Last month we discussed tools and techniques for polishing your airplane. That article focused on primary structures: wings, fuse, etc. In this article we’ll focus on more detail-oriented polishing—small parts and working around paint—as well as repolishing and other tips and tricks to make the job easier.
For small parts or narrow corners, the 7-inch compounder and Cyclo may prove unwieldy. Here are three options for detail polishing:
1. Downsize. In addition to 7-inch wool pads, PerfectPolish (perfectpolish.com) sells a small compounding kit that includes a 3-inch backing plate with drill chuck adapter. Compound just as you would with the larger pad. For buffing, I used a 5-inch random orbit palm sander. The 4-inch diameter foam rubber pads used with the Cyclo attach to the backing pad of the palm sander with Velcro. There’s no real good way to secure the fleece, so just twist it up tight and hold it with your free hand.
2. Micro-Mesh. For hand-polishing small parts (fuel caps, canopy handles, steps, etc.), a Micro-Mesh kit works well (you can also use the Micro-Mesh kit for Plexiglas repair). For example my fuel caps were aluminum, but supplied with a dull black finish. I left the caps in the wing while I polished, hoping they would polish up like the adjacent metal but no such luck. I therefore manually wet-polished them (water plus a few drops of detergent) with Micro-Mesh pads, using 800 to remove the black paint and moving up to 4000 before finishing with F7 and S. Compared to Alclad material, using Micro-Mesh on the cast aluminum caps did not cause any clouding issues.
Gas cap after sanding with 4000 grit Micro-Mesh. Like Nuvite, finer grades of Micro-Mesh will remove scratches from coarser grades. Once you are satisfied with the surface finish, manually polish with F7 and S on cotton fleece to bring to a mirror finish.
3. Buffing wheel. After watching a hot-rod parade during a trip to California, I decided I needed to polish my exhaust pipe turndowns. This turned out to be a fool’s errand, since the pipes immediately discolor with heat. In any event, it sent me looking for another way to polish objects not amenable to the above methods (the pipes are stainless steel and I was making no headway with the Micro-Mesh). That led me to wheel buffing.
For detail work, downsize the pads and use a drill for compounding and an orbital palm sander (not shown) for Cyclo. The picture shows a Cyclo pad attached by Velcro to a drill chuck adapter. The wool pads also have Velcro backing. The yellow and white foam pads at the bottom are used for polishing paint.
Wheel buffing involves fitting a (usually) sewn fabric wheel to a benchtop electric motor. The wheel is dressed with a polishing compound appropriate to the material to be polished. Since the variety of wheels, polishes, and techniques goes beyond the scope of this article, I highly recommend Caswell Plating’s short booklet, An Introduction to Buffing and Polishing, available on their web site in PDF form (www.caswellplating.com).
If you are building from a kit and know early on you want to polish the plane, prevention is the best medicine: leave as much of the protective plastic covering on as possible until polishing. You can remove strips of plastic for rivet lines, seam overlaps, etc. by running a soldering iron along a wooden straightedge on the plastic to “cut” it without harming the aluminum underneath (wood won’t suck heat from the iron like metal). Beware though that even this can leave scratches if you are not careful; be sure to round and polish the tip of the iron with a Scotch-Brite pad, and draw the iron lightly across the aluminum. Practice on scrap first. Avoid scratches at all costs!
The dark streak (indicated by the arrow) was caused by overly aggressive scratch removal (F7 applied with a finger).
If you do have a scratch, hold the compounder at a 45-60° angle and work it over the scratch, being careful not to get the aluminum too hot. I have not found any difference in working the compounder parallel versus perpendicular to the scratch. Scratches that do not grab a fingernail are amenable to this approach.
Faced with some serious scratches (much of my RV-4 kit was rescued from an old barn and was admittedly a poor candidate for polishing), I initially tried sanding some of them out with aluminum oxide sandpaper (silicon carbide paper is not advised as it tends to leave a black haze). The 2000 grit paper did indeed take out the scratch but left a hazy cloud that no amount of polishing, or even an acid wash with Alumiprep, would remove. If you decide to try sanding out a scratch, practice on a piece of unused aluminum first to perfect your technique. For minor scratches, I have had luck lightly feathering out the scratch with just a fingertip and F7, but even this technique will leave a cloud if you are too aggressive.
I’ve also tried Micro-Mesh pads (stepped from 2400 to 12,000) but encountered the same issue with clouding. If someone out there has a foolproof method of removing scratches that doesn’t leave clouding, please let us know!
Polishing first, then painting means that the depth of polish will be consistent right up to the edge of the paint.
Polishing around Paint
Most polished planes will need to have at least the fiberglass parts painted. However, it’s also quite common to have leading edges or trim lines painted on the aluminum. If you plan to have polished metal adjacent to painted metal, the question arises of whether to paint and then polish, or polish and then paint. Based on my experience with both approaches, I’d highly recommend polishing first, for two reasons.
1. Polishing disassembled structures is generally much easier than polishing once the airplane is assembled (see last month’s article). In contrast, painting after assembly is not generally an issue, and given the paint scheme, the painter may in fact want the airplane assembled (as mine did) for painting in order to assure matching color depth and trim lines.
2. Polishing aluminum adjacent to paint presents two problems: first, you risk damaging the paint. You’ll need to mask along the trim line (a pain, especially if you have a curving paint line) to avoid damaging the paint with the coarser grades of polish, and you’ll need to keep an eye on the masking to make sure that you don’t accidentally wear through it. Second, the depth of shine will fade near the paint line since it will be hard to do a properly aggressive F7 polish adjacent to the paint line.
Therefore, either (A) polish the entire airplane, and figure your paint scheme out later, or (B) once you know the approximate location of your paint line, polish 4–6 inches beyond that to ensure the depth of shine is consistent, right up to the paint line.
Failure to completely remove polishing residue from around the rivet heads resulted in the paint contamination seen in this picture.
Once you’ve figured out where the exact paint line will be, go back and meticulously clean around any polished rivet heads (both flush and protruding) or seams that extend into the planned paint area with MEK or another aggressive solvent. Since the polish is petroleum based, any residue left behind in the crevices of seams and rivet heads can cause paint problems. You’ll also want to leave a couple of microfiber towels with the painter in case they need to clean any polished surface of overspray, etc. Also be aware that although a polished plane will require less paint, dealing with a polished plane presents certain challenges to the painter, so labor charges can be higher than you might expect. Ask your painter if they have experience painting polished planes and if they have any specific recommendations on prepping the plane for them.
So, if polishing next to the paint line is such a hassle, what about repolishing? Well, assuming you’ve done a good job with your initial polish and you don’t go too long between repolishing (6–18 months, depending on the climate), the repolishing process can be as simple as a single Cyclo pass with S—a whole plane can be done in a matter of a few hours. From my experience and the accounts of others, S will not scratch the paint (although Tom Numelin points out that, after many years, you may polish through the paint of protruding rivet heads). That said, when I repolished my RV-4, I masked over the paint, just to be on the safe side.
Prep for repolishing by hosing off any dust and using a microfiber towel to wipe dry. If water or bug guts have been allowed to dry on the metal, S won’t cut it—you’ll need to hit it with F7 first (compound and Cyclo for tough stains, Cyclo only if the deposits aren’t too heavy) followed by S. Don’t forget to clean with spirits before S if you use F7.
Repolish with S does not seem to harm vinyl decals, although it may discolor them. I’ve had luck lightly wiping vinyl trim with kerosene to remove black polishing smears (aggressive solvents will attack the vinyl). That said, I mask around vinyl just as I do with paint for repolishing. Regular masking tape works quite well: it has enough tack to avoid being lifted by the Cyclo, and as long as you remove it immediately after polishing, you shouldn’t have any problems with adhesive residue. Use a hair dryer to warm the tape as you remove it if you are concerned about residue or lifting the edge of the decal. If you’ve had your decals NC cut, you may want to have a few sacrificial masking overlays cut at the same time as your graphics to save time with future masking.
Remember, prevention is the best medicine here! Consider a paint scheme with trim in high bug-gut areas, i.e. the cowl, wheelpants and wing/tail leading edges. It’s much easier to keep paint clean than polished aluminum. In addition, keep a microfiber and spritzer in the hangar so you can immediately wipe away bug guts or moisture after flying. Although I have not had a chance to test it out yet, Nuvite’s NuImage is a cleaner/degreaser/debugger that purportedly will not cloud polished aluminum like other cleaners may.
Low-wing aircraft need to pay special attention to light reflected off the wing to the canopy. This picture shows the distorted canopy optics caused by a polished wing at just the right angle generating sufficient reflection to warp the canopy. Static cling window tint actually warped itself to the Plexiglas. Damage occurred in less than 15 minutes of exposure on a summer day.
Care and Feeding of Your Polished Plane
Given all the effort that goes into polishing a plane, it’s no wonder that an owner’s next thought is how to keep it that way with minimal effort. Unfortunately, according to Numelin, there is no foolproof coating to keep the shine. Most waxes only cloud the shine and remove the protectant left by the S polish. One possible exception is Nuvite’s NuImage polish (mentioned earlier). In any event, here’s what you can do to keep your plane looking its best after polishing:
1. Remove any moisture, bug guts, or raindrops immediately after flight with a microfiber cloth, as these attract dust and will leave a dot of dissolved pollutants and minerals if allowed to evaporate. Bug guts and bird droppings are surprisingly corrosive.
2. Use only microfiber and a spritz of water to clean polished surfaces. Most fabrics, including cotton, will scratch.
3. Corrosion occurs most slowly in cool, dry environments and most quickly in warm, damp environments. There’s a reason why aviation boneyards are usually in the desert. Find someone in your area who owns a polished plane, find out how often they have to polish it, and ask yourself if you are prepared to invest a similar amount of time.
4. For low-wing aircraft, monitor the canopy closely the first time you wheel the aircraft out on a sunny day. Reflected heat from polished wings has been known to warp or even melt Plexiglas, especially if there is anything dark (a sticker, suction cup, etc.) stuck to the canopy.
Polishing leaves a nasty black soot of aluminum oxide on your clothes and surrounding environment. Some of this is flung off by the compounder, while some just rubs off onto your clothes as you work. The clothes you use to polish will be ruined when you are finished, so dress accordingly, from your collar down to your shoes (you will turn carpet black if you walk into a house after polishing). In addition, I’d strongly recommend wearing nitrile gloves and a respirator.
1. Like painting, mask or blanket any proximal aircraft structure you don’t want getting covered in polishing soot. Also like painting, work with the best lighting available.
2. Temperature-wise, I’d suggest polishing in the cooler months if possible. The polish is suspended in a petroleum-based carrier which can dry quickly on hot days (it will also separate in the can, so be sure to give it a good stir before each polishing session). In addition, the aluminum itself gets quite hot from the compounder, and can really oil-can. In hot weather, waiting for a section to cool down before making another pass can really slow you down. In addition, remember that you’ll probably be clothed head to toe, which will be pretty uncomfortable if you are working in the heat of summer. Obviously, you should avoid polishing in direct sunlight; if you must polish outdoors, wait for a cloudy day.
3. When polishing, cleanliness is next to godliness. All it takes is a single aluminum burr or speck of dirt for a compounder to do serious damage. Carefully inspect pads and fleeces before use, and when finished store them in a Ziploc bag. Use a Sharpie and write the polish grade on the rear of each pad; do not use the same pad for different grades. Wool pads should be cleaned regularly with the spur while working, soaked overnight in TSP at the end of each work session, and rinsed clean the following day. Always set down your compounder or Cyclo with the pads facing up. A little care in your approach will avoid time wasted dealing with avoidable scratches.
This concludes our two-part series on polishing. I hope the tips and tricks outlined help you create your own version of shiny eye candy. Be sure to send KITPLANES® a high-resolution picture of your completed project, and if you have any particular tricks you’ve learned (regarding polishing, or otherwise), email them to me and I’ll collate them for a future tech tips article. Send photos and tips to firstname.lastname@example.org and put “polishing tips” or “polished plane photo” in the subject line.
The author would like to thank Jack Davis for the pictures which graced the cover and first page of Part 1 of this article.