Compared to old fashioned fabric finishes, iron-on film is easy. However, there are some important techniques to be mastered if you want to achieve the best results. The best way to learn is by doing. Even if you tear your first attempt off and do it over, it’s not really a waste. You’ll have to spend some money, but my goal is to help you at least get a discount on your tuition to the school of hard knocks.
The first step to covering a model is to decide what you want it to look like. Do you want two colors? Three colors? Pin stripes? What colors are easiest for you to see? I always favor designs with two contrasting colors for visibility, but as I’ve gotten older I find that I can’t see a red and yellow airplane as well as I used to. So now I usually use yellow only with purple or blue, and my favorite light color is white. So figure out what works for you. Put rolls of film next to each other, and even go outside and hold them up to the sky so you can see what they will look like together on an airplane. I figured this out the hard way. I covered a bunch of airplanes with bad color schemes, and then I learned not to. For instance my first Cloud Dancer was black with some bright highlights. It looked great on the ground, but it always looked like a silhouette in the air and I couldn’t tell what it was doing. I still use black, but now it’s only for stripes. I have covered a few airplanes with tiny random scraps from my scrap box, and they looked really cool. But this has to be done correctly because anything covered with random spots will look camouflaged at a distance. I had very good results with a Q-Tee covered with scraps, but only the fuselage was done that way. The wings were solid yellow, which allowed me to see what the plane was doing. On another occasion I covered an aerobatic trainer with stripes. Each rib bay was a different color, and the fuselage was covered in stripes as if it were wearing a bunch of belts of all different widths. I couldn’t tell what that plane was doing in the air at all, so that experiment was classified as a disaster. So I eventually came up with a good idea that I use on everything. If you don’t want to think about it and want to just do it my way, see my article on high visibility color schemes.
Now that you have that settled, here are the three rules of what order to apply pieces of iron-on film.
- Cover the bottom first, then the sides, and finally the top.
- Cover the rear first and the front last.
- Apply light colors first, then dark.
- Rule 2 is superior to Rule 1, and Rule 3 is superior to Rule 2.
Let’s assume that you are covering an RCM Basic Trainer just like the one in the article in the above link, except that you want it all red. For the fuselage you start with the bottom, then add the sides, and finally cover the top. Now let’s assume that you want it to look just like mine. Start with the white film on the sides. Then apply the white top. Then apply the red bottom, then the red sides, then the red top just behind the engine. Nothing to it.
I’ve heard a lot of questions about ironing film onto an airplane, and I’ve heard a lot of answers, most of them disagreeing with each other.
First, which film should you use? The old standby is Top Flite Super Monokote, also known simply as Monokote, or for obvious reasons, Moneykote. Much like the Coke vs. Pepsi rivalry, Ultracote has its share of loyal users as well. So what’s the difference?
Monokote is durable. It has a good shrink rate but it has its limits, so you have to know what you’re doing. Once you put it on you can’t take it off and reuse it. If you have to take it off, you’ll need to replace it with a new piece. If you mark your balsa with a ballpoint pen, Monokote will cover the marks and the ink won’t bleed. (The mark may show through white, yellow, and some shades of red, though.) It stretches well around curves, but you have to know what you’re doing. It comes in a wide variety of colors. Some of the red colors are not entirely opaque, unfortunately, and some colors, particularly green and purple, have wide variations in color from one dye lot to another. Monokote is rather expensive at retail price.
Ultracote is just as expensive as Monokote. If you put it on and decide to move it, you can reheat, lift, and re position Ultracote. Sometimes this is a bad thing because you iron it on, then try to shrink it with a heat gun, then the edge will lift and shrink into the middle, ruining the piece. Ultracote comes in a wide variety of colors. Unfortunately if you mark your balsa with a ballpoint pen, any remaining ink will bleed into the adhesive and be visible through Ultracote. Ultracote fans say that it shrinks and stretches better than Monokote and is easier to apply.
I’ll tell you my bias. I’m a big fan of Monokote, and I’ve been using it since I started. I like the way it goes on. If you develop your skills, you will be rewarded with good results. My main gripe with Ultracote is the thing about unsticking and resticking. Sometimes this attribute is offered as an advantage, but I say that if you know what you’re doing, you should be able to put it on and trust that it will stay on. To be fair, Monokote will loosen and shrink away from the edge, too. But for this to happen you have to blast it with a heat gun beyond reason, and you shouldn’t be doing that anyway.
So use what you want, and I hope you form an informed opinion and have many good looking planes as a result.
Next question is how to prepare the plane for film. Well, I have seen lots of guys spend way too much time sanding, filling, etc. My philosophy is that filling is kind of a waste because your film should bridge the gap anyway. Not much more to say about that. Lots of guys sand with 220 grit, then 400 grit so the balsa surface feels like a baby’s bottom. I never found that necessary either. I have two sanding blocks. One is always loaded with 120 grit and the other 180. Good enough for me. If you’re six feet away from the plane, guess what it looks like. It looks like a model airplane.
Have you heard about Balsarite, sanding sealer, and other preparations? Some people swear by them, others not so much. Sanding sealer is supposed to prevent a fuzzy grain from coming up on sanded balsa. It’s probably more important when the plane is being covered with fabric, or simply painted. I’ve always covered with film, so sanding sealer is something I’ve never used. Maybe I should, but I don’t think I’m missing anything. My planes look good on the ground and in the air, and then either I sell them or they crash. I don’t think sanding sealer will change that. Balsarite is a different story. This is a product that comes in a can and is brushed onto the air frame before covering. It comes in fabric formula and film formula, the only difference being that the former is much thicker than the latter, which means that if you are buying the latter you are buying more solvent. The idea is that you can brush the fabric formula onto the wood and then use any fabric or film as an iron-on product even though it has no adhesive on it. There are a few aircraft covering products that are provided without adhesive, so this is a useful product. The film formula is advertised for use with iron-on film that already has its own adhesive, to make it work better, theoretically. I have my doubts. Interestingly, the manufacturer recommends fabric formula for any film or fabric without its own adhesive, and the film formula for any film or fabric with adhesive. So what they’re saying is that you should use the highly thinned product if you already have glue and don’t need more. (Wink wink. Get it?)
My take on Balsarite is that it is useful around the engine compartment as a fuel proofer. You can paint any surface in the engine compartment that is intended to not be covered with film, and extend the Balsarite an inch or so in all directions where there will be film. Then iron the film on and you have a thoroughly fuel proof installation. Also if you are repairing crash damage or re covering an old plane, Balsarite can be used in areas that have suffered a bit of oil-soak to help the film adhere better. So, it’s a good product, but you can also fuel proof with epoxy after covering, which is something I usually do. One other practical note is that I’ve heard Balsarite is discontinued, but Sig sells another product called Stixit, which is supposed to be the same thing.
How about trim irons, Wood Peckers, tack cloths, and other specialty tools and products? I bought a trim iron a long time ago, used it a couple of times, and got rid of it. Use a regular iron, use a hot butter knife, or whatever. I wouldn’t advise you to spend extra money on a trim iron.
The Wood Pecker is a product that was advertised a while back and I don’t know if it’s still available. The theory is that airplane film tends to release gas when you are ironing it down, which creates bubbles under the film. So if you roll the woodpecker, which looks like a lawn aerator, over your balsa wood, it will leave it full of holes and allow your film to stick with no bubbles. Yeah, whatever. I think it’s just another gimmick. Wood is already porous, so the only time I have problems with gas bubbles is when applying film over film. Lower temperatures usually solve this problem, or you could float the top piece of film into place with solvent.
Regarding the use of a tack cloth, that’s a good idea. The less dust you have on the surface to be covered, the better your film will stick. But here’s the secret. You can get excellent results with a T shirt.
If you have any other questions related to covering with film, let me know and I’ll include them.