What is Slotcar Racing.
By Ray Gardner
Wheelie Car Basics.
by Peter Shreeves
What You Want To Know About Magnets.
By John Sojak, Trik Trax, Inc.
Improve The Handling Of A Slotcar Chassis.
By Ray Gardner
Build and repair a Slotcar Track!
by Ray Gardner with a slight edit by Bob Herrick
Body Painting, Trimming And Mounting Techniques.
By Ray Gardner
An International Affair.
By Dan Green
Last modified: September 29, 2005

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BODY PAINTING, TRIMMING AND MOUNTING TECHNIQUES
by Ray Gardner.

  • 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 characteristics.
  • 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 hand:
  • 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 Leo's.
  • 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!