SECTION 13 PAINTING
RV AIRCRAFT
13-1
sect 13.pub 3/5/01
An entire book could be written on the subject of aircraft painting and still leave many questions unanswered. There
are many surface preparations, primers, and paints available, and more coming on the market every day. Paints
range anywhere from the older enamels and acrylic lacquers up through the newer acrylic enamels, urethanes, and
epoxy finishes. Which one is best probably depends on the end result desired by the individual builder. However,
the urethanes seem to be favored by most builders now because of their relative ease of application and shiny,
maintenance free finish. The purpose of this section is only to present some general ideas, not to provide the ‘‘best
way’’ of applying the ‘‘best’’ paint.
COLOR SCHEME
Before getting serious about the type of paint to be used and the method and technique of application, most
builders spend many months (or years?) while building trying to decide their paint scheme. Toward this end, little
can be offered other than the suggestion that conservative colors and paint scheme will always look good on the
basically good lines of an RV. More daring combinations of colors and patterns may result in a ‘‘fabulous’’ paint
scheme, or could result in an eyesore which is too ‘‘busy’’ or gaudy to be appealing. Unless you have a very good
eye for colors and patterns, it may not be worth the gamble. We have provided two drawings; one perspective, and
the other a three view, for you to practice on. Just run off a few dozen copies of these drawings on your office
copier (when the boss isn’t looking), buy a box of colored pencils and start sketching out your dream scheme.
Aside from the aesthetic aspects of color scheme selection, you might also give serious thought to recognition; i.e.;
how well will your combination of colors stand out from the background when in flight. How visible will it be to pilots
of other aircraft in flight? With the dense air traffic and haze of air pollution encountered around many airports, see-
and-be-seen should be a major safety concern to all pilots. Light colors are generally considered to be the most
visible against typical backgrounds found while flying in the USA. Yellow is probably the most universally visible,
and can also be trimmed to provide very attractive paint schemes.
The question of whether a painted or bare aluminum airplane goes faster is often raised. Experience with the
prototype RVs has not provided a definitive answer, so it would appear that there is little difference in skin friction
drag from a typical painted surface to a typical bare aluminum surface.
PAINTING HEALTH HAZARDS
Spray painting can present a health hazard, particularly with most of the newer two-part paints. Chemicals used in
the hardeners of urethane, acrylic enamel, and epoxy paints cause them to be potentially very hazardous if
breathed, and can be harmful even through excessive exposure to the skin. For this reason, the painting area must
be well ventilated and a UL approved respirator must be used. A simple particle filter is just not good enough. Also,
full coverage clothing should be used to prevent skin exposure. Builders sometimes disregard warnings on the likes
of paint cans because they become indifferent after daily exposure to warnings on all sorts of relatively benign
household items. But where modern paints products are concerned, the warning should be taken very seriously
PLEASE TAKE PAINT CAN TOXIC WARNINGS SERIOUSLY!!!
PAINTING: ONE EXAMPLE
While we are not presenting this to be the proven ‘‘most ideal’’ paint and procedure, it was used on the prototype
RV-4 under ‘‘home’’ conditions and by amateur painters. It consists simply of preparing the bare ‘‘alclad’’ aluminum
surface with an acid wash (DuPont 255S cleaner, Martin Senour 6879 Twin Etch, etc.), followed by an application of
Alodine, and then directly by DuPont Imron Polyurethane paint. While a primer or primer/surfacer could be used
between the Alodine and the Imron, it was left off as a weight saving measure. Only the minimum thickness of
Imron was used to get the desired flow-out for a slick surface. After the Alodine application, the skins were
completely dried to remove any moisture which might later contribute to filiform skins corrosion. This was done with
an air nozzle and repeated passes over all metal seams and rivets. The RV-6 prototype was painted with a similar
‘‘Minimum weight’’ approach, but in this instance Ditzler Durethane paint was used.
Painting an airplane obviously adds to its weight. The amount of weight depends on the type and amount of paint,
primer and surface filler used. The ‘‘No-primer’’ Imron process described above will weigh about 15 lbs; about
minimum for a complete paint job. A really elaborate paint job with all the extras could add two or three times this
weight. In addition, heavy paint jobs will tend to shift the Center of gravity rearward because of the paint weight on
the empennage. Control surface balance on the RVs has not been found to be critical. A normal (light) paint
application on the ailerons and elevator will not upset their balance to a noticeable degree. However, a heavy paint
job will require that these surfaces be re-balanced and additional counter balance weight added if necessary.
SECTION 13: PAINTING
RV AIRCRAFT
SECTION 13 PAINTING
13-2
sect 13.pub 3/5/01
MASKING
Application of masking tape for color separation and pin-striping is perhaps the most time consuming part of
painting. Masking a straight line is tough enough, but getting just the right curve or ‘‘sweep’’ to a line is an art.
Common hardware store masking tape usually gives poor results for distinct line separation because it permits too
much ‘‘bleed under’’. Plastic ‘‘decorator’’ tape yields a nice crisp edge, but is rather expensive. Plastic electricians
tape works fairly well and is relatively cheap. ‘‘Scotch’’ tape also works well, but is hard to remove after painting.
There is no doubt that a smooth, wave free surface offers less aerodynamic drag than an imperfect one, but it is not
known how much effect this will have on the speed of an RV. Probably not much unless the entire airframe is filled
and smoothed before painting, and then the paint is rubbed-out perfectly smooth. This would entail much work,
would add weight, and would probably not be advisable unless the builder wanted a 100% perfect airplane rather
than a 98% perfect one. The price for that last 2% would be high in terms of added work required.
For the typical paint job, the builder obviously should try to work in a dust free environment so the paint surface will
be as smooth as possible without the need for rub-out. Spanwise trim stripes should be avoided very near the wing
leading edge. Much is being written about the effects of spanwise surface irregularities on the boundary layer
control on airfoils, particularly those on canard configuration airplanes. The concern is that any surface irregularity
near the wing leading edge, particularly spanwise ones, can disrupt the boundary layer airflow, upset laminar flow,
and cause an increase in drag and a decrease in lift. On canard airplanes this can seriously affect not only
performance, but also stability and control. On an RV, with its conventional configuration and non-laminar flow
airfoil, the effects of surface irregularities are relatively minor. However, a rough paint trim line within the first few
inches of the wing leading edge would probably cause a measurable effect on stall and top seeds. Trim lines more
than 8-9 inches from the leading edge have a minimal effect, but even then should be rubbed out as smoothly as
possible.
