Model Rocket Finishing Techniques

By: Dave Davis

When you finish a model, does it have streaks and bubbles in the paint? Do the fins have deep grain marks in them? Do you hesitate to show it to experienced modelers? A good model rocket doesn't look like it's made of paper and balsa. It looks like a perfect miniature of the real thing, as though it was made of a solid piece of mirror smooth metal or plastic. There's nothing secret about good appearance. It's the result of extra care and right materials, with the purpose of this article to give you a general overview of finishing techniques and a process for insuring an improved, consistent appearance to your model vehicle.

Preparing the surface

The finish of a rocket starts with the very first steps of assembly. Sloppy gluing and other messy habits will ruin the appearance of a rocket so that nothing can be done to get the perfect appearance which is desired. On the other hand, careful construction will make a model look good even before the paint is applied.

Before anything is glued to it, the body tube should be prepared for finishing. Most regular commercial kits utilize a spiral wound body tube and due to this spiral nature, there are often gaps along the spiral lines on the outside of the body tube. In order to fill this gap, first squeeze a 1" length of Squadron Green Putty into a small glass container an mix it with an equal amount of Aero Gloss thinner and then brush this thinned mixture into the spiral gap and let dry. After the putty dries sand the gap smooth with 3M Wet or dry 400 grit sand paper and if any gap still shows repeat the process. After sanding, all dust is removed with a soft cloth. For you family types, a discarded cloth diaper works very well. The fins should be sanded to shape and smoothed out with the 400 grit wet or dry paper also. Since it is easier to sand the fins before they are glued in place, as much sanding as possible should be done now. Do not apply balsa filler or paint yet, however, as eithe material will fill the pores in the wood enough to keep the glue from penetrating and making a good joint.

The nosecone can generally be finished separately from the rest of the model. When working on it, hold it in a scrap piece of body tube. Sand it smooth, then follow with the normal sealing and painting procedure as described later in this article.

Using Sealer

After all parts have been glued in place, apply a coat of Aero Gloss Balsa Fillercoat to all exposed balsa surfaces. Avoid getting the filler coat on white glue or the body tube. After you have painted on the first coat, follow immediately behind it with a second coat while the first coat is drying. Set the model aside and let it dry thoroughly. Four hours is often the best drying time. When the humidity is high it's better to allow a full day.

When the balsa filler is completely dry, sand thoroughly with 400 grit "Wet or Dry" sandpaper. Wipe the dust off the surface, and repeat this filling cycle. Continue applying balsa filler and sanding until all the grain in the balsa is filled. This requires patience and a minimum of three cycles. The actual number of coats of balsa filler necessary varies from one sheet of balsa to the next and also depends on how thoroughly the surface is sanded. Practically all of the fillercoat should be sanded off after each coat. The purpose of this procedure is to fill the grain, not the smooth areas of the sheet. Models with basswood or plywood fins can also be filled in this manner, however, fewer coats are needed.

The Primer Coat

With all of the balsa filled on the vehicle, you are now ready to start full scale painting. But, before the paint goes on the surface must be primed. As in the professional world the base material surface should be primer coated to provide a binding surface for the finish paint coats an to finish out any surface irregularities. Any good auto spray primer will work with white primer used in light colors, gray used in medium colors and black used with dark colors. Spray the primer on as you would any spay paint and let dry. Sand off any dimples or dust marks and finish off a final sanding with 3M 600 grit "Wet or Dry" sandpaper.

Apply the Base Color

Once you are satisfied that the surfaces of the model are perfectly smooth and that all of the grain has been filled, it's time to apply the base color. If the model is going to be painted all one, non-fluorescent color, the base coats will be the final coats. When the rocket is to be painted a fluorescent color, the base coats should be flat white. In all other cases, the base color should be the lightest of the final colors. For example, when a rocket is to be finished with red, black and yellow, the yellow should be applied first. Enamel and Acrylic/Enamel type paints are recommeded, in that there are too many application problems with butarate dope and enamel based paints are lighter.

To build a good spray wand to support your vehicle, a three foot length of 1/2 inch dowel rod is needed. The dowel will fit inside BT-5 and RB-50 tubes and a regular engine casing will fit over the dowel for BT-20 and RB-74 birds. A "D" engine casing will fit over the regular engine casing for your BT-50 and RB-93 vehicles. This spray wand allows you to rotate the vehicle easily while you are painting it and allow you to dry the vehicle in a horizontal position lessening the chance of runs.

Apply a light, even coat of the base color and set the model aside to dry. It is important to apply only a light coat; if too much paint is put on the rocket at once, it will run. Since a run in the paint is virtually impossible to hide or correct, it is wise to use many thin coats rather than a few thick coats. When the first coat has dried, apply a second, keeping it light and thin, Continue until enough coats have been applied to give a clean, pure color. Finally set the model aside in a dry, warm, dust free area for at least a day to let the paint dry completely. The longer the paint cures, the fewer problems will be apt to arise when further colors are applied.

Add the Second Color

When the base color has cured completely, cover all the areas on the model which are to remain this color. Small areas should be covered by applying masking tape directly to the surface. Large areas should be covered with ordinary typing paper and the edges sealed with masking tape. It is important to seal the tape down tightly along the edge. A light coat of clearcoat over the seal area is a definite plus. If you have a steady hand, it's possible to apply the second color by brush without masking. However, unless you're very sure of your abilities, it's best to go ahead and mask. Apply the second color at the same rate as you did the first color remembering to keep the coats thin and even and remembering to let each dry properly before putting more on. Try to use just enough paint to get a clean color. Too thick of a layer of paint can cause trouble when removing the masking.

After the last coat of the second color is in place and has dried so it can be handled safely, remove the masking. There are two accepted procedures used here, and the modeler should experiment to see which will work best for you. One way is to simply pull the tape with a sharp knife blade before pulling it up. In either case, the tape should be peeled off by pulling almost parallel to the rocket surface. When the paint is completely dry, sand the edges of the second color very lightly with very fine sandpaper.

A third color is applied in the same manner as the second, with the areas which are to remain the first tow colors masked over. Often it is best to leave the masking which protected the first color in place and add more masking to protect the second color area. In this way it will not be necessary to try to line up another piece of tape between colors.

Finishing Touches

Decals should be applied following the instructions which come with the decal sheet. Warm water soaking times and handling methods will vary slightly. However, in almost all cases the decal should be slid on the backing so one edge is barely off the paper. This edge is then positioned against the vehicle and held in place with a moist finger. Pull the backing sheet out from under the decal and smooth it down and blot away any excess water with a damp rag. That old discarded diaper comes in handy here too.

Roll patterns, stripes and bands may be applied with either decals, Chart-Pak chart tape or adhesive backed Monokote. The pieces should be cut to size before application. When using decorating tape, narrow stripes can be made by laying a length of tape, adhesive side down, on a smooth, hard surface and cutting the correct width wit a ruler and a sharp knife.

When a model has been finished with fluorescent paint it helps to apply a light coat of clear spray before adding decals or tape. The clear coating keeps the paint from rubbing, pulling or washing off. It is generally best to apply several coats of clear to the entire vehicle after the decals have dried completely, whether the paint is fluorescent or not. The clear coats seal down the edges of the decals and help prevent chipping and peeling.

Before applying wax, be sure that any fluorescent paint is covered with several coat of clear. Waxing will smear unprotected fluorescent paint. The same precaution should be taken with most metallic paints. Wax should be applied with a clean, soft cloth. Here comes that old diaper again. Future floor wax is excellent, as it applies easily and does not yellow. Only a very thin layer is needed; if too much is applied it's only wasted. Polish with another clean, soft, dry cloth. (Who's ever heard of a polishing diaper). Waxing does not make a surface particularly smoother; what it does do is protect the smooth surface below. If the vehicle doesn't shine as much as you'd like after waxing, the best thing to do is to work the vehicle over with automotive rubbing compound and rewax.

By practicing finishing the right way and paying close attention to detail, the modeler can produce a professional quality finish. Some modelers, in fact, will produce better than professional finishes.