HYPERION
Easy Film Polyester Covering for Model Aircraft

Hyperion ARF models - from 10e to 70e size classes - wear this covering with beautiful results. Hyperion Easy Covering is "mid-range" in terms of tensile strength, weight and application heat. As such, it is easy to apply, and easy to use with many other covering brands, yet resistant to punctures and sagging under warm conditions.

COVERING TIPS

Your finish will only be as good as the preparation job you do first; so be sure that all wood surfaces are sanded smooth with 320~400 grit sandpaper, and all dust removed afterward.

Wood shrinks quite a bit when dry, and expands when in humid air.  As such, the model should be covered after resting in a dry room. If your location has high humidity, it is best to keep the model in an air-conditioned room for a few days before covering (or a room with de-humidifier running).  After you finish shrinking down the covering, you can take the model outside and the humidity will only improve the tautness of the covering film as the model gets a little bigger.  But if you cover a "humid" model and then take it out on a dry day, you will find that the covering may sag...

If using multiple cover colors, or stripes, be sure to arrange it so that the LIGHTER color is under the darker. A Darker color below can show through when a lighter color is on top.

When applying stripes be careful to have the iron only hot enough for glue adhesion, but not so hot it causes the covering to shrink. Otherwise the stripe lines can be distorted.  Move the iron along the stripes at a steady pace to avoid concentrating too much heat in one place.

Bubbles which appear in covering can be removed using a heat gun (some hair dryers are hot enough, on HIGH setting), a needle, and a cold wet cloth.  Use the heat gun to apply heat just until the bubble expands and rises a bit, quickly pop the bubble with the needle, then press the wet cloth firmly against it.  The cold cloth will shrink the covering rapidly while allowing to re-adhere to the wood, while the needle hole allows the trapped air to escape.  It is well to have one person hold the model and heat gun, while a friend takes care of the needle and cold cloth applications...

Hyperion Easy Covering takes most paints well.  Test the paint on a scrap of covering first, to be sure it is compatible. However, do NOT use model dope or butyrate-based paint on the covering.
Install the covering on the model, shrink it down fully, then prep the surfaces to be painted with ScotchBrite pads (or fine steel wool). It is important that ALL the gloss of the covering be removed during this preparation.  Then a lightly dampened soft cloth should be used to thoroughly clean all surfaces. After dry, brush to insure that no dust or fibers remain. Spray the first two paint coats in a very light mist, and allow to dry fully.  The third coat should just be enough to give solid color, without building a thick layer of paint.
(note: Hyperion Flat Olive models are painted at the factory. As such, we can not offer "replacement" covering, per se.  We suggest you install the Hyperion Gloss Olive covering on your model, prep as above, and repaint with military flat olive spray paint)

Any excess adhesive can be removed from the iron or model using most paint thinners, or acetone. Test on scrap covering first. Apply only a small amount of solvent on a soft cloth, wiping gently to remove the adhesive.

Small "Hobby" irons are popular for model covering, but on the Hyperion ARF production line we use only standard irons, as shown left.  The larger face allows one to completely span openings, so that pressure is not applied inappropriately to the film.  We recommend the attachment of a soft cotton "sock" (old t-shirts work), as shown, to avoid scratching the film, for a perfect finish. Our irons are small, 800W~1000W units.

COVERING STRUCTURES

We'll start with the bottom of an open-structure wing, for example (see diagram below). At this point, we want the temperature of the iron so that the film adhesive will readily melt, but the film itself will not yet shrink.  90~100C is good.  Water boils at 100C, so set the iron temperature dial to about 60~70%, wait till the iron is hot, then dribble a little water on the iron face.  It should take at least 10 seconds for the water to boil away.  It boils immediately on contact and sizzles, you should turn the iron down 10%, wait a few minutes, and try again.

Start by cutting the film with a few inches (5~7 cm) overlap compared to the outlines of the wing bottom.  Follow this procedure on each wing side: Start with the bottom. Remove the plastic backing from the oversized film you already cut. Use the iron to tack the film to the center root end of the wing panel (1) then - pulling gently to keep the film taut - at center of wing tip (2). Next fix the covering at leading edge of wing root (3), then pull the covering diagonally from root leading edge to tip trailing edge (4) and tack down. Repeat for tip LE (5) to root TE (6).  Finally tack covering at LE center span (7), then pull taut and tack down the film at TE center span(8). Between all eight points the covering should be smooth and free (or almost free) of loose spots or wrinkles. Loosen with iron and re-tack if necessary to achieve smooth covering between all points.

Next, we'll just lightly seal around the leading (LE) and trailing (TE) edges.  While Lightly gliding along with the iron - little pressure should be applied - work from: TE span center (8) to wing root(6); LE span center (7) to wing root, and finally LE and TE centers (7,8) to wing tips (5,4). Last, seal the film well to wing tip and wing root sections while pulling the covering tight as you go.

Now trim the film on wing bottom using a straightedge and SHARP hobby knife, such that at least 3/16" (5mm) of overlap will occur when top covering is trimmed later on vertical center of LE (or slightly below LE center).  At TE, bottom film should wrap around the back of the wing and be trimmed flush with top edge of the wing.  Once trimming is complete, slide the iron lightly around all edges to seal all film down well to the wood.

Follow the same procedure now to tack the TOP covering and seal to LE and TE.  Trim the top film such that at least 5mm overlap exists with bottom film all the way around the wing. Seal the edges with light pressure of the iron, working back and forth gradually along LE and TE from "inside" of wing toward the cut edges of the top covering. At corners, such as inside of aileron bays, cut film at 45 degrees so you can freely fold the film into place, then seal and trim as needed. You may sometimes need to apply a small extra piece of film to wood first, then seal down top covering to avoid a bare spot.

After trimming top film appropriately, we will shrink the film tight.  Set the iron to 120C (dial 10% higher than your previous setting, to start) and check that water droplets boil soon after contact with the iron.  Avoid "too hot" to your best ability.  Note that we want to use the lowest possible temperature at this point, just enough to get the shrinkage we want.  A key point:  If the film is shrunk at a certain temperature, to increase the shrinkage later we must set a higher temperature than previously used.  So if we set the temperature too high now, we may not be able to re-shrink, or increase tautness enough, later.

Note also that light structures can be distorted during film shrinkage.  In most cases, this can be corrected by flexing the structure in the opposite direction while shrinking the second side. However, whenever possible it is well to control the distortion by placing structures against a flat table surface while shrinking.

Starting at span center of wing bottom, slide the iron gently along from TE to LE, over the open wing bay at span center, while spanning at least two ribs with the iron. Stop just short of the Spar Centerline for now.  Continue from span center toward wing root, shrinking the cover over open bays, then do bays from span center toward wing tip.

At this point the shrinkage over the wing bays should have pulled the covering slightly tight over the solid wood wing sections.  Now lightly glide the iron from span center LE to spar centerline, working toward root, then LE center to tip.  Do the same for and remaining solid balsa. And finally run the iron down spar centerline. Do the same to shrink down the top film.  Done!

For fully sheeted wings some prefer to fix the covering firmly to spar center then pull taught while working the iron from span center spar line to LE to root, to tip; and then span center spar line to TE, to root, to tip. In this case you are activating adhesive and slightly shrinking the film in a single step.  You certainly don't want the iron too hot. Right around 115C is best, controlling the shrinkage with the rate at which you move the iron.

Repairs typically involve Ironing one piece of film over another.  Whenever possible, try to minimize the area of covering over covering, while leaving just enough overlap to insure strong adhesion of the two pieces.  Avoid trying to repair the center of open areas, such as open wing bays. Instead, remove all the old covering from the damaged wing bay AFTER you have run your iron over the adjoining ribs, TE, and Spar Centerline, to insure the covering is firmly attached.  After removing the old film, cut a new piece with 4~5mm overlap to adjoining bays, and iron firmly down along the rib tops and other areas which have supporting wood under the covering.

TIP:  If someone you know has a good thermometer, use it to calibrate ADHESIVE (100C), SHRINK (120C) and MAX (135C is good) for your iron.  For each temperature, use a dot of paint to indicate dial setting. If you can't get access to a thermometer, be sure to mark the iron as you use it and find "best" dial settings for adhesive and first shrink...

Learning to cover well takes some practice, and can be frustrating at times.  But don't give up!  Will a little time invested, and a few mistakes made, your skills will improve.  And it is EXTREMELY rewarding when you do a "perfect" covering job for the first time.