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 | 2-21. Dope Application Procedure (natural Fabrics)
9/27/01
AC 43.13-1B CHG 1
identify the manufacturers’ products sold un
der proprietary trade names may or may not
have a fungicidal additive.
(5) The viscosity of the dope should be
adjusted to uniformly wet the fabric, indicated
by the fabric becoming translucent so that it
penetrates through the fabric but does not drip
or run down the opposite side. Any dope-runs
or pooling on the opposite side will shrink and
distort the fabric, and may be visible on the
finished surface.
(6) The ideal temperature for application
of dope or other coatings is 65 to 75 F and the
humidity should be less than 65 percent. As a
general rule, each 10 F increase or decrease in
ambient temperature will increase or decrease
drying time by 100 percent. Dope should be
allowed to warm to room temperature prior to
attempting to adjust the viscosity.
e. Step 4. After the covering is a dressed
out, one or more coats of clear dope are
brushed over all finishing tapes and fabric re
inforcing patches. This will balance the thick
ness of the dope film with the previously
coated areas of the fabric. It is very important
that the porosity of the fabric be filled while
brushing to avoid pinholes showing in the fin
ish.
f. Step 5. After drying at least 2 hours at
70 °F, a third heavy coat of clear dope is ap
plied over the entire surface, preferably with a
paint spray gun if brush marks are to be
avoided. After the third coat of dope has dried
at least 2 hours at 70 °F, the fabric should be
taut and the dope film should show a gloss,
depending upon the dope quality and the ratio
of thinner added. If not, a fourth coat of clear
dope may be applied, in the same manner as
the third coat.
b. Step 2. Depending upon the quality of
the dope and the ratio of thinning, the fabric
should start to become taut after the first
brushed coat of dope has dried approximately
1 hour at 70 °F. A second, heavier coat is ap
plied by cross brushing at 90°F=to the first
coat. Viscosity should be adjusted only as
necessary to brush out a heavy uniform coat.
If the fabric is not taut, with all sag removed,
after the second coat has dried approximately
2 hours, a third coat may be applied.
c. Step 3. After the fabric has become
semi-taut and stabilized with the initial dope
application, and the rib lacing and other fabric
attachments are completed as detailed in para
graphs 2-9 through 2-12, it is ready for
“dressing out” as described in paragraphs 2-13
and 2-14.
d. NOTE: “Dressing out” means applying
all the finishing tapes, reinforcing patches, in
spection access ports, and drain grommets, etc.
NOTE: Three to four clear coats of
dope film showing a uniform gloss
combined with the aluminum-
pigmented coats and finish coats is
considered satisfactory for light air-
craft up to 9 lb. per square foot wing
loading. Five to eight clear coats, de-
pending upon the quality of the dope
and resulting film thickness, are rec-
ommended for higher wing loading
aircraft to assure the covering does
not stretch and lose tension.
g. Step 6. After the clear coats are found
to be satisfactory, two heavy cross-coats of
aluminum-pigmented dope are applied with a
spray gun to provide protection from ultravio
let (UV) rays. Tests have shown that UV ra
diation will deteriorate cotton, linen, and poly
ester fabric; however, polyester fabric deterio
rates at a rate half that of cotton or linen under
identical exposure conditions. UV radiation
Par 2-21
Page 2-27