RC Plane Covering Guide: Applying MonoKote and UltraCote Film

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Finishing a balsa kit and staring at a roll of film, wondering what to set the iron to, is the moment that separates a clean airframe from a wrinkled one. Covering is not difficult, but it punishes guesswork. Each film bonds and shrinks at its own temperatures, and advice that says only "follow the instructions" never prints a number. This guide prints the numbers the makers publish.

A note on sources: the temperatures, tool lists and steps below come from Horizon Hobby's product pages and instruction sheets for Top Flite MonoKote and Hangar 9 UltraCote, not from our own covering work. Oracover and Oratex are well-known European products, but their maker sites could not be reached for this guide, so they are not covered here. The guide is for builders finishing a balsa kit or a scratch build, or anyone recovering an older airframe. A ready-built plane arrives covered, and the ARF, RTF and PNP guide explains how to tell what you are buying. Some entry-level kits include covering, as the beginner kits guide points out.

The Films: MonoKote and UltraCote

Top Flite MonoKote

Search for Top Flite MonoKote on Amazon

Per Horizon, MonoKote is a thin, clear, protective film with a pigmented, heat-activated adhesive on the back. It is applied with a sealing iron, and the heat shrinks the film while activating the adhesive. The adhesive is not sticky until heated, and a clear backing on the adhesive side must be removed before use. Horizon lists the film as 0.20 oz per sq ft with a tensile strength of 25,000 psi, and says it is best suited to medium-size models in the 2 lb (1000 g) range and up. Smaller, lighter models may suit EconoKote, which Horizon describes as MonoKote's lighter, low-heat, low-shrink cousin.

Availability. Horizon lists some MonoKote items as discontinued (such as clear and flat jet white) and others as out of stock (such as Cub yellow and trim sheets). The status of the whole line is not confirmed, so check the color you need before planning a build around it.

Hangar 9 UltraCote

Search for Hangar 9 UltraCote on Amazon

Per Horizon, UltraCote is a polyester covering with a multi-temperature-controlled adhesive and shrinkage system. A patented process fuses the color to the film and permits repositioning. Horizon says it can both shrink and stretch, which helps around tight curves and wingtips, and that it is fuel proof (glow fuel, gas and smoke oil) and waterproof. The instruction sheet says it is made in Germany. Standard rolls are 2 m (78 in) long and 60 cm (23.5 in) wide at 0.3 oz per sq ft. White was on backorder and Pearl White and Chrome were in stock in October 2026.

ParkLite. Horizon positions UltraCote ParkLite for lightweight indoor and outdoor electric aircraft. It is 13 microns thick, weighs about 0.12 per sq ft, and comes in 16 UltraCote colors.

Temperatures side by side

The golden rule is to shrink at the lowest temperature that removes the wrinkle, not the highest the iron allows. These are film temperatures. Dial irons show a dial position, not a temperature. Horizon's MonoKote instructions suggest starting around dial 2 to 2-1/4, with "medium" heat of about 300 F measured on the surface of the cover sock, and one example in its ARF-tightening guide gives a dial setting of 325 F producing about 280 F at the sock. Horizon's digital sealing iron displays a set temperature, can switch between Celsius and Fahrenheit, and notes that tacking and shrinking are often done at different temperatures. A scrap test helps.

Tools

Per the makers, a basic kit is:

• A sealing iron with a cover sock. Horizon says the sock cushions the shoe, spreads heat evenly and prevents marking. For UltraCote, the instruction sheet says to increase the iron temperature by 10% when using a sock. Search for the Hangar 9 Digital Sealing Iron on Amazon
• A trim or sealing tool for corners and tight spots. Horizon's Hangar 9 ProTrim Sealing Tool, with a round and a flat Teflon-coated shoe, is listed as discontinued.
• A heat gun, useful on open bays. Horizon's Hangar 9 heat gun is also listed as discontinued.
• A covering glove, an insulated mitt that glides over the film, which Horizon lists in stock.
• Hobby knives with new #11 blades, scissors, a straightedge and a cutting mat. Horizon's MonoKote instructions suggest two knives: one for cutting on the mat and one reserved for cutting on the model.
• Sandpaper and a vacuum or compressed air.
• CA debonder, which Horizon suggests for wiping up residual MonoKote pigment.

Step 1: Prepare the Airframe

Covering shows every flaw underneath, and Horizon's instructions say MonoKote "usually won't hide" blemishes and can magnify them, especially darker colors. Sand all surfaces smooth with progressively finer paper. For MonoKote, Horizon says there is no need to go finer than 400 grit. For UltraCote, the sheet calls for finishing with 320 grit, wiping with a damp cloth, letting the model dry, sanding again with 320, and vacuuming. Fill gaps and dents with a good filler, using a tan filler under light-colored covering.

UltraCote's instructions add a note about humidity: cover in as dry a climate as possible, and place the model in a room with a dehumidifier for several days before covering, to prevent sagging. Remove dust right before covering with compressed air or a shop vacuum.

Step 2: Cut and Tack

Cut each piece oversize. Horizon's MonoKote guide suggests about 3 in around a wing tip and 2 in elsewhere, so you have something to hold. UltraCote's sheet says to cut a few inches larger than needed.

Do small details first. Horizon recommends sealing corners and inconspicuous areas, such as aileron cutouts, before the main sheets go on.

Then tack the main piece. For MonoKote, Horizon describes the "inside-out" technique: bond the film in the middle of the part, then heat and pull as you work outward, so the film is pre-tensioned and ends up tight and wrinkle-free. Work from the middle toward the tip, then back to the middle and toward the leading and trailing edges in a zig-zag pattern while pulling the film. For UltraCote, set the iron to 220 F (104 C), tack at the spar or high point, and gently pull toward the root and tip. The sheet says to press gently and let the heat, not pressure, activate the adhesive.

On a solid-sheeted wing, work from the spar to the trailing edge, then the leading edge. On an open-structure wing, UltraCote's sheet says to work from the spar toward the trailing edge with the iron touching only two ribs at a time, then adhere the remaining ribs.

On a fuselage, UltraCote's sheet says to start with the bottom, then the sides, then the top.

Step 3: Seal Edges and Corners

Switch to the trim or sealing tool for edges and tight corners. Trim the excess with a sharp blade, leaving a small overlap. Horizon's MonoKote guide says about 1/8 in (3 mm) is typical. UltraCote's sheet says to leave a minimum of 1/4 in (6.35 mm) and then reseal the leading and trailing edges at 220 F.

For rounded edges, cut small triangular "petals" in the overhang, which lie down individually instead of bunching. The tighter the curve, the smaller the petal. Horizon uses this method around wing roots and curved hatch corners.

Finish openings such as servo hatches by cutting the covering 1/4 in (6 mm) inside the edges, slitting in from the corners and ironing the film down around the inside.

Step 4: Wing Tips and Compound Curves

Wing tips take heat and a firm pull. Horizon's MonoKote guide says to elevate the wing, weigh it down, pull on a small area while touching it with the iron, and work around the tip in small increments, holding the pull for a few seconds after the iron leaves so the film cools in place.

UltraCote's sheet gives temperatures: set the iron to 300 F (149 C) for the wing tip, up to 350 F (177 C) if the curvature is sharp, and pull and stretch the covering around the tip while applying the iron.

The warbirds guide covers models with rounded tips and cowls where these skills matter most.

Step 5: Shrink

With every edge sealed, shrink out the remaining wrinkles. UltraCote's sheet says to set the iron to 300 F (149 C), or use a heat gun, starting from the spar and working outward, and to increase the heat only as needed to remove wrinkles.

Bubbles and blisters happen. Per Horizon's MonoKote instructions, go back over the spot with more pressure, try a little less heat if they persist, and poke tiny vent holes with a #11 blade over areas hardened with glue, where air has nowhere to go. On open-structure tail surfaces, cut air passage holes through the ribs and add a final vent hole in an inconspicuous place, or puncture small holes in the covering on the underside, but only on parts large enough to take the holes without losing strength. UltraCote's sheet gives a different method for a stubborn blemish: heat it with a heat gun until it rises, pop it with a needle, and wipe the area with a cold, wet washcloth. It may take several attempts.

Step 6: Trim, Stripes and Graphics

Apply trim after the base color is on and cool.

• MonoKote over MonoKote: Horizon says graphics are best applied wet with window cleaner. Wet the adhesive side, position the piece, wipe off most of the solution, then squeegee the rest out with a soft piece of balsa. Let it dry at least overnight (24 hours or more is better), then iron it down with medium heat.
• Where possible, avoid layers. Horizon's care sheet suggests putting trim color over bare surfaces with a 1/8 to 1/4 in (3 to 6 mm) overlap, to save weight and avoid air bubbles.
• UltraCote: for two colors, UltraCote's sheet says to apply the lighter color under the darker one so the dark does not show through. The wet method is documented for MonoKote, not UltraCote, so follow the UltraCote sheet for UltraCote.

Horizon also advises buying all the covering for one model from the same place at the same time, because color can vary slightly between production runs, and keeping scraps for repairs.

Covering Foam Airframes

This section is general building guidance, not a maker procedure. A foam wing with a thin sheeted skin of balsa, plywood or fiberglass can be covered much like a wood panel, because the film bonds to the skin. Bare foam is another matter. Film adhesives are activated by heat, and foam can distort when it gets hot, so test on scrap from the same sheet before committing, and use the lowest temperature that works. Horizon's ParkLite is intended for lightweight electric aircraft, but its pages do not give foam instructions, so check the product notes for your film.

Many foam planes are simply left uncovered or are finished with tape or paint. The foam types guide explains the materials, the painting guide covers paint and the glue guide covers adhesives.

Painting Over Covering

UltraCote's sheet says most polyurethane, epoxy and automotive acrylic paints are acceptable, while model dope and butyrate-based paint should not be used. It suggests scuffing the surface with steel wool or a scouring pad and cleaning with isopropyl or denatured alcohol before painting.

Care and Repair

Per Horizon, dents in MonoKote can usually be removed by applying heat, while a field puncture can be patched with MonoKote trim and replaced with a clean patch at home. For cleaning, Horizon recommends a covering cleaner and polish, or detergent. To remove adhesive from a model or iron, UltraCote's sheet says to use acetone or a mild thinner.

If you are tightening factory covering on an ARF, Horizon's guide says to find the right temperature by gliding the iron over covering above wood and watching for bubbles. If bubbles appear, it is too hot. Go over the whole model, not just the visible wrinkles. After that, a covered airframe can sit on a display stand, and the stand guide covers the options. Fuel-powered builders should also read the gas versus electric guide, since UltraCote is described as fuel proof for glow fuel, gas and smoke oil.

Common Mistakes

• Shrinking at maximum heat on the first pass. Film that has been shrunk at a high temperature leaves no headroom for later fixes.
• Ironing over dust. It shows as a bump that no amount of heat will remove.
• Skipping the scrap test, especially on foam.
• Stacking trim layers. More weight and more bubbles.
• Mixing up the wet method. It is documented for MonoKote trim, not for UltraCote.
• Ignoring humidity. UltraCote's sheet specifically recommends a dry climate and a dehumidifier.

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