The Birmingham age-herald., 1920-02-15
REDUCING SHIPS
 WATER FRICTION
 BY 5 PER CENT
English Experiments in Wa ter Tank Important Con- tributiOn to Ship
 Construction
By GEORGE G. BYE.


 News Service e.)-British shipowners at first scoffed at the idea of scientific experimenters working with ship mod els in an imitation ocean to develop the pest designs for speed and stability. That was in 1911, when the great frcude tank was built at the National Fhyslcal laboratory, Teddington, to fos- ter these experiments. "Our shippers can tell us what to do with our lfulIs." declared the shipowners. "We want no advice from landlubber scientists"
 But few ship builders with faith in science, listened to the laboratory's eXpostulation that there was at that tlme 50 per cent surface friction on the null of the average ship, and that at least 35 per cent might be removed by attenuation in design, which would not diminish cargo capacity "We can prove to you that for each 1 per cent or surface friction removed, your ship Will save you $12000 in coal each year" the laboratory promised This saving was in coal at pre-war value
 The tank staff is today busy with tests for shipbuilders from all over the United Kingdom. They have cut off So per cent of surface friction of late types of British merchantmen. Large Ieets are patterned after single models evolved in the tank. One owner who built ten 400-foot cargo ships from a tank model recently made the declara- tlon that he has saved nearly $7O0, 900 year In coal, that his ships make much quicker runs, and that he re gards them as much more seaworthy than any he had owned previously 8l
 The tank is $50 feet long, 30 feet wide and IF fet inches deep A trayeline. carnage, moving on rails and pro- pelled by four electric motors, straddKes the tank and propells the models up and down the waterway al speeds up to s5 miles an hour. Waves which in the past have been stirred up by manual means, will soon be generated by ma chlnery, so that the operator and ob- server on the bridge of the electric carl riage may have light swells or heavy rollers responsive to his switch control.
 Models Of either ferry boats or ocean liners vary in length up to IS feet. They are first cast roughly in wax. which is hewn smooth to exact desien by combination pantograph and whit tling machine, An operator traces the lines Of ship architects drawings. The machine does all the rest except the polishing and ballasting. So fine are the tests that when the model is fixed under the travelling Carriage and started on its trial run. it must first pass through a series of brushes which remove any air bubbles that might have chung to it's sides during it's stand in water.
 The, observer on his bridge is not de- pended upon for testimony An electric finger marks all of the resistance and motions of the model on a rolling chart. ihe model is subsequently, altered until IL presents the least resistance at the enRiDe fn ba
 Some very difficult problems come to the naval experts at the tank for soIu tion They had to design a fleet of ships of given length and beam which were to be used on trips outward from Great Britain for carrying machinery or other very heavy compact cargoes On return trips they were intended to carry ba- ranas and other fruit. The machinery would put them low in the water. but would not fill up the hold. The bananas. though filling the hold and every inch of deck space, would. because of their lightness, leave the ship high out of water and therefore top-neavy
 All these experiments when undertaken by commission from shpbulding or ship owning firms, cost fees ranging from $500 to s1ooo or more. Ship firms that are sub seribers to the tank maintenance fund are given special discounts The lab oratory carries on special research of it's own. so that it not only follows the latest ideas of commercial ship yards. but continues to lead in it's fight against surface friction.
 It's latest progress is in the invention of highly sensitive device for the de- lection and measurement or eddies caused by surface friction. A concavity of a ccnvexity in the hull of a ship make ed- dies at certain speeds. Eddies are in- dicative of unnecessary resistance, usu- ally, To reduce eddies to minimum at a given average speed is the principal 1 function of the tank department. ~.
 | Many discoveries have been made to show the effect of speed on design. The difference of mile, or even a fraction of mile an hour in the speed of a ship | immediately affects it's surface friction shipping firm that was losing money on fleet of cargo boats built before the war recently asked the tank department to advise alterations in the vessels so that they might be run more economically. They were 10-knot boats It was found by in- creasing the power slightly and makins | a slight alteration in the shape of the hulls, the boats would do nearly 15 knots an hour with lower consumption oi {, coal. Their original designer had beer 1 a practical shipbuilder who knew good lines, but was ignorant of the delicate relation of speed to surface friction. | Great speed means vast outlay of coal A transatlantic liner of the size of tn, 1 Aquitania consumes more than 5000 1 tons a voyage. Most of this expenditure of coal is for the last four or five extra miles per hour. The tank department has charted the relation of speed witl power consumption, and has found that speed can be increased in the averag, fast boat at proportionate increase 1T l the fuel consumption up to F or IS knot per hour From this point on the in l crease in coal consumption rises on tho | chart on a precipitate slant
 Although ships have been improving in design from remotely ancient times