58 
CONCRETE SILOS 
Yi of 14 feet less 1 inch, or 6 feet 11 inches. To lay out the ribs for the inner 
form, lay 2x12 inch planks down upon the barn floor or other flat surface 
and mark the arc of the circle on each one with a sweep. The arc must be 
made tangent to the outer edge of the board. This arc gives the outer 
curved edge of the rib. Measure off the distance "C" (from table of ma- 
J'o//7t In Out^/de form 
f/ei^at/on 
Plan of home-made wall forms, and details of outside form. 
terials) along the curved edge of the rib, then mark off the ends of the rib 
in a radial direction using the sweep for a guide as it revolves around the 
center. 
After the ribs are cut out along the lines indicated all that remains to 
be done is to drill the holes for the bolts by which the ribs are to be joined 
