Fiberglass Repairs; Fiberglass Touch-Up And Surface Repairs - Piper Navajo PA-31 Service Manual

4-97. FIBERGLASS REPAIRS. The repair procedure in this manual describes the methods for the repair of
fiberglass reinforced structures. Paragraph 4-98 describes Touch-up and Surface Repairs such as blisters, open
seams, delaminations, cavities, small holes and minor damages that have not harmed the fiberglass cloth
material. Paragraph 4-99 describes 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, that will
furnish that necessary material for such repairs is available through Piper Aircraft Distributors.
NOTE
Very carefully follow resin and catalyst mixing instructions
furnished with repair kit.
4-98. 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, continue
to Step h.)
c.
Pour a small amount of resin into a jar lid or on a piece of 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 maybe
present. Fill the scratch or hole above the surrounding undamaged area about 1/16 inch.
e.
Lay a piece of cellophane or waxed paper over the repair to cut off air and 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 cellophane
and trim flush with the surface, using a sharp razor blade or knife. Replace the cellophane and allow 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 and edges of the hole with the electric burr attachment or rough sand
paper. Feather hole into surrounding gel coat; do not undercut.
h.
Pour out a small amount of resin, add catalyst and mix thoroughly, using a cutting motion rather
than stirring. Use no fibers.
i.
Using the tip of a putty knife or finger tips, fill the hole to about 1/16 inch above the
surrounding surface with the gel coat mixture.
j.
Lay a piece of cellophane over the patch to start the curing process. Repeat Step f, trimming
patch when partially cured.
k.
After trimming the patch, immediately place another small amount of gel coat on one edge of the
patch and cover with cellophane. Then, using a squeegee or the back of a razor blade, squeegee level with area
surrounding the patch; leave the cellophane on patch for one or two hours or overnight.
1.
After repair has cured for 24 hours, sand patched area, using a sanding block with fine wet
sandpaper. Finish by priming, resanding and applying color coat.
Revised: 3/11/81
STRUCTURES
PIPER NAVAJO SERVICE MANUAL
1H3