(1) Cut a rectangular patch large enough to encompass damaged area on face sheet. Patch material must
be same thickness as panel face sheet.
(2) Using patch as a template, mark rectangle on face sheet covering damaged area. This will ensure that
patch will fit snugly in face sheet cutout when patch is installed.
(3) Cut out damaged face sheet within rectangle, using a router bit chucked in a 1/4-inch drill, a fine-tooth
keyhole type hacksaw, or a circular saw.
(4) Cut and remove core material to opposite face sheet using a knife.
(5) If both sides of panel are damaged, repeat steps (1) through (3) for opposite side of panel. Second
cutout should be identical to and directly opposite first cutout.
(6) File cutout edges smooth, using fine cut, half round file, or rotary file chucked in 1/4-inch drill.
(7) Remove loose fragments of foam, dust and metal. Use a vacuum, if necessary.
(8) Remove paint from panel face around each cutout for a distance of 1-1/2 inches (up to two inches for
very large cutouts). Paint may be sanded off or removed with solvent. All traces of paint must be
(9) If only one face sheet has been cut out, clean bonding (interior) surface of opposite face sheet until
If cutouts have been made in both sides of panel, steps (10) through (15), (17), (18) and
(21 ) through (25) apply to both face sheets.
(10) Cut a doubler for patch. Make doubler one inch larger all around that cutout (up to two inches for very
(11) Lay out rivet hole pattern in patch and doubler. Rivet holes should be 1/4 to 1/2 inch from edge and one
inch apart. (Hole spacing may be increased to two inches when distance between two corner holes
exceeds 20 inches.) Drill holes using a no. 11 or no. 12 drill (no. 12 or no. 30 for large patches).
Remove all metal chips and burrs from drilled holes.
(12) Center patch on doubler and drill rivet holes in doubler, using drilled holes in patch as a template.
Secure patch to doubler by temporarily inserting rivets.
(13) Center doubler (with patch temporarily fastened) over cutout in panel, making sure patch fits snugly and
flush in cutout.
Drill two diagonally opposite corner holes first, then other two corner holes, then drill