Figure 14-4.Approved edge attachment for solid plastic.
hard and to which buffing compound is applied, is
used for removing the deeper scratches. The finish
wheel, which is soft, is then used to bring the plastic
to a high polish.
Both wheels are made up of
numerous layers of cloth discs, but the abrasive wheel
is made hard by several rows of stitches, as shown in
the illustration. The finish wheel is unstitched with
Figure 14-5.Approved edge attachment for laminated
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 14-3. 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.
Hand polishing is recommended in critical
plastic, by buffing, induces internal stresses
and optical distortions.
Installing Plastic Panels
There are a number of methods for installing
transparent plastic panels in aircraft, some of which
are shown in figures 14-4 through 14-7. Which
Figure 14-6.Typical sighting dome attachment.