A A View - A A Repair for crack on lightening hole flange Stop drill ends of crack use #40 drill Patch is same material and thickness as web Repair for crack between lightening holes Figure 4-181.  Repair of lightening holes.  Former or Bulkhead Repair 4-103 4.  Install rivets. 3.  Attach the doubler to the part with clamps and  drill holes. 2.  Fabricate a doubler of the same material but one size  thicker than the part being repaired. The doubler  should be of a size large enough to accommodate  1 ⁄ 8- inch rivet holes spaced one inch apart, with a minimum  edge distance of 0.30-inch and 0.50-inch spacing  between staggered rows.  [Figure 4-189] 1.  Stop drill the crack ends with a No. 40 size drill. given in the maintenance manual or SRM for the aircraft.  Bulkheads are identified with station numbers that are very  helpful in locating repair information.  Figure 4-188  is an  example of a typical repair for a former, frame section, or  bulkhead repair. Bulkheads are the oval-shaped members of the fuselage  that give form to and maintain the shape of the structure.  Bulkheads or formers are often called forming rings,  body frames, circumferential rings, belt frames, and other  similar names. They are designed to carry concentrated  stressed loads. There are various types of bulkheads. The most common type  is a curved channel formed from sheet stock with stiffeners  added. Others have a web made from sheet stock with  extruded angles riveted in place as stiffeners and flanges.  Most of these members are made from aluminum alloy.  Corrosion-resistant steel formers are used in areas that are  exposed to high temperatures. Bulkhead damages are classified in the same manner as  other damages. Specifications for each type of damage are  established by the manufacturer and specific information is 