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Film Covering |
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The following brief text and pictures describe a lecture very kindly given to The Country Squire Modelers at our February 2002 meeting.
With thanks to Irwin Weisbrot for the text and Mike Minty for the photographs.
Faye used a typical wing and Monocote
He says: all films are basically polyester, but there are some manufacturing differences that make each brand slightly different, especially temperature of glue set, stretch, shrink, and burn.
MUTT to prevent a dog.
M minimal film to avoid sag: stretch during application minimizes amount of film on structure
U uniform tautness: if the amount of tightness (stretch) varies, the tight areas will loosen when exposed to heat of sun.
T tight application cold: pull film during initial tacking
T tighten some more: using heat gun like a brush, pulling the film from the center to the edges with a gloved hand.
Start with a generous piece of film so it is east to grasp. Use small flat detail iron.
Tack a small area in center of LE and TE, pulling across chord of wing, then:
Tack a small area at each end of the panel. This will produce large FOLDS or WRINKLES in a Diamond pattern. This is good. Wrinkles or folds oriented in straight lines or across are no good because they cannot be easily pulled out
Next, working from the centers out to the ends, pull and tack in small increments alternating LE and TE while pulling at a slight angle out and away from the center towards the ends of the wing. This has the effect of opening up the "diamond" pattern of folds.
Next, the heat gun is" brushed" from the center to the LE or TE while pulling on the excess film progressing along the length of the wing.
At the tip, especially if rounded, tend to pull the heated film away from the center as it is gradually adhered to the wing tip edge. Then the final tack down around the tip using a hot trim iron to stretch the film around, making a sharp margin to cut extra film away.
Then, you may wish to use a regular iron to glue the film to the underlying wood. But that is a final step after all the stretching has been accomplished.
Note that Faye emphasizes stretching rather than shrinking.
Stripes: place the film glue side down on a piece of slightly moistened clean glass. Use only water. Smooth out and cut the stripe. Place on the site and adhere by PATTING down with the iron; don't push or smooth down; it will distort the strip.
If you want a fancy double stripe, cut out the center one and lay some low tack 3M tape to hold the spaced stripes in position. It comes off easily after the stripes have been adhered.
Faye uses a good metal straight edge and single edge razor blades.
You've really got to see it to appreciate how it works. So, come to the meetings!
For further articles by Faye, visit Model Airplane News or click below: