30

MECHANICS OF MATERAILS PROBLEMS CURTISS-WRIGHT ENGINEERING
Course B-4 Seely: Arts. 33-41; 116-131; CADETTES 21D0-A-129
58

21D0-l. Fig. 21DO-l shows a 4-motored low-wing monoplane in flight. Each wing
has four aluminum alloy spars with the cross-section at the root as
shown in Fig. 21D0-2. Assume the loads to be evenly distributed among
the 4 spars.

For the loading shown,
(a) Draw complete shear and noment[moment] diagrams.
(b) Determine the maximum fiber unit stress and state where it occurs.
Assume constant cross-section for a spars, and neglect the effect
of the rivet holes.
(c) Determine the shearing unit stress at a point 2 in. from the top
on a section where the total shear is maximum.
(d) Determine the deflection the wing tip would have if the spars
were of constant cross-section, and there were no rotation at the
root (that is, assume the spars fixed at the fuselage) for,
(a) The motor loads alone.
(b) The distributed load alone.

[image]
Fuselage Reaction Points
FIG. 21D0-1

[image]
FIG. 21D0-2