- BODY PAINTING, TRIMMING AND MOUNTING TECHNIQUES There's truth to the rumor that
"Gardner's always been a man of too many words." This article will be no
exception. So, with apologies to Paul Meiers, here's something that should be of help to
everyone who's ever become frustrated trying to mount a body on a slot car. Next to a
good-handling chassis, a "rocket" motor, a smooth gear mesh, round tires, level
guide flag, clean and flat braid, good lead wires and all the proper electrical
connections, the most important facet of a good handling slot car is a body that is
properly painted, detailed, trimmed, reinforced and mounted. We'll go step by step through
all the points you need to know to insure each car will have excellent handling
- PREPARATION AND PAINTING It's easier to mount a body before it is painted. However, you
must be careful when painting a pre-trimmed body to prevent overspray from getting on the
outside. If you decide to trim-to-fit before painting, cover the outside with masking
tape. We prefer to paint the untrimmed body first. Clear Lexan bodies are always painted
from the inside. First, mask off the windshield and side windows. You can use masking
tape, then trim carefully around the window lines with a sharp #11 or #16 X-acto blade in
your knife. The best method for window masking we've found is STS-10 liquid mask. It's a
yellow liquid, cheap at $2.19/bottle, comes with its own brush applicator, and will do a
lot of bodies if you keep the lid on tightly between uses. A light coating on the window
areas is all that's needed. Allow it to dry thoroughly before proceeding. Once dry, place
the body over your chassis. Make sure to allow for proper guide flag clearance at the
front in order for the flag to turn freely from side to side and not hit the nose.
Usually, 1/8" to 1/4" back from the nose is sufficient and should be positioned
in such a manner as to fit any rise at the front, molded into the body. On low-slung
"wedge" bodies, such as the Parma Challenger, Outisight Tigas, etc, or any body
which already has a molded-in flat Diaplane, the flag must be behind that, fitting into
the raised area. (Looks like a small "hump.") Many racers cut the excess
material off the guide flag post to insure enough front end clearance and get the body as
low as possible. Once correctly positioned, put a small dot opposite the front axle on the
outside of the body with a Sharpie pen. Lift the body off the chassis. Using round,
3/4" Avery labels, center one each on the inside over the tiny dots you made to mask
off where the front wheels will show. Press down firmly so paint will not seep under the
edges. You must avoid getting greasy fingerprints on the inside of Lexan bodies. These can
be removed with a dab of lighter fluid or denatured alcohol on a clean rag. Some racers
will wash the inside of a body using hot water and scouring powder before they begin
masking operations. This generally isn't needed any longer since the paint used today, is,
for the most part, lacquer based. This paint will "eat" into the polycarbonate
material from which all modern bodies are vacuum formed. Commercial body painters have
expensive, sophisticated and well-ventilated spray booths. Most use Paasche or other
airbrush systems with the air coming from compressors. For the person painting only a few
bods, Pactra or other spray cans are more than sufficient. Another coloring product that
works on Lexan are spray cans of shoe dye. These also come in a variety of colors and are
available from any shoe repair shop that dyes women's dress shoes. Bodies can also be
brush painted, but the serious racer dislikes the added weight. Use extreme caution with
any lacquer-based paint. This material is highly flammable and should always be used in
well-ventilated areas. We recommend you go outdoors so as to prevent breathing the fumes
or getting overspray all over everything! For the serious hobbiest, Badger makes a good,
reasonably priced spraying system that uses cans of propellant. If you like stripes or
other wild designs, Pactra makes a good masking tape in sizes 1/16" to 1/2"
wide. Again, lay the tape in where you want a second color and carefully press it down
onto the body. Since we're painting the inside of the body, always start with the darkest
color first, ending with the lightest. For the racer who likes the three numbers placed
against a white circle background, use three more of the 3/4" round dots. Put one on
the inside on the left front fender and one on each side, either on the doors or the rear
quarter panels. On low-slung bodies, some will place them on the top at the rear of the
body. When all your other painting is done, carefully peel these circles using the edge of
your knife blade, then spray with white paint. (Don't remove your windshield/window
masking or the front wheel opening dots until you are completely through with the painting
operation.) Before you attempt painting your first clear body, look closely at one
produced by a commercial painter. If you hold it up to a light you'll instantly notice
that the paint has been applied rather sparingly. You can almost see through the sides!
The joke is that California painters spray the paint in the air, then wave the body
through the mist! Once you're ready to begin spraying, start with the darkest color. If
you use "candy" colors, they should be backed with silver or gold spray paint to
make the "candy" color look metallic. If you prefer bright colors, such as
florescent, these must be backed with white spray paint to make them "glow."
Move the spray can back and forth to prevent a buildup of paint. (You don't want it
applied so thickly as to cause the paint to "run.") Apply light coats, allowing
each to dry or at least get "tacky" before putting on the next color.
Remember...darker colors are harder to see through than light colored hues. Let the
primary color dry, then peel off any masking tape you've put in place where you want a
second or third color. Spray paint will not go up into the narrow space between the inside
and outside "wings" of Challenger-type bodies. Don't worry about it. Just get as
even and smooth a coating as possible. When the painting is complete, set the body aside,
preferably overnight. Next, remove the front wheel dots and the windshield/window masking.
The liquid mask can sometimes be removed by pressing a piece of masking tape over the
area, then gently lifting. Generally, lacquer based paints will dry to the touch rather
quickly. Be patient!
- TRIMMING THE BODY FOR FIT We've stressed the importance of how low bodies should be
mounted. For optimum handling, and to be sure you pass all tech inspections, there should
be 1/16" clearance under the front and both sides of the body as well as under the
entire chassis and rear spur gear. Some rules state that front wheels must touch and roll
on certain classes of cars. Other classes state that the front tires must touch and roll
before the chassis hits the track. By the time you're racing International 15's and up,
you only have to have front wheels on the car. Some are mounted in such a manner as to
never touch. They're just there because the rules state all cars must have four wheels and
a guide flag. (When you get to these higher levels you're basically running a tripod-the
flag and rear tires are the only things touching. We've seen cars where the Diaplane
actually rests on the running surface, picking up glue as the car goes around the track.
This can adversely affect handling because glue on the Diaplane can deslot a car. Plan to
start with 1/16" clearance all the way around. Air, moving across the body will force
the car down, almost to the track surface. We'll get to this later. First, rules state
that no molded-in detail, such as grills, openings, etc. may be removed. Other than bodies
which have a molded in Diaplane (i.e. Challenger), all should maintain at least some
semblance of a front bumper-a vertical portion remaining at the front. For NASCAR and/or
GTP, this needs to be at least 1/8" to 1/4" in height. The easiest way to trim
this and make sure the line across the front is straight, lay a 1/8" wide strip of
Pactra masking tape on the outside. Using a pair of sharp, regular, straight scissors,
trim along the bottom of the tape. Then cut the rear of the body out by starting on an
angle near the back. Cut up, then across the rear of the body, and down the other side. On
a Group 10 body leave at least 1/4" of down-turned material at the back for a bit of
additional strength. On bodies to which you will later add rear spoilers and side dams,
cut the back off at the mold line. You've now removed the front and the rear, but still
retain the sides. Before we proceed, here is a list of important items for you to have on
- 1. In addition to the straight scissors, have a pair of good curved (cuticle) scissors.
- 2. A body mounting block. The best is a JK #171 which has milled slots for the flag and
all four wheels to fit into, so the chassis sits flat on the block. Your second choice
would be a 3" wide wooden body block with a slot.
- 3. A good ball point pen. We use a Uni-Ball fine with black ink.
- 4. An X-acto knife with a new #11 or #16 blade. We recently discovered a new knife made
by ProEdge. (#12042) It won't roll off the table and you tighten the blade by twisting a
knurled knob at the bottom rather than the top.
- 5. A trim guide made from a piece of .032" thick K&S brass strip. We use one
1/2" wide by 8" long. We also have several made for different bodies. We've
soldered pieces of piano wire on one end. (See diagram of the one we use for Challengers.)
- 6. Champion or Parma Diaplanes.
- 7. Assorted rolls of tape: A. 1/2" wide double-sided Scotch tape. B. Rolls of
1/2", 3/4" and 1" strapping tape.
- 8. Pre-painted interior. We have ours painted by Ron Jones and also sell a lot of Big
- 9. A set of Champion racing numbers and assorted Parma decals.
- 10. One each black Parma or Sharpie detailing pens-fine and ultrafine.
- 11. A 6" steel rule.
- 12. A pin-vise with a needle or straight pin installed. This is used to pre-punch holes
to later mount the body to the chassis using either body clips or straight pins. We
received a neat gadget for punching holes from one of our racers. You can get one of these
wooden handled items from any printers supply house. They retail for around $5.50 and are
well worth it. They are called litho needles and used to scratch film negatives. The trade
name of the one we have is Zupanc (pronounce "Zoo-pank"). The Zupanc needles
come in a variety of sizes, starting with #1. You'll want one with a needle the same
diameter as a straight pin.
- You're now ready to trim off the excess material on both sides of the body. You will
want to have the body low, but still clear the guide flag in the front and be at least
1/16" above the motor at the rear. Place the body on its side. Measure down 1
3/8" from the top of the inside at the back and make a mark with your ball point pen.
Repeat on other side. Lay the strip of brass plate even with the trimmed area at the front
and on the mark at the back. If you're REAL careful, you can trim this off with an X-acto
knife. I prefer to draw the line, using the brass as a guide, then cut it off with my
long, straight scissors. Once both sides are trimmed, lay the body sideways across your
block and look from the back of the body. Be sure both sides are the same and the body
sits level. If not, re-trim one side until both sides are the same and level. Before doing
any reinforcing to the body, you are now ready to mount it to the chassis.
- MOUNTING THE BODY You must start with a chassis/motor/tire combination which is flat and
not "tweaked" or bent in any way, shape or fashion. Place the chassis onto your
body block. If you have a body block which has the milled holes, so much the better. Place
the body on top of the chassis making sure you have adequate guide flag clearance at the
front. The body should sit level and flat, even with the bottom of the chassis. If you
must use a wooden body block, (which has a slot cut for the guide flag) tape or super glue
two 4" pieces of 1/16" piano wire across the width of the block between the
front and rear tires-approximately 2" to 2 1/2" apart. The body will rest on top
of these, flush with the bottom of the chassis and should look as it will when it rests on
the running surface of your track. You should be able to see the front wheels on both
sides through the clear wheel well areas at the front of the body. Holding the
block/chassis/body combination up to a light, you should be able to "see"
through the sides of the body and locate the mounting holes of the chassis pans. This is
more difficult if you've already installed pin tubes. Once the body is sitting flat and
where you want it, use your body pin gadget and punch the two holes. If you're using body
clips, install one on this side. If using pins, install the two on this side. Turn block
around. Holding body and chassis together, pick it up and check for squareness by looking
at the bottom. Make any slight adjustments until the front and rear wheels are square and
properly aligned in relation to the body. Carefully return the combination to the block
and punch the holes on the other side. Install the other body clip or two straight pins
into the tubes. Check the finished mounting before proceeding. If not square on the
chassis, re-do one side. Check body/chassis level by laying it sideways across the block.
Is there at least 1/16" clearance between the top of the body and the top of the
motor, especially above the solder tab? When you set the car on your body block or the
track, does the body have 1/16" clearance at the front and both sides? Is the front
and back of the body level? If not, don't be discouraged...just start again. While going
through this learning process you'll probably end up with a body or two that looks like a
piece of swiss cheese from all the holes you've punched. Don't worry about it. We're going
to reinforce those pin holes anyway.
- REINFORCING THE BODY FOR RACING There are many who do not reinforce their race bodies,
feeling that if a body gets knocked off in the heat of a big race, they've lost anyway.
But they are good drivers, and don't crash that often. Until you get to this point in your
driving skills, take the extra precaution and add some life to your bods. Remove the clips
or pins and sit the chassis aside. The first thing we're going to do is to add some
strength to the front end. Using a Champion or Parma Diaplane, put double-sided Scotch
tape on one side. Place this up inside the front of the body. If you're mounting a
Challenger, trim off 1/4"-to the fold line-but leave the "legs." Once in
place, cover with a 3-1/4" x 3/4" strip of strapping tape, folding 1/8"
around the front and up over the top of the molded Diaplane of the body. Now add another
piece of 3/4" or 1" strapping tape on the inside, just behind the first piece.
You may want to cut two small "notches" so this piece will fold down into the
recess where the guide flag will ride. Be careful not to put any strain on the tape. Just
lay it in, press it down and trim off the excess level with the bottom of the body. Lay
another piece of 1/2" or 3/4" strapping tape (cut exactly 3-1/4" wide) at
the back. Tuck it into place to reinforce the top rear of the body. While not necessary,
you can also add 3/4" strips on the inside going down both sides from the back to the
front which will protect and add life to the top of the body. We also put a small piece
directly about the solder tab to prevent body movement from scraping paint off the inside
where the body sits directly above the motor. To reinforce the mounting holes for body
clips, lay one or two thicknesses of 1/2" or 3/4" strapping tape down both
sides. Make them long enough to go from the front wheel clear area all the way to the back
of the body. Reinforcing for pin mounts requires a careful and slightly more tedious
procedure. Lay the body on its side and install a strip of double sided Scotch tape long
enough to cover the holes. Choose either Slick 7 (#118) pin hole reinforcements (we call
'em 1/24" Ninja Stars) or use a hole punch and cut four circles of Diaplane material.
Lay these on a piece of cardboard and punch pin holes through them. Install straight pins
through the pre-punched holes and double-stick tape on one side of the body. Install a
"Ninja Star" or the Diaplane circles over the pins. Press these down firmly onto
the double stick tape and remove the pins. Cover the reinforcing pieces with 1/2" or
3/4" strapping tape, then stick the pins back through the holes. If you've been
careful, the body should now mount to the chassis with ease and no trouble. You are now
ready to use your curved cuticle scissors and trim away for rear tire clearance. Always
cut away enough of the body to give you at least 1/8" clearance around the rear
tires. Now, remove the body from the chassis and do your race detailing.
- MAKING YOUR BODY RACE LEGAL AND A CONCOURS WINNER Even if you're a beginner you should
start now to take pride in your cars. These are not toys. They are sophisticated pieces of
high-tech equipment. Rules state that no car can be raced without three numbers and a
driver interior. We've seen people enter races with tiny numbers drawn with a Sharpie pen.
Ugly! You've got more pride than that! Install a set of Champion or other printed numbers.
Buy a Parma decal sheet and put a few appropriate sponsor decals on the car. Take the
ultrafine end of the Parma or Sharpie pen and blacken-hood vents, door lines, etc.-on the
top and sides. Use the fine black Sharpie or the other end of the Parma detailing pen and
draw black lines around the windshield and side windows. Trim the driver interior and
install the driver in the cockpit. Secure interior to the body with a couple of small
strips of strapping tape. Remount the body. If using the body clips, cut small pieces of
strapping tape and cover the clips on both sides, letting part of it fold under the body
and attach to the chassis. This will prevent the body from coming loose in a crash. We
prefer the use of body pins since they are much neater and easier to use. However some
low-end class rules-Group 10, Womps, etc. do not allow the use of body pins. Check with
your raceway owner as to what is allowed. Play by the rules for whatever class you're
racing. With practice, and doing several bodies to gain experience, you'll be able to do
all these things in less time than it took to read my ramblings. If you have difficulty,
check with your local raceway professional for answers to all your questions.Once you've
become proficient at painting, trimming, reinforcing and mounting bodies, share your
knowledge with newer racers. Sharing help and ideas are two things which make our
hobby/sport the great activity it is!