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New Hull Form is Developed for Increased Economy known the world over wherever ships are built as the originator of the longitudinal and the bracket- less systems of hull construction. These systems have been successfully used in the building of many ships. The announcement recently made that he has developed still another hull design, is therefore, of special interest to all shipowners and ship- builders. The new design is known as “‘areform,’’ and is intended to pro- duce efficiency without increased first costs, by giving reduced fuel con- sumption or increased speed, in- creased cubic capacity, improved bal- last conditions, increased strength and increased deadweight carrying capacity. It is well recognized that in re- cent years a marked improvement has been made in propulsive machinery for merchant ships. This has re- sulted in a substantial gain in economy. Improvements have also been made in certain hull features such as streamlined rudders and fixed fins on rudder posts of stern frames. Hull forms have been modi- ved at the fore and after ends. Pat- ented forms have been applied to the fore end and the general tendency for the after end has been to use fine lines to facilitate the run of water to the propeller. These modifications have given generally satisfactory re- sults. S IR JOSEPH W. ISHERWOOD is Improvement in Hull Design The new forms, however, are primar- ily of advantage in large high speed vessels. In smaller and slower speed vessels, it is more difficult to estab- lish the advantage of these modifica- tions over the lines along established general practice. In cargo carrying vessels, it has been shown that it is an advantage to locate the center of buoyancy somewhat further forward of amidships than used to be the custom. This was learned from the necessity of locating the center of buoyancy well forward in. tankers. Improvement in hull design, general- ly speaking, has not kept up with the very definite improvement in pro- pulsive machinery which has resulted in large economie; in the reduction of fuel consumption, Beginning with the introduction of the longitudinal method of. con- struction, many improvements and economies have also been made in *The facts on which this article is based were supplied by J. W. Stewart, director, Sir Joseph W. Isherwood & Co. Ltd., New York. 20 the construction and arrangements of hulls. Within the. lifetime of the inventor, nearly 2000 vessels with an aggregate deadweight carrying ca- pacity of over 15,000,000 tons have been built using this system. The new form of hull now devel- oped, is to be applied to six vessels which are about to be ordered. In a recent interview Sir Joseph Isher- wood expressed the opinion that the truly economical vessel must not sac- rifice strength for lightness in con- struction by cutting down scantlings to the danger point. He has consist- ently practiced and advocated both the strength and efficiency of vessels, and in the designs he has sponsored he has kept rigorously to these prin- ciples. He has long been of the opinion that the effective power to drive a ship through the water was too high and that the necessary increase of power to gain an increased speed, of let us say a knot, was entirely dis- proportionate. He recognizes, of course, that an increase in power pro- portionate to the increase in speed is unavoidable, but he has maintained that the efficiency for certain ranges of speed should not fluctuate so drastically as at the present time. He is also of the opinion that some means should be found for overcom- ing the tremendous loss of efficiency and consequent disproportionate in- crease in power necessary today for comparative vessels with the same length, but of different displace- ments. In other words the fuller model ship should not need to be penalized to such an extent as it now is; Middle Body Hitherto Neglected He believes that while the fore and after lines are of great import- ance and also that the ‘‘cod head and salmon tail’ theory still holds good, that sufficient consideration has not been given to the greater middle body portion of the ship and its ul- timate effect on the streamlines or rather the flow lines of water past this great comparative bulk of the ship. The most economical stream- lines, he feels, are not obtainable through modification of the fore and aft lines only. For some time, in collaboration with a highly trained technical and theoretical staff. he has given this matter close study with the view of establishing the basie principles of true economy and as perfect stream- lining as the many exacting practical conditions of ship design will permit. Following the results of these MARINE REVIEW—March, 1933 studies he has made a bold change in the usual midship section contour. The new middle body portion so de- veloped was fitted with the forward and after ends of an actual vessel of about 8500 tons deadweight and which was known to be giving satis- factory results in service. By experi- ments at the National Physical lab- oratory at Teddington, the correct- ness of his theory was demonstrated; the new form giving an additional 180 tons displacement secured by an increase of three inches in draft. While, of course, proportionately greater power is required for a rea- sonable range of speed, the efficiency was maintained over a spread of 3 knots. This was due to the fact that the resultant admiralty constant was not reduced by more than 2 per cent between the range of speeds of 9 and 12 knots. These experiments es‘ab- lished the principle of the change of the middle body portion wherein lies the bulk of the displacement of the vessel. Model Tests Show Advantage The model tested was for a vessel 395 feet in length. Another model was then built, adding some 220 tons - displacement, without altering the predetermined midship section con- tour. The tests with this model showed substantially that no more power was needed to drive the vessel over the range of 9 to 12 knots. The resultant admiralty constant did not vary by more than 5 per cent within this range of speed. It was 409 at 9 knots and 389 at 12 knots, both being based on indicated horsepower. Further proof was thus obtained that wi hin the considerable range of speed from 9 to 12 knots, efficiency was not sacrificed. A third model was made with a further additional displacement of 250 tons. The resultant admiralty constant continued exceptionally high, and it suffered a reduction of less than 4 per cent between 12 knots and 9 knots. These tests were begun on the basis of a 10-knot model of ordinary form with a comparable block coeffi- cient of something under .77. For the final tests of the new form of vessel, the displacement was increased by 475 tons. The comparable block co- efficient of the vessel of normal form was increased to so much as .80, and the corresponding admiralty constant based on indicated horsepower were 391 at 9 knots and 378 at 12 knots. These facts and figures are based on the results of the Teddington tank tests, and there appears to be no rea- son to question their complete accur- acy. Still better results, it is believed, may be attained by the use of specially designed propellers, rud- ders and similar well recognized economy features. Though a firm believer in the ac- (Continued on Page 21)