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Aviation History
1921
1921 - 0389.PDF
JUNE 9, 1921 which are of fabric and goldbeaters skin. In cross section the hull is not absolutely circular, but slightly elongated near the bottom. From the third to the eighth gas compartments the sides are parallel. The corridor, or keel, in " R. 38 " is much wider than in previous ships, providing greatly improved accommodation for crew, petrol tanks, water ballast and bombs. The corridor provides communication from end to end of the hull, to the various cars and control stations and to the entrance at the extreme bow from the mooring mast. On the top of the hull, near the bow, is a gun platform, which will carry a i-pdr. automatic. This platform is shown in one of the accompanying illustrations. There is also a gun trap- door on the bottom of the hull at the rear of the aft wing cars. Altogether there are seven cars, the arrangement of which is as follows ;—Right forward, at the third gas compart- ment, is the main control cabin and W.T. room. This car, which has no power plant, is not suspended from the hull, but is rigidly attached thereto, and is comparatively small. At a point between the fourth and fifth compartments are two wing cars, port and starboard, suspended from the hull (by cables) fairly close together, practically level with the keel. Amidships (compartments 6 and 7) are two more wing cars, and these are suspended much higher up and farther apart. Aft of these, at compartments 8-9, are another pair of wing cars, which, as far as we could see, are located simi- larly to the forward wing cars. Each of these wing cars is of clean streamline shape, with aluminium covering, and con- tains a 350 h.p. Sunbeam " Cossack " engine, driving a large two-bladed propeller. The forward and aft wing cars are of similar design, and the mid-wing cars appear to be slightly OOOOOOOO O O o The"ZR.2 " (R38): O The platform on the Q top of the hull, near the bows, for a 1-pounder auto- ° matic gun. O 11 Flight" Copyright O o o o 000000 00 smaller. All have enclosed nose radiators, the front of the car having adjustable shutters. Communication from the wing cars to the hull is by means of a ladder, which folds up to a streamline strut when not in use, and a trapdoor in the side of the hull. We noticed a slight difference in the arrangement of the tail, in that the balanced portions of the rudders and elevators are formed by projecting surfaces at the extremities. In previous types, it will be remembered, the balanced portion extended from end to end. It is intended that after trials have been carried out—and it is expected that these may take place any moment now— and the airship has been handed over to the American Govern- ment, the American crew which is now completing airship- training in this country will, after a few further flights to accustom themselves to the behaviour of the airship, fly across the Atlantic to a base in America, where a shed has been built to accommodate the ship and where, it is under- stood, a mooring mast is also to be erected. In view of the interest which is being taken at the moment in the use of airships for commercial purposes, it is worthy of note that an airship of the " R. 38 " class, adapted for trans- port, could carry 40 passengers and 2 tons of freight in a non-stop flight to Egypt in about 48 hours. As a result of the experience gained in the design and construction of " R. 38," a new design has been produced for an improved type of airship with a gas capacity of about 4,000,000 cu. ft., which would be capable of carrying 50 passengers and 13^ tons of freight on a non-stop flight to Egypt in about 40 hours. A NEW AMERICAN AIRCRAFT MATERIAL—" PLYMETL" ACCORDING to Aviation, the Haskelite Manufacturing Corpora- tion of Chicago have Invented and patented a new material which may prove of considerable importance in the con- struction of aircraft. The new material, which is known as Plymetl, is made by cementing thin sheet-metal faces to a relatively thick core of light material such as, for instance, wood. Owing to the metal faces the material should be practically impervious to moisture, provided of course that the edges are properly covered, while the layer or layers of wood inside should help greatly towards reducing local dents in the very thin sheet-metal, thus making it possible to approach much nearer to realising the full strength of the sheet-metal faces. At present the material is supplied in panels 30 ins. by 96 ins. by -fa in. thick, but there does not appear to be any reason why other sizes and thicknesses should not be available: It is stated that the material can be cut with either circular saws or band saws. For fuselage construction, for instance, one would imagine that Plymetl might be very suitable in thinner sheets, while in the form of very thin panels it might prove very useful as wing covering, when probably it could be made to take part of the wing loads and thus enable lighter spars to be used. According to tests carried out, the results of which we print below, the material is very strong, even when a cork core is used, and one can imagine developments of it which would add greatly to the strength. For instance, instead of plain sheet metal, corrugated sheets with a light core of cork or Balsa wood might be used, when the risk of local buckling should be greatly reduced. In this form it is even conceivable that it might be possible to build a relatively thin wing shell which would be strong enough without any, or with very little, internal structure. If this should prove to be the case the problems of cantilever wings would be much simplified. Below we publish the results of tests on the material under- taken by the Haskelite company :— Thickness over all: t\ in. Faces : Black sheet steel, 30 gauge. Core : Fir wood veneer, planed. Weight : 1.8 fbs./sq. ft., or practically the same as sheet steel of No. 19 gauge. Stiffness: Five times as stiff as T\ in. solid wood panel, or eighty times as stiff as sheet steel of the same weight. No. 19 gauge. Elastic limit in bending : 75 in.-lb. per inch width, or about five times the elastic limit of sheet steel, No. 19 gauge. Impact test : A panel 12 ins. by 12 ins. was placed on a steel frame having a clear opening of 10.5 ins. by 10.5 ins. A steel hammer weighing 12.5 lbs. was dropped 20 ins. on to the middle of the panel, producing a permanent deflection of about 0.09 in., but not injuring it otherwise. Same test on a panel of sheet steel of No. 20 gauge produced permanent deflection of about | in., buckling the sheet badly out of shape. Shearing strength of joints : Bending a short end causes the wood core to fail in shear in the wood, showing that the shearing strength of the cement that binds the metal to the core is even greater than the shearing strength of the wood. Fatigue test: Strip 24 ins. long was supported at ends, and the middle was oscillated $ in. in opposite directions, fibre stress in steel about 24,000 lbs./i sq. in. At 4,200,000 oscillations the steel faces were broken about 2 ins. from the middle. Similar test on j^ in. strip with cork core showed. similar result at about 5,400,000 oscillations. 389
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