Arches (kerfing):

1. Kerfing is the process of making evenly spaced cuts in a piece of wood to make it bendable. Kerfing is used on arch windows or eyebrow arch windows. (An arch is shown in this example.)
2. Kerfing is done by making cuts in the wood with a saw blade. The more severe the radius, the closer the cuts in the wood. The saw blade cuts are within 3/16" of cutting through the board. (see dia. 1 & 2 - dia. 2 has been enlarged to show kerfing)
    
   
    
   
3. The spacing between kerfs on eyebrow arches are even further apart than a regular arch.
   1. 40" arch window & under, space kerfing cuts approx. 1½" apart
   2. 40" - 60" arch windows, space kerfing cuts approx. 2" - 2½" apart
   3. Eyebrow arch windows, space kerfing cuts approx. 3½" - 4½" apart
4. A skill saw, table saw or radial arm saw can be used to kerf wood.
5. Formula to figure the length of wood needed: Ex: 40" (FW of treatment) The size of the board is half the diameter which is 20" x pi (3.1416) = 62.83" or 62f" (length of board).
6. Use 1 x 4, 1 x 6, or 1 x 8 board for an outside mount.
7. Completely wet the board before bending. Let the water absorb into the wood for an hour or two or until the board bends easily into the arch shape. The wood will crack or break if it is not soaked.
8. Use 1½" nails, 1 3/8" staples or screws to secure shaped plywood to kerfed board. (A brad nailer or staple gun can be used.) (see dia. 3 & 4) (See Quick Tips - Tools for the workroom)
    
   
    
9. Cover plywood face with blackout lining. Cover kerfed board with straight strips of blackout lining. (wood grain can show through regular lining) Use gimp to cover all inside edges. Cover top of kerfed board with face fabric. Add a layer of interlining under the face fabric cover to soften the edges of the mounted treatment. Welting can be added to top edge of the arch. Edges of face fabric should be turned under & pressed, then glued to top of arch.