Project Extra Volume V: Covering and Paint

Covering
and Paint
Volume V:
TRADITIONALLY, Giant Scale models have used varying methods
of finishing, from fiberglass and paint to Stits cloth and dope. Although
the results with these methods can be beautiful, many of them are
geared more toward appearance than overall final performance. That’s
not to say we aren’t concerned with appearances in Scale Aerobatics
(SA), just that we want the airplane to be aesthetically pleasing and
remain as light as possible. SA aircraft are finished like
most sport airplanes—with iron-on plastic coverings and
paint for the fiberglass parts.
Admittedly, there are craftsmen in the modeling
community who are better suited to a tutorial on
covering, so I’m not going to go too deep into the
subject. But I will try to share several tips and hints for
getting a professional-looking finish for an SA airplane.
I’ll also discuss fitting the canopy and finishing the
cockpit, and I’ll touch on methods of painting the
fiberglass parts. If you want some information on the
basics, go to www.monokote.com/monoinst1.html for
MonoKote and try http://horizon.hobbyshopnow.com/
articles/1115.asp for more info on UltraCote.
Most SA modelers use UltraCote- or MonoKotebrand
coverings. There has been a long-standing debate
about which works better and which is easier to apply.
As anybody who has ever finished a model with one of
these brands can tell you, it takes a bit of practice to get
the knack of working with iron-on coverings no matter
which one you choose. The answer to which is easier to
■ Mike Hurley
The author’s model bears his signature Bulldog Competition Aerobatics logo. Companion and mascot
Spike inspired the logo.
use is simple: the one you are used to. Erik Richards and I have more
experience with MonoKote, so we will use that.
Before the covering can begin, we have a few last-minute items to
finish up. It’s time to fit and trim the canopy. Cut the front and rear
sections out of the canopy so you can fit it onto the model. Center the
canopy side to side as close as possible. Since this canopy was
May 2003 35
With a new skin and a fresh set of colors, Project
Extra starts to take on a personality of its own.
36 MODEL AVIATION
originally designed to fit another aircraft, it is a tad too big. We cut the
canopy to the size indicated on the plans, which should knock
approximately four inches off the rear portion of the canopy.
Tape the canopy in place on the airplane. Using 1⁄4-inch Fine Line
tape (or any striping tape), mark out where you want to cut. The tape
works well for fine-tuning placement and ensuring that you get
straight lines. Carefully trim and fit the canopy. At the front edge of
the canopy where it fits over the top of the hatch, Erik left in a slight
amount of the curved fillet to give a slightly better fit and more gluing
surface.
Erik decided to finish the cockpit with a speckle-texture paint.
There are many types of texture paint; some are made to simulate
granite or stone. We used paint from Pep Boys auto parts that is made
for finishing automobile trunks.
There are a few tricks to using this speckle paint. It’s best to use a
primer base coat before applying the paint. The speckle goes on wet
and does not cover well, so the base color gives you the ability to use
much lighter coats. Be careful to keep the coats of paint and speckle
light and fairly dry, or you might warp the wood. A few dry coats are
much better than one heavy coat. Mask off the hatch well so you don’t
get overspray on the wood.
Mask the area for your dash panel. For a lightweight dash we used
a composite of some of my digital photographs that I put together on
my computer. I printed it on glossy paper and spray-glued it directly to
the wood. If you go to the Project Extra Web site (viewable at
www.modelaircraft.org/mag/index.htm), you can download the dash
image to use in your Extra.
At this point Erik has not decided on a pilot. Remember that the
cockpit area is not built to hold any significant weight, so a bit of
reinforcement to the hatch floor will be necessary if a pilot is added.
Before you begin to apply any covering, it is important to prepare the
wood surfaces. As I discuss the way we like to do it, know that there
are many ways to accomplish a great finish; ours is not the only way.
Erik likes to final-sand everything with 320-grit 3M Tri-M-ite Fre-
Cut sandpaper; it has a gray color. The 3M papers stay sharp longer
and resist loading up. Erik likes to spray-glue the sandpaper to a scrap
foam block. The foam is soft and contours to the shape of the wood
but does not allow problems from palm or finger pressure points. Use
a good-quality filler to fix any hangar rash or imperfections. We used
NHP Micro-Fill model filler. It’s easy to sand and super light.
You can seal the wood with a light coat of Aqua Net hairspray
before you sand. Once sealed, the tiny balsa fibers created from
sanding come off easier and a smoother surface can result. The
downside is that with a sealed surface, the gas created from heating
the MonoKote is more likely to get trapped as you apply the covering.
The result can be a smoother finish, but it’s much harder to avoid the
dreaded bubbles.
We decided not to seal the wood for our airplane. Once filling and
sanding are done, it’s a good idea to thoroughly vacuum all of the
surfaces to be covered using a brush attachment. The vacuum pulls the
dust from the wood’s pores. Wiping with a tack rag alone can leave
dust particles in the wood’s grain. We also spent a great deal of time
vacuuming and cleaning the shop to keep airborne dust to a minimum.
In my estimation, one of the hardest elements of any finishing job is
designing an exciting but tasteful trim scheme. Since this is a Scale
aircraft, we wanted to start with ideas from full-scale Extra trim
schemes and see if there was anything that looked good. Go to the
search engines on the Internet and type in “Extra 300.” You will
eventually find many photographs of current schemes.
Mike and Erik used three-view template, felt-tip pens to devise a color scheme. Erik used a software program to finalize the design.
Photos by the author Graphic Design by Carla Kunz
Another good source for scale information is Bob’s Aircraft
Documentation at www.bobsairdoc.com. I ordered the three-views to
use as a template for designing my trim schemes. Besides three-views,
Bob carries scale documentation for more than 650 aerobatic
airplanes—and 80 of them are Extras!
Erik and I made a bunch of copies of the three-view and spent an
entire day trying to come up with a new scheme for his Extra. We
came up with many interesting and unusual designs but decided on a
derivative of the scheme on the prototype with our bulldog mascot
Spike as the main graphic element.
Things to keep in mind as you design your color scheme are to use
colors that are easy to see and give the airplane good definition when
it’s in the air. The shape of the model—not just the outline—should be
easy to see. Dark colors tend to create a flat silhouette that makes
orientation more difficult. I use the analogy that dark covering tends to
create a “hole in the sky” wherever it’s used.
The direction of the design’s lines can also aid in orientation. If the
general design has elements that go from side to side on the top of the
airplane, orienting the design longitudinally for the bottom of the
model will help differentiate the top from the bottom. It can also help
to use colors for the bottom that contrast with the colors on the top of
the aircraft. The idea is to be able to instantly know your airplane’s
orientation without any real thought. A good design will have that
effect on a subconscious level.
Once you’ve decided on a color scheme, trace all of the outlines for
the fuselage side, wing, and stabilizer in full size. Drafting vellum
Use 1⁄4-inch masking tape to mark the canopy for trimming. Fit
the canopy to the fuselage, then apply tape as a marker.
Masking-tape cut line ensures straight line, accurate positioning.
Erik finished the interior of his Extra’s cockpit with speckle-type
paint. This method is quick and attractive.
38 MODEL AVIATION
To save weight,
Mike made a photo
c o m p o s i t e
instrument panel.
You can download
the full-size panel
from the AMA Web
site and use it in
your Extra.
works well for tracing the plans. When the outline is done, use it to
finalize the separate color details in full size. Erik used it to cut fullsize
templates from poster board. After a template is used for one
wing panel, it can be turned over and used on the other side to ensure a
uniform pattern.
To make the curves of any rounded corners come out with smooth,
flowing lines we used ship’s curves. You can get a set of inexpensive
plastic ship’s curves or French curves from the hobby store, an art
store, or a drafting-supply shop. Using these as templates, complex
curves can be drawn in a smooth and precise manner.
When you’re ready to start covering, following are a few hints that
have worked for us that may help you too. I like to keep any part being
covered on a suitable piece of upholstery foam to keep it from being
damaged during the covering process. Cover the ends and edges first.
That way, the main body of the covering hides the corner intersections
or loose ends and makes for a neat finish.
In tight inside corners, such as the transition from the turtledeck to
the vertical stabilizer, start with a strip of covering ironed into the
corner using a trim iron. With that you can cut your top layer into the
corner without having to transition the covering. The result is a seam
that is almost impossible to detect.
Stay away from putting covering over covering as much as
possible by trimming your pieces to fit the shape needed before they
are ironed on. I like to overlap the edges of neighboring covering
sections by roughly 1⁄4 inch. Put the most transparent colors on first,
and overlap with the more opaque colors.
In some cases it will be impossible to avoid putting covering over
other covering because of material expanses that transition open bays,
such as the fuselage sides on this model or between the ribs of a builtup
wing on other models. Covering adhesive is activated with heat,
and when it is too hot it will convert to a gas. When covering goes
over covering there is no place for trapped air or gasses created from
overheating the glue to escape, and the result is ugly bubbles in the
finish!
The trick is to be sure that no air is allowed between the two layers
of covering while heating the glue, and to heat it only warm enough to
make it adhere without giving off a gas. This is a tricky process that
May 2003 39
Only cursory smoothing is required on wing panels. Take care
not to remove any material from wood at risk of weakening wing.
Designing a color scheme is one of the most challenging steps
in the process. Mike and Erik kept Spike nearby for inspiration.
Vacuuming wood before covering is important. Brush
attachment helps lift sanding residue from grain, helps
covering material stay put.
takes patience, practice, and a lot of willpower, but it can be done.
There are many methods to get a smooth finish with multiple
layers. The following works well and stays put. Smaller pieces are
easier than large sections. Let’s use a stripe as an example. Measure
and cut the stripe to the needed size. The top layer of covering will be
tacked down at the starting point and held off of the surface as it’s
heated, so you must first mark off an outline of the shape to be ironed
on. Use a felt-tip pen to outline the section or to make intermittent
dashed lines. Be sure to keep it wide enough so the covering doesn’t
go over the ink. The guideline will keep you on track. It may take
some trial and error to get your covering iron’s temperature just right,
so try a few practice strips first.
The temperature should be approximately two-thirds of what you
normally use to seal MonoKote to wood. Tack down the covering at
your starting point. Using only the edge of the iron, slowly heat the
covering while holding the unheated portion up away from the
surface. Slowly work along the stripe, taking it down and heating just
to the point where no bubbles form. Use your free hand to hold the
MonoKote off the surface and guide its path.
Be sure to only heat a section the size of the iron’s edge. If you lay
the iron flat, it will heat too large an area and cause bubbles. Work
your way to the end of the stripe, holding the free end of the covering
up and guiding with one hand while heating with the other. Don’t
worry that it’s not strongly attached; it needs to hold only to the point
where there are no loose sections or trapped gasses.
After you complete the section, use MonoKote Trim Solvent to
remove the felt-tip-marker outline and seal the edges along the stripe.
The solvent will secure the stripe in place in lieu of using a high level
of heat. Be sure to get all of the stripes laid out on the fuselage before
you begin the cowl-painting process. That way you can line up the
cowl to match the stripes in paint.
For a nice finished look, any hole that needs to be cut after
covering can be executed cleanly with an old soldering pencil. The
high heat melts through the covering like butter and seals the edges so
they don’t come loose.
Paint: As with the covering, I’ll touch on a few tips and materials that
are common among SA builders that can give you a first-rate finish
for painted parts. The first step is to wash all of the fiberglass parts
with soap and water to remove any leftover mold-release agent.
The fiberglass parts from Aeroglass are smooth and have few
pinholes. Be careful not to oversand the parts. If you remove too much
of the thin top gel coat, you could expose trapped air pinholes under
the topcoat. So only a cursory dulling of the surface with fine paper is
needed. We used 400-grit paper sanded wet. I like to use automotivegrade
primer, but you must be careful that you don’t get too much
buildup. A thin coat is usually all that’s needed. Final-sand with 400
wet just to the point of an even, dull surface.
Because gasoline is less harsh than glow fuels that contain
nitromethane, you can use many types of aerosol spray-can paints with
a gasoline airplane that won’t stand up to glow fuels. I know people
who have used Krylon or Rust-Oleum paints with good results, but
finding matching colors may be a stretch. I’ve done a few nice finishes
using TopFlite LustreKote topped with catalyzed automotive clear
enamel. The two or three colors I’ve sprayed matched well and, with
ample time to dry, allowed a wet application of acrylic enamel clear
with no adverse reactions.
When using paints from an aerosol can, be aware that they must airdry,
and with that there is a fair amount of shrinkage. When the paint
shrinks, it seems to magnify any imperfections in the prepared surface,
so small sanding scratches or pinholes really show.
Erik and I prefer to paint our models with automotive paints. They
are expensive and require a little experience and special equipment. If
you’ve never painted with professional equipment and paints, you
might want to check with others in your club who have painting
experience to see if they can help.
Automotive paints are usually activated with a hardening agent and
are often topped with a catalyzed clear. Radio South sells PPG
polyurethane paint systems in the small quantities we need. The
company has done all of the work of matching the covering colors and
can advise you on everything you need to get the job done. Visit the
Web site at www.radiosouthrc.com/r_c_flying_colors.htm.
Most local paint suppliers can computer-match your covering for
you. To get a match, iron a large swath of covering—roughly 6 x 6
inches—to a piece of balsa, and bring that in to the shop. That way
you’re sure to get the truest reading possible from the computer.
Another good choice in auto paints is DuPont’s ChromaBase twostage
system. ChromaBase is slightly harder to shoot but has a distinct
advantage over other painting systems. The base colors are not
catalyzed; they go on flat (no gloss) and dry quickly. You’re ready to
remask and shoot the next color within 30 minutes each in succession.
Having proper tools for making smooth, even lines and precise
cuts gives the finished product a professional look.
Once the color scheme was finalized, Erik made full-size
poster-board templates which ensure smooth lines and a
symmetrical look.
For a high-quality finish, cover the ends first, allowing an even
overlap for the main body of the covering material.
Templates weren’t used for every piece of covering, but it
helps to make full-size drawing to fit all pieces together before
cutting covering.
40 MODEL AVIATION
Because you need not be worried about the gloss, the colors can go on
thin—just enough for even coverage, meaning you also keep the weight
down. The last layer is an activated clear that gives a smooth, highgloss
finish. Expect to spend $200-$300 for all of the supplies you’ll
need from your local automotive paint store.
Be sure to paint in a well-ventilated area. I recommend using a
good-quality charcoal-type respirator. If you’re painting yellows or any
colors that have some transparency, it’s best to shoot over a white base.
A white primer would be ideal, but that may be hard to find. You can
do a light but even coat of white base paint before you add the colors.
For perfect lines on all of your stripes, use 3M Scotch Fine Line
masking and striping tape. It is specially treated to make the paint
A quick and easy way to make clean holes and cutouts in the
covering is to use an old soldering iron with a pointed tip.
Putting covering on top of covering is the trickiest part of the
process, but with practice the results can be nice.
Lay the most transparent colors of covering on first so that the
overlapping seams don’t show through.
Many modelers prefer to use automotive paints and spray
equipment to achieve a professional finish on their aircraft.
May 2003 41
Covering a large model isn’t much different from a small one, but
working with larger sections of material takes patience and
attention to detail.
The Project Extra series is presented on the
AMA Web site at www.modelaircraft.org.
adhere to it, so a sharp, defined line results when it’s pulled away. This
tape also stretches easily so it can go around corners and curves and
create odd shapes with relative ease.
Good luck and have fun putting a quality finish on your latest project. I
think most of you will find that covering large models is almost easier
than covering the small ones. The big pieces are easy to hold, stretch,
and work with. Again, my aim was not to teach you the basics of
covering or painting, but hopefully you were able to pick up a few tips
that will help you along the way.
Next month will be the final installment of “Project Extra.” We’ll set
up the airplane for the first flights, set the control throws, do a little
computer mixing, and touch on the basics for trimming in all
attitudes. MA
Mike Hurley
11542 Decatur Ct.
Westminster CO 80234
[email protected]
A white base coat is essential for uniform finish and correct
color match. Specially treated 3M Fine Line masking tape is key
to clean paint edges and symmetrical curves.
With white base coat, only a light, even coat of color is needed
for coverage, keeping weight down and color edges clean.
Carefully remove masking paper and peel back Fine Line tape
while paint is still soft, to keep paint from chipping along edges.
42 MODEL AVIATION

Covering
and Paint
Volume V:
TRADITIONALLY, Giant Scale models have used varying methods
of finishing, from fiberglass and paint to Stits cloth and dope. Although
the results with these methods can be beautiful, many of them are
geared more toward appearance than overall final performance. That’s
not to say we aren’t concerned with appearances in Scale Aerobatics
(SA), just that we want the airplane to be aesthetically pleasing and
remain as light as possible. SA aircraft are finished like
most sport airplanes—with iron-on plastic coverings and
paint for the fiberglass parts.
Admittedly, there are craftsmen in the modeling
community who are better suited to a tutorial on
covering, so I’m not going to go too deep into the
subject. But I will try to share several tips and hints for
getting a professional-looking finish for an SA airplane.
I’ll also discuss fitting the canopy and finishing the
cockpit, and I’ll touch on methods of painting the
fiberglass parts. If you want some information on the
basics, go to www.monokote.com/monoinst1.html for
MonoKote and try http://horizon.hobbyshopnow.com/
articles/1115.asp for more info on UltraCote.
Most SA modelers use UltraCote- or MonoKotebrand
coverings. There has been a long-standing debate
about which works better and which is easier to apply.
As anybody who has ever finished a model with one of
these brands can tell you, it takes a bit of practice to get
the knack of working with iron-on coverings no matter
which one you choose. The answer to which is easier to
■ Mike Hurley
The author’s model bears his signature Bulldog Competition Aerobatics logo. Companion and mascot
Spike inspired the logo.
use is simple: the one you are used to. Erik Richards and I have more
experience with MonoKote, so we will use that.
Before the covering can begin, we have a few last-minute items to
finish up. It’s time to fit and trim the canopy. Cut the front and rear
sections out of the canopy so you can fit it onto the model. Center the
canopy side to side as close as possible. Since this canopy was
May 2003 35
With a new skin and a fresh set of colors, Project
Extra starts to take on a personality of its own.
36 MODEL AVIATION
originally designed to fit another aircraft, it is a tad too big. We cut the
canopy to the size indicated on the plans, which should knock
approximately four inches off the rear portion of the canopy.
Tape the canopy in place on the airplane. Using 1⁄4-inch Fine Line
tape (or any striping tape), mark out where you want to cut. The tape
works well for fine-tuning placement and ensuring that you get
straight lines. Carefully trim and fit the canopy. At the front edge of
the canopy where it fits over the top of the hatch, Erik left in a slight
amount of the curved fillet to give a slightly better fit and more gluing
surface.
Erik decided to finish the cockpit with a speckle-texture paint.
There are many types of texture paint; some are made to simulate
granite or stone. We used paint from Pep Boys auto parts that is made
for finishing automobile trunks.
There are a few tricks to using this speckle paint. It’s best to use a
primer base coat before applying the paint. The speckle goes on wet
and does not cover well, so the base color gives you the ability to use
much lighter coats. Be careful to keep the coats of paint and speckle
light and fairly dry, or you might warp the wood. A few dry coats are
much better than one heavy coat. Mask off the hatch well so you don’t
get overspray on the wood.
Mask the area for your dash panel. For a lightweight dash we used
a composite of some of my digital photographs that I put together on
my computer. I printed it on glossy paper and spray-glued it directly to
the wood. If you go to the Project Extra Web site (viewable at
www.modelaircraft.org/mag/index.htm), you can download the dash
image to use in your Extra.
At this point Erik has not decided on a pilot. Remember that the
cockpit area is not built to hold any significant weight, so a bit of
reinforcement to the hatch floor will be necessary if a pilot is added.
Before you begin to apply any covering, it is important to prepare the
wood surfaces. As I discuss the way we like to do it, know that there
are many ways to accomplish a great finish; ours is not the only way.
Erik likes to final-sand everything with 320-grit 3M Tri-M-ite Fre-
Cut sandpaper; it has a gray color. The 3M papers stay sharp longer
and resist loading up. Erik likes to spray-glue the sandpaper to a scrap
foam block. The foam is soft and contours to the shape of the wood
but does not allow problems from palm or finger pressure points. Use
a good-quality filler to fix any hangar rash or imperfections. We used
NHP Micro-Fill model filler. It’s easy to sand and super light.
You can seal the wood with a light coat of Aqua Net hairspray
before you sand. Once sealed, the tiny balsa fibers created from
sanding come off easier and a smoother surface can result. The
downside is that with a sealed surface, the gas created from heating
the MonoKote is more likely to get trapped as you apply the covering.
The result can be a smoother finish, but it’s much harder to avoid the
dreaded bubbles.
We decided not to seal the wood for our airplane. Once filling and
sanding are done, it’s a good idea to thoroughly vacuum all of the
surfaces to be covered using a brush attachment. The vacuum pulls the
dust from the wood’s pores. Wiping with a tack rag alone can leave
dust particles in the wood’s grain. We also spent a great deal of time
vacuuming and cleaning the shop to keep airborne dust to a minimum.
In my estimation, one of the hardest elements of any finishing job is
designing an exciting but tasteful trim scheme. Since this is a Scale
aircraft, we wanted to start with ideas from full-scale Extra trim
schemes and see if there was anything that looked good. Go to the
search engines on the Internet and type in “Extra 300.” You will
eventually find many photographs of current schemes.
Mike and Erik used three-view template, felt-tip pens to devise a color scheme. Erik used a software program to finalize the design.
Photos by the author Graphic Design by Carla Kunz
Another good source for scale information is Bob’s Aircraft
Documentation at www.bobsairdoc.com. I ordered the three-views to
use as a template for designing my trim schemes. Besides three-views,
Bob carries scale documentation for more than 650 aerobatic
airplanes—and 80 of them are Extras!
Erik and I made a bunch of copies of the three-view and spent an
entire day trying to come up with a new scheme for his Extra. We
came up with many interesting and unusual designs but decided on a
derivative of the scheme on the prototype with our bulldog mascot
Spike as the main graphic element.
Things to keep in mind as you design your color scheme are to use
colors that are easy to see and give the airplane good definition when
it’s in the air. The shape of the model—not just the outline—should be
easy to see. Dark colors tend to create a flat silhouette that makes
orientation more difficult. I use the analogy that dark covering tends to
create a “hole in the sky” wherever it’s used.
The direction of the design’s lines can also aid in orientation. If the
general design has elements that go from side to side on the top of the
airplane, orienting the design longitudinally for the bottom of the
model will help differentiate the top from the bottom. It can also help
to use colors for the bottom that contrast with the colors on the top of
the aircraft. The idea is to be able to instantly know your airplane’s
orientation without any real thought. A good design will have that
effect on a subconscious level.
Once you’ve decided on a color scheme, trace all of the outlines for
the fuselage side, wing, and stabilizer in full size. Drafting vellum
Use 1⁄4-inch masking tape to mark the canopy for trimming. Fit
the canopy to the fuselage, then apply tape as a marker.
Masking-tape cut line ensures straight line, accurate positioning.
Erik finished the interior of his Extra’s cockpit with speckle-type
paint. This method is quick and attractive.
38 MODEL AVIATION
To save weight,
Mike made a photo
c o m p o s i t e
instrument panel.
You can download
the full-size panel
from the AMA Web
site and use it in
your Extra.
works well for tracing the plans. When the outline is done, use it to
finalize the separate color details in full size. Erik used it to cut fullsize
templates from poster board. After a template is used for one
wing panel, it can be turned over and used on the other side to ensure a
uniform pattern.
To make the curves of any rounded corners come out with smooth,
flowing lines we used ship’s curves. You can get a set of inexpensive
plastic ship’s curves or French curves from the hobby store, an art
store, or a drafting-supply shop. Using these as templates, complex
curves can be drawn in a smooth and precise manner.
When you’re ready to start covering, following are a few hints that
have worked for us that may help you too. I like to keep any part being
covered on a suitable piece of upholstery foam to keep it from being
damaged during the covering process. Cover the ends and edges first.
That way, the main body of the covering hides the corner intersections
or loose ends and makes for a neat finish.
In tight inside corners, such as the transition from the turtledeck to
the vertical stabilizer, start with a strip of covering ironed into the
corner using a trim iron. With that you can cut your top layer into the
corner without having to transition the covering. The result is a seam
that is almost impossible to detect.
Stay away from putting covering over covering as much as
possible by trimming your pieces to fit the shape needed before they
are ironed on. I like to overlap the edges of neighboring covering
sections by roughly 1⁄4 inch. Put the most transparent colors on first,
and overlap with the more opaque colors.
In some cases it will be impossible to avoid putting covering over
other covering because of material expanses that transition open bays,
such as the fuselage sides on this model or between the ribs of a builtup
wing on other models. Covering adhesive is activated with heat,
and when it is too hot it will convert to a gas. When covering goes
over covering there is no place for trapped air or gasses created from
overheating the glue to escape, and the result is ugly bubbles in the
finish!
The trick is to be sure that no air is allowed between the two layers
of covering while heating the glue, and to heat it only warm enough to
make it adhere without giving off a gas. This is a tricky process that
May 2003 39
Only cursory smoothing is required on wing panels. Take care
not to remove any material from wood at risk of weakening wing.
Designing a color scheme is one of the most challenging steps
in the process. Mike and Erik kept Spike nearby for inspiration.
Vacuuming wood before covering is important. Brush
attachment helps lift sanding residue from grain, helps
covering material stay put.
takes patience, practice, and a lot of willpower, but it can be done.
There are many methods to get a smooth finish with multiple
layers. The following works well and stays put. Smaller pieces are
easier than large sections. Let’s use a stripe as an example. Measure
and cut the stripe to the needed size. The top layer of covering will be
tacked down at the starting point and held off of the surface as it’s
heated, so you must first mark off an outline of the shape to be ironed
on. Use a felt-tip pen to outline the section or to make intermittent
dashed lines. Be sure to keep it wide enough so the covering doesn’t
go over the ink. The guideline will keep you on track. It may take
some trial and error to get your covering iron’s temperature just right,
so try a few practice strips first.
The temperature should be approximately two-thirds of what you
normally use to seal MonoKote to wood. Tack down the covering at
your starting point. Using only the edge of the iron, slowly heat the
covering while holding the unheated portion up away from the
surface. Slowly work along the stripe, taking it down and heating just
to the point where no bubbles form. Use your free hand to hold the
MonoKote off the surface and guide its path.
Be sure to only heat a section the size of the iron’s edge. If you lay
the iron flat, it will heat too large an area and cause bubbles. Work
your way to the end of the stripe, holding the free end of the covering
up and guiding with one hand while heating with the other. Don’t
worry that it’s not strongly attached; it needs to hold only to the point
where there are no loose sections or trapped gasses.
After you complete the section, use MonoKote Trim Solvent to
remove the felt-tip-marker outline and seal the edges along the stripe.
The solvent will secure the stripe in place in lieu of using a high level
of heat. Be sure to get all of the stripes laid out on the fuselage before
you begin the cowl-painting process. That way you can line up the
cowl to match the stripes in paint.
For a nice finished look, any hole that needs to be cut after
covering can be executed cleanly with an old soldering pencil. The
high heat melts through the covering like butter and seals the edges so
they don’t come loose.
Paint: As with the covering, I’ll touch on a few tips and materials that
are common among SA builders that can give you a first-rate finish
for painted parts. The first step is to wash all of the fiberglass parts
with soap and water to remove any leftover mold-release agent.
The fiberglass parts from Aeroglass are smooth and have few
pinholes. Be careful not to oversand the parts. If you remove too much
of the thin top gel coat, you could expose trapped air pinholes under
the topcoat. So only a cursory dulling of the surface with fine paper is
needed. We used 400-grit paper sanded wet. I like to use automotivegrade
primer, but you must be careful that you don’t get too much
buildup. A thin coat is usually all that’s needed. Final-sand with 400
wet just to the point of an even, dull surface.
Because gasoline is less harsh than glow fuels that contain
nitromethane, you can use many types of aerosol spray-can paints with
a gasoline airplane that won’t stand up to glow fuels. I know people
who have used Krylon or Rust-Oleum paints with good results, but
finding matching colors may be a stretch. I’ve done a few nice finishes
using TopFlite LustreKote topped with catalyzed automotive clear
enamel. The two or three colors I’ve sprayed matched well and, with
ample time to dry, allowed a wet application of acrylic enamel clear
with no adverse reactions.
When using paints from an aerosol can, be aware that they must airdry,
and with that there is a fair amount of shrinkage. When the paint
shrinks, it seems to magnify any imperfections in the prepared surface,
so small sanding scratches or pinholes really show.
Erik and I prefer to paint our models with automotive paints. They
are expensive and require a little experience and special equipment. If
you’ve never painted with professional equipment and paints, you
might want to check with others in your club who have painting
experience to see if they can help.
Automotive paints are usually activated with a hardening agent and
are often topped with a catalyzed clear. Radio South sells PPG
polyurethane paint systems in the small quantities we need. The
company has done all of the work of matching the covering colors and
can advise you on everything you need to get the job done. Visit the
Web site at www.radiosouthrc.com/r_c_flying_colors.htm.
Most local paint suppliers can computer-match your covering for
you. To get a match, iron a large swath of covering—roughly 6 x 6
inches—to a piece of balsa, and bring that in to the shop. That way
you’re sure to get the truest reading possible from the computer.
Another good choice in auto paints is DuPont’s ChromaBase twostage
system. ChromaBase is slightly harder to shoot but has a distinct
advantage over other painting systems. The base colors are not
catalyzed; they go on flat (no gloss) and dry quickly. You’re ready to
remask and shoot the next color within 30 minutes each in succession.
Having proper tools for making smooth, even lines and precise
cuts gives the finished product a professional look.
Once the color scheme was finalized, Erik made full-size
poster-board templates which ensure smooth lines and a
symmetrical look.
For a high-quality finish, cover the ends first, allowing an even
overlap for the main body of the covering material.
Templates weren’t used for every piece of covering, but it
helps to make full-size drawing to fit all pieces together before
cutting covering.
40 MODEL AVIATION
Because you need not be worried about the gloss, the colors can go on
thin—just enough for even coverage, meaning you also keep the weight
down. The last layer is an activated clear that gives a smooth, highgloss
finish. Expect to spend $200-$300 for all of the supplies you’ll
need from your local automotive paint store.
Be sure to paint in a well-ventilated area. I recommend using a
good-quality charcoal-type respirator. If you’re painting yellows or any
colors that have some transparency, it’s best to shoot over a white base.
A white primer would be ideal, but that may be hard to find. You can
do a light but even coat of white base paint before you add the colors.
For perfect lines on all of your stripes, use 3M Scotch Fine Line
masking and striping tape. It is specially treated to make the paint
A quick and easy way to make clean holes and cutouts in the
covering is to use an old soldering iron with a pointed tip.
Putting covering on top of covering is the trickiest part of the
process, but with practice the results can be nice.
Lay the most transparent colors of covering on first so that the
overlapping seams don’t show through.
Many modelers prefer to use automotive paints and spray
equipment to achieve a professional finish on their aircraft.
May 2003 41
Covering a large model isn’t much different from a small one, but
working with larger sections of material takes patience and
attention to detail.
The Project Extra series is presented on the
AMA Web site at www.modelaircraft.org.
adhere to it, so a sharp, defined line results when it’s pulled away. This
tape also stretches easily so it can go around corners and curves and
create odd shapes with relative ease.
Good luck and have fun putting a quality finish on your latest project. I
think most of you will find that covering large models is almost easier
than covering the small ones. The big pieces are easy to hold, stretch,
and work with. Again, my aim was not to teach you the basics of
covering or painting, but hopefully you were able to pick up a few tips
that will help you along the way.
Next month will be the final installment of “Project Extra.” We’ll set
up the airplane for the first flights, set the control throws, do a little
computer mixing, and touch on the basics for trimming in all
attitudes. MA
Mike Hurley
11542 Decatur Ct.
Westminster CO 80234
[email protected]
A white base coat is essential for uniform finish and correct
color match. Specially treated 3M Fine Line masking tape is key
to clean paint edges and symmetrical curves.
With white base coat, only a light, even coat of color is needed
for coverage, keeping weight down and color edges clean.
Carefully remove masking paper and peel back Fine Line tape
while paint is still soft, to keep paint from chipping along edges.
42 MODEL AVIATION

Covering
and Paint
Volume V:
TRADITIONALLY, Giant Scale models have used varying methods
of finishing, from fiberglass and paint to Stits cloth and dope. Although
the results with these methods can be beautiful, many of them are
geared more toward appearance than overall final performance. That’s
not to say we aren’t concerned with appearances in Scale Aerobatics
(SA), just that we want the airplane to be aesthetically pleasing and
remain as light as possible. SA aircraft are finished like
most sport airplanes—with iron-on plastic coverings and
paint for the fiberglass parts.
Admittedly, there are craftsmen in the modeling
community who are better suited to a tutorial on
covering, so I’m not going to go too deep into the
subject. But I will try to share several tips and hints for
getting a professional-looking finish for an SA airplane.
I’ll also discuss fitting the canopy and finishing the
cockpit, and I’ll touch on methods of painting the
fiberglass parts. If you want some information on the
basics, go to www.monokote.com/monoinst1.html for
MonoKote and try http://horizon.hobbyshopnow.com/
articles/1115.asp for more info on UltraCote.
Most SA modelers use UltraCote- or MonoKotebrand
coverings. There has been a long-standing debate
about which works better and which is easier to apply.
As anybody who has ever finished a model with one of
these brands can tell you, it takes a bit of practice to get
the knack of working with iron-on coverings no matter
which one you choose. The answer to which is easier to
■ Mike Hurley
The author’s model bears his signature Bulldog Competition Aerobatics logo. Companion and mascot
Spike inspired the logo.
use is simple: the one you are used to. Erik Richards and I have more
experience with MonoKote, so we will use that.
Before the covering can begin, we have a few last-minute items to
finish up. It’s time to fit and trim the canopy. Cut the front and rear
sections out of the canopy so you can fit it onto the model. Center the
canopy side to side as close as possible. Since this canopy was
May 2003 35
With a new skin and a fresh set of colors, Project
Extra starts to take on a personality of its own.
36 MODEL AVIATION
originally designed to fit another aircraft, it is a tad too big. We cut the
canopy to the size indicated on the plans, which should knock
approximately four inches off the rear portion of the canopy.
Tape the canopy in place on the airplane. Using 1⁄4-inch Fine Line
tape (or any striping tape), mark out where you want to cut. The tape
works well for fine-tuning placement and ensuring that you get
straight lines. Carefully trim and fit the canopy. At the front edge of
the canopy where it fits over the top of the hatch, Erik left in a slight
amount of the curved fillet to give a slightly better fit and more gluing
surface.
Erik decided to finish the cockpit with a speckle-texture paint.
There are many types of texture paint; some are made to simulate
granite or stone. We used paint from Pep Boys auto parts that is made
for finishing automobile trunks.
There are a few tricks to using this speckle paint. It’s best to use a
primer base coat before applying the paint. The speckle goes on wet
and does not cover well, so the base color gives you the ability to use
much lighter coats. Be careful to keep the coats of paint and speckle
light and fairly dry, or you might warp the wood. A few dry coats are
much better than one heavy coat. Mask off the hatch well so you don’t
get overspray on the wood.
Mask the area for your dash panel. For a lightweight dash we used
a composite of some of my digital photographs that I put together on
my computer. I printed it on glossy paper and spray-glued it directly to
the wood. If you go to the Project Extra Web site (viewable at
www.modelaircraft.org/mag/index.htm), you can download the dash
image to use in your Extra.
At this point Erik has not decided on a pilot. Remember that the
cockpit area is not built to hold any significant weight, so a bit of
reinforcement to the hatch floor will be necessary if a pilot is added.
Before you begin to apply any covering, it is important to prepare the
wood surfaces. As I discuss the way we like to do it, know that there
are many ways to accomplish a great finish; ours is not the only way.
Erik likes to final-sand everything with 320-grit 3M Tri-M-ite Fre-
Cut sandpaper; it has a gray color. The 3M papers stay sharp longer
and resist loading up. Erik likes to spray-glue the sandpaper to a scrap
foam block. The foam is soft and contours to the shape of the wood
but does not allow problems from palm or finger pressure points. Use
a good-quality filler to fix any hangar rash or imperfections. We used
NHP Micro-Fill model filler. It’s easy to sand and super light.
You can seal the wood with a light coat of Aqua Net hairspray
before you sand. Once sealed, the tiny balsa fibers created from
sanding come off easier and a smoother surface can result. The
downside is that with a sealed surface, the gas created from heating
the MonoKote is more likely to get trapped as you apply the covering.
The result can be a smoother finish, but it’s much harder to avoid the
dreaded bubbles.
We decided not to seal the wood for our airplane. Once filling and
sanding are done, it’s a good idea to thoroughly vacuum all of the
surfaces to be covered using a brush attachment. The vacuum pulls the
dust from the wood’s pores. Wiping with a tack rag alone can leave
dust particles in the wood’s grain. We also spent a great deal of time
vacuuming and cleaning the shop to keep airborne dust to a minimum.
In my estimation, one of the hardest elements of any finishing job is
designing an exciting but tasteful trim scheme. Since this is a Scale
aircraft, we wanted to start with ideas from full-scale Extra trim
schemes and see if there was anything that looked good. Go to the
search engines on the Internet and type in “Extra 300.” You will
eventually find many photographs of current schemes.
Mike and Erik used three-view template, felt-tip pens to devise a color scheme. Erik used a software program to finalize the design.
Photos by the author Graphic Design by Carla Kunz
Another good source for scale information is Bob’s Aircraft
Documentation at www.bobsairdoc.com. I ordered the three-views to
use as a template for designing my trim schemes. Besides three-views,
Bob carries scale documentation for more than 650 aerobatic
airplanes—and 80 of them are Extras!
Erik and I made a bunch of copies of the three-view and spent an
entire day trying to come up with a new scheme for his Extra. We
came up with many interesting and unusual designs but decided on a
derivative of the scheme on the prototype with our bulldog mascot
Spike as the main graphic element.
Things to keep in mind as you design your color scheme are to use
colors that are easy to see and give the airplane good definition when
it’s in the air. The shape of the model—not just the outline—should be
easy to see. Dark colors tend to create a flat silhouette that makes
orientation more difficult. I use the analogy that dark covering tends to
create a “hole in the sky” wherever it’s used.
The direction of the design’s lines can also aid in orientation. If the
general design has elements that go from side to side on the top of the
airplane, orienting the design longitudinally for the bottom of the
model will help differentiate the top from the bottom. It can also help
to use colors for the bottom that contrast with the colors on the top of
the aircraft. The idea is to be able to instantly know your airplane’s
orientation without any real thought. A good design will have that
effect on a subconscious level.
Once you’ve decided on a color scheme, trace all of the outlines for
the fuselage side, wing, and stabilizer in full size. Drafting vellum
Use 1⁄4-inch masking tape to mark the canopy for trimming. Fit
the canopy to the fuselage, then apply tape as a marker.
Masking-tape cut line ensures straight line, accurate positioning.
Erik finished the interior of his Extra’s cockpit with speckle-type
paint. This method is quick and attractive.
38 MODEL AVIATION
To save weight,
Mike made a photo
c o m p o s i t e
instrument panel.
You can download
the full-size panel
from the AMA Web
site and use it in
your Extra.
works well for tracing the plans. When the outline is done, use it to
finalize the separate color details in full size. Erik used it to cut fullsize
templates from poster board. After a template is used for one
wing panel, it can be turned over and used on the other side to ensure a
uniform pattern.
To make the curves of any rounded corners come out with smooth,
flowing lines we used ship’s curves. You can get a set of inexpensive
plastic ship’s curves or French curves from the hobby store, an art
store, or a drafting-supply shop. Using these as templates, complex
curves can be drawn in a smooth and precise manner.
When you’re ready to start covering, following are a few hints that
have worked for us that may help you too. I like to keep any part being
covered on a suitable piece of upholstery foam to keep it from being
damaged during the covering process. Cover the ends and edges first.
That way, the main body of the covering hides the corner intersections
or loose ends and makes for a neat finish.
In tight inside corners, such as the transition from the turtledeck to
the vertical stabilizer, start with a strip of covering ironed into the
corner using a trim iron. With that you can cut your top layer into the
corner without having to transition the covering. The result is a seam
that is almost impossible to detect.
Stay away from putting covering over covering as much as
possible by trimming your pieces to fit the shape needed before they
are ironed on. I like to overlap the edges of neighboring covering
sections by roughly 1⁄4 inch. Put the most transparent colors on first,
and overlap with the more opaque colors.
In some cases it will be impossible to avoid putting covering over
other covering because of material expanses that transition open bays,
such as the fuselage sides on this model or between the ribs of a builtup
wing on other models. Covering adhesive is activated with heat,
and when it is too hot it will convert to a gas. When covering goes
over covering there is no place for trapped air or gasses created from
overheating the glue to escape, and the result is ugly bubbles in the
finish!
The trick is to be sure that no air is allowed between the two layers
of covering while heating the glue, and to heat it only warm enough to
make it adhere without giving off a gas. This is a tricky process that
May 2003 39
Only cursory smoothing is required on wing panels. Take care
not to remove any material from wood at risk of weakening wing.
Designing a color scheme is one of the most challenging steps
in the process. Mike and Erik kept Spike nearby for inspiration.
Vacuuming wood before covering is important. Brush
attachment helps lift sanding residue from grain, helps
covering material stay put.
takes patience, practice, and a lot of willpower, but it can be done.
There are many methods to get a smooth finish with multiple
layers. The following works well and stays put. Smaller pieces are
easier than large sections. Let’s use a stripe as an example. Measure
and cut the stripe to the needed size. The top layer of covering will be
tacked down at the starting point and held off of the surface as it’s
heated, so you must first mark off an outline of the shape to be ironed
on. Use a felt-tip pen to outline the section or to make intermittent
dashed lines. Be sure to keep it wide enough so the covering doesn’t
go over the ink. The guideline will keep you on track. It may take
some trial and error to get your covering iron’s temperature just right,
so try a few practice strips first.
The temperature should be approximately two-thirds of what you
normally use to seal MonoKote to wood. Tack down the covering at
your starting point. Using only the edge of the iron, slowly heat the
covering while holding the unheated portion up away from the
surface. Slowly work along the stripe, taking it down and heating just
to the point where no bubbles form. Use your free hand to hold the
MonoKote off the surface and guide its path.
Be sure to only heat a section the size of the iron’s edge. If you lay
the iron flat, it will heat too large an area and cause bubbles. Work
your way to the end of the stripe, holding the free end of the covering
up and guiding with one hand while heating with the other. Don’t
worry that it’s not strongly attached; it needs to hold only to the point
where there are no loose sections or trapped gasses.
After you complete the section, use MonoKote Trim Solvent to
remove the felt-tip-marker outline and seal the edges along the stripe.
The solvent will secure the stripe in place in lieu of using a high level
of heat. Be sure to get all of the stripes laid out on the fuselage before
you begin the cowl-painting process. That way you can line up the
cowl to match the stripes in paint.
For a nice finished look, any hole that needs to be cut after
covering can be executed cleanly with an old soldering pencil. The
high heat melts through the covering like butter and seals the edges so
they don’t come loose.
Paint: As with the covering, I’ll touch on a few tips and materials that
are common among SA builders that can give you a first-rate finish
for painted parts. The first step is to wash all of the fiberglass parts
with soap and water to remove any leftover mold-release agent.
The fiberglass parts from Aeroglass are smooth and have few
pinholes. Be careful not to oversand the parts. If you remove too much
of the thin top gel coat, you could expose trapped air pinholes under
the topcoat. So only a cursory dulling of the surface with fine paper is
needed. We used 400-grit paper sanded wet. I like to use automotivegrade
primer, but you must be careful that you don’t get too much
buildup. A thin coat is usually all that’s needed. Final-sand with 400
wet just to the point of an even, dull surface.
Because gasoline is less harsh than glow fuels that contain
nitromethane, you can use many types of aerosol spray-can paints with
a gasoline airplane that won’t stand up to glow fuels. I know people
who have used Krylon or Rust-Oleum paints with good results, but
finding matching colors may be a stretch. I’ve done a few nice finishes
using TopFlite LustreKote topped with catalyzed automotive clear
enamel. The two or three colors I’ve sprayed matched well and, with
ample time to dry, allowed a wet application of acrylic enamel clear
with no adverse reactions.
When using paints from an aerosol can, be aware that they must airdry,
and with that there is a fair amount of shrinkage. When the paint
shrinks, it seems to magnify any imperfections in the prepared surface,
so small sanding scratches or pinholes really show.
Erik and I prefer to paint our models with automotive paints. They
are expensive and require a little experience and special equipment. If
you’ve never painted with professional equipment and paints, you
might want to check with others in your club who have painting
experience to see if they can help.
Automotive paints are usually activated with a hardening agent and
are often topped with a catalyzed clear. Radio South sells PPG
polyurethane paint systems in the small quantities we need. The
company has done all of the work of matching the covering colors and
can advise you on everything you need to get the job done. Visit the
Web site at www.radiosouthrc.com/r_c_flying_colors.htm.
Most local paint suppliers can computer-match your covering for
you. To get a match, iron a large swath of covering—roughly 6 x 6
inches—to a piece of balsa, and bring that in to the shop. That way
you’re sure to get the truest reading possible from the computer.
Another good choice in auto paints is DuPont’s ChromaBase twostage
system. ChromaBase is slightly harder to shoot but has a distinct
advantage over other painting systems. The base colors are not
catalyzed; they go on flat (no gloss) and dry quickly. You’re ready to
remask and shoot the next color within 30 minutes each in succession.
Having proper tools for making smooth, even lines and precise
cuts gives the finished product a professional look.
Once the color scheme was finalized, Erik made full-size
poster-board templates which ensure smooth lines and a
symmetrical look.
For a high-quality finish, cover the ends first, allowing an even
overlap for the main body of the covering material.
Templates weren’t used for every piece of covering, but it
helps to make full-size drawing to fit all pieces together before
cutting covering.
40 MODEL AVIATION
Because you need not be worried about the gloss, the colors can go on
thin—just enough for even coverage, meaning you also keep the weight
down. The last layer is an activated clear that gives a smooth, highgloss
finish. Expect to spend $200-$300 for all of the supplies you’ll
need from your local automotive paint store.
Be sure to paint in a well-ventilated area. I recommend using a
good-quality charcoal-type respirator. If you’re painting yellows or any
colors that have some transparency, it’s best to shoot over a white base.
A white primer would be ideal, but that may be hard to find. You can
do a light but even coat of white base paint before you add the colors.
For perfect lines on all of your stripes, use 3M Scotch Fine Line
masking and striping tape. It is specially treated to make the paint
A quick and easy way to make clean holes and cutouts in the
covering is to use an old soldering iron with a pointed tip.
Putting covering on top of covering is the trickiest part of the
process, but with practice the results can be nice.
Lay the most transparent colors of covering on first so that the
overlapping seams don’t show through.
Many modelers prefer to use automotive paints and spray
equipment to achieve a professional finish on their aircraft.
May 2003 41
Covering a large model isn’t much different from a small one, but
working with larger sections of material takes patience and
attention to detail.
The Project Extra series is presented on the
AMA Web site at www.modelaircraft.org.
adhere to it, so a sharp, defined line results when it’s pulled away. This
tape also stretches easily so it can go around corners and curves and
create odd shapes with relative ease.
Good luck and have fun putting a quality finish on your latest project. I
think most of you will find that covering large models is almost easier
than covering the small ones. The big pieces are easy to hold, stretch,
and work with. Again, my aim was not to teach you the basics of
covering or painting, but hopefully you were able to pick up a few tips
that will help you along the way.
Next month will be the final installment of “Project Extra.” We’ll set
up the airplane for the first flights, set the control throws, do a little
computer mixing, and touch on the basics for trimming in all
attitudes. MA
Mike Hurley
11542 Decatur Ct.
Westminster CO 80234
[email protected]
A white base coat is essential for uniform finish and correct
color match. Specially treated 3M Fine Line masking tape is key
to clean paint edges and symmetrical curves.
With white base coat, only a light, even coat of color is needed
for coverage, keeping weight down and color edges clean.
Carefully remove masking paper and peel back Fine Line tape
while paint is still soft, to keep paint from chipping along edges.
42 MODEL AVIATION