LANCE
II SERVICE
MANUAL
j. Remove
cardboard
or aluminum
sheet
from
outside of
hole and
rough-sand
the patch
and edge of
hole. Feather
edge
of hole about
two inches
into undamaged
area.
k.
Mask area
around hole
with tape
and paper
to protect surface.
Cut
a piece of
fiberglass
mat about one
inch larger
than the hole
and one or
more pieces
of fiberglass
cloth
two inches larger
than the hole.
Brush catalyzed resin
over hole, lay mat
over hole and wet
out with
catalyzed resin.
Use a daubing
action
with brush.
Then apply
additional layer
or
layers
or fiberglass cloth
to build up patch
to the surface
of structure. Wet out
each layer
thoroughly
with resin.
1. With a squeegee
or broad knife,
work out all air
bubbles in the patch.
Work from
center to edge.
pressing patch firmly
against the structure.
Allow patch
to cure for 15 to 20
minutes.
m. As soon as the
patch begins to
set up. but while still
rubbery, take a
sharp knife and
cut away extra
cloth and mat. Cut
on outside edge of
feathering. Strip cut
edges of structure.
Do
this before
cure is complete,
to safe
extra sanding.
Allow
patch to cure
overnight.
n. Using
dry 80 grit sandpaper
on a power sander
or sanding block,
smooth patch
and
blend
with surrounding
surface.
Should air
pockets appear
while sanding.
puncture
and fill
with
catalyzed
resin. A hypodermic
needle
may be used
to fill cavities.
Let cure
and resand.
o.
Mix catalyzed
resin and
work into
patch with
fingers. Smooth
carefully
and work
into any
crevices.
p. Cover with
cellophane and squeegee
smooth.
Allow to cure completely
before
removing
cellophane.
Let
cure and
resand.
q. Brush or spray a coat
of catalyzed resin to seal patch. Sand
patch, finish by priming,
again sanding
and applying
color coat.
NOTE
Brush and hands
may be cleaned in solvents
such as acetone
or methylethylketone.
If solvents
are not available, a strong
solution
of detergent
and water may be
used.
4-21.
THERMOPLASTIC
REPAIRS.
The following procedure
will assist in
making field
repairs to
items made of thermoplastic
which
are used throughout
the airplane. A list
of
material needed
to perform these
repairs is given along
with suggested
suppliers of the
material. Common
safety precautions
should be
observed when handling
some of the
materials
and
tools used
while making
these
repairs.
a. Surface Preparation:
1. Surface dirt
and paint if applied
must be removed
from the item
being repaired.
Household
cleaners have
proven most effective
in removing
surface dirt.
2. Preliminary
cleaning of
the damaged area
with perchlorethylene
or VM&P
Naphtha will
generally insure
a good
bond between
epoxy compounds
and
thermoplastic.
b. Surface
Scratches.
Abrasion or
Ground-in-Dirt:
(Refer to Figure
4-6.)
1. Shallow
scratches and abraded
surfaces
are usually repaired
by following
directions on
containers
of conventional
automotive
buffing
and rubbing
compounds.
2.
If large dirt
particles are
embedded
in thermoplastic
parts,
they can be
removed
with a hot air
gun capable of supplying
heat in the temperature
range of
300
°
to 400
°
F. Use
care not to
overheat the material.
Hold the nozzle
of the gun about
1/4 of an inch away
from
the surface and apply
heat with a circular
motion until the
area is sufficiently
soft to remove the
dirt particles.
Issued:
1/3/78
STRUCTURES
1E18
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