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Aviation History
1920
1920 - 0209.PDF
FEBRUARY 19, 1920 filGHT]9 1* fjgfj^)! ratio the more efficient the design. As previously explained, the fixed weight is made up of hull, fabric and miscellaneous weights and machinery and car weights. The last set depends upon the speed, and to a first approximation for present designs of engines, may be taken as W in lbs. = -0038 x (max. speed in m.p.h.)8 x (total lift on tons)"5. The ratio of the hull, fabric and miscellaneous weights to the total lift measures the efficiency of the design from the ship designer's point of view. No law can rationally be given as to the variations of the remaining fixed weights to total lift, as the design of the various parts is so far not advanced sufficiently to enable any deduction as to the variation of weight with dimensions to be made. As illustrative of this, it is interesting to note that with practically the same total lift, the weight of hull, fabric and miscellaneous items was reduced from 28-9 tons in L 33 to 19 tons in L 65. Subsequent Developments This paper has dealt almost entirely with the principles of airship construction with special reference to the Zeppelin types. Of all types which have been examined this appears to be the most practical and promising form, the develop- ment of which has been marked by the greatest progress. It also lends itself most readily to adaptation to larger sizes principally on account of the relatively economical disposition of material from an engineering standpoint. As mentioned previously in the paper, the actual design of girders, however, will most probably be materially and radically modified, chiefly by the introduction of steel in •construction, and possibly some saving in weight by the use of welding instead of riveting. With present sizes of ships the thickness of steel sections, however, would be so small as to be impracticable. Another item which will profoundly influence the type of construction is cost. Steel construction will be much cheaper than duralumin, both in material and labour. Developments in gasbags may be expected in the direction of finding a substitute for the expensive goldbeater's skin. Various substitutes have been tried, but so far have not proved successful, lor although a compound may look pro- mising on a test piece, yet when worked into a bag and crumpled, it usually has a high permeability. The relative merits of gastightness or lightness have not yet been satis- factorily settled ; if gas is expensive, as for instance helium, then gastightness is of prime importance. Helium, however, has a permeability of only about o • 65 that of hydrogen, so that the loss of helium through the bag will probably be less than the present rate of hydrogen. The Germans, however, appeared to have attached more importance to light weight, relying on the frequent purging of the gas through refilling after flight to maintain the requisite purity. It is probable that the outer cover will remain doped fabric. Aluminium plate, even in the thinnest sections, would be too heavy, and would require to be very carefully supported. Conclusion I am indebted to Sir Eustace d'Eyncourt, K.C.B., the Director of Naval Construction, for permission to read this paper, and to the Air Ministry for permission to publish the information contained therein. MORE N.P.L. REPORTS AVAILABLEHLIST No. 3)* REPORTS AND MEMORANDA :— Tests on Two Models of Caquot Kite Balloons. (247, November, 1916. 3d.) Experiments on Models of Aeroplane Wings. (248, May, 1916. is.) Tests on the Complete Model of F.E. 5 Aeroplane. (249, June, rgi6. is. 3d.) Tests on Aeroplane Bodies. (251, August, 1916. 4d.) Model Test on Fairing and Chassis Axle. (255, May, 1916. 3*-) Instruments. (295, May, 1916. is. 6d.) Preliminary Reports on Measurements of Accelerations on Aeroplanes in Flight. (New Series.) (376, September, 1917. 2d.) On a Method ot Estimating from Observations on the Slipstream of an Airscrew, the Performance of the Elements of the Blades, and the Total Thrust of the Screw. (460, June, 1918. 4d.) Notes on the Prediction and Analysis of Aeroplane Per- formance. (474, May, 1918. is.) Full Scale Stability Experiments with R.A.F. 14 Wing Section. (505, June, 1917. 3d.) Influence of Time on the Breaking Load and Elasticity •of Spruce Members of Aeroplanes. (510, February, 1918. 9d.)Preliminary Report on the Permeability Variation of the Hydrogen of Rubber Membranes with Alteration in Tempera- ture. (513, August, 1917. 2d.) Report on Protective Varnishes for use on Aeroplanes in Hot Climates. Part 2. Experiments in Sunlight. (514, August, 1917- 4^-) On the Dissipation of Heat from the Surface of an Air-cooled Engine when Running and when at Rest. (520, October, 1917. 6d.) Flying as Affected by the Wind. (521, November, 1917. 6d.) Experiments on Models of a " Duplex " Wind Channel. I522, November, 1917. is. 6d.) On the Steady Flight of an Aeroplane, when the Gradual Loss of Weight owing to the Consumption of Petrol is taken into Account; with special reference to the Minimum Con- sumption of Petrol. (527, January, 1918. 6d.) A Preliminary Investigation of Certain Elastic Properties •of Wood. (528, February, 1919. is.) Full Scale Experiments with different shapes of Tail Plane. • 532, March, 1918. 3d.) High Altitude Flying. (534, March, 1918. id.) * Previous lists were [published in "FLIGHT" for July 3, 1919, andOctober 23, 1919. Effect of Compressibility on Streamline Motions. (555, December, 1918. 6d.) Description of an Apparatus for Measurement in a Wind Tunnel of the Performance of an Airscrew or the Windage Torque of a Rotary Engine. (563, July, 1918. 3d.) Critical Loading of Struts and Structures, Part 6. Effect on Variation and Strength of a Strut or Spar due to Variation along the Bay of Longitudinal Thrust, Flexural Rigidity, and Mass per Unit Length. (566, November, 1918. 2d.) Tests Swivelling Pressure Heads. (567, October, 1918. 4d.)Report on Tests of a Model of the Proposed No. 2 7-ft. Wind Channel at the R.A.E. (574, December, 1918. is.) Some Experiments with Models of an Airscrew, a Rotary B.R. 2 Engine, Two different Types of Engine Cowling, and a Body of the Snipe Aeroplane. (591, February, 1919. 6d.) Accidents to certain Aeroplanes with special reference to " Spinning." (Communicated by the Accidents Investiga- tion Committee.) (592, December, 1918. 6d.) Summary of Present State of Knowledge with Regard to Airscrews. (594, February, 1919. 6d.) Rotation of an Aerofoil about a Fixed Axis. (595, March, 1918. 4d.) Experiments on a Twisted Aerofoil. (601, April, 1919. 4d.)Gliding Tests of a Modified S.E. 5 Aeroplane. (603, April, 1919. 6d.) Some Further Experiments on Tandem Airscrews. (605, November, 1918. gd.) Reduction of Aeroplane Trials for the Purposes of Aero- dynamic Comparison and Prediction. (608, September, 1918. 9d.)The Decay of Eddies. (609, April, 1919. 4d.) Errors of the Readings of Altimeters and Airspeed Indica- tors due to Variations of Temperature of the Air. (610, May, 1919. id.) The Effect of Accelerations on the Resistance of a Body. (612, May, 1918. 6d.) Measurement of the Effect of Accelerations on the Longi- tudinal and Lateral Motion of an Airship Model. (613, June, 1918. 3d.) The Inertia-Coefficients of an Ellipsoid moving in Fluid. (623, October, 1918. 2d.) Vibration Speeds of Airscrew Blades. (626, May, 1916. 3d.) INTERNAL COMBUSTION ENGINE SUB-COMMITTEE REPORTS :— Effect on the Resistance to Fatigue of Crankshafts of a Variation on the Radius of Curvature of Fillets. (15, October, 1919. 3d.) 209
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