8 6 4 2 0 I0 PRESSURE Repair area Breather cloth Heat blanket Breather cloth Thermocouple 0.50 inch minimum Partial depth core replacement Full depth core replacement 7-35 Figure 7-57.  Core damage removal.  Figure 7-56.  Vacuum bag method for drying parts. Trim out the damage to the face sheet to a smooth shape with  rounded corners, or a circular or oval shape. Do not damage  the undamaged plies, core, or surrounding material. If the  core is damaged as well, remove the core by trimming to the  same outline as the skin.  [Figure 7-57] Use a flexible disk sander or a rotating pad sander to taper  sand a uniform taper around the cleaned up damage. Some  manufacturers give a taper ratio, such as 1:40, and others  prescribe a taper distance like a 1-inch overlap for each  existing ply of the face sheet. Remove the exterior finish,  including conductive coating for an area that is at least 1 inch  larger than the border of the taper. Remove all sanding dust  with dry compressed air and a vacuum cleaner. Use a clean  cloth moistened with approved solvent to clean the damaged  area.  [Figure 7-58] Use a knife to cut the replacement core. The core plug must  be of the same type, class, and grade of the original core. The  direction of the core cells should line up with the honey comb  during the elevated temperature cure cycle and the face sheets  blow off the core, resulting in more damage. Water in the honeycomb core could also freeze at the low temperatures  that exist at high altitudes, which could result in disbonding  of the face sheets.  Step 3: Remove the Damage Step 4: Prepare the Damaged Area Step 5: Installation of Honeycomb Core (Wet Layup)