one is dependent on men with shovels to

put the coal where it is wanted in the

furnaces, and to slice and rake and clean

fires.

The Authors, refer to vessels with someF

Paper by Captain IC. Macdonald, 0.B.E., and Dr. E. V. Teller; Vice President. _{(See p. 227 ante.)}

what round midship sections and great beam, and suggest that these will suffer from excessive rolling due to great

meta-centric heights. Will that not depenkon whether the maximum beam is at, or

above, or below the waterline ? I

remember a freak type of ship built on the

Tees in the 1890's in which the designer exhibited a most greedy desire for saving deck-beam length and consequently also

deck-beam depths. These ships had their greatest beam just about the upper turn of the bilge, and had a big tumble-home

from there to each deck.

These ships were "as stiff as a rock" when empty, but as they had raised quarter decks and "part-awning deck" forming bridge and forecastle in one, they listed like sailing yachts when filled with light grain, lying over as the wind blew them. A skipper

taking one of them to the Baltic and

trying to load her with timber got the

surprise of his life : a few tons of wood

on one side or the other on deck put her on her beam ends. She was probably an ideal ship for ore.

In their references to pitching, the

Authors have not mentioned pounding.. Perhaps there is just a doubt whether they

would accept relative freedom from

pounding in ballast trim in heavy weather as one feature of sea-kindliness, but as this is a matter which can be modified by design, I think there is good reason for bringing it within the scope of a paper such as this. We perhaps hear less of

damage under fore-ends of vessels from this

cause than we used to, in spite of increase of average speeds of cargo ships ;

fore-ends of bottoms are now much

more strongly constructed than thirty yearsago,

and a little has been done to obviate flat surfaces near the forefoot.

In spite of

that, a modern ship often takes a blow

under the fore-end which makes her vibrate from end to end, and some in-creased fining may still be advisable for ships intended to keep going when in ballast, in heavy weather. These blows,

and the vibration resulting, probably have

their effect in increasing the actual_stresses arising amidships in heavy weather.

The Authors comment on the effect of a topgallant forecastle in causing a ship

to fall away in a head wind. I have

gathered many reports on this matter from

ships With and without forecastles. In

ships of the 1890's with forecastle and not much power, I have heard complaints of falling away, and in one or two of those ships I believe a trysail was sometimes used and found helpful ; but from more modern ships, with more power, and with a considerable mass of deck-houses for crew's entrances, steering-engine house,

lavatories and lockers on after end of shelter deck, there has been no complaint

from the

ships with forecastles from masters who have handled ships both with

and without forecastles, and all agree that the topgallant forecastle is a valuable

protection to No. I hatch, especially where

side extension houses are continued till abreast of or abaft of hatch corners.

Admittedly a balance of beam wind load

is highly desirable ; the less helm one

has to use in keeping a ship on her course, the more economically she will be propelled,

either in moderate or extreme winds. The

turtle-back forecastle

would no doubt

help both in cutting down head resistance in a head gale, and reducing tendency for

head to fall away to leeward in beam

winds. I can remember many fast old

paddle passenger cross-channel boats so

built. If adopted in its full features, the windlass would have to go underneath no doubt good for the windlass, but pro-ducing somewhat "blind working. I wonder, too, whether there would be any

difficulty about handling fenders and moorings from a turtle-back.

Regarding entrances to housesI think most saloon houses are now entered at after end, but I have been surprised to find recent steamers with entrances to

accommodation alongside the engine

casings from an outside alleyway. This

is the part of ship with lowest freeboard,

and appears to get the worst of the weather

with wind and sea approximately abeam.

The Authors' references to clipper stems

rather puzzled me at first, but I find they refer by that term rather to what we used to call " Pyman's teapot spout" rather than to the graceful clipper stem head such as originally supported a bowsprit

and a figurehead. It had its disadvantages when a ship had to be swung in a crowded

basin, however beautiful it looked with

ship underway. In looking up references

to overhaul my definition of a clipper stem I happened on a quotation from Hovgaard

which backs up the Authors' contention

about poor course-keeping qualities of the heavily raked stem. Hovgaard asserts

that the square forefoot is an aid to the

rudder when ship is moving at high speed.

The Authors suggest that the training of ships' officers should compulsorily

* Engineering, Vol.48 1889, p. 128.

include a spell in small craft, either sail or

steam. It would be difficult to find the sailing craft, unless like the German and some other foreign nations we equip and

run special seagoing sail or auxiliary power

ships, and then one risks a large number of hopeful lads in one bottom. (ft will be remembered that the Danes lost many youths and a fine sailing ship some years

ago.)

Small steam or motor craft are

plentiful and are becoming more so. (I sometimes wonder why some of the young

men with a little capital who hanker after adventure do not try owning and running

motor

coastersif

they really want

adventure without having it " Cook's-toured " for them). Still, I think good shipmasters could train good steamship masters in steamers, and make sure that the youngsters got a hold of most of what matters by using a little good sense in the

training.

But I have often advocated that the

training of every young naval architect ought to

include a few winter North

Atlantic voyages. I would not condemn him to the smallest ships for that run, because on the one hand I would not like him to be so helpless as to be unable to observe what was happening, and on tha other, it is possible that the larger ships

may strain somewhat more in North

Atlantic seas.

I certainly have it on very good authority

that in the North Atlantic in fairly heavy head seas,

the 400-foot ship has the

curious fault of flooding over the stern. This is not pooping with a following sea, but presumably dipping her stern unduly

with a head seaanother lack of sea.=,

kindliness ?

CAPT. H. STONEHOUSE (Hull) : The Authors of this Paper should be

complimented on choosing a subject

which is a very difficult one to which to give a really constructive answer.

How-ever, taking sea-kindliness, I would first of all say, that ships are like children while they may be sisters, they have quite

different actions in many cases in a sea-way,

and so many attributes to this can arise

from different causes, namely Nature of cargo. Distribution of weight.

Handling of vessel in a sea-way.

Explained as follows :

Coal, of all bulk shipments, is one

of the best to my mind for sea-kindlinessi if stowed as explained below in No. 2.

In colliers where there is little

sub-division, to get the most out of sea-kindliness, the coal cargo should be loaded by filling the centre holds full,

"

:

DISCUSSIONSEA-KINDLINESS AND SHIP DESIGN D 113

and the balance tapered off in the end holds to suit draught. This position

I would point out, however, would cause

the technical and commercial managers to disagree, as an equal distribution of the coal is more essential to quick

despatch. Practically the same thing applies to homogeneous cargoes.

3. This is a purely practical proposition

and can only be really dealt with by a master with some experience of the

actions of his vessel in a sea-way. I personally had experience of a 5,000-ton

steamer broken down in the North

Atlantic in the month of December, with

tail-end shaft broken, and for

twenty-three days this vessel drifted 1,000 miles under a fore and main trysail, and while some heavy water occasionally came on

board, the vessel did not labour. This experience leads me to say that a vessel

can be manceuvred into a position to

make her sea-kindly.

Ship Design was, I think, given in the Paper as seaworthiness. This raises the question of the forecastle head which, I

will say quite definitely, I consider to be a

great asset when a vessel is ploughing into a head sea ; but there should be a

big flair on the forecastle head, so that when

the vessel takes a sea the first incentive to lift will be given, instead of the vessel

dipping right into the sea and awaiting the

sea getting well aft before making an

attempt of lifting the ship.

As far as the forecastle head is concened as being a drawback to the vessel keeping

bow to wind, I am of the opinion that this is negatived in most modern vessels

by the erections at the after end.

CAPT.

0. FLETCHER

(Newcastle-on-Tyne):

I have been master of theSilverpine,one of the two vessels mentioned in the Paper,

for the past two years. The Authors have said that it would be of interest to learn

whether the subsequent service performance

of these ships has shown any definite

lesson on fine versusfull sterns. Speaking

for the Silverpine, I would say that her performance compares most favourably with that of the fuller cruiser-stern type of

ship. Even when running before very heavy Western Ocean weather, I have .experienced no trouble whatsoever, and at no time has the vessel shown any tendency

to poop. In the case of the Silverpine, I

have found that the Authors' suggestion that the fine stern may result in a less

vertical pitch aft than forward is correct.

With regard to the Authors' remarks dealing with topgallant forecastles, I am of the opinion that the only disadvantage occurs when a ship is in either the light or

ballast conditions. In connection with topgallant forecastles, I would like to

mention one factor which sometimes

seems to be overlooked by shipbuilders,

that is, the respective heights of forecastle and bridge. I have been in three vessels where it has been impossible to see over the forecastle from the navigation bridge, and navigating had therefore to be done

from the flying bridge, which only afforded very meagre weather protection.

I agree entirely with Captain Stonehouse

in his remarks about stopping the engines altogether as a means of heaving-to in

heavy weather.

As regards sea-kindliness in general, I feel that most present-day ships would be

sea-kindly if loaded to the best advantage, and in this connection I think that the

ship-builder would assist greatly by supplying

the navigator with fuller information regarding stability, trim, etc., than has been hitherto customary.

MR. R. C. THOMPSON, Member of Council :

With regard to the Authors' reference to the motor ships Silverpine and

Silver-larch and the alteration to the sterns of

these ships which is described in my paper

of 1936,* I am very pleased that Captain Fletcher is present at the meeting and has been able to describe his experience with

one of these ships since the alterations were made. I think it

can now be

stated definitely

that a

fine-lined cruiser stern properly designed, tends to a reduction in

pitching and assists a vessel to maintain her speed in heavy following seas without risk of pooping ". It should be borne in

mind, however, that the shape of the stern

is not by any means all important, as far as the amount of pitching and also as far as the liability to "pooping" is concerned, as the shape of the fore-end and position

of longitudinal centre of buoyancy are also important features.

I have received a letter from the captain of theSilverlarch describing his experience

of typhoon conditions off the Philippine

islands with his vessel in ballast conditions

as follows :

" I regret to inform you that we ran

into the region of a very severe typhoon

on passage from Hongkonglloilo. Commencing as a strong breeze on 9th inst., around 6.0 a.m., weather got

gradually worse, freshening into a whole

gale with squalls of hurricane force on

10th inst. Exchanging frequent weather

reports with the Observatory at Manilla

it was found that the typhoon was almost stationary. Under the circumstances I decided to carry on on the Southerly course we were steering, not wishing to be caught when the typhoon

corn-Loc. cit.

menced moving as they invariably take a North or North West direction and this naturally would have put the vessel in the track of the storm. The vessel

was behaving very well indeed with a high confused sea on port quarter and a

very heavy swell on port beam, she had

to be kept up considerably to clear the

Scarborough Reef.

Passing the line of bearing of typhoon

with centre a matter of forty miles

distant, weather improved slightly for about one hour when wind backed to West and weather got worse than ever. Barometer continued to

fall and at

2.0 p.m. wind reached hurricane force, and vessel by this time was

unmanage-able, having little room she was drifting

fast onto a lee shore. Tanks with the

exception of No. 3, which was filled with

water prior to leaving Hongkong, had all been prepared for the loading of

general cargo, so that all hands were put

to preparing Nos. 1 and 4 deep tanks ready for flooding and I must say that

everyone, realising the seriousness of the position, worked with a will under great difficulties as by this time it was impos-sible to stand on one's feet without

grasping something firm and holding on for grim death.

At 3.30 p.m. I commenced pumping up Nos. 1 and 4 deep tanks and at 5.15

p.m. the vessel feeling the benefit of the additional weight, I was able to coax her into a position so that it was possible to heave her to, when she rode

a very steep mountainous sea splendidly.

At 1.30 this morning weather had moderated slightly, vessel was turned round and dredging in slowly. Cabra

Island light was sighted at 3.30 a.m. Vessel was then put to full speed and

voyage continued."

I think this letter represents further

evidence of the advisability of classification

societies and owners taking more interest in the ballast capacity of ships. In this

case No. 3 deep tank carrying 1,000 tons

of water was full and yet it was necessary to put considerably more ballast intothe ship to keep the vessel manageablein the

particularly severe weather conditions experienced.

There are several different aspects to be borne in mind on the subject of the

relation-ship between beam and draught and the

question of circular versus box-shaped forms. I

do not think

that stability

measured in terms of metacentric height

in the vertical position as a

straight-forward calculation, is as important as is often thought. The moment of inertia of the cross section plays an important part

in that it affects the periodic time of rolling and also I am of the opinion that inthe case

of ships with square or box-form sections,

the square shape produces a damping effect on rolling, similar to bilge keel effect.

As far as tramp vessels are concerned the question of stability is a very difficult one from the designer's point of view

because the vessel may be required to carry

iron ore one voyage and a timber cargo with a large quantity of timber on deck the next voyage, so that all the designer can do is to aim at a happy mean. The

same problem arises when one starts to

discuss the question whether a shelter-deck

ship should also have a topgallant

fore-castle. I think it can definitely be stated

that in ballast such a vessel would be better without a forecastle, and when fully loaded would be better with a forecastle. Bearing

in mind that modern tramp vessels often

have to make long ballast voyages, I think

such a vessel would be better without a forecastle, but with a well raked stem and as much flare as possible to prevent shipping heavy head seas when loaded.

On p. 233 the Authors give a figure for

minimum power. I suggest that this figure

needs considerable qualification to take into account the different types of super-structure which may be fitted. 1 suggest

the vessel with a square four-tier bridge

with large head-wind resistance would

require a minimum power appreciably higher than the vessel with carefully shaped deck erections of modest proportions. The difference between the former and the latter

might fairly be stated as being about

10%, in so far as minimum power require-ments are concerned. I do not, however,

suggest there will be a difference of 10%

in the average service performance of such

vessels, this probably being in the nature of 3 to 4%.

I would like to endorse the Authors' remarks on the subject of the training of sea-going people in properly recording

their experiences. Until such time as this can be properly done, it is very difficult

to form correct conclusions from reports

received.

On the

subject of heaving-to, the

Authors' remarks are very interesting, but I suggest that the aim of designers should be to produce vessels that are sufficiently sea-kindly and seaworthy for completely heaving-to to be unnecessary. 1 suggest that in the case of a well designed 10,000-ton vessel, fully loaded, all that should be necessary in very bad weather conditions, would be to ease down and possibly change course somewhat. This introduces rather a complicated problem because it is now

generally agreed that in moderately bad

weather it is advisable to keep the machinery running at the highest possible power to maintain a good service performance with the modern

words, the captain is now faced with

instructions to increase power in moderately

bad weather and then if the weather gets too bad he must ease down, and as it is only if this process is properly carried out

that the best service results will be achieved,

it will be seen that the navigating officers

can play a very important part in achieving the best service results

on a modern

economy steamer.

On the subject or steering tests, I would like to ask exactly what is "normal

response" on a modern vessel ? It would

be interesting to have this laid down both with the vessel going ahead and astern. In my experience the response is not the same in the case of vessels with semi-balanced and ordinary rudders,

particu-larly when manoeuvring in port, and

further-more it does not appear that modern

vessels with well designed lines, behave in

the same way as the old-fashioned type of

ship built 10 years ago.

MR. H. W. WILLCOX, Member :

At the time I was at sea I do not think

shipbuilders ever thought of or considered sea-kindliness. I sailed in a Tyne-built

vessel trading between London and Australia. She was a flush-deck vessel,

brig rigged and instead of being fitted with ordinary hatches to the holds, she had two

hatches athwartship to each hold. The

accommodation was below deck, and the berths in the Tropics were so hot that the

Devil himself could not have slept in them.

At certain periods of the weather the

waves would synchronize with the rolling of the ship, so much so that she would roll

the hatches partly under water. On one occasion I was working at the winches and had the connecting rod and bearings on the main hatch adjusting same, when without any warning the vessel gave a sudden lurch which sent the gear over-board, and I nearly followed. The angle

of roll was so great that the boatswain

ran up one side of the engine-room casing and coming down the other side broke his leg. The coals ran out of the bunkers into the stokehold, and the coolie firemen were up to their shoulders in coal.

After I left the vessel, she was trading between New Zealand and the Mediter-ranean and disappeared on one of these voyages with all hands, presumably in

the Gulf of Lyons. I personally am of the

opinion the vessel turned turtle.

I am in agreement with the Authors regarding propellers, namely, low pitch ratios and large diameters ; but I do not agree that a propeller just submerged is

definitely less effective than one

three-quarters submerged.

The use of sail, I agree, is too important to be neglected. I was an engineer in a

vessel proceeding via the Cape of Good Hope to Australia, and while running the

casting down three of the propeller blades

were thrown and had it not been for the

sails the vessel carried (she was brig rigged), Jam afraid we would have fared very badly ;

as it was, with the assistance of the sails the vessel covered over 1,2J0 mites with

one blade.

MR. A. G. AKESTER, Member :

At the outset, I am not altogether sure

that I like this term " sea-kindliness."

Seaworthiness on the other hand is an

all-embracing term and has many ramifica-tions, and the Authors admit that in some circumstances at least, it includes

sea-kindliness. Happily the distinction made between the two qualities helps us to

understand better the aims of the Paper. Before leaving this question, however, I

wonder whether the Authors are right in putting such a rigid interpretation upon

seaworthiness as they do in the beginning of section 2. It is indeed a high standard if a ship has to do her work under all conditions "with complete safety to both ship, machinery and cargo," leaving out

of the picture for the moment the question

of safety of life. I believe the Marine

Insurance Act says a ship is deemed to be seaworthy when she is reasonably fit in all

respects to encounter the ordinary perils

of the seas of the adventure insured.

The fact that voyage and cargo are

introduced as factors of seaworthiness would indicate that seaworthiness is not measured by an absolute standard, but

that it expresses a relationship between the state of the ship and the perils it has to meet in any situation.

Reverting once more to sea-kindliness, it is certain that marine insurance companies and classification societies generally would be only too pleased if ships had this quality to the maximum degree. One of the most prolific forms of damage met with in regard

to underwriting and survey work is that due to heavy weather. The Authors stress the importance of "efficient handling and loading in adverse weather conditions,"

and rightly so.

The ship's schedule is also of importance, and it is sometimes this lack of time margin

necessitating the ship "ploughing through it" which leads to trouble.

The Authors compare the sea-kindliness

of sailing ships with that of power-driven

vessels and give the advantage to the sailing ship. Indirect confirmation of this may perhaps be taken from the fact that some

fifty odd years ago the rudder heads of iron sailing vessels were generally from inch to 1 inch less in diameter than those of steam vessels of corresponding size.

On p. 229 the Authors refer to the list that timber carriers generally take with impunity towards the end of a loaded

voyage ; I think it is a requirement, however, that on leaving a port after a

deck cargo of wood goods has been loaded, a ship must not have a list.

On p. 232 the Authors suggest that

classi-fication societies might introduce in their rules a minimum value of rudder area. This could be done, no doubt, for the ordinary rectangular rudder : in fact such

a formula is put forward as representing existing practice ; but on trying this in

several instances (principally large tankers),

the actual areas are found to be about

5 per cent, less than those obtained by the use of the formula.

The reference to steering gear in the Paper has raised during the discussion the

some-what controversial question of secondary

means of steering, and whether this should

be by hand gear or by arrangement of blocks and tackle.

The Report of the

Steering Gear Committee recommended

that hand gear of the right and left-handed

screw and nut type should not be fitted

on ships exceeding 3,500 tons gross. Some

steering-gear makers have developed a hand gear of the worm-geared friction-clutch type, which has given good results

in service.

As regards the arrangement of blocks and tackle, it is perhaps only fair to say that with the gear stowed ready for an

emergency, as it is now required to be, and the crew more accustomed to its use, there

is a better chance than formerly of this type of auxiliary gear proving effective,

especially if the winch be given some form of protection.

While the question of steering gear in

relation to a ship is,

of course, of the utmost importance, it should be borne

in mind that of something like 10,000 ship

casualties reported in the public press in

a year, less than of 1% are in any way related to steering gears. On the other hand, casualties due to fires on board

ships are more like ten times this number, and as we know only too well, occur even on some of the largest vessels.

MR. W. SPENCER PAULIN, Associate

Member :

I was very much interested in the remarks as to how the steering of a vessel is affected

by the structure of the

ship and the

difference between the steering of a sailing

ship and a steamer. My knowledge of the steering of a sailing ship is almost negligible, but from what I have gathered

there seems to be quite a different technique in steering the two types of vessel. In the

sailing ship very much less use is made of the helm ; the sails themselves are used to assist steering. In fact I read a paper some

time ago written by the inventor of the

steam steering gear in which he described the gear and its effectiveness ; a high admiral in the discussion said it was quite

unnecessary to have these things (steering

gears) and that on his ships the helmsman had printed orders not to use his helm at all, but to steer entirely by the sails. Of

course he made no allowance for the fact

that the steam steering gear was introduced

and proposed for steamships, which in

those days, though they were assisted by a sail, still needed more steering power from the helm than a purely sailing ship.

A lot of my experience is obtained on

trial trips, where the men are unaccustomed to the ship, and I find the worst things done

with the best sort of steering gear ; thus

the easier the steering gear works, the worse

the steering is as a rule. There can, of course, be a great difference between one

helmsman and another. The man who has

learnt his steering on a sailing ship had to be very careful in his use of the helm and

had to watch his

sails carefully when

moving it. Such helmsmen on steam ships

handle the steering wheel with restraint,

and wait for the ship to respond to a

move-ment of the wheel. The bad helmsman who may have to operate a small easily turned handwheel, keeps spinning it back and forward, not even giving the steering

engine time to keep up with his movements,

much less waiting till the ship feels the effect of the rudder movement.

We have found this difference in men

brought out very strongly lately with a new

type of steering gear which, instead of having a helm indicator pointer geared to the handwheel, has no such pointer, but an indicator worked by the rudder, so that what the helmsman sees is the actual rudder movement and not just the position

which the rudder will move if he gives it time. Some men steer perfectly with this gear straight away and prefer it to the normal type, but others find it very difficult to handle at first, because when they move

the wheel and the indicator pointer does not move immediately, with and as far as

the wheel, they think nothing has happened,

and turn the wheel further ; the indicator

pointer then comes over at the speed of the

rudder movement, and goes far further

than necessary, so that a frantic movement in the other direction results. Fortunately unless the man is very stupid, he soon gets

the hang of the thing, especially after a

little explanation.

There have recently been modifications in

the attitude of the Board of Trade and

classification societies to emergency steering gears. They are limiting the use of hand emergency steering gears to small

ships, and preferring an emergency arrange-ment of wire rope connecting the tiller to a power winch. The reason for this is that

they state that hand emergency gear is too slow in operation to keep the head of a

DISCUSSIONSEA-KINDLINESS AND SHIP DESIGN D117

ship to the sea in heavy weather, claiming

that frequent rudder movements of 200 to

each side are necessary and that it must be possible

to make a movement of this

magnitude in a few seconds. I would like

to know whether the Authors agree with

this view. Personally I do not, since there are hundreds of small craft with only hand

steering gears, and even the smallest take

over a minute to go from mid- to hard-over.

Small ships of this type would be much

livelier in heavy weather than a large ship

and require much more helm to keep it to the seas, yet these small craft weather storms very successfully.

In my view the main thing is to get the ship under control as quickly as possible

when the main steering gear breaks down,

and in this respect the hand emergency gear is very much superior to the gear advocated by the Board of Trade and

classification societies.

It would be as well at this point to make it clear that there are two main types of hand emergency steering gear, the right and left

hand screw gear and the worm-geared friction-clutch type of gear. The screw gear is not a sound proposition except for very small ships, as the full shock of a blow on the rudder from a heavy sea is taken solidly by the gear without any

resilience. This has led to these gears

breaking up under very severe conditions. Such breakdowns have caused hand

emergency steering gears to be viewed with suspicion. The friction-clutch type

of gear is quite a different proposition. It is mechanically sounder, and is provided with a friction drive which will slip under extreme forces, relieving all parts from undue mechanical strain.

It is this second type of hand gear that I advocate for larger ships than are at present

allowed to have hand emergency gear, the present maximum being ships with

9 in. diameter rudder stocks.

I would very much appreciate the

Authors' views on these points as there is a lack of available data from men who have had actual experience of emergency

steering in bad weather.

The method quoted on p. 234 for keeping

a ship with damaged steering gear up to

the weather by locking the rudder hard over and steering at such a speed that the turning

effort of the weather and rudder balance

is very interesting. How would it be

possible to put the rudder hard over if the breakdown was such that no means of

steering was left ?

MR. W. MUCKLE, Associate Member:

With regard to heavy rolling in the

ballast condition, there are two methods that have been adopted in order to reduce

the metacentric height

The fitting of boilers on deck. The fitting of topsides ballast tanks.

This latter method, it would appear, is

ideally suited to the collier and particularly the self-trimming collier.

In reducing the metacentric height, one must bear in mind that there is some

minimum value which the ship must have

in order to provide sufficient dynamical

stability.

Again, the transverse stability of a vessel,

and hence the rolling, must depend to a

large extent on the nature of the cargo and

in the vessel which may be dealing with

cargoes of very different densities, as in the case of the tramp steamer, it is impossible to obtain suitable metacentric height in all conditions. This leads to a question I should like to ask the Authors. If rolling

has an adverse effect on the manceuv ing

capabilities of the ship, would it be advisable to fit some automatic means of stabilization

such as the anti-rolling tank, gyroscopes,

or the Denny-Brown ship stabilizer, which appears to have been very successful on the

Isle of Sark? I know that the argument against such equipment is that the weight is considerable, being about 14 per cent.

of the displacement for an anti-rolling tank,

which may amount to about 2 per cent, of the deadweight.

On the

other hand, however, if the fitting of such equipment improved the sea qualities of the vessel, this should compensate for the loss in

deadweight.

It is suggested in the Paper that heavy

rake of stem makes for a full entrance and

hence bad steering properties. I would suggest that the modern tendency to have the longitudinal centre of buoyancy well forward of also tends to give a full

entrance.

While on this question of steering, I

should like to ask the Authors' opinions

on deadwood aft, and also if they have any

data with regard to the steering qualities of Maier-form vessels and vessels with

bulbous bows.

CAPT .W. E. SOMMERVILLE, Newcastle:

As a

seaman, the expression " sea-kindliness " strikes me as being particularly apt. It describes just that quality which many a seaman has at times desired that

his ship should possess above all.

It is a peculiar point that two ships much the same in form may not possess this particular quality in anything like the same degree, and it would be interesting to have the results of some comparisons in design between actual ships of known good and bad behaviour. I have happy

recollections of some ships of very ordinary

design which were noticeably sea-kindly,

and in

them, perhaps without special consideration for improvement in the quality, a very successful balance in design seems to have been attained.

The chief functions of cargo ships are to