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The External Forces on an Airship Structure*

Published online by Cambridge University Press:  28 July 2016

Harold Roxbee Cox
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Extract

A system of external forces on the structure of a rigid airship can be analysed into two or more of the component systems due to

  1. 1. W. The Weights of the members of the structure and the weights of the masses carried by it;

  2. 2. L. The Lift and pressure of the gas;

  3. 3. A. The Aerodynamic forces consequent on the relative motion of the airship and the air;

  4. 4. T. The Thrusts of the airscrews;

  5. 5. R. The Reactions due to either the mooring arrangements, the hauling-in guys, the supports used in the shed, or handling on the ground.

As these component systems, though restricted by their interdependence, are individually variable, a very large number of complete systems is represented by the possible combinations and variations that can occur. It becomes necessary, therefore, for the purposes of design, to attempt to limit the number of combinations to be considered, and to restrict the variations of the components, but in such a way that the structure designed to carry the resulting systems with adequate factors of safety, shall be able to carry any other possible system with an appropriate factor of safety.

Type
Research Article
Information
The Aeronautical Journal , Volume 33 , Issue 225 , September 1929 , pp. 725 - 811
Copyright
Copyright © Royal Aeronautical Society 1929

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Footnotes

*

Submitted March, 1928.

References

1 It has occurred once in the history of British airships.

2 Negative.

3 U.S.A. National Advisory Committee for Aeronautics, Report No. 204.

4 R. & M. 970, p. 10.

5 Journal of the Royal Aeronautical Society, Vol. XXX., p. 577.

6 Journal of the Royal Aeronautical Society, Vol. XXX., p. 465.

7 R. & M. 970, p. 9.

8 It is probably, in any case, covered by Cases 89-104. §13.

9 R. & M. 978

10 §15.

11 loc. cit. §1.233.

12 For definitions of primary and secondary stresses see R. & M. 970, p. 6.

13 The use of this figure allows the ship sufficient lift when the purity of the gas has deteriorated.

14 See “Some Modern Developments in Rigid Airship Construction,” by Lieut.-Colonel V. C. Richmond, Proc. Inst. Naval Architects, March 30th, 1928.

15 §1.22.

16 “A Detailed Consideration of the Effects of Meteorological Conditions on Airships,” by Major Scott and Lieut.-Colonel Richmond, Journal of the Royal Aeronautical Society. Vol. XXVIII., p. 189.

17 loc. cit. Table 13.

18 cf. §§7.2, 7.5,

19 In R. & M. 600, R. & M. 780, and in “The Distribution of Normal Pressures on a Prolate Spheroid,” Trans. Royal Society of London, Series A, Vol. 226, pp. 231-268.

20 Trans. Roy. Soc, loc. cit., p. 239.

21 “A Review of the Present Position with Regard to Airship Research and Experiment,” Journal of the Royal Aeronautical Society, Vol. XXX., p. 552.

22 If the skin friction force f on an element is supposed tangential to the surface there, the normal component will be f(ðy/ðs) and the longitudinal component will be f(ðx/ðs)

24 There are of course, four different constant values for (W—L) implied—one for each of theconditions (Wa, La) . . . (Wd, Ld), §§1.21, 1.22.

25 Jones, loc. cit. Journal of the Royal Aeronautical Society, Vol. XXVIII., p. 107.

26 R. & M. 970, p. 9.

27 “The Aerodynamical Characteristics of the Airship as deduced from Experiments on Models,” by R. Jones, Journal of the Royal Aeronautical Society, Vol. XXVIII., p. 112.

28 λ is best found from the tables for mya for hull only and for hull and fins with rudders amidships, taking the average value for the first 8° of yaw.

29 The local aerodynamic lateral forces due to the cars are not specially represented.

30 loc. cit. §7.2, Trans. Royal Soc, p. 235.

31 Alternatively, of course, the pitch rotation may be performed first and the yaw rotation second.

32 The worst value of (dw/dt) + (rdΩ/dt) is about ½g.

34 §10.4.

35 loc. cit.

36 R. & M. 607 and T.2034.

37 loc. cit. §6.1.

38 Plotted as shape 10 for d = 4, l = 10.

39 The natural fineness1 ratio is 2.5. Shape 11 is the natural curve modified by a constant multiplier.

40 See Table 3.

41 See Table 3.