Cessna 150M - Cracks

WOOD REINFORCEMENT
B
ALWAYS DRILL END OF CRACK CUSHION OF
RUBBER
TO
RELIEVE STRAIN OR FABRIC
SOFT WIRE
LACING
TEMPORARY
REPAIR
OF CRACKS
CEMENTED
FABRIC PATCH
SANDING
REPAIR
Figure 3-1. Repair of Windows and Windshield
pressure and cover an area large enough to prevent
formation of "bull's-eyes" or other optical distor-
tions.
ICAUTION\
Do not use a coarse grade of abrasive. No.
320 is of maximum coarseness.
b. Continue sanding operation, using progressively
finer grade abrasives until scratches disappear.
c. When scratches have been removed, wash area
thoroughly with clean water to remove all gritty par-
ticles. The entire sanded area will be clouded with
minute scratches which must be removed to restore
transparency.
d. Apply fresh tallow or buffing compound to a
motor-driven buffing wheel. Hold wheel against plas-
tic surface, moving it constantly over damaged area
until cloudy appearance disappears. A 2000-foot-per-
minute surface speed is recommended to prevent
overheating and distortion. (Example: 750 rpm
polishing machine with a 10 inch buffing bonnet. )
NOTE
Polishing can be accomplished by hand but
will require a considerably longer period
of time to attain the same result as pro-
duced by a buffing wheel.
e. When buffing is finished, wash area thoroughly
and dry with a soft flannel cloth. Allow surface to
cool and inspect area to determine if full transpar-
ency has been restored. Apply a thin coat of hard
wax and polish surface lightly with a clean flannel
3-2
cloth.
NOTE
Rubbing plastic surface with a dry cloth
will build up an electrostatic charge which
attracts dirt particles and may eventually
cause scratching of surface. After wax
has hardened, dissipate this charge by rub-
bing surface with a slightly damp chamois.
This will also remove dust particles which
have collected while wax is hardening.
f. Minute hairline scratches can often be removed
by rubbing with commercial automobile body clean-
er or fine-grade rubbing compound. Apply with a
soft, clean, dry cloth or imitation chamois.
3-8. CRACKS. (Refer to figure 3-1.)
a. When a crack appears, drill a hole at end of
crack to prevent further spreading. Hole should be
approximately 1/8 inch in diameter, depending on
length of crack and thickness of material.
b. Temporary repairs to flat surfaces can be ac-
complished by placing a thin strip of wood over each
side of surface and inserting small bolts through
wood and plastic. A cushion of sheet rubber or air-
craft fabric should be placed between wood and plas-
tic on both sides.
c. A temporary repair can be made on a curved
surface by placing fabric patches over affected areas.
Secure patches with aircraft dope, Specification No.
MIL-D-5549; or lacquer, Specification No. MIL-L-
7178. Lacquer thinner, Specification No. MIL-T-
6094 can also be used to secure patch.