FAA Advisory Circular 43.13-1B
Acceptable Methods, Techniques, and Practices
Aircraft Inspection and Repair
AC 43.13-1B | 2. Fabric Covering | 2. Application of Dope | 2-22. Covering Over Plywood
AC 43.13-1B CHG 1
9/27/01
does not deteriorate glass fabric. Aluminum-
pigmented dope blocks UV radiation and pro
vides a sanding base. A gauge of ultraviolet
protection in the field is to block all visible
light from penetrating through the fabric.
Drying time between the two coats should be
at least 1 hour at 70 °F.
(1) An option to premixed aluminum
dope is to use aluminum-pigment paste. Alu
minum paste should be prepared per the manu
facturer’s instructions. If no manufacturer’s
instructions are available, mix 3 ounces (by
weight), of 325-mesh aluminum-pigment
paste, to 1 gallon of unthinned, clear dope.
The aluminum paste should first be mixed to a
cream consistency with a 50/50 ratio of dope
and thinner before mixing into the unthinned
clear dope. A higher ratio of aluminum-
pigment added to the dope may cause a loss of
primer-coat and finish-coat adhesion, and
peeling may occur especially when high tack
tape is used to mask for the trim colors and
registration numbers.
(2) The viscosity of the mixed alumi
num-pigmented dope should be adjusted for
satisfactory spray gun application.
h. Step 7. After two coats of aluminum-
pigmented dope have dried at least 4 hours at
70 °F, the surface may be wet sanded with
# 280 grit (or finer) waterproof sandpaper. The
aluminum-pigmented dope should be sanded
only to develop a smooth surface, not sanded
completely off to the clear dope undercoats.
Do not sand over screwheads, rib lacing, or
any structural sharp edges that will quickly cut
through fabric and require patching. Addi
tional coats of aluminum-pigmented dope may
be applied and sanded, depending on the final
finish desired. The last coat should not be
sanded
to
assure
ultraviolet
protection along the edges of the finishing
tapes and reinforcing patches is maintained.
i. Step 8. Three coats of pigmented color
finish are applied with a paint spray gun, al
lowing adequate drying time between coats.
The color finish may be wet sanded between
coats, if desired, with a fine grit waterproof
sandpaper. Adding blush retarder to the final
dope finish will improve the gloss. After dry
ing several weeks, a rubbing compound may
be used to buff the finish and increase the
gloss. A periodic application of a wax polish
will help protect the finish from the weather
and environmental pollution.
NOTE: Drain holes should be opened
soon after all finishing is complete to
insure drainage and to aid ventilation
of the structure.
(1) When exposed to the sun, dark col
ors absorb more sun energy and convert that
energy to heat more easily than light colors.
High temperatures dry out wood structures and
deteriorate organic materials in an aircraft
structure. Preferably the lighter color shades
are applied first and then overcoated with
darker trim and registration number colors.
(2) Only high-quality, solvent-resistant
crepe paper or polypropylene masking tape
should be used to avoid finish bleed under the
tape edge. Newspaper printing ink may trans
fer to a fresh finish and should not be used for
masking paper. Plastic sheeting should not be
used as a dust cover on a fresh finish due to
possible bonding and damage.
2-22. COVERING OVER PLYWOOD.
Exposed, stressed plywood surfaces, such as
wings, must be protected from weather
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