Work with light plastic film for Micro FlyersInexpensive and easy to useBy Dave Robelen Very small, light models are becoming quite popular. In the past, most of these models have been covered with some form of tissue paper. Although tissue covering can be quite attractive and light, there are occasions when an alternate material would serve better. There are plenty of plastic films on the market designed for standard RC models, but they are often too heavy for the lightest models (those being flown with micro equipment). Several commercial films that are not specifically designed for RC models are quite thin and light, and they are well-suited to light models. These products are usually marketed by specialty suppliers and are therefore less well-known. Reynolds Plastic Wrap (plastic film, sold in grocery stores) does an excellent job as a light model covering and comes in a variety of colors. Other products, such as trash-bag liners and dry-cleaner bags, have also been used with some success. This article compares three products-Reynolds Plastic Wrap, Mylar and RA Microlite-and shows a typical application. Let's begin by comparing approximate weights: Reynolds Plastic Wrap weighs 0.00833 gram per square inch; 0.0015-inch-thick clear Mylar weighs 0.0055 gram per square inch; RA Microlite weighs 0.00333 gram per square inch. Both the Reynolds plastic film and the clear Mylar will weigh slightly more when applied because the adhesive is not coated onto the film and must be added separately. To get an idea of how this affects a model's weight, consider my Plinker, which has a wing area of 60 square inches covered on both sides. It gained 1.8 grams with the Reynolds plastic film, about 1 gram with the clear Mylar and 0.7 gram with the RA Microlite film. In terms of warping power, Mylar tends to have the most "pull," which causes the wing to bow noticeably. RA Microlite film causes some bowing, while Reynolds plastic film has minimal warping tendencies and won't bow the most fragile parts. Reynolds plastic film seems to be the most damage-resistant; it is better able to resist being punctured and torn, while the other two films are more easily punctured and tend to tear more readily once punctured. Because of Reynolds plastic film's unique characteristics, I am going to describe in more detail its application on a model. The Reynolds film technique is unique because both the covering material and the adhesive come from non-hobby sources. In fact, all of the materials you need may be found in a modern "super store" such as Wal-Mart. The wrap itself is in the grocery department, the spray glue can be found in the hardware or crafts section, the lighter fluid is from the smoke shop and the tools are from other departments! The 0.0015-inch-thick clear Mylar is sold by Model Research Labs, and the RA Microlite film is available from David Lewis. Balsarite film adhesive, distributed by Coverite, is available from the usual hobby channels. The most distinct difference among the covering methods is the minimal heat required by the Reynolds plastic film; the other two films are attached with a trim seal covering iron. When I cover a larger part, such as a wing, I find that, because of Reynolds plastic film's "clingy" nature, it is easier to smooth out over a sheet of poster board. You can glue "handles" to the sections of plastic with a glue stick. Small, flat parts such as the tail surfaces can be coated with the adhesive and pressed onto the smoothed-out plastic, while the strips for the fuselage are small enough to lift off the poster board and apply to the model without a problem. 3M Super 77 spray contact cement works well with the Reynolds plastic film. I spray small amounts of this into a spray-can cap, thin it slightly with lighter fluid and then brush it onto the frame. I apply the plastic while the glue is still sticky. Allow the glue to dry for several hours before you shrink the film. The Reynolds film shrinks with very little heat compared with the Mylar products. I have had fine results with a hair dryer, a floodlight bulb and even a furnace vent as sources of heat for shrinking. Modellers in warm climates have reported good results by putting the model parts in a closed automobile that is sitting in direct sunlight. To apply clear Mylar film, first coat the framework with Balsarite for film, and when that has dried, attach the film using a trim seal iron set on high heat. You can shrink the film with the same tool. RA Microlite film comes with an adhesive coating that's quite adequate, except for use on the bottom of under-cambered ribs, where I use Balsarite. Use the trim seal iron to attach and shrink the film. These films, used with the adhesives described, are suitable for all model types that do not use glow fuel. Most of these adhesives are not fuel proof, although they can withstand moisture.
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