Mylar covering film
Film thickness is measured in micrometres (um). One micrometre is one-millionth of a metre (= 3.94 x 10-5 inches).Weight per unit area is specified in grams per square metre (g/m2). One ounce per square foot = 305g/m2.
To cover with clear Mylar
Apply a coat of dope first to the balsa where you want the mylar to stick. Paint all the way around the LE and TE to give plenty of gluing area. Let the dope dry for a few minutes. Then rub a glue stick along the perimeter of the flying surface. Elmer's, Avery Permanent, and Uhu are reliable brands. You can moisten the glue stick if it's too dry to give even coverage.
Glue stick may also be applied to balsa with a moistened artist brush. This is a good method to use for confined areas or delicate structure.
Use glue stick full strength on carbon rod structures (diluted glue stick doesn’t have enough holding power to wrap around small radii). Lay the mylar on top of the surface while at the same time pulling it taut. After it's on, keep pulling on the excess wherever you have wrinkles. You can usually adjust it a little if you lay it on lightly at first. Then burnish down and make sure it wraps all around the circumference of LE and TE in order to maximize gluing area. For flat structures, mylar may be taped to the building board (or held in place with magnets) and the structure laid on top. Let dry overnight. For heat shrinking, use a very hot MonoKote iron or a heat gun. Do not touch carbon rod with a hot iron.
Which type to use where
For small balsa airplanes, 2um or 3um mylar is usually the best choice. For carbon rod flying surfaces or in those cases where more durability is desired, 4um or 5um is used. When using aluminized mylar, 2um usually shrinks more tightly and is easier to apply to compound curves than the 4um. 4um is recommended for use around window openings, windshield reveal molding or other detail applications, especially where it will not be heat shrunk. Small pieces such as trim strips are easier to handle if fabricated from 4um or 5um.
Clear mylar can be brush painted with ordinary model enamel, such as Testors, or equivalent. Tamiya enamel is recommended for transparent colors. Make a cartoon of the color scheme first and lay it under the clear mylar.
Aluminized mylar is generally painted in situ after application is complete. Apply rivets and panel separation lines with a pen, e.g. Sanford Sharpie Ultra Fine permanent marker.
Ink can be removed with acetone or dope thinner.
Stencil masks can be made from clear plastic (plastic bag or sheet protector) by laying the plastic over the model and tracing the desired outline with a felt tip pen. Cut out the plastic stencil and adhere it to the covering with glue stick. Paint may be applied via artist brush or airbrush. When the paint is dry, remove the stencil using a paintbrush dipped in water.
Hold a piece of clear plastic over the damaged area and trace the outline of the nearest adjacent structure. Cut away the damaged mylar covering up to the nearest adjacent structure. Glue-stick the clear plastic to an oversize scrap of mylar covering material and cut out the plastic/mylar sandwich along the line you drew.
Apply a thin bead of 5-minute epoxy around the periphery of the mylar patch and stick it to the frame. After the epoxy has cured, remove the clear plastic using a paintbrush dipped in water.
Heat shrink the patch if desired.