From the body plan of the ship,i.e., that portion of the draught plan representing the vessel’s form by a series of equidistant transverse sections—any convenient number of sections lip to the load water-line are pricked upon and then cut out of a sheet of drawing paper of uniform thickness. These sections are then gummed together in their correct relative positions, care being taken to spread the gum thinly and evenly. This paper model—greatly foreshortened, of course—represents the immersed portion of the ship (in other words, the displacement) when she is floating upright. By suspending this model from two different points, and taking the intersection of two vertical lines through the points of suspension—or better still, by balancing it horizontally on a pin and fixing the point when the model is in equilibrium—the centre of gravity of the model, or in other words, the actual centre of buoyancy is obtained.Water lines at various angles of inclination are then drawn on the body plan, all intersecting the water line for the upright condition at the centre line of ship. The displacement represented by the inclined water lines thus drawn, generally not being equal to that for the upright position, a correcting layer has to be added or subtracted for each inclination, in order to obtain this end. By employing the planimeter the necessary thickness of this layer can be most readily ascertained. Where a planimeter is not available the actual floating line may be obtained, after the model has been made, by cutting off layers, allowance having been made for this purpose. The same number of sections as before are then cut out to each of the inclined corrected water-lines, the paper model prepared and the centre of buoyancy obtained as already described.Through this new centre of buoyancy a line is drawn perpendicular to the inclined water line, and the distance between this line and the centre of gravity of the ship, already obtained, is the righting arm. If this process is repeated for each angle of inclination, it is thus seen a complete curve of stability may be approximately obtained.
From the body plan of the ship,i.e., that portion of the draught plan representing the vessel’s form by a series of equidistant transverse sections—any convenient number of sections lip to the load water-line are pricked upon and then cut out of a sheet of drawing paper of uniform thickness. These sections are then gummed together in their correct relative positions, care being taken to spread the gum thinly and evenly. This paper model—greatly foreshortened, of course—represents the immersed portion of the ship (in other words, the displacement) when she is floating upright. By suspending this model from two different points, and taking the intersection of two vertical lines through the points of suspension—or better still, by balancing it horizontally on a pin and fixing the point when the model is in equilibrium—the centre of gravity of the model, or in other words, the actual centre of buoyancy is obtained.
Water lines at various angles of inclination are then drawn on the body plan, all intersecting the water line for the upright condition at the centre line of ship. The displacement represented by the inclined water lines thus drawn, generally not being equal to that for the upright position, a correcting layer has to be added or subtracted for each inclination, in order to obtain this end. By employing the planimeter the necessary thickness of this layer can be most readily ascertained. Where a planimeter is not available the actual floating line may be obtained, after the model has been made, by cutting off layers, allowance having been made for this purpose. The same number of sections as before are then cut out to each of the inclined corrected water-lines, the paper model prepared and the centre of buoyancy obtained as already described.
Through this new centre of buoyancy a line is drawn perpendicular to the inclined water line, and the distance between this line and the centre of gravity of the ship, already obtained, is the righting arm. If this process is repeated for each angle of inclination, it is thus seen a complete curve of stability may be approximately obtained.
FIG. 16.Drawing of Stability Balance ModelMODEL IN UPRIGHT POSITION
MODEL IN UPRIGHT POSITION
FIG. 17.Drawing of Stability Balance ModelMODEL IN INCLINED POSITION
MODEL IN INCLINED POSITION
A further method of arriving at results by experiment, involving principles not unlike those of the “paper section” method just described, has recently come under the author’snotice, and through the courtesy of its inventor—Mr John H. Heck, of Lloyd’s surveying staff at Newcastle—the following general description of the apparatus and fundamental principles is made public for the first time:—
By means of a “stability balance,” roughly illustrated by Figs 16 and 17, in conjunction with either an outside or inside model of the vessel, the moments of stability can be practically determined. In practice, an inside model has been found the most convenient to employ. This consists of a number of rectangular pieces of yellow pine of any uniform thickness, out of which a portion has been cut, respectively to the form of the vessel at equidistant intervals of say 15 feet. These pieces, together with two end pieces, are kept together by four or six bolts, thus forming a contracted model, the inside of which is of a similar form tothat of the vessel. If this model is filled with water to a height corresponding to any draught, it will represent a volume of water having the same form, and proportional to the displacement of the vessel at that draught.The stability balance consists of a frameAattached to a steel barZ, having knife edges working upon the supportC; a tableDattached to a spindle working freely in the bearingsE, and capable of being turned through any angle; a sliding weightFto balance the weight of the model when empty; a sliding weightHto balance and measure the weight of the water contained in inside or displaced by outside models; a sliding balance weightKwhich by adjustment will locate the centre of gravity of the combined weights of the tableD, the model and the weightKin the axis of the tableD, so that the model will remain when empty in any inclined position, and be balanced by the weightF.In order to determine the moments of stability, the model is first fixed on the tableD, and the weightsFandKso adjusted thatFwill balance the model at all inclinations. The table is then brought into the upright position, and water is poured into the model to the height corresponding to the desired draught of water, and the weightHshifted until the whole is balanced. The weight of water in the model will evidently be = weightH× its distance from the fulcrum ÷ distance centre of model is from fulcrum.If the table with the model is now turned through any angle, the distance the centre of gravity of the water has moved from the axisEof the table can easily be determined by shifting the weightHuntil the whole is balanced, then evidently from the principles of the lever,H× by its distance from fulcrum = weight of water in model × by the distance the centre of gravity of the water in the model is from fulcrum. Since the weight ofH× its distance from fulcrum ÷ the weight of water in model is known, the distance that the centre of gravity of the water has shifted from centre line is easily ascertained and the righting lever determined.
By means of a “stability balance,” roughly illustrated by Figs 16 and 17, in conjunction with either an outside or inside model of the vessel, the moments of stability can be practically determined. In practice, an inside model has been found the most convenient to employ. This consists of a number of rectangular pieces of yellow pine of any uniform thickness, out of which a portion has been cut, respectively to the form of the vessel at equidistant intervals of say 15 feet. These pieces, together with two end pieces, are kept together by four or six bolts, thus forming a contracted model, the inside of which is of a similar form tothat of the vessel. If this model is filled with water to a height corresponding to any draught, it will represent a volume of water having the same form, and proportional to the displacement of the vessel at that draught.
The stability balance consists of a frameAattached to a steel barZ, having knife edges working upon the supportC; a tableDattached to a spindle working freely in the bearingsE, and capable of being turned through any angle; a sliding weightFto balance the weight of the model when empty; a sliding weightHto balance and measure the weight of the water contained in inside or displaced by outside models; a sliding balance weightKwhich by adjustment will locate the centre of gravity of the combined weights of the tableD, the model and the weightKin the axis of the tableD, so that the model will remain when empty in any inclined position, and be balanced by the weightF.
In order to determine the moments of stability, the model is first fixed on the tableD, and the weightsFandKso adjusted thatFwill balance the model at all inclinations. The table is then brought into the upright position, and water is poured into the model to the height corresponding to the desired draught of water, and the weightHshifted until the whole is balanced. The weight of water in the model will evidently be = weightH× its distance from the fulcrum ÷ distance centre of model is from fulcrum.
If the table with the model is now turned through any angle, the distance the centre of gravity of the water has moved from the axisEof the table can easily be determined by shifting the weightHuntil the whole is balanced, then evidently from the principles of the lever,H× by its distance from fulcrum = weight of water in model × by the distance the centre of gravity of the water in the model is from fulcrum. Since the weight ofH× its distance from fulcrum ÷ the weight of water in model is known, the distance that the centre of gravity of the water has shifted from centre line is easily ascertained and the righting lever determined.
From a lengthened series of experiments, conducted by Mr Heck—latterly in Messrs Denny’s Works where an apparatus from a special design by Mr Heck has been constructed for the firm’s use—the method gives promise of taking a firm place as an extremely simple and approximately accurate means of arriving at the stability of vessels.[18]
While a vessel’s qualities with respect to stability may be determined with great precision by the naval architect, his investigations are only directly applicable to the ship whileempty or when in certain assumed conditions of loading which may or may not often occur in actual service. He cannot for obvious reasons estimate, far less control, the amounts and positions of centre of gravity of the various items of weight that may make up the loading.[19]This aspect of the subject has received attention at the hands of naval architects for a considerable time, but the forcible way in which it has been brought under view by recent experience has resulted in special efforts being made to practically meet the necessities of the case. In 1877 Mr William John read a paper before the Institution of Naval Architects, in which he dealt with the effect of stowage on the stability of vessels, and since that time such authorities as Martell, White, and Denny have given valuable papers or made suggestive comments bearing on this important matter. Much has also been done by several builders in the way of devising diagrams useful for regulating stowage and manipulating ballast with regard to initial stability. At the last meeting of the Institution, Professor Elgar read a paper on “The Use of Stability Calculations in Regulating the Loading of Steamers,” distinguished by its eminently practical character, and forming an important contribution to the solution of this problem. The author disapproved of curves of stability being supplied with vessels, as had been advised and was then becoming the practice. General notes, giving in a simple form easily applied in daily practice, particulars respecting the character of a ship’s stability in different conditions, are what the author recommended and had found through actual experience to meet the case most effectually. In the discussion which followed itwas intimated by Mr William Denny that his firm had already resolved to furnish every new steamer produced by them with a volume containing general and special notes and diagrams dealing not only with stability but with several other important technical properties (seefootnote, page 59). After consultation with Professor Elgar, however, he had abandoned his intention of supplying stability curves.
An arrangement designed to readily find the position of the centre of gravity experimentally by inclining, and to indicate at once the stability of loaded vessels as represented by metacentric height, has been devised and introduced on board several ships by Mr Alexander Taylor, of Newcastle—already referred to in connection with the triple expansion principle in marine engines. The instrument and apparatus, which he appropriately names the “Stability Indicator,” was described in a paper read by him before the Institution of Naval Architects at its last meeting. When once an inclining operation has been made, the degree of inclination is read from a glass gauge and the position of centre of gravity and corresponding metacentric height from a previously prepared scale set up alongside the gauge, or from tabulated figures.
The advance made within recent years in connection with steam propulsion comprises many matters necessarily left unconsidered in the chapter on speed and power of modern steamships. Scientific methods have undoubtedly contributed in no small degree to the realization of the remarkable results therein outlined. The achievement of one triumph after another as demonstrated in the actual performances of new vessels, and especially the confidence with which pledges of certain results are given and received long before actual trials are entered upon—and that sometimes with regard to ships embodying very novel features—are evidences of the truth of this.
The oldest method of approximating to the horse-power required to propel a proposed vessel at a given speed is to compare the new ship with ships already built by the use of formulæ known as “co-efficients of performance” deducedfrom the results of their speed trials. Two such co-efficients have been deduced from Admiralty practice, the one involving displacement, the other area of mid-section, with speed as the variable in both cases. Another method which has been largely used, consists in first determining the ratio of the indicated horse-power to the amount of “wetted surface,” or immersed portion of the vessel’s skin, in the exemplar ship, and then estimating from this ratio the probable value of the corresponding ratio for the proposed ship at her assigned speed. Inasmuch as these methods of procedure do not take account of theformsof the hulls, and consequently of that factor in the total resistance due towave-making, they cannot be used with any degree of confidence, or without large corrections, except in connection with vessels whose speeds are moderate in proportion to their dimensions: those in fact in which the resistance varies nearly as the square of the speed. A further method, somewhat resembling the one based upon the relation between indicated horse-power and the “wetted surface,” was proposed by the late Prof. Rankine, but has never been extensively employed. Apart from the unreliable nature of the results which an application of it gives—except for certain speeds—it is open to several serious objections in practice.
A method of analysis and prediction, meeting with considerable acceptance from shipbuilders on the Clyde and elsewhere, has been introduced within recent years by Mr A. C. Kirk, of Messrs R. Napier & Sons.[20]The method consists in reducing all vessels to a definite and simple form, such as readily admits of comparison being made between their immersed surface, length of entrance and angle of entrance and their indicated horse-power, and from this judging of the form and proportions best suited to a given speed or power in proposed vessels. The form in question consists of a block model, having a rectangular midship section, parallel middle body, and wedge-shaped ends; its length being proportioned to that of the ship, itsdepth to the mean draught of water, its girth of mid-section to the girth of immersed mid-section of the ship, and the surface of its sides, bottom and ends, to the immersed surface of the ship. By finding from one or more exemplar ships—the selection of which is obviously governed by the conditions of analysis—the rate of indicated horse-power required per unit of wetted surface at the speed assigned for the proposed vessel, the appropriate rate for the latter may easily be determined.
The data afforded by the modern system of progressive speed trials, especially when taken in conjunction with that of experiment with models as systematised by Mr Froude, supplies in a reliable way much of what is most lacking in the older methods of comparison and prediction. Progressive speed trials on the measured mile were first systematically instituted by Mr William Denny about nine years ago, since which it has been the practice of his firm to make such trials with all their vessels. The practice has been followed by other firms on the Clyde and elsewhere, and there is every probability it will be still more widely adopted in the future. The system consists in trying the vessel at various speeds, ranging from the highest to about the lowest of which she is capable. The several speeds are the mean of two runs—one run with the tide and one against, the object being to eliminate the tide’s influence from the results.[21]
Essentially noteworthy in connection with the system is the manner in which the data obtained from the trials is recorded for future use. This consists of a series of curves, representingthe chief properties of ship, engines, and propeller—e.g., “speed and power,” “revolutions” and “slip”—which show to the eye, more easily and clearly than bare figures, the whole course and value of a steamer’s performances. For that of speed and power the various speeds made at the trials are set off to convenient scale as horizontal distances, and the indicated horse-power corresponding to those speeds are set off to scale as vertical distances. The intersection of the offsets so made, give spots for the curve. The other curves alluded to aresimilarly constructed, the requisite data being the direct or deduced results of the measured mile trials.
From the accumulation of trial results thus graphically recorded the designer of new ships can proceed to estimate with greater assurance of attaining satisfactory results than by employing the older methods. If, for example, a ship is to be built of virtually similar dimensions and form to one for which such information is available, but of less speed, the task is simply one of measurement from the curves, with some allowance for probable differences in the constant friction of the engines. If the speed is to be greater than that of the exemplar ship, but still within the limits when wave-making resistance assumes relative importance, the case is also one of simple reading from the curves, with slight corrections. When both the speed and size are different, but the form is approximately the same, the case is more difficult, but it can be dealt with approximately by employing the “law of comparison” or of “corresponding speeds” enunciated by Mr Froude. Formulæ based upon this law—which will be more fully referred to presently—have been devised by one or two designers, and applied by them to problems of the latter class as they occurred in the course of their professional work. Mr John Inglis, junr., described a method of analysis he had adopted, involving the use of Mr Froude’s law, in a paper read before the Institution of Naval Architects in 1877.
When unusual speeds are aimed at, or when novel types of vessels have to be dealt with, the only available method of making a trustworthy estimate of the power required lies inthe use of direct or deduced results from model experiments. Mr Froude began the work of speed experiments with ships’ models on behalf of the Admiralty at the Experimental Tank in Torquay about 1872, carrying it on uninterruptedly until his death in May, 1879. Since that lamented event the work has been continued with most gratifying results by his son, Mr R. E. Froude. Experiments had, of course, been made by many other investigators previous to Mr Froude, but none before or since have made model experiments so practically useful and reliable. Since the value of the work carried on at Torquay has become appreciated, several experimental establishments of a similar character have been instituted. The Dutch Government, in 1874, formed one at Amsterdam, which, up till his death in 1883, was under the superintendence of Dr Tideman, whose labours in this direction were second only to those of the late Mr Froude. It is now superintended by Mr A. J. H. Beeloo, Chief Constructor, and under him by Mr H. Cop. It was here, it may be remembered, that experiments were made with a model of the Czar of Russia’s yachtLivadia, previous to the construction of that extraordinary vessel being begun by Messrs Elder & Co. On the strength of the data so obtained, together with the results of the trials made on Loch Lomond with a miniature of the actual vessel, those responsible for her stipulated speed were satisfied that it could be attained. The actual results as to the speed of the novel vessel amply justified the reliance put upon such experiments. In 1877 the French naval authorities established an experimental tank in the dockyard at Brest, and the Italian Government have formed one in the naval dockyard at Castellamare. The only experimental tank hitherto established by a private mercantile firm is that in the shipyard of Messrs Denny, Dumbarton. This establishment is on a scale of completeness not surpassed elsewhere, and is fitted with every appliance which the latest experience in such experiments shows to be advantageous. A special staff of experimentalists, forming a branch of the general scientific body, are engaged conducting experiments and accumulating data, which, besides being of service in their presentdaily practice, must ultimately yield fruit of a very special kind to this enterprising firm.[22]
From mathematical reasoning, and by means of an extended series of experiments with models and actual ships, Mr Froude determined that for two vessels of similar form—for instance a ship and her model—the “corresponding speeds” of ship and model are to one another as the square roots of the similar dimensions, and at corresponding speeds the resistance of ship and of model are to one another as the cubes of the similar dimensions—subject to a correction concerned with skin friction necessitated by the difference in the lengths of ship and model.[23]Having obtained the resistance of a model, and from it, by an application of the above law, deduced the resistance of the full-sized vessel, the effective horse-power is found by multiplying the resistance by the speed of the vessel in feet per minute, and dividing by 33,000. From the effective horse-power an estimate of the indicated horse-power required can be made by using ratios which the one bore to the other in former ships, as obtained from a comparison of their model experiments with their measured mile trial results.
The value of progressive speed trials and of experiments with models as affording convenient means whereby analysismay be made of the several sources of expenditure of power in propelling vessels can scarcely be over-estimated.
From a study of the graphic records of progressive trials, and from model experiment results, Mr Froude discovered a method whereby the power expended in overcoming the frictional resistance of the engines could be determined, and estimates made of the amount of power absorbed by other elements. The method in question was communicated in full in a paper read before the Institution of Naval Architects in 1876, and has since been extensively used. Methods of analysis resulting from a simultaneous study of this subject, were also proposed by Mr Robert Mansel, a prominent Clyde shipbuilder and noted investigator, but they failed in meeting with the acceptance which was at once accorded to Mr Froude’s propositions.[24]
Although the results obtained by an application of Mr Froude’s analysis to the trials of a large number of merchant vessels have undoubtedly thrown considerable light on the relative efficiency of hull and engines, and of various types of engines, still, for several reasons adduced by extended experience—most of which, indeed, were foreseen and perfectly appreciated by Mr Froude himself—the need has been felt for some means of directly measuring the power actually delivered to the propellers by the engines when working at different speeds. One of Mr Froude’s latest inventions, the perfecting of which was not accomplished until after his death, consisted of a dynamometric apparatus designed to accomplish this important end.[25]The construction of the instrument was undertaken for the Admiralty, and trials were made with it on H.M.S.Conquestin the early part of 1880. The results of these experiments have not yet in any form been recorded, but there can be no question as to the benefit that would accrue to the profession if the Admiralty could be induced to publish these, as well as the results of other experiments with this instrument.
Experiments with actual vessels todetermine directlytherelative efficiency of hull, engines, and propellers have on several occasions been undertaken. A series of trials of this nature were made in 1874 by Chief-Engineer Isherwood, U.S. Navy on a steam launch, the results of which may be found detailed in the Report of the Secretary of U.S. Navy for 1875. Similar trials have been made recently on the United States steamerAlbatros, an interesting account of which appeared inEngineeringof October 17 of the present year. These experiments are referred to as notable examples of what might be carried out with great advantage on other and larger vessels, although they are such, perhaps, as few single firms can well be expected to follow extensively.
The economies which may be obtained by changes in the propellers fitted to ships, and the great value of progressive speed trials as a means of measuring the effects of such changes, received most remarkable illustration in the results of the trials of H.M.S.Iris, carried out for the Admiralty in 1880. These showed that by simply varying the propellers—all other conditions remaining practically unchanged—the speed of the ship was increased from 16½ to 18½ knots per hour. Scarcely less striking improvements in the performances of vessels due to changed propellers might be found from the records of trials made with merchant vessels within recent years.
Inasmuch as measured mile trials are usually carried out when vessels are in the light or partially loaded condition, the results are far from being so valuable as they might be made; alike for the purposes of the naval architect, the shipowner, and ships’ officers; if they were undertaken with vessels in the completely laden condition. The information obtained from the trials of incompletely laden vessels does not yield that knowledge of a vessel’s qualities under the conditions necessarily imposed by actual service, which, if possessed by naval architects, would doubtless prove of immense value, nor does it furnish that standard of comparison for performances at sea which owners and captains should possess. In the interests of all concerned, it is to be hoped the practice of trying loaded vessels may become more common.
Amongst the earliest and most notable investigations involving the application of principle to the calculation of the longitudinal strength of iron vessels were those by Sir William Fairbairn, who contributed an elaborate statement of his views and methods to the first meeting of the Institute of Naval Architects in 1860. Investigation up till about this period, almost wholly concerned itself with vessels considered as girders, and in assumed conditions of fixed support, such as being pivoted on rocks. Later investigations have shown these conditions to be altogether too extreme and severe when compared with the known and estimated strains which vessels are called upon to bear in ordinary service. In 1861 Mr J. G. Lawrie, of Glasgow, in an able paper on Lloyd’s rules, read before the Scottish Shipbuilders’ Association,[26]reasoning from wave phenomenon and the probable effects attending motion in a seaway, endeavoured to deduce limits or absolute values for the extreme strains experienced by a vessel in the circumstances, the results obtained by Mr Lawrie bearing very closely on those deduced by later investigations. The late Professor Rankine made investigations involving consideration of strains in a seaway, and formulated several valuable rules which to some extent are still accepted, although giving results which are not likely to be exceeded in any case of ordinary service.[27]
For the most recent advances made in this important branch of the science of naval architecture, the profession lies under indebtedness chiefly to one or two naval architects of eminentability, whose professional province for a time has lain more especially in the way of a full consideration of the subject. Sir E. J. Reed, while Chief Constructor of the Navy, and under him several Government-trained naval architects subsequently acquiring high positions, achieved much in accurate investigation of iron-clad vessels of war. In 1870 the authority named read an elaborate paper before the Royal Society dealing at length with such work.[28]In 1874 Mr William John, formerly under Sir E. J. Reed, but at that time Assistant Chief Surveyor to Lloyd’s Register, read a valuable paper before the Institution of Naval Architects, in which he gave the results of investigations of specific cases, and of long and careful study of the general problem as concerned with merchant vessels. In this paper, Mr John advanced the proposition that the maximum bending moment likely to be experienced on a wave crest may be taken approximately as one thirty-fifth of the product of the weight of the ship into her length. Proceeding on this assumption Mr John’s paper further gave valuable results of calculations made into the strength of a series of vessels representing large numbers of mercantile steamers then afloat.[29]Of this paper and the conclusions it pointed to, Mr John, in a later paper on “Transverse and other Strains of Ships,” said:—
“The investigations showed unmistakably that as ships increased in size a marked diminution occurred in their longitudinal strength, and the results caused some surprise at the time, although they might perhaps have been easily inferred from the writings of others published at an earlier period. Those results, in spite of their approximate character, impressed two conclusions strongly on my mind: firstly, that there was cause for anxiety as to the longitudinalstrength of some very large iron steamers then afloat, and that the longitudinal strength of large ships needed on all hands the most careful vigilance and attention; and secondly, that in small vessels, and even vessels of moderate dimensions, the longitudinal strength need cause but little anxiety, because it is amply provided for by the scantlings found necessary to fulfil the other requirements of a sea-going trade.”
“The investigations showed unmistakably that as ships increased in size a marked diminution occurred in their longitudinal strength, and the results caused some surprise at the time, although they might perhaps have been easily inferred from the writings of others published at an earlier period. Those results, in spite of their approximate character, impressed two conclusions strongly on my mind: firstly, that there was cause for anxiety as to the longitudinalstrength of some very large iron steamers then afloat, and that the longitudinal strength of large ships needed on all hands the most careful vigilance and attention; and secondly, that in small vessels, and even vessels of moderate dimensions, the longitudinal strength need cause but little anxiety, because it is amply provided for by the scantlings found necessary to fulfil the other requirements of a sea-going trade.”
Using the formula as to the maximum bending moment advanced by Mr John many investigations have been made subsequently into the longitudinal strength of vessels, and this increased interest in the subject has not been without its effect on subsequent structural practice.
Mr John followed up his investigations on the longitudinal strength of merchant vessels viewed as girders by an inquiry into the transverse and other strains of ships, and in 1877 gave a valuable paper on the subject, from which a quotation has already been made, before the Institution of Naval Architects. The results of Mr John’s inquiry were such as demonstrated the need for systematic and thorough investigation of the subtle and intricate questions involved. This subject has been matter of study at Lloyd’s Register for several years, and in March, 1882, the results of inquiries conducted by Mr T. C. Bead and Mr P. Jenkins, members of the staff in London, and former students of the Royal Naval College, Greenwich, were communicated in an able paper by these gentlemen, read to the Institution of Naval Architects.
It will of course be understood that many investigations of strength are instituted not necessarily out of fear that maximum strains may not be adequately allowed for, but because the dual quality of strength-with-lightness may possibly be better attained by modifications in the arrangements of material or sufficiently met by reduced scantling. The functions and influence of the Registration Societies, already commented upon (seefootnote, page 103), are such as to obviate the need for strength investigations generally, or at least are such as to discourage shipbuilders from independently instituting them. Nevertheless, some well-known shipbuilders, who are also notable investigators, amongst whom may be named Inglis, Mansel, Denny, and Wigham Richardson, have done muchvaluable work in this connection. Mr Denny, in particular, has vigorously devoted himself to strength analysis on the basis of Lloyd’s methods of fixing scantling, and read several papers on the subject, in which strong exception is taken to present practice. The healthy criticism which such labours have enabled those making them to offer regarding the Registry systems of scantlings has not doubtless failed in influencing the legislation of the Registries.
Reverting to the subject of agencies for education in naval architecture, a few remarks are due relative to Government institutions as having hitherto failed in being of immediate service to the mercantile marine. The training given to naval architects and marine engineers at the Admiralty Schools is admirably adapted for creating a staff of war-ship designers and expert mathematicians, such as are employed in the various departments of the Admiralty service. The course of instruction has been framed expressly with a view to this, and a very high standard of mathematical knowledge is necessary before students can enter upon it. The principle of requiring one to become a first-class mathematician before attempting to teach him much of the science of naval architecture and its application in practice, is of questionable merit: at any rate it cannot be carried out in the mercantile marine. Again; economy of time and of cost of production are conditions which largely govern the methods followed in mercantile practice. Short methods of calculation, or of tentative approximation, for the purpose of enabling tenders to be made for proposed vessels, and of quickly proceeding with the work when secured, form no inconsiderable feature in the training required by mercantile naval architects. These, however, do not as a rule enter to any extent into Admiralty modes of procedure.
The want of satisfactory means for obtaining a sound scientific and practical training in mercantile naval architecture has for some time been felt to be very pressing. The evening classes conducted in most of the shipbuilding centres under the auspices of the Science and Art Department, South Kensington,are fitted to supply a part of this want so far as elementary teaching is concerned. Until recently the antiquated character of the questions set for examination was subject of general complaint, both on the part of students and teachers. In August, 1881, Mr William Denny read a paper on “Local Education in Naval Architecture” before the Institution of Naval Architects, in which adequate expression was given to these complaints, and at the same time proposed amendments offered. As a consequence of this paper, and of the steps taken by the Institution in appointing a deputation to wait upon the Government, the questions have been considerably improved, and are now so framed as to form a fairly crucial test of a young student’s knowledge of the science and practice of modern shipbuilding.
During the past three years efforts have been made by the Council of the Institution of Engineers and Shipbuilders in Scotland[30]to supply more adequate means of advanced education. In 1880, the Council had before them a project, promoted, for most part independently, by Mr Robert Duncan and others, to establish a Lectureship of Naval Architecture and Marine Engineering. It was proposed to collect funds sufficient toendow the lectureship under the auspices of the University, and promises of substantial aid were obtained from several members. Mr J. G. Lawrie volunteered to give the first course of lectures and did so, according to arrangement, during the winter months of 1881-82 before a considerable number of students, the lectures being delivered in the University of Glasgow during the day, and repeated in the Institution rooms in the evening. These praiseworthy efforts were still being carried on when, in November, 1883, the gratifying announcement was made of a gift of £12,500 by Mrs John Elder, widow of the late eminent engineer, for the endowment of a Chair of Naval Architecture in the University. The founding of this chair, and the subsequent election by the University Court of Mr Francis Elgar to the Professorship, have thus doubtless obviated the need for further efforts to found the lectureship, but there are many commendable objects connected with the University Chair to which the continued efforts of the gentlemen who supported the lecture project might fittingly be directed. Many students who can afford it will doubtless study the higher branches of naval architecture at Glasgow University, and if a few small University scholarships were established, for which all classes of workers in the shipyards and drawing offices might compete, the highest professional training would then be within the reach of the poorest of lads.
Evidences have recently been given of a strong desire on the part of many engaged in the shipbuilding and engineering industries of the Tyne and Wear for the founding of a Chair of Naval Architecture in some educational institution in that district. Along with this movement a desire has been shown for the establishment of an Institution of Engineers and Shipbuilders such as has been so long carried on successfully in the Clyde district. Definite steps are about to be taken for the realisation of these important objects, and doubtless no great time will elapse before they are accomplished.
List of Papers and lectures dealing with scientific problemsin shipbuilding, to which readers desiring fuller acquaintance with thetechniqueand details of the subjects are referred:—
The Progress of Shipbuilding in England:Westminster Review, January, 1881.History of Naval Architecture.Lecture delivered by Mr Wm. John at Barrow-in-Furness:Iron, Dec. 8th, 1882.
The Progress of Shipbuilding in England:Westminster Review, January, 1881.
History of Naval Architecture.Lecture delivered by Mr Wm. John at Barrow-in-Furness:Iron, Dec. 8th, 1882.
DISPLACEMENT AND CARRYING CAPABILITY.
On a Method of Obtaining the Desired Displacement in Designing Ships, by Mr R. Zimmerman: Trans. Inst. N.A., vol. xxiv, 1883.On Freeboard, by Mr Benjamin Martell: Trans. Inst. N.A., vol. xv., 1874.On the Load Draught of Steamers, by Mr W. W. Rundell: Trans. Inst. N.A., vol. xv., 1873: vol. xv., 1874; and vol. xvi., 1875.On the Load Line of Steamers, by Mr John Wigham Richardson: Trans. Inst. N.A., vol. xix., 1878.On the Basis for Fixing Suitable Load Lines for Merchant Steamers and Sailing Ships, by Mr Benjamin Martell: Trans. Inst. N.A., vol. xxiii., 1882.On the Assessmentof Deck Erections in Relation to Freeboard, by Mr H. H. West, vol. xxiv., 1883.Tonnage Measurement, Moulded Depth, and the Official Register in Relation to the Freeboard of Iron Vessels, by Mr W. W. Rundell: Trans. Inst. N.A., vol. xxiv., 1883.
On a Method of Obtaining the Desired Displacement in Designing Ships, by Mr R. Zimmerman: Trans. Inst. N.A., vol. xxiv, 1883.
On Freeboard, by Mr Benjamin Martell: Trans. Inst. N.A., vol. xv., 1874.
On the Load Draught of Steamers, by Mr W. W. Rundell: Trans. Inst. N.A., vol. xv., 1873: vol. xv., 1874; and vol. xvi., 1875.
On the Load Line of Steamers, by Mr John Wigham Richardson: Trans. Inst. N.A., vol. xix., 1878.
On the Basis for Fixing Suitable Load Lines for Merchant Steamers and Sailing Ships, by Mr Benjamin Martell: Trans. Inst. N.A., vol. xxiii., 1882.
On the Assessmentof Deck Erections in Relation to Freeboard, by Mr H. H. West, vol. xxiv., 1883.
Tonnage Measurement, Moulded Depth, and the Official Register in Relation to the Freeboard of Iron Vessels, by Mr W. W. Rundell: Trans. Inst. N.A., vol. xxiv., 1883.
STABILITY.
On the Calculation of the Stability of Ships and Some Matters of Interest Connected Therewith, by Mr W. H. White and Mr W. John: Trans. Inst. vol. xii., 1871.On the Relative Influence of Breadth of Beam and Height of Freeboard in Lengthening out the Curves of Stability, by Mr Nathaniel Barnaby: Trans. Inst. N.A., vol. xii., 1871.On the Limits of Safety of Ships as Regards Capsizing, by Mr C. W. Merrifield:The Annualof the Royal School of Naval Architecture and Marine Engineering, No. 1, 1871; London, H. Sotheran & Co.On Curves of Buoyancy and Metacentres for Vertical Displacements, by Mr George Stanbury:The Annualof the Royal School of Naval Architecture and Marine Engineering, No. 2, 1872, London, H. Sotheran & Co.The Geometrical Theory of Stability for Ships and other Floating Bodies:Naval Science, vol. iii., 1874, and vol. iv., 1875 (Three Articles).On the Metacentre and Metacentric Curves:Naval Science, vol. iii., 1874.On Polar Diagrams of Stability, by Mr J. MacFarlane Gray: Trans. Inst.N.A.,vol. xvi., 1875.On the Stability of Ships, by Mr Wm. John: Trans. Inst. N.A., vol. xviii., 1877.On the Geometry of Metacentric Diagrams, by Mr W. H. White: Trans. Inst. N.A., vol. xix., 1878.On the Stability of Certain Merchant Ships, by Mr W. H. White: Trans. Inst.N.A., vol. xxii., 1881.On Curves of Stability of Some Mail Steamers, by Mr J. H. Biles: Trans. Inst. N.A., vol. xxiii., 1882.On the Reduction of Transverse and Longitudinal Metacentric Curves to Ratio Curves, by Mr Wm. Denny: Trans. Inst. N.A., vol. xxiii., 1882.On the Advantages of Increased Proportion of Beam to Length in Steamships, by Mr J. H. Biles: Trans. Inst. N.A. vol. xxiv., 1883.On the Stability of Ships at Launching, by Mr J. H. Biles: Trans. Inst. Eng. and Ship., vol. xxvii., 1883-84.On Approximation to Curves of Stability from Data for Known Ships, by Mr F. P. Purvis & Mr B. Kindermann: Trans. Inst. E. and S., vol. xxvii., 1883-84.On Cross-Curves of Stability, their Uses, and a Method of Constructing them, obviating the Necessity for the usual Correction for the Differences of the Wedges of Immersion and Emersion, by Mr William Denny: Trans. Inst., N.A., vol. xxv., 1884.On a New Method of Calculating and some New Curves for Measuring the Stability of Ships at all Angles of Inclination, by M. V. Daymard: Trans. Inst., N.A., vol. xxv., 1884.The Uses of Stability Calculations in Regulating the Loading of Steamers, by Professor F. Elgar: Trans. Inst., N.A., vol. xxv., 1884.On some Points of Interest in Connection with the Construction of Metacentric Diagrams and the Initial Stability of Vessels, by Mr P. Jenkins: Trans. Inst., N.A., vol. xxv., 1884.On the Uses of J. Amsler’s Integrator in Naval Architecture, by Dr A. Amsler: Trans. Inst., N.A., vol. xxv., 1884.Contributions to the Solution of the Problem of Stability, by Mr L. Benjamin: Trans. Inst., N.A., vol. xxv., 1884.The Graphic Calculation of the Data Depending on the Form of Ships required for Determining their Stability, by Mr J. C. Spence: Trans. Inst., N.A., vol xxv., 1884.Description of Alexander Taylor’s Stability Indicator for showing the Initial Stability and Stowage of Ships at any Displacement, by Mr Alex. Taylor: Trans. Inst., N.A., vol. xxv., 1884.
On the Calculation of the Stability of Ships and Some Matters of Interest Connected Therewith, by Mr W. H. White and Mr W. John: Trans. Inst. vol. xii., 1871.
On the Relative Influence of Breadth of Beam and Height of Freeboard in Lengthening out the Curves of Stability, by Mr Nathaniel Barnaby: Trans. Inst. N.A., vol. xii., 1871.
On the Limits of Safety of Ships as Regards Capsizing, by Mr C. W. Merrifield:The Annualof the Royal School of Naval Architecture and Marine Engineering, No. 1, 1871; London, H. Sotheran & Co.
On Curves of Buoyancy and Metacentres for Vertical Displacements, by Mr George Stanbury:The Annualof the Royal School of Naval Architecture and Marine Engineering, No. 2, 1872, London, H. Sotheran & Co.
The Geometrical Theory of Stability for Ships and other Floating Bodies:Naval Science, vol. iii., 1874, and vol. iv., 1875 (Three Articles).
On the Metacentre and Metacentric Curves:Naval Science, vol. iii., 1874.
On Polar Diagrams of Stability, by Mr J. MacFarlane Gray: Trans. Inst.N.A.,vol. xvi., 1875.
On the Stability of Ships, by Mr Wm. John: Trans. Inst. N.A., vol. xviii., 1877.
On the Geometry of Metacentric Diagrams, by Mr W. H. White: Trans. Inst. N.A., vol. xix., 1878.
On the Stability of Certain Merchant Ships, by Mr W. H. White: Trans. Inst.N.A., vol. xxii., 1881.
On Curves of Stability of Some Mail Steamers, by Mr J. H. Biles: Trans. Inst. N.A., vol. xxiii., 1882.
On the Reduction of Transverse and Longitudinal Metacentric Curves to Ratio Curves, by Mr Wm. Denny: Trans. Inst. N.A., vol. xxiii., 1882.
On the Advantages of Increased Proportion of Beam to Length in Steamships, by Mr J. H. Biles: Trans. Inst. N.A. vol. xxiv., 1883.
On the Stability of Ships at Launching, by Mr J. H. Biles: Trans. Inst. Eng. and Ship., vol. xxvii., 1883-84.
On Approximation to Curves of Stability from Data for Known Ships, by Mr F. P. Purvis & Mr B. Kindermann: Trans. Inst. E. and S., vol. xxvii., 1883-84.
On Cross-Curves of Stability, their Uses, and a Method of Constructing them, obviating the Necessity for the usual Correction for the Differences of the Wedges of Immersion and Emersion, by Mr William Denny: Trans. Inst., N.A., vol. xxv., 1884.
On a New Method of Calculating and some New Curves for Measuring the Stability of Ships at all Angles of Inclination, by M. V. Daymard: Trans. Inst., N.A., vol. xxv., 1884.
The Uses of Stability Calculations in Regulating the Loading of Steamers, by Professor F. Elgar: Trans. Inst., N.A., vol. xxv., 1884.
On some Points of Interest in Connection with the Construction of Metacentric Diagrams and the Initial Stability of Vessels, by Mr P. Jenkins: Trans. Inst., N.A., vol. xxv., 1884.
On the Uses of J. Amsler’s Integrator in Naval Architecture, by Dr A. Amsler: Trans. Inst., N.A., vol. xxv., 1884.
Contributions to the Solution of the Problem of Stability, by Mr L. Benjamin: Trans. Inst., N.A., vol. xxv., 1884.
The Graphic Calculation of the Data Depending on the Form of Ships required for Determining their Stability, by Mr J. C. Spence: Trans. Inst., N.A., vol xxv., 1884.
Description of Alexander Taylor’s Stability Indicator for showing the Initial Stability and Stowage of Ships at any Displacement, by Mr Alex. Taylor: Trans. Inst., N.A., vol. xxv., 1884.
ROLLING.
Considerations Respecting the Effective Wave Slope in the Rolling of Ships at Sea, by Mr William Froude: Trans. Inst., N.A., vol. xiv., 1873.On an Instrument for Automatically Recording the Rolling of Ships, by Mr Wm. Froude: Trans. Inst. N.A., vol. xiv., 1873.On the Graphic Integration on the Equation of a Ship’s Rolling, by Mr Wm. Froude: Trans. Inst. N.A., vol. xv., 1874.On the Rolling of Sailing Ships, by Mr W. H. White: Trans. Inst. N.A., vol. xxii., 1881.On a Method of Reducing the Rolling of Ships at Sea, by Mr P. Watts: Trans. Inst. N.A., vol. xxiv., 1883.
Considerations Respecting the Effective Wave Slope in the Rolling of Ships at Sea, by Mr William Froude: Trans. Inst., N.A., vol. xiv., 1873.
On an Instrument for Automatically Recording the Rolling of Ships, by Mr Wm. Froude: Trans. Inst. N.A., vol. xiv., 1873.
On the Graphic Integration on the Equation of a Ship’s Rolling, by Mr Wm. Froude: Trans. Inst. N.A., vol. xv., 1874.
On the Rolling of Sailing Ships, by Mr W. H. White: Trans. Inst. N.A., vol. xxii., 1881.
On a Method of Reducing the Rolling of Ships at Sea, by Mr P. Watts: Trans. Inst. N.A., vol. xxiv., 1883.
RESISTANCE, SPEED, AND POWER.
On Stream Line Surfaces, by Prof. W. J. Macquorn Rankine: Trans. Inst. N.A., vol. xi., 1870.On Experiments with H.M.S. Greyhound, by Mr William Froude: Trans. Inst. N.A., vol. xv., 1874.On the Difficulties of Speed Calculation, by Mr Wm. Denny: Trans. Inst. Eng. and Ship. in Scotland, vol. xvii., 1874-75.On the Ratio of Indicated to Effective Horse Power as Elucidated by Mr Denny’s Measured Mile Trials at Varied Speeds, by Mr Wm. Froude: Trans. Inst. N.A., vol. xvii., 1876.On the Comparative Resistances of Long Ships of Several Types, by Mr Wm. Froude: Trans. Inst. N.A., vol. xvii., 1876.On Experiments upon the Effect Produced on the Wave-Making Resistance of Ships by Length of Parallel Middle Body, by Mr Wm. Froude: Trans. Inst. N.A., vol. xviii., 1877.On Steamship Efficiency, by Mr Robert Mansel: Trans. Inst. Eng. and Ship. in Scotland, vol. xxii., 1878-79.On the True Nature of the Wave of Translation and the Part it Plays in Removing the Water out of the Way of a Ship with Least Resistance, by Mr J. Scott Russell: Trans. Inst. N.A., vol. xx., 1879.On the Leading Phenomena of the Wave-Making Resistance of Ships, by Mr R. E. Froude: Trans. Inst. N.A., vol xxii., 1881.Mr Froude’s Experiments on Resistance and Rolling:Naval Science, vol. i., 1872, and vol. iv., 1875.Mr Froude’s Resistance Experiments on H.M.S. Greyhound:Naval Science, vol. iii., 1874.On a Method of Recording and Comparing the Performances of Steamships, by Mr John Inglis, jun.: Trans. Inst. N.A., vol. xviii., 1877.On a Method of Analysing the Forms of Ships and Determining the Mean Angle of Entrance, by Mr Alex. C. Kirk: Trans. Inst. N.A., vol. xxi., 1880.On Some Results Deduced from Curves of Resistance and Progressive M M Speed Curves, by Mr J. H. Biles: Trans. Inst. N.A., vol. xxii., 1881.On Progressive Speed Trials, by Mr J. H. Biles: Trans. Inst. N.A., vol. xxiii., 1882.
On Stream Line Surfaces, by Prof. W. J. Macquorn Rankine: Trans. Inst. N.A., vol. xi., 1870.
On Experiments with H.M.S. Greyhound, by Mr William Froude: Trans. Inst. N.A., vol. xv., 1874.
On the Difficulties of Speed Calculation, by Mr Wm. Denny: Trans. Inst. Eng. and Ship. in Scotland, vol. xvii., 1874-75.
On the Ratio of Indicated to Effective Horse Power as Elucidated by Mr Denny’s Measured Mile Trials at Varied Speeds, by Mr Wm. Froude: Trans. Inst. N.A., vol. xvii., 1876.
On the Comparative Resistances of Long Ships of Several Types, by Mr Wm. Froude: Trans. Inst. N.A., vol. xvii., 1876.
On Experiments upon the Effect Produced on the Wave-Making Resistance of Ships by Length of Parallel Middle Body, by Mr Wm. Froude: Trans. Inst. N.A., vol. xviii., 1877.
On Steamship Efficiency, by Mr Robert Mansel: Trans. Inst. Eng. and Ship. in Scotland, vol. xxii., 1878-79.
On the True Nature of the Wave of Translation and the Part it Plays in Removing the Water out of the Way of a Ship with Least Resistance, by Mr J. Scott Russell: Trans. Inst. N.A., vol. xx., 1879.
On the Leading Phenomena of the Wave-Making Resistance of Ships, by Mr R. E. Froude: Trans. Inst. N.A., vol xxii., 1881.
Mr Froude’s Experiments on Resistance and Rolling:Naval Science, vol. i., 1872, and vol. iv., 1875.
Mr Froude’s Resistance Experiments on H.M.S. Greyhound:Naval Science, vol. iii., 1874.
On a Method of Recording and Comparing the Performances of Steamships, by Mr John Inglis, jun.: Trans. Inst. N.A., vol. xviii., 1877.
On a Method of Analysing the Forms of Ships and Determining the Mean Angle of Entrance, by Mr Alex. C. Kirk: Trans. Inst. N.A., vol. xxi., 1880.
On Some Results Deduced from Curves of Resistance and Progressive M M Speed Curves, by Mr J. H. Biles: Trans. Inst. N.A., vol. xxii., 1881.
On Progressive Speed Trials, by Mr J. H. Biles: Trans. Inst. N.A., vol. xxiii., 1882.
STRUCTURAL STRENGTH.