Agriculture Reference
In-Depth Information
Langley has an error of scale in his
Fig 1.
by placing closers in each course of
voussoirs of the straight arch, which has a face height of four vertical courses.
He does not create the closer by a dummy joint in the stretcher but places it
next to the stretcher, the resultant space left for the header would in reality
only allow a closer. This is incorrect unless the stretcher in reality has been
reduced to three-quarters in length. One can only correctly aesthetically bond
with a closer in each course when the arch has a face height of five vertical
courses - normally 13¾ ins (350 mm), or 15 ins (380 mm) as in his
Fig II.
Observers are frequently mystified as to the reasons for the small sections
of cut bricks above the horizontal cross-joints of stretcher voussoirs, on either
side of the springing of an arch; as can be seen in Fig. 103. The explanation
is simple. Springing bricks in a flat, camber, or indeed a Queen Anne arch are
always the longest in terms of their overall voussoir length, as opposed to the
'key brick', which is the shortest. When setting out arches to establish individual
templet lengths, given that the majority of rubbers during this period were the
same size as standard bricks, it was impossible to cut the longest voussoirs from
full-size stretchers. To use a craft term, the bricks would not 'hold-out' to the
overall required length.
Figure 103
A gauged camber arch
with a face height of
five vertical courses
showing closers in
alternate courses of the
arch voussoirs. Note the
use of dummy joints
to create closers. Also
the first five springing
bricks are lengthened
to bond with cut bricks,
the joints of which
would have originally
been 'blinded-out' to
hide them.
The problem and one common solution can be explained as follows. The
prepared stretcher would be placed upon the full-size drawing to extend suf-
ficiently below the intradosial line in order to allow the brick to be scribed to
its bevel, or soffit. The brick was then cut with the hand-saw leaving it correctly
angled to its radial position; a process known as 'soffiting'.
