stitches, as shown in the illustration. The finish wheel is
unstitched with spacers (washers) mounted between
every fourth or fifth cloth disc. Power for turning the
buffing wheel may be supplied by mounting it in a
portable drill, as shown in figure 5-3. At the start of
each buffing operation, the plastic must be clean and
dry. Some of the buffing compounds now available will
leave the surface clean so that washing is not necessary.
Where necessary, however, washing should follow each
step in buffing. If a panel has been sanded previously or
is deeply scratched, the abrasive wheel should be used
first. Apply fresh compound to the wheel and buff
lightly along and across all scratches. Keep the plastic
or wheel in motion to prevent generating too much heat,
thus damaging the plastic. Complete the buffing
operation by using the finish wheel, bringing the plastic
surface to a high gloss. After all scratches have been
removed with the finish wheel, a coat of wax should be
applied by hand.
Figure 5-4.--Approved edge attachment for solid plastic.
The following general rules apply to all types of
mountings. Fitting and handling should be done with
CAUTION
masking paper in place, although the edges of the paper
Hand polishing is recommended in critical
may be peeled back slightly and trimmed off for
vision areas. Overheating transparent plastic, by
installation.
buffing, induces internal stresses and optical
Since transparent plastic is brittle at low tem-
distortions.
peratures, installation of panels should be done at
normal temperatures. Plastic panels should be mounted
Installing Plastic Panels
between some type of gasket material to make the
installation waterproof, to reduce vibration, and to help
There are a number of methods for installing
distribute compressive stresses on the plastic.
transparent plastic panels in aircraft, some of which are
Minimum packing thickness is one-sixteenth of an
shown in figures 5-4 through 5-7. Which method the
inch. Rubber, fiber glass impregnate, and nylon are the
aircraft manufacturer uses depends upon the position of
most commonly used gasket materials.
the panel in the aircraft, the stresses to which it will be
subjected, and a number of other factors. In installing a
replacement panel, always follow the same mounting
method used by the manufacturer of the aircraft.
Figure 5-5.--Approved edge attachment for laminated plastic.
Figure 5-3.--Buffing wheel mounted in portable drill.
5-4
