368 



FOREST AND STREAM. 



[Oct, 26, 1895. 



ETHELW YNN, SHOWING "WILSON" JIB. 

 Prom Photo by J. S. Johnson. N. Y. Copyright, 1S95. 



getting our anchors, we headed out into the Sound, pass- 

 ing between two nasty-looking rocks which we were 

 unable to see the night before on account of the darkness. 

 We left the crew of the sloop, which was a New London 

 fisherman, repairing some very badly torn sails, and after 

 a hard beat to windward in a very rough sea we passed 

 the New Haven Light, and in four hours from the time 

 we left Leet's Island we cast anchor off the club house 

 and were boarded by Mr. James Gallagher, Jr., of the 

 regatta committee, who informed us that Wayward had 

 won the first prize and Stranger second. They got in the 

 morning before, so that they escaped the storm. 



Mr. Gallagher seemed as much pleased, though, over 

 the performance of the little 18ft. Roamer, the next 

 smallest boat being 27ft., as I would have been if we had 

 won one of the prizes, which we never expected to do. 



W. H. Avis. 



An Experimental Tank and Model Testing. 



The subject of naval design has now reached a point in this country 

 where practical experience can well be supplemented by abstract 

 scientific research and by the most improved appliances of modern 

 science, one of the greatest of which is the experimental tank for the 

 determination of the qualities of the completed ship from experiments 

 on miniature models. As in other things relating to naval matters 

 the United States is still behind the times in this detail; if it pays a 

 private firm of builders to own and use such a tool, to say nothing of 

 the smaller European powers, it would certainly seem that this Gov- 

 ernment, with the millions which it is now expending in naval con- 

 struction, could not afford to go on much longer without one. The 

 mechanical details of the latest experimental tank and its testing ap- 

 pliances were described in the Forest and Sthbam of April 6, 1893, 

 but the following further particulars are given in the New York 

 Times: 



A subject that has engaged the attention of naval experts for a 

 number of years is the testing of naval vessels in advance of their 

 construction. Experimental tanks, as they are called, have been 

 established in almost every country in Europe, in which the models of 

 both war and commerce ships are subjected to preliminary trials as 

 to their speed, stability, friction and turning qualities, before the 

 work of actual construction is begun. England, Prance, Germany 

 and Italy test their models in this manner, and these experiments 

 have been found to be of great value. The Construction Department, 

 of the navy of this country has been trying for several years to secure 

 the establishment of such an experimental' tank at the navy yard at 

 Washington, where the models of warships could be given a trial to 

 settle the important questions in connection with their construction. 



A recommendation was first made by Chief Constructor Wilson, 

 who asked for an appropriation of $60,000 for that purpose. Congress 

 has so far never been irduced. however, to consider the question 

 Chief Constructor Philip Hichborn, however, the successor to Con- 

 structor Wilson, has made detail reports to the head of the depart- 

 ment, and the next CongresB will be ashed for nn appropriation of 

 $100,000 for the purpose of building an experimental tank at the 

 Washington Navy Yard, in the slip between the old shiphouse and the 

 main branch of the Potomac 



Chief Constructor Hichborn in a recent interview said that the 

 bureau desired to renew most earnestly previous recommendations in 

 relation to the establishment of an experimental tank. "One of the 

 greatest obstacles encountered by this bureau in designing vessels is 

 the determination of a reasonably exact speed which can be obtained 

 with a ship of known displacement, horse power and under-water 

 form. At present our only data for su* purposes is derived from 

 more or less inaccurate reports of the performance of foreign 

 vessels, and is necessarily very unsatisfactory. The bureau in the 

 past has not even had the benefit of experience gained from thorough 

 and exhaustive speed trials of our own ships, exigencies of the service 

 usually preventing a complete series of progressive speed trials, such 

 as have been found of so much value in other services. The lack of 

 reliable data, which can only be accurately obtained from these two 

 sources, has hampered the bureau in its previous designing work, and 

 placed it at a decided disadvantage in fixing upon the approximate 

 speed to be expected from any given design " . 



The bureau in no sense desires to depart from the custom of giving 

 premiums for speed in excess of that stipulated in the contract. Past 

 experience proves most conclusively that the inducement of a sub- 

 stantial speed bonus compels a contractor to use his utmost endeavor 

 to allow none but the best material and workmanship to enter into 

 the construction of the propelling machinery, thereby insuring to the 

 navy a high quality of work, such as could not be obtained by any 

 mere system of Government inspection, no matter how rigid. 



"The commercial value of an experimental tank has been well 

 demonstrated by the experience of a private establishment on the 

 Clyde, which has had one In full operation for ten years. Aside from 

 the scientific value of the information derived, they claim that it has 

 been the means of saving them thousands of dollars by enabling them 

 to determine accurately the best form of ship to attain a certain 

 speed, the dimensions of the ship being restricted by certain definite 

 considerations." 



Experiments to determine the resistance of ships in advance of 

 construction by towing models of the proposed ships were begun by 

 the late Dr. Wm. Froude in 1872, in a tank built by him at Torquay. This 

 tank was 280ft. long, 36ft. wide and 10ft. deep, and in it experiments 

 were carried on for the Admiralty, and in connection with the towing 

 experiments with the Greyhound certain laws and deductions were 

 established beyond question. Since the death of Dr. Froude, iu 1879, 

 the work has been carried on by his son, Mr. R. E Froude, and many 

 useful and valuable results have been obtained, the designs of many 

 proposed ships have been altered after model trials, notably in the 

 case of the Polyphemus and the Medway class of gunboats, the de- 

 ductions being afterward verified by the performance of the vessels. 

 In 1882 a tank of the same dimensions, and with practically identical 

 appliances, was constructed by Denny Bros., of Dumbarton, in which 

 many thousands of experiments have been conducted with both en- 

 gineering and commercial success; the tank having enabled them, as 

 the case in point, to successfully construct a high-speed vessel for the 

 Belgian Government under conditions so rigid that under ordinary 

 circumstances surety of fulfilling them would have been impossible. 



Mr. William Denny, one of the most progressive and well-Informed 

 Scotch ship-builders, in a letter written in 1887 relative to the import- 

 ance of the assistance that an experimental tank may render to the 

 naval designer, expresses himself thus: 



"The truth is that, of all the problems about a steamship, the only 

 one at the present moment incapable of being solved bv a priori 

 methods in extreme cases is that of the speed and power. No ability 

 and no training will enable even the most skillful naval architect to 

 overcome the want of an experimental tank in coping with these 

 questions. My partners are so firmly convinced of the value of the 

 tank that every one of them regards the large amount of money sunk 

 in it in the form of a capital, and the large amount of money still to 

 be sunk in it, as one of our best investments, and have met without 

 grudging the annual outlay required for its administration " 



The establishment of an experimental tank would not only benefit 

 the naval service, but would greatly promote the shipbuilding inter- 

 ests of the country at large, by furnishing reliable information as to 

 the future performance of new types of commercial vessels that 

 would aid American shipbuilders to compete on more equal terms 

 with foreign yards in which similar information is already available. 



The British Admiralty considered the results obtained so valuable 

 that in 1886 a new tank was constructed at Haslar, near Portsmouth, 

 and the apparatus at Torquay was removed to that place, and in- 

 stalled there, with many improvements and additions, under the 

 charge of Mr. B. E. Froude. The new tank is 400ft;. long, 20ft. wide 

 and 0ft. deep, and commodious offices are attached with a view of 

 entering extensively upon the work of experimental investigation. 

 In 18S9 an apparatus was constructed by the Italian Government at 

 Soezzia, which is practically a duplicate of the British plant at Haslar, 

 except that the tank is 500tt. long and 22ft. wide. 



The latest apparatus constructed is that installed by the Russian 

 Government at St. Petersburg in 18P2. To duplicate such a plant, 

 including cost of all apparatus and the necessary buildings but ex- 

 clusive of ground, would cost about $85,000. 



The primary object is to obtain the actual resistance of the model 

 at a speed corresponding to the proposed speed of the full-sized ship 

 The speed at which the model is to be towed is ascertained by Froude's 

 "law of comparison," which is "for similar forms, corresponding 

 speeds are as the square root of the length, and resistance at cor- 

 responding speeds is as the cube of the length." The experiment 

 may develop the fact that the intended lines produce an abnormally 

 high resistance, or are in some other way unsuitable, in which case 

 the model is easily altered or a new one made, and the ship saved 

 from probable failure. 



In conducting the experiments absolute nicety of observation and 

 measurement is required. The model is carefully ballasted to the 

 exact draft and trimmed to correspond with the proposed displace- 

 ment. These factors are observed by inserting needles at. intervals 

 around the proposed waterline projecting horizontally, and the model 

 is adjusted so that all the needles just break the water. In- this con. 

 dition the weight of the model, plus the ballast, should agree with the 

 calculated displacement. In towing, the change of trim Is carefully 



observed apd automatically registered by the machine, and exact, ob- 



servation of the currents, caused by the drafts of air and by the 

 movement of the model, are made, and the general deductions cor- 

 rected therefor. 



The models are made of parafllne wax, a material which seems well 

 •adapted for the purpose, because it does not absorb water to change 

 its weight, is easy to finish and make changes in if necessary, and 

 when the experiments with a given ship are finished the material may 

 be remelted and used for others. They are cast in a clay mold made 

 to cross sections of the proposed lines, allowing about a quarter of an 

 inch around for finishing. They are cored to allow a finished thick- 

 ness of about lin. The core is formed of a wooden framework covered 

 with cloth and coated with a solution of clay to make it impervious to 

 the melted parafflne, and is filled with water to prevent its being 

 floated on the liquid wax, which is cast at a temperature of about 

 160°. 



After cooling, the model is placed in a specially devised machine, 

 by which the lines of the half-breadth plan of the proposed ship are 

 automatically copied on both sides of the model at their respective 

 heights above the keel. The model iB rigidly held in a frame capable 

 of vertical adjustment, and after being carefully set to the proper 

 height for the line to he cut, the attendant simply passes a tracer 

 around the line on the drawing, which is placed on the attached draw- 

 ing board. The cutting is accomplished by two rotary cutters, which 

 are run at a high rate of speed, and connected by a pantograph gear 

 with the tracing arm. In this way the successive lines are cut, and 

 the model is then taken from the machine, the material between the 

 lines is removed, and the model faired and smoothed by hand. It is 

 then fitted with suitable interior strengthening and carefully weighed 

 and ballasted, and is then ready to be placed in the dynamometric 

 towing machine. This machine is placed on a truck which moves 

 freely on rails situated on the top of the side walls of the tank, the 

 under side of the machine being about 18in. above the water. The 

 model is so connected that, while rigidly held against lateral devia- 

 tion, it is free to oscillate vertically and horizontally. The resistance 

 is received on the short arm of the bell crank lever, and automatically 

 traced to an enlarged scale on a sheet of cross-section paper wrapped 

 on the surface of a cylinder. The same cylinder also records the time 

 and distance run. The time pen records half seconds, and the dis- 

 tance pen records intervals of 10ft, both being actuated by electric con- 

 tacts. There are also cylinders at each end of the model for recording 

 the change of trim, by means of rods free to move vertically, their 

 lower ends resting on the model. 



A secondary speed-recording register is also provided as a check, 

 and a carriage is mounted in the rear of that, containing the model 

 dynamometric machine, fitted with another machine on similar prin- 

 ciples, for testing the efficiency of model screw propellers, and also 

 their efficiency in different positions relative to the hull of the ship. 

 The truck is attached to an endless wire rope, moving over drums at 

 each end of the tank, to which motion is given by a "tower spherical 

 engine," having a specially deviBed governor, capable of very delicate 

 adjustment to any desired speed from 50 to 1,000ft. per minute. The 

 models are tested at varying speeds of small interval between certain 

 fixed limits, and also at varying drafts of water and conditions of 

 trim. The results, after beiDg corrected, are plotted and curves 

 drawn, giving in advance full data of just what the completed ship 

 will do in all conditions with smooth water. 



Many advantages are realized from the results of these experiments. 

 The most suitable form for a certain speed may be determined and 

 the proper adjustment of power to form arranged. On the other 

 hand, a ship having a given form, the most suitable speed can be 

 selected, at which it can be most economically propelled. The form 

 and position of the waves created by the passage of a ship through 

 the water at any speed may be determined. The settling or subsid- 

 ence of the ship while running may be measured, this being an im- 

 portant feature in light-draft or low-freeboard vessels. The speed at 

 which models may be run being relatively great, the performance of 

 ships at higher speeds than have been realized may be predicted, and 

 the possibilities of further advancement, so far as the form is con- 

 cerned, determined. Much power is frequently wasted in driving un- 

 suitable forms at abigh rate of speed, and waste of power involves 

 both heavier machinery and boilers, Bnd increased coal consumption, 

 over what would be necessary with the proper form. Displacement 

 is often sacrificed to attain a certain speed, when the same speed 

 might have been realized with largely increased carrying capacity. 

 Many other minor advantages might be specified. Toe time neces- 

 sary to prepare a model from a given set of lines and make a com- 

 plete record of regi»tSP!?9 at varying Bpeede has bpeo found to he 

 about two days* * 



Lord Dunraven and Mr. Rose. 



Thk following was cabled to New York late on Monday. 



London, Oct. 21 —Dixon Kemp, the well-known yachting authority 

 and editor of the Yacht Racing Calendar and Review, has furnished 

 to the United Press exclusively the substance of a second interview 

 with Lord Dunraven. The latter expressed himself as being still 

 strong in the belief that the Valkyrie HI. i3 the superior of the De- 

 fender in sailing to the windward in moderate breezes and very much 

 faster than the American boat, in running dead before the wind. He 

 admitted, however, that the Defender was the faster boat in reach- 

 ing. 



"What I should particularly like," said Dunraven, "would be to 

 have the Defender fight it out with the Valkyrie in the Mediterra- 

 nean." If this could be arranged, he added, he would then have the 

 Valkyrie prepared to meet the American boat. He thought that the 

 two yachts would have a fair trial in the Mediterranean regattas, but 

 the Valkyrie would doubtless be greatly handicapped by the French 

 rigging rules, which include measurement of beam and girth besideB 

 sail area. 



Ifithe Defender should proceed to the Mediteranean it would settle 

 once and for all the question whether the American boat is built and 

 rigged sufficiently strong to cross the Atlantic on her own bottom. 

 Lord Dunraven told Kemp that he believed a decision to bring the 

 Defender over to the Mediterranean lies entirely with W. K. Vander- 

 bilt, who owns eight-tenths of the boat, while Messrs. Iselin and 

 Morgan each own one-tenth. 



The prizes in the coming Mediterranean regatta are much more 

 valuable than ever before, and the Earl is convinced that grand races 

 could be sailed with the Britannia, Ailsa, Satanita, Valkyrie III., and 

 Defender, 



A representative of the United Press having shown to Mr. Charles 

 D. Rose, the challenger for the America's Cup through the Royal 

 Victoria lacht Club, a copy of an interview published in yesterday's 

 New York papers, that gentleman said this morning: 



"I am very sorry that such things should continue to be published. 

 They do no good and only tend to stir up bad feeling." 



Mr. Rose then dictated to the reporter the following: 



"I very much regret that the question of my challenge should be 

 construed as in any way having anything to do with the action of the 

 New York Y. C. My challenge was made simply and solely with the 

 object of trying to recover the America's Cup. I shall take the earli- 

 est opportunity to see Lord Dunraven, and should I learn that my 

 challenge should not have been made before consulting him I shall at 

 once withdraw it. No one is concerned in this challenge except myself." 



Society of Naval Architects and Marine Engineers. 



Thk third annual meeting of the Society of Naval Architects and 

 Marine Engineers will be held on Nov. 7-8, at the rooms of the society, 

 13 W. 31st St., New York. Judging from the preceding meetings, the 

 coming one will be very interesting: the gathering is a representative 

 one of the leading men in the shipbuilding and allied industries; a 

 number of important papers will be read, and the discussions are 

 thorough and sometimes exciting. The second volume of the "Trans- 

 actions," issued last April, is a large quarto of 350 pages and seventy 

 folding plates, containing the fifteen papers read at the meeting last 

 year, with the stenographic reports of the discussion on each. These 

 papers cover a wide range of subjects; the construction of the new 

 navy naturally comes first, the subj-ct of several important papers 

 by Rear-Admiral Meade, vice-president of the society; George W. 

 Melville, Engineer-in- Chief, U. S. Navy; Philip Hichborn, Chief Con- 

 structor, U. S. Navy, and others, with papers on cellulose, electricity 

 on shipboard, face-hardened armor, launching, water-tube boilers, etc. 

 The paper on yachting, by Mr. Lewis Nixon, brought out a very- 

 animated discussion. The work of the society, and especially the 

 meetings, is well worthy of the attention of yachtsmen; who are 

 eligible as associates, this class of members being defined in the con- 

 stitution as consisting of "all persons who. by profession, occupation 

 or scientific attainments, are qualified to discuss the qualities of a 

 ship." The membership roll, which is already quite large, though the 

 society is but two years old, includes such representative yachtsmen 

 as Mr. A. Cass Canfleld, E D. Morgan, Henry Bryant and W. Butler 

 Duncan, Jr. The entrance fees of the society are $5, and the annual 

 dues also $5, Applications for membership are made on blanks pro» 

 vided by the gec'y.Treas., W. L, CappB, U, 8. N., 1710 F. at., Wash, 



