4-50. STRUCTURAL REPAIRS.
Structural repair methods used must be made in accordance with the regulations set forth in FAA Advisory
Circular 43-13-1 A. To assist in making repairs and/or replacements, Figure 4-9 identifies the type and thickness
of various skin material used. Never make a skin replacement or patch plate from material other than the type of
the original skin, or of a different thickness than the original skin. The repair must be as strong as the original
skin. However, flexibility must be retained so the surrounding areas will not receive extra stress.
—WARNING—
NO access holes are permitted in any control surfaces.
4-51. FIBERGLASS REPAIRS.
The repair procedure in this manual will describe the methods for repair of fiberglass reinforced structures.
Paragraph 4-52 describes Fiberglass TouchUp and Surface Repairs such as blisters, open seams, delamination,
cavities, small holes and minor damages that have not harmed the fiberglass cloth material. Paragraph 4-53
describes Fiberglass Fracture and Patch Repairs such as puncture, breaks and holes that have penetrated through
the structure and damaged the fiberglass cloth. A repair kit, part number 756 729 will furnish the necessary
material for such repairs, and is available through Piper Aircraft Dealers.
—WARNING—
The use of patch plates for repairs of all movable tail surfaces is prohibited. The
use of any filler material normally used for repair of minor dents and/or materials
used for flling the inside of surfaces is also prohibited on all movable tail surfaces.
4-52. FIBERGLASS TOUCH-UP AND SURFACE REPAIRS.
a. Remove wax, oil and dirt from around the damaged area with acetone, Methylethylketone or equivalent
and remove paint to gel coat.
b. The damaged area may be scraped with a fine blade knife or a power drill with a burr attachment to
roughen the bottom and sides of the damaged area. Feather the edge surrounding the scratch or cavity. Do not
undercut the edge. (If the scratch or cavity is shallow and penetrates only the surface coat, skip to step h.)
—NOTE—
Very carefully follow resin and catalyst mixing instructions
furnished with repair kit.
c. Pour a small amount of resin into a jar lid or on a piece of clean cardboard, just enough to fill the area
being worked on. Mix an equal amount of milled fiberglass with the resin, using a putty knife or stick. Add
catalyst, according to kit instruction, to the resin and mix thoroughly. A hypodermic needle may be used to inject
gel into small cavities not requiring fiberglass millings mixed with the gel.
d. Work the mixture of resin, fibers and catalyst into the damaged area, using the sharp point of a putty knife
or stick to press it into the bottom of the hole and to puncture any air bubbles which may be present. Fill the
scratch or hole about 1/16 inch above the surrounding undamaged area
e. Lay a piece of cellophane or waxed paper over the repair to start the cure of gel mixture.
f. Allow the gel to cure 10 to 15 minutes until it feels rubbery to the touch. Remove the covering and trim
flush with surface, using a sharp razor blade or knife. Replace the covering and allow the patch to cure
completely for 30 minutes to an hour. The patch will shrink slightly below the structure surface as it cures. (If
wax paper is used, ascertain wax is removed from surface.)
g. Rough up the bottom edges of the hole with the electric burr attachment or rough sand paper. Feather hole
into surrounding gel coat, do not undercut.
PIPER AIRCRAFT
PA-28-161 CADET
AIRPLANE MAINTENANCE MANUAL
STRUCTURES
1F5
Issued: FEBRUARY. 28, 1989