The area of the cross section of a diagonal stay is found as follows : —
I'ind the area of a direct stay to support the same area of plate, and
niultiply it by the length of the diagonal stay, and divide by the length



312 MACHINE DRAWING AND DESIGN.
of its projection on a plane at right angles to the surface supported. Or,
using symbols, let —

S = area of cross section of diagonal stay.
8 = area of cross section of direct stay to support the same area of

surface.
L = length of diagonal stay.
• I = length of projection of diagonal stay on a plane perpendicular to
the surface to be supported.
Then S = ?^.
GtLsset Stays. — A gusset stay is a diagonal stay in which a flat plate is
used instead of a bar or rod.
Perhaps the most important application of the gusset stay is to be
found in Cornish and Lancashire boilers for staying the flat ends to the
cylindrical shell.
