Airplane Kit Finishing
Now that you have built up your airplane kit , you will need to finish it with covering material or paint. Here we'll describe various covering materials and paints and how they are applied.
Covering
Most wooden airplane kits actually do not look like wood. They are covered with a material that bonds to the wood structure. These coverings come in a variety of types. I'm used many of these, here a few brief thoughts:
Tissue
This is not Kleenex, but more like gift wrap tissue. It really is paper, and comes in different grades (weights). I'd suggest that you use the Japanese tissue available at the hobby shop, although I've gotten by with gift wrap tissue in a pinch.
Tissue works best on the lightest models, usually balsa models designed for freeflight (not RC). It has a noticeable grain to it, and this grain should be applied in the direction needing most strength (e.g. spanwise for wings). It is traditionally applied to the wood frame with dope, although I prefer thinned white or yellow glue as these work fine and the fumes are less harmful.
Once the tissue is applied to the structure, it is shrunk tight with a light mist of water, then sealed with dope. You can also seal with Testors or Krylon spray enamel, which are more convenient to apply.
Silk
This covering is actually woven silk fiber. Applied with dope. You don't see this one very often these days.
Silkspan
This is like tissue but contains other fibers, and is generally stronger but heavier. Can be applied in the same manner as tissue. Is also a good covering for foam.
Fiberglass
This woven material is great on solid structures, but no good over open areas. Can be used to seal balsa wood or foam. Comes in a great variety of weights, the lightest (0.5 per square yard) being very light but flexible. This is a great substitute for silkspan when covering foam. May be applied with expoy (wood) or water-based polycrylic (foam). Adds great surface strength for very little weight. Here is some more info on applying this material over wood:
http://home.fuse.net/ryan/glassing.htm
Plastic Coverings
Plastic coverings are also known as polyester films, or heat-shrink coverings. These are applied to the wood frame with heat, which activates an adhesive layer on the underside of the film. Once the film is attached to the finished airplane kit frame, it is then shrunk tight with heat. This is generally more convenient that using glues or dope. I've used several types of these over the years, here are some mini-reviews:
Monokote
One of the most common plastic films. Has a great variety of colors, including flat military colors not found in other brands. Generally easy to work with.
Ultracote (Oracover)
This is my favorite plastic covering. Similar to Monokote but in my opinion, easier to work with.
Litespan
This film is much lighter than Monokote or Ultracote. It has no adhesive on the underside so Balsaloc must be applied around the airframe edges with a brush. Doesn't shrink quite as drum tight as the other films.
Solite (Litefilm)
This film is super light and has adhesive on the underside. I find it easy to work with, although there are reports that some colors have static cling issues. Also note that some of the "opaque" colors are somewhat translucent. Still, an all-around good choice for a light weight parkflyer kit.
If you need to know how to apply this type of covering, check out the Heat Shrink Covering Procedure.
Painting
Another option for finishing an airplane kit is painting. In general this applies to solid wood or foam structures. In some cases, plastic film or fabrics are applied over open structures, then later painted.
The wood or foam structure must be sealed before painting. This produces a smooth surface to deposit paint. It also means that less paint needs to be used, reducing the overall weight of the finished airplane. A primer coat is often applied after sealing.
Its function is to create a surface that will bond well (chemically) with the paint layer, producing a long-lasting paint coat. Follow the paint manufacturer's recommendation on which primer to use.
There are several types of paint, each with its own benefits. Some examples are: dope, enamel, acrylic and latex. Dope was at one time the standard, but other paints have emerged. Enamel gives a great finish but is tricky to cleanup and dries slowly.
My favorite is water-based acrylic: dries quickly, easy to cleanup, and does not attack foam or wood.
Acrylics tend to dry flat, so gloss finishes are best achieved with a separate clearcoat. If your model plane kit will use glow or gasoline fuel, the paint finish will need to be fuel proof.
Many common paints are not fuel proof (e.g. acrylic will be attacked by alcohol). So make sure to apply a fuel proof clear topcoat. Paint can be applied by several methods: Brush, Spray Cans, Airbrush. Brushing is perhaps the lowest cost solution, although it can be tricky to get nice smooth even coats of paint.
Spray cans deliver even paint coats, but are a limited supply. The best painting solution is really the airbrush.
When equipped with an air compressor as the air source, it becomes like a never-ending spray can, with the added benefits of control of the air pressure and of the paint amount.
A good airbrush can paint small plastic display models as well as large RC airplane kits. It is somewhat of a luxury tool, but the committed modeler will eventually want to own one. Badger makes high quality airbrushes for reasonable prices.
I have also been impressed with the Paasche line. Go here for our comprehensive Airbrush Tutorial.
So now your airplane kit is built, and you're wondering, "How do I fly this thing?" Go here for flight instruction.