content_image/584712.jpg content_image/584713.jpg
ing moment to be expected from such bumpy weather as would be en› countered in mountainous country: 

<img src='content_image/584712.jpg'>

where Mb = the maximum bending moment in foot-pounds. 

L = the length of the airship in feet. 

Use of this formula enables the pilot to calculate rapidly maximum stresses to which his velocity in bumpy air may be subjecting his airship. 

b. Where surfaces are designed in approximate accordance with the formula A = 0.13 ( vol) $^{2}$1 3 , the total transverse force on either vertical or horizontal surfaces may be computed quickly by the relation: 

In above formulas 

A=total area of either surface. 

F = total force on either surface. 

<img src='content_image/584713.jpg'>

43. Method of calculating shear and bending moment on hull.-a. The designer and also the pilot in determining shear and bending moments on the airship must consider both static and dy› namic loads. Both must be computed independently and then added together algebraically. I t often happens that dynamic loads serve to reduce stresses due to static loading, but naturally the dangerous case occurs when stresses are arithmetically additive. 

b. The method to be described applies more particularly to rigid airships, but the principle can be applied to a nonrigid. In the latter case, the load instead of being distributed throughout the length of the hull is swung from the envelope by suspension cables which by their tensions control very largely distribution of loading on the envelope. 

c. For calculation of stresses, the hull is considered as a beam loaded with the weights acting downward, lift of gas cells acting upward and aerodynamic forces acting in any longitudinal plane whatsoever. All loads . are considered as concentrated at the frames rather than as uniformly distributed. The calculations may be divided into steps, as follows: 

( 1) Calculation of static load. 

(2) Calculation of shear due to static loading. 

(3) Calculation of bending moment due to static loading. 

( 4) Calculation of load, shear, and bending moments due to aero› dynamic forces. 

( 5) Algebraic summation of effects of static and dynamic loading. 

