REPAIR INSTRUCTIONS USING FIBER GLASS MATERIAL Figure 26.  - Covering Repair Area with Separating Film 5. Then, using a cardboard template (Figure 27), cut the required pieces of mat large enough to extend 2 inches beyond the edges of the repair area. NOTE-The  number  of  layers  of  mat  used  in the backing patch depends on the  thickness of  the  body  panel  being  repaired.    Refer  to Figure  28  to  determine  the  number  of  layers required.    Automotive  parts  are  normally  2.5 mm (0.100 In.) thick.  Therefore, the minimum backing   patch   thickness   must   be   3.2   mm (0.126  In.)  or  three  layers  of  42g  (1-1/2  oz.) mat. Figure 27.  - Cutting Fiber Glass Mat THICKNESS OF ORIGINAL PIECE LAYERS OF FIBER GLASS MAT REQUIRED FOR PATCH mm Inch quant g OZ 2.5 0.100 3 42 1-1/2 2.8 0.110 3 42 1-1/2 3.0 0.120 2 42 1-1/2 1 57 2 3.3 0.130 1 42 1-1/2 2 57 2 3.6 0.140 3 57 2 4.3 0.170 2 42 1-1/2 2 57 2 Figure 28.  - Backing Patch Mat Layer Requirements 6. Mix the recommended amount of polyester resin according to the manufacturer’s instructions. 7. Apply some resin to the working area of the separating film (Figure 29). Figure 29.  - Applying Resin to Separating Film 8. Soak the first layer of mat in resin; then’ place it over the repair area and allow it to harden slightly. 9. Now lay-up by hand the remaining piece or pieces of resin-soaked mat (Figure 30). NOTE-To prevent the patch from sliding on a vertical  surface,  tape  a  piece  of  plastic  film over the patch. CTS-4049 Page 10