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)
AC 43.13-1B
9/8/98
marks will be noticeable in the finish. With
increasing environmental concerns, high pres
sure airless and high-volume low-pressure
(HVLP) paint spray equipment is recom
mended over conventional siphon and pressure
pot spraying equipment. High pressure airless
and HVLP paint spraying equipment will
greatly reduce paint over-spray and fogging. A
spray gun, single coat is applied by overlap
ping each consecutive pass 50 percent of the
fan width. A double coat is applied by re
peating the coating application in the same di
rection, or at a 90°€angle to the first coat
(cross coat) before the first coat has flashed off
or dried dust free. For safety and helpful tips
for doping, see tables 2-3 and 2-4.
TABLE 2-3. Safety tips for dope/paint.
SAFETY TIPS.
Always ground the aircraft structure while sanding and
painting.
Do not use an electric drill as a dope/paint mixer.
Wear leather-soled shoes in the dope/painting area.
Have an adequate, approved ventilation system.
Wear cotton clothes when doping or painting.
Wear an approved face mask or respirator when
spraying.
Follow all the manufacturer’s instructions.
2-21. DOPE APPLICATION PROCE-
DURE (Natural Fabrics).
a. Step 1. After the cotton or linen fabric
is installed in accordance with the procedures
specified in paragraphs 2-7 and 2-8, the fabric
is wetted with distilled water to remove wrin
kles and fold creases, which will show in a
gloss finish. Water may be applied by rubbing
with a clean sponge or rag, or by using a paint
spray gun. Do not use tap water. It may con
tain minerals which will contaminate the fab
ric.
(1) As water is absorbed by the fibers,
the threads swell, resulting in temporary
tauting of the fabric panel. The fabric should
be allowed to dry before dope application, oth
erwise the water in the fibers will interfere
with the dope penetration and adhesion.
(2) After the fabric has dried, the first
coat of dope is applied, brushing in one direc
tion to set the nap with a clean, non-shedding,
2-to 6-inch wide, semi-soft, long bristle paint
brush.
TABLE 2-4. Tips for doping.
HELPFUL TIPS FOR DOPING.
Limits for optimum application of dope: relative hu-
midity 20 to 60%; temperature range 65° to 75 °F.
Drying time will vary with temperature, humidity,
amount of thinner used, and whether or not retarder
was added to the mixture.
Do not recoat until the surface is completely dry and
all active solvents have left the dope film.
Spray all coats except the first three or four clear
coats, to avoid brush marks.
Over thinning is preferred to under thinning.
Addition of retarder will produce a smoother coat, but
drying time between coats will be extended.
To get a clean line for the trim colors, apply a light
coat of clear dope directly on the masking tape prior
to painting. This will help eliminate the trim color
from running under the masking tape.
Remember to always bring the dope to room
temperature before using.
Rubbing compound and wax polish may be applied
after all solvents have escaped (usually 2 weeks,
depending upon the weather).
(3) To offset the deteriorating effect of
mildew or other fungus on natural fibers, espe
cially in damp climates, it is recommended that
a fungicide be added to the first coat of dope.
The preferred fungicide is zinc dimethyldithio
carbamate powder, which should be prepared
per the manufacturer’s instructions. If no
manufacturer’s instructions are available the
zinc powder may be stirred in at a ratio of
4 ounces, to one gallon of un-thinned nitrate or
butyrate dope, after the powder is wetted to a
paste with a 50/50 ratio of dope and thinner.
(4) Pre-mixed fungicidal dope, manu
factured in accordance with the formula speci
fied in MIL-D-7850, will have a transparent
purple tint to indicate the fungicide additive.
Dope manufactured with other colors to
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