Figure 7-48.  Vacuum bagging of contoured part. Figure 7-47.  Different layup techniques. Figure 7-49.  Examples of balance laminates. The traditional bleedout using a vacuum bag technique places  a perforated release film and a breather/bleeder ply on top of  the repair. The holes in the release film allow air to breath  and resin to bleed off over the entire repair area. The amount  of resin bled off depends on the size and number of holes  in the perforated release film, the thickness of the bleeder/ breather cloth, the resin viscosity and temperature, and the  vacuum pressure.  Controlled bleed allows a limited amount of resin to bleed  out in a bleeder ply. Place a piece of perforated release film  on top of the prepreg material, a bleeder ply on top of the  perforated release film, and a solid release film on top of the  bleeder. Use a breather and a vacuum bag to compact the  repair. The breather allows the air to escape. The bleeder can  only absorb a limited amount of resin, and the amount of resin  that is bled can be controlled by using multiple bleeder plies.  Too many bleeder plies can result in a resin-starved repair.  Always consult the maintenance manual or manufacturer tech  sheets for correct bagging and bleeding techniques. Prepreg systems with 32 to 35 percent resin content are  typically no-bleed systems. These prepregs contain exactly  the amount of resin needed in the cured laminate; therefore,  resin bleedoff is not desired. Bleedout of these prepregs results  in a resin-starved repair or part. Many high-strength prepregs  in use today are no-bleed systems. No bleeder is used, and the  resin is trapped/sealed so that none bleeds away. Consult the  maintenance manual to determine if bleeder plies are required  for the repair. A sheet of solid release film (no holes) is placed  on top of the prepreg and taped off at the edges with flash  tape. Small openings are created at the edges of the tape so  that air can escape. A breather and vacuum bag are installed  to compact the prepreg plies. The air can escape on the edge  of the repair but no resin can bleed out.  [Figure 7-48] Figure 7-50  presents examples of the effects caused  by nonsymmetrical laminates. These effects are most  pronounced in laminates that are cured at high temperature  in an autoclave or oven due to the thermal stresses developed  in the laminate as the laminate cools down from the cure  temperature to room temperature. Laminates cured at room  temperature using typical wet layup do not exhibit the same  degree of distortion due to the much smaller thermal stresses. In order to minimize any residual thermal stresses caused  during cure of the resin, it is always good practice to design  a symmetrical, or balanced, laminate. Examples of balance  laminates are presented in  Figure 7-49 . The first example  uses unidirectional tape, and examples 2 and 3 are typical  quasi-isotropic laminates fabricated from woven cloth. Horizontal (or edge) bleedout is used for small room  temperature wet layup repairs. A 2-inch strip of breather cloth  is placed around the repair or part (edge breather). There is no  need for a release film because there is no bleeder/breather  cloth on top of the repair. The part is impregnated with resin,  and the vacuum bag is placed over the repair. A vacuum is  applied and a squeegee is used to remove air and excess resin  to the edge breather.  Ply Orientation Warp Clock Bleedout Technique No Bleedout (+45, –45, 0) S (±45, 0/90)2S ([±45] 2, 0/90) S 1 2 3 ±45°, –45°, 0°, 0°, –45°, +45° ±45°, 0°/90°, ±45°, 0°/90°, 0°/90°,  ±45°, 0°/90°, ±45° ±45°, ±45°, 0°/90°, 0°/90°, ±45°, ±45° Example Written as Lamina 7-29