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Academy of Model Aeronautics
Charter Club #1012

Building


THE BUILDING BOARD – Covering R/C Airplanes with Plastic Film

 

By Bob Crawford

 

This article is a compilation of 5 articles that appeared in the GCRCC Flightline between July 1997 and March 1998. The five topics are the following:

 

1.        Surface Preparation

2.        Covering Tools

3.        The Stretch Rule, Part 1

4.        The Stretch Rule, Part 2

5.        Using the Trim Iron

 

The articles were originally aimed at beginners to the hobby who were faced with applying covering for the first time to a trainer. These days, almost all newcomers start with ARF trainers, and those who continue with ARF’s will have little need to learn covering techniques. For the subgroup of enthusiasts who decide to do their own building, there have been numerous how-to books and articles published about covering with film. I remember reading everything I could find when I started covering, and I still had to learn and develop many of my own techniques, some of which may be contrary to “conventional wisdom.” I hope this article will afford an additional “head start” to these beginners.

 

One disclaimer is necessary. The only film covering I use is Ultracote (aka Oracover). I am sure that the general techniques described here are applicable to most covering films, but it is certainly possible that some modifications will be necessary when using other materials.

 

1.       SURFACE PREPARATION

 

Everyone knows that a paint job on anything, whether a model airplane or a house, is only as good as the preparation job on the underlying surface. The same is true for covering models with heat shrink film. In fact, there are probably fewer ways to get around poor surface preparation with film than there are with paint.

 

Obviously, surface preparation is done with sandpaper, so let's talk about this essential tool. The brand of sandpaper product you use is a matter or personal preference. The various sandpapers available are all different routes to the same end. All I can say here is that I've settled on 3M garnet sandpapers as my personal favorite. This paper needs changing fairly frequently, but I like the way it performs so well I'm willing to live with this deficiency. I also like the aluminum T- bars for sanding blocks, but each builder will settle on a product that feels most comfortable. You just have to start trying different things and pick the one you like best.

 

The sandpaper grits I use are 60, 100, and 220. I also use 3M silicon carbide 400 grit paper for final finishing (more on that later). The 60 grit paper is used mainly for hardwoods, and for large balsa blocks (wingtips, cowls, etc.) that need some fast persuasion to get close to their final shape.

 

The 100 grit paper is the real workhorse in building balsa models. I use it for every aspect of final shaping, as well as smoothing sheeting joints, and even smoothing the surface of parts that are already cut to shape. When I have a model ready for covering, there won't be a square inch on it that hasn't been touched with 100 grit paper at some point.

 

With 220 grit paper, the objective is not shaping but finishing. Here, we're removing the roughness left by the 100 grit paper. Once again, I will go over the entire model with 220 to prepare for covering. When sanding with 220 on flat surfaces, I usually use the sanding bar. With curved surfaces, however, I just use my hand to back up the sandpaper. For example, I'll hand sand wing leading edges, wingtips, fuselage edges, tail feather edges, contoured cowls, etc. If you recoil at the idea of hand sanding, simply glue the sandpaper to a piece of foam instead.

 

I mentioned earlier the use of 400 grit paper for final finishing. I'll admit that 220 grit sanding is probably perfectly adequate for film covering. It's just that I'm a bit fussier than necessary (you already know that, don't you?) so I like to go over everything with 400 for that extra degree of smoothness. Once again, It's a personal choice.

 

The final procedure in covering preparation is balsa dust removal. Here I've developed a method that's a bit different from usual practices. Most builders vacuum the wood, or clean it with a tack rag (or both). In my experience, a little more aggression is needed to really get all the dust out. I think dust removal is extremely important. Every microscopic area of covering adhesive that's bonded to dust is not bonded to the model.

 

My principal tool for dust removal is a roll of Scott Shop Towels, which are blue in color. The technique is to use the paper towels as if they were a 10000 grit sandpaper, rubbing all wood surfaces with a vigorous swirling motion, and using even more downward pressure than you'd use with sandpaper. The advantage of the blue towels is that the beige balsa dust being removed shows up very clearly against the blue background. I keep rubbing the wood with fresh surfaces of towel until no more dust is visible. When this happens, the surface is truly dust free. Everyone knows how smooth sanded balsa feels, but when you remove all the dust, it actually has a sticky feeling to the touch.

 

At this point, the model is ready for covering. As I work on each piece of the model, I will cut the piece of covering from the roll, and just before removing the backing I'll give the piece to be covered a quick rub-down with my bare hand to brush off any dust that may have settled from the air. Then, peel the backing and get the covering ironed down as soon as possible.

 

2.       COVERING TOOLS

 

Covering Irons: Most of my own covering work has been done with one of the basic "15 dollar" covering irons. This iron works fine, and I've never had any complaints about it. I always keep a hot sock on my iron, and replace it when it begins to look "toasted." More recently, I decided to treat myself to the 21st Century iron, which costs in the $30 range. I've seen two principal benefits from the extra cost. First, the 21st Century iron has rounded edges. The sharp edges of the standard iron can create grooves in the covering if you're not careful. Second, the control dial is calibrated in degrees, so you can set the desired temperature directly. Most of the time, I set this iron in the 300-325 degree F range for use with Ultracote. On the "el cheapo" irons, the dial has arbitrary numbers, so you need to buy a covering iron thermometer and calibrate the dial yourself. On a more subjective level, the 21st Century iron is lighter, and has a better balance and "feel." You'll have to decide if these features are worth the extra money.

 

Trim Irons: The Top Flite trim iron is a tool I consider absolutely essential in covering. I've found that a lot of newcomers to the hobby haven't been informed about the usefulness of this tool, and don't bother to acquire one. On many occasions I've been asked how it's possible to apply covering to complex rounded surfaces such as wing and tail feather tips without wrinkles. The answer is the trim iron. Although the areas of a model that require the trim iron are small, I probably spend more time with this tool in my hand than the main sealing iron. Use of the trim iron is discussed in Part 5 of this article.

 

I mentioned above that I had switched to the 21st Century covering iron. When 21st Century came out with their own trim iron, I was excited enough to run out and buy one immediately. What a mistake! It turns out that this trim iron has a maximum temperature around 300 degrees F, which is far lower than the hot setting on the Top Flite iron. The 21st Century tool is completely useless for the techniques described in Part 5, and for me was a waste of money.

 

Heat Guns: Some modelers use the heat gun very extensively in applying covering. I prefer to use the iron for solid surfaces, and only use the heat gun to shrink covering over open wing bays. Another less obvious use of the heat gun is removing covering. If you have to strip off covering to repair a crashed plane, blast it with full heat from the gun and it will peel right off. If you try to do it cold, you'll probably pull off chunks of balsa and create a bigger mess than you have already.

 

Cutting Tools: I probably do 99% of my trimming using #11 blades mounted in a standard 5/16" handle. And 99% of that uses only the pointed tip of the blade. I've estimated that the tip of a new #11 blade will effectively cut only 10 to 20 inches of covering before it is dull enough to be replaced. As a result, I normally use 30 or more blades to cover an entire model. This isn't as wasteful as it sounds, since blades used for trimming covering are essentially equivalent to new, unused blades for any other cutting application. My spent covering blades are recycled to a box on my building table for use in cutting balsa and everything else that requires #11 blades.

 

Using a sharp, new blade is especially critical when you're trimming covering that overlaps another section of covering, and you only want to cut the top layer. This is another topic that will be discussed later.

 

Razor blades are also useful, but I have found no use whatsoever for single-edge razor blades in covering. These blades are great for housepainters to use in their scrapers, but, in my opinion, they are just not sharp enough for use with plastic film. When I need a razor blade, I use the double edge blades (preferably stainless steel) used for shaving. For obvious reasons these must be handled with great care. You can break them in half and use the edges separately, or cover one edge with tape for protection.

 

Alignment Tape: Perhaps my favorite covering tool is one that most modelers don't seem to be aware of yet. It is 3M Scotch brand 2070 "Safe Release" masking tape. This stuff looks like ordinary 3/4" masking tape, but has the same adhesive used in Post-It notes. If you've ever used regular masking tape on covering, you probably found it will pull the covering right off the wood when you remove it. Not so with the Safe Release tape. It sticks to film covering very securely, but peels off as easily as Post-Its come off paper.

 

The number of uses I've found for this tape could probably fill a whole article. To mention a few, I always use it as a blade guide for making long trim cuts that I want to come out straight. Use it to pre-align stripes and other decorations to eliminate the "eyeball" and guesswork factor. Use the tape as a marker when you need to create an even 1/8” overlap with two pieces of covering. This product is so useful in covering, I think it should be available in every hobby shop and catalog. Until more modelers discover it, though, you'll have to go to elsewhere to get it. It is available in different widths, but I like the ¾” best. I’ve had luck finding it at the Michael’s art supply stores.

 

Miscellaneous Tools: It's important to own a good quality scissors (e.g. Fiskars). When making trim pieces, you'll be cutting covering from the roll with a knife on some sort of cutting surface (and you can use the "used" #11 blades for this). You need a variety of metal straightedges ranging in length from 6" to 36." Some people use glass as a cutting surface. I prefer to use Plexiglass sheets, which are more expensive than glass, but not nearly as expensive as the "self-healing" cutting mats you can get. I occasionally use the Top Flite Smartstripe device for cutting really long stripes, but find a straightedge and knife to be adequate for shorter ones. I once tried to use the Top Flite Smartcut trimming tool, but decided the amount of practice I'd need to learn to use the thing would probably waste a whole roll of covering.

 

3.    THE STRETCH RULE

 

This is a fundamental principle of plastic film covering that I've decided to call the "Stretch Rule." This is just a name I made up for the convenience of this article. The stretch rule itself is nothing I can claim credit for. I first learned about it while watching a video about covering techniques. I think most modelers learn it on their own through experience. Stated as simply as possible, the stretch rule is this: Plastic film covering must always be stretched at the same time it is being attached to a model using a heat source. The bottom-line message here is that the techniques you use in covering, and how the job turns out, will depend a great deal on how literally you interpret the word "always."

 

In order to illustrate the stretch rule, let's imagine a simplest possible case. We're going to cover a horizontal stabilizer for a typical 40-size trainer. The stabilizer has been cut from 1/4" sheet balsa, the trailing edge is straight, the leading edges are straight but tapered back, and the tips are rounded. The leading edge and tips have been sanded to a rounded cross section. The stabilizer is not attached to the fuselage, and we'll cover the right and left sides separately, leaving the center fuselage connection uncovered. We'll cover the bottom first, since this makes the edge seams for the top covering less visible.

 

Let's cover the bottom left side of the stabilizer with total disregard for the stretch rule. Lay the stabilizer bottom-side up on your work table, cut a piece of film large enough to cover it, peel the backing and position the film on the part. Now, with one hand held behind your back or in your pocket, iron the covering down using your other hand. Since the part we're covering is perfectly flat, there's a good chance this "one-handed" technique will turn out OK. There's also a good chance that a few wrinkles will appear during the ironing process, in which case you'll need to "mash" the wrinkles down using heavy iron pressure. In that case, you'll be left with telltale ridge lines that show where the wrinkles were.

 

Now let's cover the right bottom using the stretch rule. Set-up is the same as before, but this time we'll use both hands. Also, be sure there is at least 1" of excess covering extending beyond the edges. Begin by ironing down about 1/2" of covering chordwise along the fuselage joint (this can be done with one hand). Next, grasp the excess covering at the stabilizer tip with your thumb and index finger, and using the other three fingers as a lever point on the stabilizer tip, stretch the covering firmly while you iron down a wide swath spanwise working from root to tip. Finally, use the same procedure along the leading and trailing edges, stretching the covering while you finish sealing it to the wood. Move the stretch points along as you iron, so that the section being sealed is always under stretching tension. This time there shouldn't be a hint of a wrinkle.

 

Imagine what would have happened if this stabilizer were a bit thicker, and had been sanded to an airfoil cross section. In this case, the non-stretch procedure would likely have generated a complex pattern of wrinkles, and squashing them out would have produced a rather unsightly job. With the stretch rule method, however, the airfoil shape would have been irrelevant to the covering procedure or the wrinkle-free outcome.

 

Getting back to our stabilizer job, next we have to iron down the edges. When doing edges and seams, many modelers use a technique I call "pre-trimming." This simply means that you leave approximately 1/4" to 1/8" of the covering unsealed adjacent to the edge or seam, trim off the excess film, and then iron down that last 1/4" or 1/8." There are several tools you can use for the trimming: a razor blade, the cutting edge of an Xacto blade (rather than the tip), or even a scissors, whichever you prefer. Pre-trimming is necessarily a violation of the stretch rule. This should be obvious, since you've removed the excess covering needed to do the stretching.

 

Let's use pre-trimming on the stabilizer left half, to maintain consistency with our stretch rule violation. Trim the excess so the edge will come out at the 50% point of the stabilizer's thickness, and iron down the edges. The leading and trailing edges are straight lines, so they should iron down smoothly. When we get to the tip, however, we encounter a compound curve. There is simply no way to iron down this pre-trimmed edge without creating lots of small wrinkles. Once again, these have to be mashed down to make them as unnoticeable as possible. The resulting wrinkle lines should be small enough to be invisible from a distance of one or two feet.

 

On the right stabilizer half, we'll iron down the edges with stretching, and trim the excess afterward. To get all the wrinkles out at the tip we'll need to use some pretty aggressive stretching, and preferably use the trim iron because of its higher heat and ease of maneuverability. Also, unless you're blessed with three hands, you'll probably need to grip the stabilizer between your knees while you're working on it. Seal the edges down slightly beyond the half thickness point, and then trim off the excess at the 50% point using the tip of a #11 blade. If you cut into the balsa slightly, don't worry about it.

 

When we cover the top left half of our stabilizer, we'll use exactly the same procedure we used on the bottom. Just be sure to gauge the pre-trim to overlap the bottom covering edge so there is no exposed wood at the seam.

 

Finally, we'll cover the top right, once again with the same strict adherence to the stretch rule that we used on the bottom. We'll need to use even more stretching at the tip because we want to seal down at least 75% of the radius to get a good overlap of the bottom edge. Now we're suddenly facing a nasty problem. How do we trim off the excess of the top covering without cutting into the bottom? If we cut through both layers, we'll create an opening for exhaust oil to get through, and the balsa will soak it up like a wick. This will dissolve the covering adhesive at this point, and we'll never get it to stick again.

 

The answer is to use the tip of a new #11 blade. In order to cut through only the top of two layers of covering, you must use extremely light cutting pressure. The only thing I've found that will work with this little pressure is a new blade. This is something you need to practice if you haven't done it before. You'll be amazed at how light a touch will produce a successful trim. Before long, however, the blade will stop cutting at this pressure level. At this point, do not increase the pressure, because you'll end up cutting both layers; instead, switch to another new blade. Remember, the "used" blade is still equivalent to a new blade for all other building applications.

 

I stated earlier that I may use 30 or more #11 blades to cover a model. For those readers who were perplexed by this, the reason should now be obvious. It is a constraint imposed by strict application of the stretch rule to all phases of covering, even the seams and edges. Another way of stating this is "zero tolerance for wrinkles."

 

The last sentence in the first paragraph of this section should now be clear. How extensively you apply the stretch rule is a matter of personal choice. Comparing the left and right sides of a "hypothetical" stabilizer was just a device to make you think about this choice. I believe it makes sense to follow the rule as much a possible when covering larger surfaces of a model using the main sealing iron. You'll end up saving time if you don't have to fight the wrinkles. In the case of the edges and seams, I'm hesitant to get into value judgements. If you enjoy getting all the wrinkles out, as I do, then the stretch rule techniques I described to cover the right stabilizer half (and lots of Xacto blades) are appropriate. If, however, you prefer the pre-trimming methods, and recognize that tiny wrinkle lines will seem inconsequential after a few landing scrapes, then there is no reason to change to a different technique.

 

4.    THE STRETCH RULE (Continued)

 

In the preceding section about applying the Stretch Rule to covering with film, I used as an example a horizontal stabilizer from a typical 40-size trainer. One half of the stabilizer was covered with total disregard for the Stretch Rule, while the other half was covered using diligent application of stretching at every phase of the operation. This was simply a contrived example to show extremes, with the hope of convincing you that the side covered with stretching would come out looking a whole lot better.

 

Now the tail feathers of an airplane are of a size and shape that make the stretching technique fairly easy to apply. What about wings and fuselages, and how do the size and shape of the covering piece affect the stretching procedure?

 

It should be obvious that a long, narrow strip of covering will be much easier to stretch uniformly than a large square. For this reason, a fuselage is probably the easiest place to use the Stretch Rule. While covering the side of a fuselage, for example, you can simply tack the covering down at the nose and then pull firmly at the tail while you iron it down, working from front to rear and keeping it under strong tension the whole time.

 

Wings, however, are another matter. One approach is to get a large group of family members together or invite your flying buddies over for beer and pizza. With a large crew of helpers standing around the perimeter of the wing tugging on the covering, you can simply iron it down while holding a beer in your free hand.

 

On those occasions where the team approach is not possible, the solitary modeler has to do things a bit differently. The most effective technique I know is to "build in" the stretch. Once again, let's illustrate this by example, using the wing from our hypothetical 40-size trainer. The wingspan is about 60", and there is a dihedral joint in the middle so we'll have to cover the left and right panels separately.

 

Begin by cutting your piece of covering so there is at least 1" excess along the leading and trailing edges and wingtip. The excess will provide gripping points to build in the stretch. Align the covering carefully at the wing center (Hint: a strip of Scotch Safe Release masking tape along the dihedral joint makes an excellent positioning guide). Iron down about a 1" diameter spot at the trailing edge center joint. Pull the covering very strongly at the leading edge center joint and tack it down here too. Now you can iron down a 1" strip along the full center joint. Next we need to attach the covering at the wingtip while stretching it strongly spanwise (Another hint: even if the plans don't call for it, installing sheeting between the outer two ribs can make a wing much easier to cover). You can stretch/tack the corners or the center first, whichever seems to work best. Just be sure you're stretching along the span at every point that you iron down.

 

We've now "built in" a spanwise stretch, next we have to do the same thing chordwise. Stretch the covering at the leading edge at the middle of the wing panel and tack it down just behind the rounded contour. Go to the point directly opposite at the trailing edge, stretch and tack. Now repeat this procedure for the leading and trailing edges at the two quarter span points. Finally, split the distances again the tack down the four remaining one-eighth span points. You've now built in enough stretch that you can iron the covering to all the wing sheeting without creating wrinkles. You'll see wrinkles in the open wing bays at this point, but these will disappear miraculously when you shrink the bays with the heat gun.

 

In the previous article I defined the Stretch Rule as a "rule" so that it can be applied to every operation in covering, including edges and seams. When the rule is followed at a fanatical level, it precludes the pre-trimming of edges and seams before they are ironed down. Obviously, if an edge is already trimmed, it can't be stretched because the excess covering used to do the stretching is gone. The consequence of this is that trimming must be done on covering that is already sealed. At least half the time, this means cutting covering that has another layer of covering under it. I pointed out that trimming the top layer and not cutting the bottom layer is a technique that has to be learned through practice, and requires lots of new #11 blades.

 

A fortunate property of rules is that they always have exceptions. I'd like to temper the discussion about edge and seam trimming by pointing out that there are numerous instances where pre-trimming is not only acceptable but even preferable. An appropriate example can be found in the trainer wing we just talked about. Since the leading and trailing edges are perfectly straight, you can pre-trim them and iron down the edges without fear of wrinkles. How you handle the wingtip depends on its shape. If it's curved, you'll need to leave the excess attached and use the Stretch Rule method if you hope to avoid wrinkles. There have been numerous occasions where I've combined the techniques and used pre-trimming on the leading and trailing edges and stretching on the wingtips.

 

One of the best opportunities I can think of for pre-trimming is the fuselage of an Ugly Stik. This is probably the easiest fuselage imaginable to cover. (Ironically, the triangular wingtips of an Ugly Stik present one of the more difficult covering challenges.) The bottom is perfectly flat from nose to tail, and the top sections are straight in front of and behind the wing saddle. The saddle itself is the only curvature present. With a little careful measurement and planning, you could pre-cut all the covering pieces to their exact shapes for this fuselage, and have no trimming to do whatsoever.

 

The bottom line here is that a rule is a rule in name only. You have to use your best judgement when to apply it and when not.

 

5.       USING THE TRIM IRON

 

The Top Flite Trim Seal Tool (its official name) described in Part 2 costs a bit less than 20 bucks. It consists of a 6" cylindrical plastic handle with an electrical cord at the back end and a 3" metal shank on the business end. You are provided with two different sealing tips, either of which can be attached to the shank with a set screw. The handle has a two-pole switch to select high or low heat settings.

 

One of the sealing tips is rounded, and is designed for sealing concave surfaces such as fillets. The other tip is flat, shaped much like the sole of a shoe. As long as I’ve been using this tool I have yet to need the rounded tip. For all the applications discussed here, use of the flat tip should be assumed.

 

No information is provided about the actual temperatures of the high and low settings. All I know is the high setting is hot! If used carelessly it will easily burn a hole right through your covering. It will burn through your skin even faster than that. I use the high setting about 99% of the time, so assume the high switch position for everything discussed here.

 

One more comment about the trim iron itself. The hot metal shank is insulated from the plastic handle by a bored out wooden dowel. The tool carries a two-year warranty, and very shortly after the warranty expires the wooden insulator will crack, allowing the shank to wobble uselessly. The solution is to tighten a small metal hose clamp around the wood piece to provide several more years of post-warranty use.

 

My fondness for the trim iron comes from the many uses I've found for it that go beyond the manufacturer's intentions. Top Flite positions the purpose of this tool to apply pin stripes and graphics (which I almost never use it for) and to cover "nooks and crannies" where the large iron won't fit. Examples might be inside cowls, cockpits, or the fuselage area between the fin and stab. The advantage of a smaller size iron for these situations is obvious.

 

In my opinion, the most important usefulness of the trim iron, by far, lies in covering compound curves. The principal examples are wing and tail feather tips. It is the extremely high heat output of the tool in its high switch position that makes this possible. Remember, I said the tip is hot enough to damage the covering. The important thing to realize is that when the heat is very high, contact time must be low. The technique I use when heating covering on a compound curve is a "patting" or "tapping" motion in which the hot tip is applied and removed repeatedly. This is combined with a very strong stretching of the heated area. The constant on-off application of this high heat transforms the film to a rubber-like consistency (without melting it) that can be stretched over any imaginable surface.

 

Let's consider an example. Assume you're covering a wing with a symmetrical airfoil and a shaped, rounded wingtip much like the one on a P-51. You started by covering the wing bottom using the stretching technique described in the preceding section. The covering is smoothly sealed to the entire airfoil, but as you begin ironing close to the rounded wingtip you begin to see serious wrinkles developing. The wrinkles will be most prominent at the wingtip leading edge where the curvature is greatest. At this point, stop! Put your main sealing iron down, you won't need it again until you cover the top of the wing. From this point on we will use only the trim iron.

 

I'll assume you're right handed (if not, reverse everything). Grab hold of the excess covering near the wingtip leading edge with your left thumb and forefinger, and stretch the covering strongly using your other three fingers as a lever point. (Hint: use the flat portion of your fingers, not the knuckles; you're going to stretch so hard that knuckles will dent the balsa.) As you stretch the covering, use your right hand to tap at the developing wrinkle with the hot trim iron. The wrinkle will vanish, but hold the stretch for a few seconds after removing the heat while the film cools. The first wrinkle will be gone, but it will be replaced by two or more new ones further along the curvature. Repeat this same procedure on the new wrinkles. Every time you remove a wrinkle, you'll create more new ones than you fixed. If this sounds tedious, it is. It's a very slow back and forth process in which you work around the perimeter of the wingtip numerous times, making no more than about 1/8" progress per pass. Do not, under any circumstances, make axial cuts in the excess covering to relieve stress during this process.

 

Eventually, you'll have de-wrinkled the covering all the way around to the centerline of the wingtip, at which point you can trim off the excess film. The covering on the wingtip will be smooth and wrinkle free, and the excess you trimmed off will consist of nothing but wrinkles. It gets even more difficult when you cover the top of the wing. This time you have to stretch a little beyond the wingtip centerline in order to overlap the bottom covering. Also, when you trim, you're cutting covering over covering, and a new #11 blade is essential.

 

Covering the tips of tail feathers is the same process, but it's easier because the total curvature is much smaller. The process I described here can be used anywhere there is a compound curve. Fuselages that are tapered and rounded in the nose area provide another good opportunity to use this technique.

 

I'll briefly mention a few more "unadvertised" uses for the trim iron. Whenever I create an overlap seam using the main iron, I always finish by making a quick pass over the seam with the trim iron. The extra heat seals the seam more securely so it will never come apart by itself.

 

The trim iron is much more effective than the main iron in sealing covering to sharp edges. Examples are the ends of ailerons, elevators, and rudders, hatch openings, cowl and cockpit edges, etc.

 

It's also a wonderful tool for repairing dents and scratches. If you ever tried to iron out a hangar rash ding using the main iron, you may have been disappointed in the result. A few taps with the trim iron at high heat will usually make the flaw disappear completely. For more severe dents, poke a tiny hole in the covering, rub a little water on the dent so the underlying wood gets moistened, and then apply the hot trim iron.

 





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